1. Introduction
Rice is a plant that has important cultural, economic, and political impacts on the Indonesian people. Currently, fertile lands have been reduced because they are inferior to development and the economy; on the other hand, farmers are also not aware of returning crop residues to agricultural land which causes the chemical quality of the soil to decline so that in the future the development of rice plants must be able to use nutrient-poor land. Nutrient-poor soils contain C 1–2 ppm, N 0.1–0.2 ppm; P2O5 HCL 15–20, and C/N 5–10 [1]. The nutrient-poor soil is an important problem because it can affect plant growth and development [2]. Disturbed plant growth and development will have a negative effect on production. Thus, to keep plant production in balance, innovation is needed in providing environmentally friendly plant nutrients through organic fertilization. Nutrient recycling can be performed using livestock waste and plant waste, which can improve soil fertility statuses [3]. In addition to this, as an effort to improve agricultural systems, greenhouse gas (GHG) emissions can be reduced, but high yields are still prioritized through the use of the varieties.
Fertilization is one of the factors that increases yield and until now it has become the dominant factor in agricultural production. According to Liu et al. [4], fertilization is important in agricultural production because it can increase soil nutrients and increase crop yields. The fact that the demand for fertilizers in lowland rice has been increasing year by year comes at a time when the productivity of the rice fields is declining. The use of inorganic fertilizers that are increasing and expensive so that production costs increase also reduces farmers’ incomes. To anticipate this incident, fertilization can be improved by adding organic matter through the provision of organic matter from straw or goat manure. Returning straw to paddy fields is an option for farmers to use environmentally friendly technologies, improve soil fertility, and reduce fertilizer costs [5,6]. Goat manure is one type of manure that contains a lot of organic compounds. Purba [7] reported that the application of chemical fertilizers in rice cultivation increased rice yield by 17.1%. According to Istanti, Triasih [8], goat manure contains 2.325% total N, 4.045% P2O5, and 2.977% K2O. That is nearly double the number of nutrients found in chicken and cow manure. The results of the research by Wulandari et al. [9], stated that goat manure had an effect on the growth of the number of offspring and yields, on the number of panicles, the weight of 100 seeds, dry weight of the harvest, and dry weight of the mill.
The benefits of using organic fertilizers, besides being able to fertilize the land, include improving environmental quality, reducing agricultural production costs, and improving crop quality [4]. Purba [7] stated that the response to Nitrogen, Phosphorus, and Potassium was strongly influenced by the use of organic matter. However, the provision of organic fertilizers and plant management has an effect on greenhouse gas emissions, especially methane gas emissions (CH4) [10,11]. Methane (CH4) is one of the sources of GHG emissions that accounts for 70% of global emissions [12]. Rice fields are the largest source of CH4 emissions and contribute 12% of the total annual rice emissions [13]. It is necessary to add data from research on safe CH4 emission thresholds in irrigated rice fields for the environment to support conclusions.
Several ways to reduce methane gas emissions are by maintaining groundwater levels, providing soil amendments, and so on [14]. Mitra et al. [15] stated that methane emissions from paddy fields are the result of the production and oxidation of methane into the atmosphere through the vascular network of rice plants. The role of rice plants in methane dynamics is a source of substrate for methanogens in the form of plant exudates, roots, plant residues from the previous period, methane transport through air cavities in the aerenchyma network, and O2 pressure in the root area (rhizosphere) [11]. The main sources of substrate for CH4-producing methanogenic bacteria come from root exudates, plant parts, and the organic matter of rice plants [16].
In addition to the use of organic fertilizers, adaptable high-yielding varieties are an important part of lowland rice cultivation eco-agricultural techniques. Purba; Giametri [17], point out that superior varieties are the most effective technology for increasing productivity. Some of these superior rice varieties have the potential to emit relatively low methane gas, including IR64, Ciherang, Way Apoburu, Tukad Balian, and Widas [18,19]. The ability of varieties to emit CH4 gas depends on the aerenchyma cavity, number of tillers, rice biomass, root pattern, and metabolic activity [20]. Aulakh et al. [21] found that rice varieties (Dular, B40, Intan, IR-72, IR-64, new type of rice IR-65597, and hybrid rice Ma-gat) have different CH4 transport capacities (methane transport capacity), which are not only affected by plant growth stages, but also by physiological and morphological differences between rice varieties. The CH4 emission data from various new high-yielding varieties of lowland rice on nutrient-poor land have not been studied in depth. The practice of implementing new high-yield varieties according to local agroecology can effectively increase crop yield, resist pests and diseases, and resist drought and waterlogging [22]. Rice producers and consumers will feel the benefits of these varieties, and these high-quality seeds are available in sufficient quantities as large-scale alternatives [23].
The purpose of this study was to determine the impact of organic fertilizers and varieties on rice yield, methane emissions, and the feasibility of growing them in nutrient-poor rice fields in Central Java.
2. Materials and Methods
This research activity was carried out in irrigated rice fields in Bulugede, Patebon Sub-district, Kendal Regency, Central Java in the second planting season (April) with C-organic content of 1.02 ppm total N 0.13 ppm. Cations can be exchanged and K 0.06 cmol(+) kg−1 classified as nutrient-poor soil he study was arranged in a with two factor using a completely randomized block design with 4 replicates. The first factor was the type of organic fertilizers (compost of rice straw and goat manure) and the second factor was the variety of rice (Ciherang, Inpari 20, and Inpari 30). The number of plots was 24 plots/plot with a size of 4 × 6 m2 per plot. Plant maintenance consistedof using 2000 kg·ha−1 of organic fertilizers (depending on treatment); inorganic fertilizers: 225 kg·ha−1 each of urea and Phonska. N fertilizer was applied in stages, i.e., 1/3 N before planting, 1/3 N at 45 days after planting (DAP), and 1/3 N at 60 DAP. Phonska fertilizer was given at once before planting. Land preparation was done perfectly. Plant maintenance in the form of pests and weed control was carried out intensively by considering the conditions in the field.
