**3.8 Fermentation of manure**

The greenhouse gas emission potential of fermented manure in the soil is low because the SOM reservoir will be quickly depleted during the fermentation process. Compared with fresh organic modifiers and a combination of urea and organic modifiers, the application of fermentation residues can reduce CH4 emissions by approximately 60% and 52%, respectively [46]. Several field studies have evaluated various organic corrections for greenhouse gas emissions (especially methane). The difference between fresh materials (straw or fertilizer) is relatively small; however, it has been reported that there is a huge difference between the greenhouse gas emissions triggered by preferred and fresh materials [47, 48]. Using fermented biogas residues can only increase CH4 emissions by 42%, while unfermented manure can increase CH4 emissions by 112–138% [49]. Other carbon benefits obtained by substituting biogas for conventional fossil fuel energy, the use of biogas residues in rice fields can provide soil fertility while reducing CH4 emissions. Nayak et al. [50] concluded that the application of livestock manure in rice fields can greatly reduce N2O emissions, while increasing CH4 emissions and soil organic carbon sequestration. Patrick and Reddy [51] reported that the application of compost in the rice field reduced N2O emissions by 50% compared to the application of urea. However, the CH4 emissions during anaerobic composting can offset the output obtained after mixing into the soil, and aerobic composting technology can minimize such emissions. Nayak et al. [50] observed that compared with fresh straw, the emissions of organic amendments produced by aerobic composting of straw were significantly reduced, indicating that it can be used as an environmentally friendly method.

### **3.9 Fertilizer management**

Fertilizer management is an important part of reducing the environmental impact of rice fields. Soil fertilizers applied to crops are not always effective [52, 53]. Improving the efficiency of fertilizer use can reduce greenhouse gas emissions, especially N2O emissions, and indirectly reduce the carbon dioxide emissions of nitrogen fertilizers [54]. Measures to improve fertilizer utilization and reduce greenhouse gas emissions include: accurately adjusting the amount of fertilizer according to crop needs [55–57] and using nitrification inhibitors or slow-release fertilizers [58, 59] adjust the timing of application and select the appropriate source, accurately locate the fertilizer in the soil, avoid excessive application or eliminate the application of nitrogen fertilizer [60].

#### **3.10 Adjusting fertilization and matching N supply with demand**

Adjusting the nitrogen and phosphorus content to meet crop demand is conducive to crop yields while controlling greenhouse gas emissions. Even in best fertilization practices, large amounts of nitrogen will be released into the atmosphere. In irrigated rice, nearly 48% of applied nitrogen is lost in gaseous form [60]. The responsible mechanism for nitrogen loss is ammonia volatilization, nitrification and denitrification. The specific meaning of all these processes may vary according to natural conditions and crop management practices [45]. The rate of fertilizer controls the emission of greenhouse gases. In general, the emission of greenhouse gases, especially N2O, increases with the increase of nitrogen input [34, 55]. The general strategy for minimizing N loss and reducing N2O emissions is to avoid excessive use of N in space and time. Reducing the amount of nitrogen fertilizer application to a level that does not reduce crop yields can also reduce the demand for nitrogen fertilizer, and ultimately reduce the indirect emissions of carbon dioxide during the nitrogen fertilizer production process. IPCC (1997) estimated that regardless of the source of N, 1.25% of the applied N would be lost as N2O. Several studies have documented the instantaneous increase in N2O emissions from rice fields due to the application of nitrogen fertilizers. [25]. It was observed that the application of urea will increase N2O emissions by 54% compared with no nitrogen fertilizer. Lu et al. [49] reported that N2O emissions in rice fields increased with the application of nitrogen fertilizer, especially at higher rates. Reducing nitrogen fertilizer has no significant impact on CH4 emissions, while the current average nitrogen fertilizer application for rice can be reduced by 33%, which can reduce N2O emissions by 27%. Recent field studies report that high nitrogen content can reduce net CH4 emissions from rice systems by roughly 30–50% [59, 60].

Aulakh et al. [34] reported that the increase in nitrogen application reduced CH4 emissions and increased N2O emissions compared with the control without nitrogen application. Zou et al. [16] also recorded that when the nitrogen application rate increased from 150 kg to 400 kg N ha−1, CH4 decreased by 75% and N2O increased by 58%. A recent meta-analysis showed that the response of CH4 emissions may be related to the N rate, where the addition of N at a low rate tends to stimulate CH4 emissions, but it may alleviate CH4 emissions at high N rates [35, 47]. However, further research is inevitably needed to deal with the compromise between nitrogenous fertilizers and CH4 and N2O. Applying nitrogen fertilizer to the soil near the active root absorption zone can reduce the loss of surface nitrogen and increase plant nitrogen use efficiency, thereby reducing N2O emissions. Khaliq et al. [30] pointed out that placing chemical fertilizers in a 6–10 cm soil layer can significantly increase nitrogen use efficiency and reduce N2O emissions. In addition, distributing nitrogen fertilizer at different growth stages of crops can also increase nitrogen use efficiency and reduce nitrogen loss.

#### **4. Conclusion**

From above all discussion it may concluded that nitrogen have positive impact on rice yield greenhouse gas emissions from rice fields can reduce greenhouse gas emissions from rice fields by changing irrigation methods and farming methods, managing organic additives and fertilizer inputs, and choosing appropriate varieties and planting methods. CH4 decreased by 75% and N2O increased by 58%. CH4 emissions may be related to the N rate, where the addition of N at a low rate tends to stimulate CH4 emissions.

*Rice: Worldwide Production, Utilization, Problems Occurring Due to Climate Changes… DOI: http://dx.doi.org/10.5772/intechopen.96750*