CH4 and Nitrogen (N2) gas fluxes were measured in several phases of plant growth using a closed chamber including early plants; maximum tillering phase, panicle or flowering phase, and ripening phase. A sampling of CH4 gas was carried out manually using a closed box (Chamber) measuring 40 cm × 40 cm × 100 cm. The chamber was made of plexiglass and was equipped with a thermometer mounted on the top of the chamber (Figure 1). Before the first gas sampling, the chambers were randomly placed in each plot for the next gas sampling at the same location. Meanwhile, the N2O gas sample was carried out manually using a box measuring 40 cm × 20 cm × 20 cm. Gas sampling was carried out in the morning (07.00–09.00). The gas sample was taken using a 10 mL valved polypropylene injector. The injector was wrapped in silver foil, which served reduce the heat of solar radiation during gas sampling. After 20 min of gas sampling, the chamber was removed and the rice plants were allowed to return to normal conditions. Each time a gas sample was taken, the temperature change in the chamber was measured. Samples were analyzed using a gas chromatograph equipped with a flame ionization detector (FID) and a Porapak N column (80/100 mesh, 0.3 cm × 2 m). The gas chromatograph (Shimadzu 8A) had been calibrated with high precision and was used only to measure methane. The flux of methane gas was determined based on the equation used [24].
The data collected included agronomic parameters (plant height, number of tillers, panicle length, number of filled and empty grain per panicle, percentage of filled grain per cluster, and 1000 grain weight) and to obtain yield productivity results, the tiling method was used for each treatment with 4 tiling points. Gain productivity in the form of dry milled grain (dmg), is achieved by converting the harvested dry grain to a moisture content of 14%. The obtained data were then tested in 4 replicates using analyses of variance (F test) at a 5% level of significance [25]. If the test results obtained a significant effect, then proceed with a comparison test between treatments with Duncan’s multiple distance test at a 5% significance level. Data were analyzed using the SAS version 9.0 program.
The CH4 gas sample data were analyzed using a Model 8A Gas Chromatograph (GC) equipped with an FID (Flame Ionization Detector) detector. The N2O gas sample was analyzed using GHG equipped with a TCD (thermal conductivity detector). To calculate the emissions of these gases, the following equations were used by the International Atomic Energy Agency [26]:
E = (δc/δt) [{h·MW·Tst}/{MV·(Tst + T)}]
where:E = gas emission rate in mg/m/hour for CO2 and CH4 and in g/m/h for N2O;
Δc/δt = change in gas concentration between tn and tn + 1 (ppm/min);
H = effective height of gas storage box (m);
MW = molecular weight of CO2 (44 g/mol), CH4 (16 g/mol), and N2O (44 g/mole);
Tst = Standard temperature (273 °C);
MV = Molecular volume (22.41 × 10−3 m3);
T = temperature inside the container box (°C);
To determine the viability of farming three criteria were used, namely income, R/C ratio, and break-even point. The input-output data observed consisted of the amount and price of production inputs, as well as the amount and price of rice produced. Farmers’ income from rice farming was calculated by the formula used by [27,28,29] as follows:
Net Income = Gross Income − Total Cost
Furthermore, R/C was calculated using the formula used by [30,31,32] as follows:
R/C = Gross Income/Total cost
The break-even point is the point at which revenue is equal to total costs or profit is equal to zero. There are 2 break-even points, the production break-even point (BEP-Y) and the price break-even point (BEP-P). The production break-even point is the minimum production yield that must be achieved so that farmers do not lose, and the price break-even point is the output price required to cover all costs at a certain level of output [33]. The break-even point is found by the following formulas:
BEP-Y = Total Cost/Harga Output
BEP-P = Total cost/Total Produksi
3. Results
3.1. Environmental Conditions
Before and after the study, an analysis of the soil used for the study [1] was carried out with the aim of knowing the level of fertility and the level of nutrient status of the soil, as shown in Table 1 and Table 2. The soil texture at the study site included clay. Soil analysis data from the initial soil test site (pre-study) showed organic carbon of 1.02 ppm (low), N total = 0.13 (low), P2O5 = very high, K2O = very high, pH 6.6 (neutral), and CEC soil = very high (Table 1). The pH in the soil can affect plant growth, but changes in soil pH should not affect plant growth. Likewise, N, P, and K were still less than 55% efficient when growing food crops on soils with a pH of 5.0. However, when the pH is increased due to raising the soil pH to the desired level of neutral, the fertilization efficiency will be maximized because there is an optimal application of fertilizers with the appropriate soil pH. This is in accordance with Yuniarti et al. [34] who say that an increase in soil pH resulted in an increase in available P, P uptake, and yield of black rice (Oryza sativa L.) in Inceptisol fields.
Based on the data in Table 2, organic fertilizers in the form of rice straw compost and organic goat fertilizers increase soil pH and C-organic, as well as soil macro=micronutrients such as N, P, K, and also cations can be exchanged but reduce the Cation Exchange Capacity (CEC) and exchangeable K of the soil. Consistent with research by Nurjani et al. [35] the data show that the addition of organic matter can increase soil pH, increase CEC, and soil N, P, and K availability, as well as increase N, P, and K nutrient uptake in these plants.
According to Hidayanti et al. [36], the increase in P was affected by a high N content, and the higher the N element content, the increase of the number of microorganisms that transformed P. Asih et al. [37] stated that phosphorus nutrients for plants function in the process of seed formation, energy transfer, and nucleoprotein formation. Siregar et al. [38], said that an increase in soil pH is possible because organic acids from decomposition can bind H+ as a cause of soil acidity. This is so that soil pH increases in addition to organic matter that has been decomposed and will produce OH- ions that can neutralize the activity.
3.2. Organic Fertilizer
Improving rice yields can be achieved through improved cultivation techniques, including improved fertilization. Manure has a good buffering capacity which can protect plants from adverse fluctuations and improve soil resistance to dsiturbances [39]. Fertilization can be improved by adding organic materials in the form of goat compost and straw organic fertilizers, as these are types of fertilizers that contain a lot of organic compounds and are environmentally friendly. Furthermore, its abundant availability can reduce production costs and increase yields by improving soil structure. The results of the analysis of organic straw fertilizer and goat compost are listed in Table 3.
3.3. Performance of Paddy Growth and Productivity
Based on the results of the statistical analysis, there was no significant interaction between the treatment of organic fertilizers and varieties on the parameters of rice plant height and the number of panicles observed at 30, 45 and 85 days after planting. Growth parameters, namely plant height, number of ears, and types of manure (i.e., straw and goat compost) were not significantly different between treatments observed at 30, 45 and 85 days after planting (Table 4). This is said to have occurred because rice cultivation in the study area usually does not use organic fertilizers but only inorganic fertilizers. The addition of organic fertilizer for the first time is not enough to supply or provide additional nutrients for cultivated plants. The effect of giving organic fertilizers can be felt in the long-term because the function of organic fertilizers is to improve soil structure, increase soil organic matter content, and improve soil biological conditions so that existing nutrients become more available to plants and nutrient absorption by plant roots will also increase [40,41].
The results of observations of the yield components of three rice varieties are presented in Table 5. There was no significant interaction between the treatment of organic fertilizers and three superior varieties of rice on the parameters of the rice yield components, namely 1000 grain weight, panicle length, number of filled and empty grains per panicle, and Harvested Dry Grain (HDG) and Milled Dry Grain (MDG). There were also no significant differences in all parameters between the organic straw manure and goat compost treatments. However, among the superior rice varieties, the productivity parameters of Harvested Dry Grain (HDG) and Milled Dry Grain (MDG) were significantly different, that is, the productivity of Inpari 20 was significantly higher than that of Ciherang and Inpari 30. Likewise, the same is true for the other yield components that are productivity determinants, namely the 1000 grain weight, the amount of grout, and the percentage of grout grains. Per panicle on Inpari 20 showed a higher trend than Ciherang and Inpari 30.
Inpari 20 was the highest compared to Inpari 30 and Ciherang (Table 6). The productivity of Inpari 20 is related to and influenced by the genetic ability of Inpari 20 to form tillers more quickly and more in the early stages of growth (30 days after planting) than the other two varieties Table 4. The 1000 grain weight and the percentage of filled grain produced also tend to be larger than the other two varieties (Table 5). These three parameters of rice yields indicate that it is important for a variety to have the ability to form more and faster tillers in the early stages of growth (before 21 DAP) because the earlier tillers are formed, then the time for panicle formation and development is longer than varieties that are slow to form tillers. The faster the panicles are formed, the faster the formation of grain in rice panicles and the positive effect as it takes longer for the kernel to fill into a full and fine grain. In this study it was proved that in the Inpari 20 variety, with the ability to form tillers early, the productivity of dry harvested grain was significantly higher than Ciherang and Inpari 30, and the productivity of dry grain harvested in Inpari 20 was significantly greater than the other two varieties. This indicated that the physiologic maturity level of the grain in Inpari 20 was higher so that at a moisture content of 14% MDG, the grain weight was still higher than Ciherang and Inpari 30. This idea means that the rice grain maturing process in Inpari 20 is more optimal than the other two varieties because it starts from an earlier panicle formation time, which has a positive impact on the formation of more tillers at the beginning of the vegetative growth phase.
3.4. Methane (CH4) Emission Results
The results of observations on methane emissions are presented in Table 6 below. According to Table 7, the results of CH4 emissions differ between fertilization treatments and rice varieties. Different levels of CH4 gas emissions are due to the influence of morphological and physiological performances of rice varieties [10]. Of the 3 varieties tested, the Ciherang variety had the highest methane emission, followed by Inpari 30, and the lowest, being Inpari 20. This was because the Ciherang variety had more tillers than the Inpari 20 and Inpari 30 varieties. Inpari 30 is higher than Inpari20 because rice variety 30 has the highest plant height compared to other varieties. The characteristics of low methane emissions from rice depend on plant height, tiller number and plant biomass, and average chemical root cavity area [42].
3.5. Feasibility of Rice Farming
To determine the feasibility of rice farming, three criteria are used, namely income, R/C ratio, and break-even point. The results of the feasibility analysis of rice farming are presented in Table 8. According to Table 8, rice cultivation costs are known to vary by treatment, ranging from IDR 19,190,000/ha–IDR 20,135,000,-/ha, where the lowest cost of farming is compost treatment. The highest cost of farming is straw compost + Inpari 20. The highest agricultural costs are other costs, namely land rent and irrigation, followed by labor costs, fertilizer costs, seed costs, and pesticide costs. The cost of rice farming as a result of this study is the same as the cost of farming rice as a result of the study in Kristanto et al. [43] in Kendal Regency, Rp. 19,549,458,-/ha. However, it is higher than the results of the study by Saediman et al. [44] in South Konawe Regency by as much as Rp. 9,354,087,-/ha and the results of research by Nearti et al. [45] in Rambutan Regency by as much as Rp. 14,337,467,-/ha. Meanwhile, the cost of rice farming as a result of this study is lower than the results of the study by Chanifah et al. [46] in Karanganyar Regency, by up to Rp. 22,682,136,-/ha.
One way to assess the feasibility of farming is to analyze the R/C ratio. Agriculture is considered viable if the R/C ratio is >1 [47]. It can be seen from Table 8 that the R/C ratio of straw composting treatment varies from 1.15 to 1.51 and the R/C ratio of Inpari 20 is the highest, followed by Ciherang and Inpari 30. The R/C ratio of goats treated with organic fertilizer varied from 1.26 to 1.47 with Inpari 20 having the highest R/C ratio of 1.47, followed by Ciherang and Inpari 30. Thus, all treatments were feasible because the R/C ratio was > 1.
4. Discussion
4.1. Environmental Conditions
The results of the initial soil analysis showed that the availability of nutrients, especially P and K, was not a problem when including soil pH values that are already at neutral standards. In a neutral soil pH the availability of nutrients is more than in pH < 5. The problem with this soil is the low soil organic C and N in the soil, as well as alkaline cations in the soil. The C-organic content in the soil is an indicator of soil fertility status [48]. Quantitatively, the addition of rice straw compost and goat organic fertilizer was able to increase the organic C-level in the soil, although it was still in the same status as the beginning of the study. The addition of rice straw compost showed an increase in organic C-levels which was higher than that of the goat organic fertilizer in all rice varieties and the highest increase was shown in Inpari 20. The organic carbon content in each organic fertilizer has a certain effect on increasing soil organic carbon. The organic carbon content of the straw compost was higher than that of the goat organic fertilizer (Table 2), so the additional organic carbon was also higher in the soil composted with straw. According to Atmojo [49], the application of organic matter that is humus can increase the C-organic content of the soil.
Organic matter added to the soil increases the availability of phosphorus in the soil. The addition of rice straw compost increased the available P in the soil on average by 3.80%, while the average increase of available P with the addition of goat organic fertilizer was 3.95%. The addition of goat compost to the Inpari 30 rice variety resulted in the greatest increase. The soil at the study site has a clay texture with up to 55% clay content which plays an important role in controlling phosphorus availability [50]. High clay content causes P to be adsorbed making it unavailable to plants. Besides clay colloids, Mg cations also play a role in controlling the availability of P by absorbing it to form MgP. However, with the addition of organic matter, the adsorbed P can be released as a result of the work of organic acids resulting from the decomposition of organic matter, such as oxalic acid, which can dissolve the adsorbed P so that the P available in the soil after the addition of organic matter is higher than the initial soil [51]. The increase in available P can also come from the mineralization process of organic matter which releases elements such as P.
Many studies have shown that the addition of organic matter or organic fertilizers will increase the soil CEC [38,52]. This is due to the increase of the negative charge of soil colloids from the carboxyl (COOH) and hydroxyl (OH) groups contained in organic compounds resulting from the decomposition of organic matter or organic fertilizers. However, in this study, it turned out that the addition of organic matter actually reduced the soil EC.
4.2. Organic Fertilizer
Based on the results of the analysis of organic fertilizers (Table 3), the water content of goat manure is 48.40% less than that of straw fertilizer which has 60.00% water content. With these conditions it means that organic goat manure is relatively hard and takes a long time to rot in the ground. In addition, the contents of C-organic, N, P, K, Fe, Mn, Zn, Cu, and other indicators of rice straw were higher than those of goat manure. Based on these results, straw compost can be used as a substitute for organic fertilizers in rice fields. The use of organic fertilizers in a sustainable manner will have a positive impact on soil fertility. The combined application of organic and inorganic fertilizers, in addition to providing high and sustainable yields, provides economic efficiency while maintaining the balance of nutrients in the soil [53]. The long-term application of organic matter can also play a positive role in mitigating climate change through carbon sequestration [54].
According to Siregar et al. [38], rice cultivation produces 7–10 tons·ha−1 of straw per growing season. The components of rice straw are mainly cellulose, hemicellulose, lignin, and a small amount of protein, and the C/N value is high. Gaur [55] pointed out that the C/N value of fresh straw is 80–130. This fact causes the decomposition process of the straw to take a long time. In this study, the straw used was a straw that had undergone complete decomposition so that the C/N ratio was already low (Table 3). In general, good C/N ratios for land use ranges from 15 to 20 [56]. However, for ideal results a C/N ratio of 10 is recommended [57].
4.3. Performance Growth and Productivity
It takes several growing seasons to be able to determine the effect of organic fertilizer application on the growth of rice plants on the land. According to Courtney et al. [58], improvement of soil fertility status takes a long time due to slow changes in composting parameters. This is consistent with the results of the study [7], which explained that the effect of organic matter added to the soil was longer than that of inorganic fertilizers. However, from the observed data, there was a consistent trend seen in the treatment of organic fertilizer types, namely the plant height in the goat compost treatment at the age of 30, 45 and 85 DAP tended to be higher and the number of panicles tended to be more than the straw treatment (Table 4). This becomes important information as a basis for analyzing the effect of the type of organic fertilizer on the production of rice produced.
In the treatment of different varieties, there was a significant difference in the growth of rice plants in the fast vegetative phase. The Inpari 20 variety showed the most significant growth in panicle numbers compared to the Ciherang and Inpari 30 varieties, but in plant height growth it was the opposite because the plant height of the Inpari 20 variety was significantly lower than the Inpari 30 variety and not significantly different from the plant height of the Ciherang variety (Table 4). Furthermore, the observations made at the age of 45 and 85 days after the three varieties showed that growth in plant height and the number of panicles were not significantly different. According to Magfiroh et al. [59], important factors that affect plant growth (weight gain, plant height, and the number of productive tillers) are genetic factors and environmental factors. In this study, the growth of the three varieties seems to be more influenced by genetic factors of each variety, although environmental factors are also involved. It is suspected that genetic factors are more expressed because during the research the microenvironmental conditions are always optimal in terms of fertilizer requirements, water requirements, and pest control so that plants are protected from environmental stresses, both abiotic and biotic. According to Asfaw et al. [60], the genetic factors of a species will be well expressed in the growing environmental conditions that are needed for growth and development or vice versa. Magfiroh et al. [59] also said that plant height is influenced by plant genetic characteristics, growing environmental conditions, and their interactions in the environment where they grow. Furthermore, plant height is also determined by the speed of the elongation of stems and leaves. According to the research of Yartiwi et al. [61], the magnitude of the elongation velocity is caused by the height of the blade water potential or the expansion pressure of the blade. Variations in water supply during the vegetative and reproductive phases determine the water statuses in soil and plants.
Based on observations, the Inpari 20 variety is known to have a faster and more tiller-forming ability than the Ciherang and Inpari 30 varieties. In this study, the seedlings of the three varieties were the same when transplanted, that is, 18 days after sowing the number of perforated seeds, that is, 2–3 plants. Sunadi [62] reported that the number of rice tillers was related to the period of Phyllochron formation. Phyllochron is the period in which individual stem, leaf, and root cells emerge from the base of the plant and subsequently germinate. The younger the seedlings are transferred, the greater the number of thalloids produced which in turn can produce more tillers.
According to Sakamoto; Matsuoka [63] and Sreenivasulu, Schnurbusch [64], vegetative formation is a key factor in the production of grains such as rice, wheat, and barley. However, tillers that grow late will not be productive and reduce the harvest index [63], Mäkelä; Muurinen [65], which means that the speed and number of tillers grown must be balanced. If only fast but not many tillers are grown, then neither will produce high yields. Based on the results of the research above, it is expected that the Inpari 20 variety has the ability to form Phyllocron faster and more before the age of 21 DAP, than the Ciherang and Inpari 30 varieties so that the number of tillers of Inpari 20 formed is more than the other two varieties. The increase in tiller formation in the Ciherang and Inpari 30 cultivars increased rapidly after 21 DAP to 85 DAP and thus became insignificant with the number of tillers in Inpari 20 (Table 4).
In the present study, the types of organic fertilizers, i.e., the treatments of straw compost and goat organic fertilizer, did not significantly differ in the growth parameters, and yield composition, and productivity of rice. This result is contrary to that of the study by [66], werethe application of organic straw fertilizer and the application of N, P, and K fertilizer (Urea and Phonska) is thought to be able to increase the plant nutrients needed in the form of Fe-P and AI-P into forms available for rice and have a significant effect on rice production. Then in [67], the results of his research stated that the use of organic fertilizer in the form of straw compost, as much as 2 tons·ha−1 + organic fertilizer (110 kg·m−1 + 55 kg·m−1, P2O5 55 kg·m −1 K2O and 500 kg·m−1 lime), was able to increase the yield of Ciherang variety rice by 26.82% (6.62 tons·ha−1) compared to the control (5.22 tons·ha−1). Wihardjaka [68] also reported that the application of rice can increase grain in the range of 5.4–9.0%. The results of this study are not in line with several other studies where the application of organic rice straw fertilizer can increase rice productivity. This event has important information regarding the application of organic fertilizers straw, either rice straw or goat compost, on paddy fields that have never been given organic fertilizer before, and on the effect of organic fertilizers not being able to significantly increase rice productivity. Organic fertilizers that have been applied only once still have the effect of increasing soil fertility. As described in Mandal et al. [38], organic fertilizers can increase soil fertility by improving the soil’s physical, biological, and chemical properties, such as increasing soil CEC so that fertilizer nutrients can be absorbed or stored. In addition, organic fertilizers can improve the development of plant roots, so improvements in chemical properties and plant root development are expected to increase the efficiency of inorganic fertilizers [69]. Funk [70] also pointed out that organic fertilizers applied to plants can be sources of nutrients. Therefore, the organic fertilizer treatments in this study did not improve rice yield, as organic fertilizers were more effective in enhancing fertility and improving the physical, chemical, and biological conditions of the soil on the land. The results of the analysis of organic fertilizers used showed that the nutrients contained were very large and if in the next season organic fertilizers were continued to be applied, the soil fertility conditions would be better, so that not only improved land conditions but would also have a significant effect on increasing rice productivity.
4.4. Methane (CH4) Emissions
The results’ CH4 emissions are controlled by a range of biogeochemical processes including interactions between soil moisture, soil redox status, soil texture, soil pH, and the availability of organic and inorganic components, as well as the combined effects of these factors [71]. Methane release from rice varieties is influenced by genetic factors, morphology, plant physiology, media, and plant growth environment [72,73]. The ability of cultivars to release CH4 depends on the chemical cavity, number of tillers, root biomass, and metabolic activity [72,74]. Rice plant biomass consists of three main components, namely cellulose, hemicellulose, and lignin. Rice straw is known to have a high cellulose content reaching 34.2% dry weight, 24.5% hemicellulose, and lignin content up to 23.4% [75].
The Ciherang variety is a rice variety that has low methane emissions and high yields. Wihardjaka [76] explained that the Ciherang variety has the potential to produce relatively low methane fluxes. Ciherang emits 170 kg·ha−1 of methane gas in the season and the grain output is 5.43 kg·ha−1. Food production is closely related to the amount of methane gas produced. Methane flux decreases after flowering as photosynthetic carbon dioxide is used for methane formation [76]. Rice varieties also produce different methane fluxes. The higher the emission index, the lower the emission capacity of the variety and the higher the grain output. The emission index of the Inpari 6 variety is lower than that of the Inpari 1 and Ciherang varieties. The Inpari 1 variety had the highest emission index and a higher grain yield than Ciherang [77]. The higher N content in straw organic fertilizer compared to goat compost (Table 3) is thought to have a positive effect so that the methane emission that can be released into the air in the treatment of organic straw fertilizer is smaller than that of goat compost (Table 6). This is consistent with the findings of Asri [78] where the use of fertilizers with more nitrogen results in fertilizers that are hygroscopic, resulting in reduced gas emissions due to the inhibition of methanogen activity.
4.5. Feasibility of Rice Farming
The rice yields obtained in this study varied by treatment. Yields from rice straw treatments varied from 5792 kg·ha−1 to 8021 kg·ha−1, with Inpari 20 cultivar yielding the highest yield, followed by the Ciherang cultivar and Inpari 30 cultivar. Yields for goat compost treatment ranged from 6417 to 7729 kg·ha−1, where the highest production was achieved in the Inpari 20 variety, followed by the Ciherang variety and the Inpari 30 variety. The production of this study was the same as that of the study [45] in Banyuasin Regency of up to 6522 kg·ha−1 and Chanifah et al. [46] of up to 7708 kg·ha−1 at Karanganyar Regency. However, the output of the results of this study is lower than that of the study by [44] in Kendal Regency by as much as 8123 kg·ha−1. With the same selling price of rice, which is Rp. 3800,-/kg, the income obtained between treatments also varies. Revenue of the rice straw treatment varied between IDR 22,009,600,-/ha IDR. 30,479,800,-/ha, where the highest acceptance was obtained by Inpari 20 variety, followed by the Ciherang variety and Inpari 30 variety. Revenue of goat compost fertilizer treatment varied, ranging from IDR 24,384,600,-/ha–IDR. 29,370,200,-/ha, where the highest acceptance was obtained by the Inpari 20 variety, followed by the Ciherang variety and the Inpari 30 variety.
The size of farm income is influenced by the amount of production, price, and production [79]. The rice cultivation income obtained varied between treatments. The income of the straw treatment varied between IDR 2,819,600,-/ha–IDR. 10,344,800,-/ha, where the highest income was achieved in the Inpari 20 variety, followed by the Ciherang variety and Inpari 30 variety. The income from the manure treatment varied between IDR. 4,969,600,-/ha–IDR. 9,370,200,-/ha, where the highest income was achieved in the Inpari 20 variety, followed by the Ciherang variety and the Inpari 30 variety. The income for this study is the same as that of Lapuerto. Lapodo; Sulaeman [80] in Sigi Regency, where the amount was IDR 3,944,169,-/ha; the result of this study is that the income from rice cultivation is the same as in South Konaway Regency, i.e., Rp. 8,291,281,-/ha [44]; Fathonah [81] in Purworejo Regency at IDR 10,227,780; Chanifah et al. [46] in Karanganyar Regency of IDR 10,078,281,-/ha. The results of this study are lower compared to the results of the study by [45] in Banyuasin Regency of IDR 15,012,038, and Kristanto et al. [43] in Kendal Regency of IDR 22,541,274 R/C results the ratio in this study is the same as the R/C ratio of research results [46] in Karanganyar Regency of 1.44; higher than the R/C ratio of research results [82] in Kendal Regency of 0.92. However, it is lower than the R/C ratio of research results [83] in Central Sulawesi Province of 1.80; Finza [42] in South Konawe Regency of 1.89; Kristanto et al. [44] in Kendal Regency of 2.30; Fathonah [81] in Purworejo Regency of 2.97; Lapodo; Sulaeman [80] in Sigi Regency of 2.40; Nearti et al. [46] in Banyuasin Regency of 2.05. The value of the R/C ratio asa result of this study is lower than in other locations, indicating that there are still opportunities for farmers to increase the productivity and efficiency of rice farming in the research location.
The break-even point is the turning point, which is the minimum production and price limit to restore farm costs so as not to lose money. Agriculture is considered viable if the break-even point of yield and price < yield and real price [48]. From Table 7 it can be seen that the production break-even point (BEP-Y) and the price break-even point (BEP-P) are different. The break-even point of production in the rice straw treatment ranged from 5050 kg·ha−1 to 5299 kg·ha−1 with a break-even point of prices ranging fromIDR 2510,-/kg–Rp. 3313,-/kg. The value in Table 7 means that at the price level of IDR 3800,-/kg, the farmer must produce rice so as not to lose a minimum of 2720 kg·ha−1, 2510 kg·ha−1, and 3313 kg·ha−1, respectively, for the variety. For Ciherang, Inpari 20, and Inpari 30, or the production obtained, the minimum price so that farmers do not lose is Rp. 5204,-/kg, Rp. 5299,-/kg, and Rp. 5050,-/kg for the Ciherang, Inpari 20 varieties, and Inpari 30, respectively.
The tolerance limits for decreasing production and prices that do not cause losses are 28.42%, 33.39% and 12.82% of the actual production and prices for Ciherang, Inpari 20, and Inpari 30 varieties, respectively. Even if yields and prices fall more than this limit, the farmers will suffer. If yields and prices fall more than this limit, farmers will suffer. Meanwhile, the production break-even point for manure treatment is between 5109 kg·ha−1 and 5263 kg·ha−1 and the price break-even point is IDR 2588,-/kg–IDR. 3026,-/kg. The value in Table 8 means that at the price level of Rp. 3800,-/kg, the farmer must produce rice so as not to lose a minimum of 2975 kg·ha−1, 2588 kg·ha−1, and 3026 kg·ha−1 for the variety. For Ciherang, Inpari 20, and Inpari 30, or the yield obtained, the lowest prices for the Ciherang varieties were IDR 5121/kg, IDR 5263/kg, and IDR 5109/kg, respectively.
In the case of no loss, the tolerance limits for production reduction and price reduction are 21.71%, 31.89% and 20.37% of the actual products and prices of Ciherang, Inpari 20, and Inpari 30 varieties, respectively. If there is a decrease in production and prices are greater than this limit, the farmer will suffer a loss. Thus, the Inpari 20 variety is the most stable if there is a decrease in production and price when compared to the Ciherang variety and the Inpari 30 variety. The tolerance limits of the results of this study are the same as those of the results of Chanifah et al. [46] with 30.76% growth at Karanganyar Regency, but lower than the results of the study by Kristanto et al. [43] in Kendal Regency by 46.68%.
Based on the feasibility criteria for farming, namely income, R/C ratio, and break-even point, it is known that the Inpari 20 variety, both in the treatment of fertilizing with rice straw and goat compost, produced the highest income and R/C ratio compared to the Ciherang and Inpari 30 varieties, as well as from the analysis of the break-even point. Compared to the Ciherang and Inpari 30 varieties, the Inpari 20 variety is the most stable.
5. Conclusions
The Inpari 20 variety with rice straw compost had the highest productivity (8.02 t·ha−1 HDG) suitable for widespread development in nutrient-poor rice fields (highest R/C ratio and break-even point) with the lowest methane emissions (22.3 kg h−1 season−1) compared to the Inpari 30 and Ciherang varieties. Studies on rice fields that have been organically fertilized for several seasons are needed to determine their effects on productivity and emissions of methane (CH4), nitrite (N2O) and carbon (CO2).
Main author, F.D.A., supporting author, M.D.P., J.T., H.P., S.M., K., Y.H., S.J., D.S. and E.N.; conceptualization, F.D.A., M.D.P., J.T., H.P., S.M., K., Y.H., S.J., D.S. and E.N.; performed research and analyzed data, F.D.A. and M.D.P.; wrote the original manuscript and draft preparation, F.D.A.; wrote, reviewed, and edited, F.D.A., M.D.P., J.T., H.P., S.M., K., Y.H., S.J., D.S. and E.N. All authors have read and agreed to the published version of the manuscript.
Not applicable.
Informed consent was obtained from all subjects involved in the study.
The data presented in this study are available upon request from the corresponding author. The data are not publicly available yet but will be in due course.
The authors express their gratitude to the Indonesian Agency for Agricultural Research and Development, Central Java Assessment Institute for Agricultural Technology, and give thanks to Nurfitriana, Warsito, and Zamawi who have helped with data collection and the implementation of research activities.
The authors declare no conflict of interest.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Enlarge this image.Figure 1. Chamber performance in the field. (a). Tools to measure NO2 gas. (b). Tools to measure CH4 gas.
Results of soil analysis before the study in Bulugede, Patebon, Kendal District (*).
| No. | Parameter | Unit | Before Research | |
|---|---|---|---|---|
| Results | Criteria | |||
| 1 | pH H2O (1:5) | - | 6.6 | Neutral |
| 2 | C-organic | (mg/kg) | 1.02 | Low |
| 3 | N-total | (%) | 0.13 | Low |
| 4 | Texture: | |||
| Sand | (%) | 9.69 | ||
| Dust | (%) | 34.60 | ||
| Clay | (%) | 55.71 | Clay | |
| 5 | P2O5 (Olsen) | (mg/kg) | 24.54 | Very high |
| 6 | P2O5 (HCl 25%) | mg/100g | 101.58 | Very high |
| 7 | K2O (HCl 25%) | mg/100g | 3143.02 | Very high |
| 8 | CEC | cmol(+)kg−1 | 48.92 | Very high |
| 9 | Cations can be exchanged | |||
| K | cmol(+)kg−1 | 0.06 | Very low | |
| Na | cmol(+)kg−1 | 0.13 | Low | |
| Ca | cmol(+)kg−1 | 3.98 | Very low | |
| Mg | cmol(+)kg−1 | 0.10 | Moderate | |
(*) Soil analysis method follows [
Results of soil analysis after research in Bulugede, Patebon, Kendal District (*).
| Parameter | Rice Straw | Goat Compost | ||||
|---|---|---|---|---|---|---|
| Ciherang | Inpari 20 | Inpari 30 | Ciherang | Inpari 20 | Inpari 30 | |
| pH (H2O) | 7.1 | 7.09 | 6.95 | 7.76 | 7.38 | 7.58 |
| C-organic | 1.68 | 1.73 | 1.69 | 1.07 | 1.31 | 1.31 |
| N-total | 47.63 | 39.65 | 44.76 | 29.22 | 36.15 | 45.73 |
| P available | 94.45 | 92.38 | 92.57 | 92.95 | 89.98 | 107.76 |
| P2O5 (HCl 25 mg/kg) | 94.45 | 92.38 | 92.57 | 92.95 | 89.98 | 107.76 |
| K2O (HCl 25%) | 135.13 | 137.26 | 138.98 | 146.72 | 146.42 | 146.62 |
| CEC | 42.43 | 24.59 | 37.52 | 43.38 | 24.37 | 37.93 |
| Cations can be exchanged | ||||||
| K | 0.04 | 0.04 | 0.05 | 0.05 | 0.05 | 0.05 |
| Na | 0.20 | 0.19 | 0.18 | 3.77 | 0.21 | 3.77 |
| Ca | 23.13 | 20.53 | 24.14 | 26.67 | 22.05 | 24.30 |
| Mg | 0.65 | 0.54 | 0.61 | 1.20 | 0.57 | 0.7 |
(*) Soil analysis method follows [
Results of analysis of organic rice straw and goat compost.
| Parameter | Rice Straw | Goat Compost |
|---|---|---|
| Kadar Air (%) | 69.00 | 48.40 |
| pH | 9.23 | 8.46 |
| C-Organic (%) | 28.30 | 24.65 |
| N-Total (%) | 2.76 | 1.28 |
| P2O5 (%) | 0.72 | 0.39 |
| K2O (%) | 4.21 | 1.97 |
| Fe (ppm) | 6229.39 | 5938.56 |
| Mn (ppm) | 494.31 | 648.43 |
| Zn (ppm) | 112.02 | 75.74 |
| Cu (ppm) | 32.02 | 63.62 |
| C/N ratio | 10.20 | 19.30 |
Plant height and number of tillers of three rice varieties at the ages of 21, 45 and 85 DAP.
| Treatment | Plant Height (cm) | Tiller Number (Clumps) | |||||
|---|---|---|---|---|---|---|---|
| 21 DAP | 45 DAP | 85 DAP | 21 DAP | 45 DAP | 85 DAP | ||
| Organic Fertilizer | Rice straw | 44.65 a | 73.63 a | 96.48 a | 11.00 a | 16.17 a | 17.50 a |
| Goat compost | 44.99 a | 75.98 a | 96.72 a | 11.17 a | 16.17 a | 18.83 a | |
| Variety | Ciherang | 44.86 ab | 75.66 a | 94.82 a | 11.00 b | 16.38 a | 18.50 a |
| Inpari 20 | 43.18 b | 72.24 a | 96.38 a | 13.00 a | 15.75 a | 19.25 a | |
| Inpari 30 | 46.44 a | 76.51 a | 98.61 a | 9.25 b | 16.38 a | 16.75 a | |
| “p”-value | Fertilizer | 0.71 ns | 0.25 ns | 0.89 ns | 0.82 ns | 1.00 ns | 0.25 ns |
| Variety | 0.03 * | 0.20 ns | 0.24 ns | 0.04 * | 0.71 ns | 0.20 ns | |
| Fertilizer × Variety | 0.85 ns | 0.32 ns | 0.41 ns | 0.71 ns | 0.69 ns | 0.32 ns | |
| CV (%) | 5.02 | 6.52 | 4.21 | 15.77 | 11.57 | 15.07 | |
Note: * significance at “p” < 0.05; numbers with the same letters in the same column are not significantly different based on Duncan’s Multiple Range Test (α 0.05). ns = not significance. DAP = Day After Planting.
Yield components of three rice varieties with different types of organic fertilizers.
| Treatment | Panicle Length (cm) | Filled Grains per Clump (Grains) | Unfilled Grains per Clump (Grains) | Percentage of Filled Grains per Clump (%) | 1000 Grain Weight (g) | |
|---|---|---|---|---|---|---|
| Organic Fertilizer | Rice straw | 26.92 a | 22.32 a | 1351.75 a | 55.47 a | 96.01 a |
| Goat compost | 26.99 a | 22.31 a | 1436.56 a | 55.11 a | 96.23 a | |
| Variety | Ciherang | 26.15 a | 22.10 a | 1347.8 a | 62.12 a | 95.58 a |
| Inpari 20 | 27.73 a | 22.49 a | 1415.1 a | 49.58 a | 96.54 a | |
| Inpari 30 | 26.98 a | 22.35 a | 1419.5 a | 54.16 a | 96.24 a | |
| “p”-value | Fertilizer | 0.95 ns | 0.32 ns | 0.96 ns | 0.71 ns | 0.91 ns |
| Variety | 0.13 ns | 0.73 ns | 0.44 ns | 0.41 ns | 0.22 ns | |
| Fertilizer × Variety | 0.89 ns | 0.46 ns | 0.76 ns | 0.66 ns | 0.28 ns | |
| CV (%) | 1.65 | 14.64 | 35.47 | 1.52 | 6.46 | |
Note: ns: not significance at “p” < 0.05; numbers with the same letters in the same column are not significantly different based on Duncan’s Multiple Range Test (α 0.05).
Productivity of Harvested Dry Grain (HDG) and Milled Dry Grain (MDG) of three varieties of rice plants with different types of organic fertilizers.
| Treatment | HDG (ton·ha−1) | MDG (ton·ha−1) | |
|---|---|---|---|
| Organic Fertilizer | Rice straw | 7.03 a | 6.02 a |
| Goat compost | 6.90 a | 5.99 a | |
| Variety | Ciherang | 6.91 b | 5.94 b |
| Inpari 20 | 7.88 a | 6.86 a | |
| Inpari 30 | 6.10 b | 5.22 b | |
| “p”-value | Fertilizer | 0.62 ns | 0.91 ns |
| Variety | 0.0003 * | 0.001 * | |
| Fertilizer × Variety | 0.14 ns | 0.10 ns | |
| CV (%) | 11.96 | 14.08 | |
Note: * significance at “p” < 0.05; numbers with the same letters in the same column are not significantly different based on Duncan’s Multiple Range Test (α 0.05). ns = not significance. HDG = Harvested Dry Grain, MDG = Milled Dry Grain.
Emissions of CH4 and NO2 in rice cultivation with different fertilization for each treatment in Bulugede Village, Patebon District, Kendal Regency.
| Treatment | Total Emission (kg h−1 season−1) | |
|---|---|---|
| CH4 | NO2 | |
| Straw—Ciherang | 56.4 | Straw—Ciherang |
| Straw—Inpari 20 | 22.3 | Straw—Inpari 20 |
| Straw—Inpari 30 | 40.8 | Straw—Inpari 30 |
| Goat compost—Ciherang | 58.9 | Goat compost—Ciherang |
| Goat compost—Inpari 20 | 36.8 | Goat compost—Inpari 20 |
| Goat compost—Inpari 30 | 42.0 | Goat compost—Inpari 30 |
Analysis of Environmentally Friendly Rice Planting Using Organic Fertilizers and Varieties.
| No. | Description | Varieties Treatment and Organic Fertilizer | |||||
|---|---|---|---|---|---|---|---|
| Straw | Goat Compost | ||||||
| Ciherang | Inpari 20 | Inpari 30 | Ciherang | Inpari 20 | Inpari 30 | ||
| 1. Cost(Rp/ha) (a + b + c + d + e) | 19,775,000 | 20,135,000 | 19,190,000 | 19,460,000 | 20,000,000 | 19,415,000 | |
| a. Seed | 315,000 | 315,000 | 315,000 | 315,000 | 315,000 | 315,000 | |
| b. Fertilizer | 2,210,000 | 2,210,000 | 2,210,000 | 2,210,000 | 2,210,000 | 2,210,000 | |
| c. Pesticide | 300,000 | 300,000 | 300,000 | 300,000 | 300,000 | 300,000 | |
| d. Labor costs | 6,990,000 | 7,350,000 | 6,405,000 | 6,675,000 | 7,215,000 | 6,630,000 | |
| e. Others (land lease, etc.) | 9,960,000 | 9,960,000 | 9,960,000 | 9,960,000 | 9,960,000 | 9,960,000 | |
| 2. Production (kg·ha−1) | 7271 | 8021 | 5792 | 6542 | 7729 | 6417 | |
| 3. Price (Rp/kg) | 3800 | 3800 | 3800 | 3800 | 3800 | 3800 | |
| 4. Revenue (Rp/ha) | 27,629,800 | 30,479,800 | 22,009,600 | 24,859,600 | 29,370,200 | 24,384,600 | |
| 5. Income (Rp/ha) | 7,854,800 | 10,344,800 | 2,819,600 | 5,399,600 | 9,370,200 | 4,969,600 | |
| 6. R/C Ratio | 1.40 | 1.51 | 1.15 | 1.28 | 1.47 | 1.26 | |
| 7. BEP-Y (kg·ha−1) | 2.720 | 2.510 | 3.313 | 2.975 | 2.588 | 3.026 | |
| 8. BEP-P (Rp/ha) | 5.204 | 5.299 | 5.050 | 5.121 | 5.263 | 5.109 | |
Source: Primary data analysis.
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; Hindarwati, Yulis 1 ; Jauhari, Sodiq 1 ; Sahara, Dewi 1 ; Nurwahyuni, Endah 1 1 Central Java Assessment Institute for Agricultural Technology, Semarang 50552, Indonesia;
2 Yogyakarta Assessment Institute for Agricultural Technology, Yogyakarta 55584, Indonesia;