Journal of Researches in Mechanics of Agricultural Machinery

Journal of Researches in Mechanics of Agricultural Machinery

Evaluation of energy flow and greenhouse gas emissions in forage crops production in rainfed condition of rasht

Document Type : Research Paper

Authors
Mohammad Rabiee
Sajjad Shaker Kouhi
Department of Seed Improvement, Rice Research Institute, Rasht, Iran.
10.22034/jrmam.2026.15055.774
Abstract
Introduction

The occurrence of fertile soils, long growing season and favorable environmental conditions from the rice harvest until its planting in the next year are significant advantages making these paddy fields a good candidate for second crop. The rice‒forage crops system, in which rice is planted as a summer crop and forage crops as a winter crop, is considered a sustainable system with various advantages. The development of forage crops as a second crop after rice harvest in paddy fields can be an effective strategy to provide fodder for livestock, increase land productivity, sustainability of rice production, increase paddy farmers' income, and thus prevent migration of villagers. Efficient use of energy is one of the principal requirements of sustainable agriculture. Continuous demand in increasing food production resulted in intensive use of chemical fertilizers, pesticides, agricultural machinery, and other natural resources. However, intensive use of energy causes considerable greenhouse gas (GHG) emissions and major environmental problems due to global warming. Therefore, it is of great importance to identify production methods that increase energy use efficiency. Achieving the sustainable production of forage crops requires analysing different energy indices and GHG emissions. Therefore, this study aimed to investigate the energy flow and GHG emissions in forage crops production as a second crop after rice harvesting in paddy fields of Guilan province.



Material and Methods

This study was conducted based on a randomized complete block design with three replications at the research fields of Rice Research Institute of Iran in Rasht during two cropping seasons of 2023-2025. The experimental treatments included eight forage plants (berseem clover, forage mustard, barley, triticale, forage safflower, vetch, forage pea and faba bean) and intercropping of triticale + vetch (50% triticale and 50% vetch). In the present research, input energy, different forms of energy, output energy, net energy, specific energy, energy productivity, energy use efficiency and greenhouse gas emission were calculated and evaluated. The greenhouse gas emissions for each treatment were expressed in terms of kilograms CO2 equivalent per hectare (kg CO2 eq. ha-1). The analysis of variance was done by SAS software and the LSD test was used for mean comparison.



Results and Discussion

The results showed that the highest energy input in forage crops production belonged to the triticale, forage mustard and barley with the averages of 24997, 22572 and 22020 MJ ha-1, respectively. The fuel and nitrogen (N) fertilizer showed higher share percentages in forage crops production than the other energy inputs. The share values of direct energy vary from 42.9% for triticale and forage mustard to 59.9 for berseem clover. Among the indirect energies, N fertilizer had more energy consumption for all forage crops. The highest share percentage of indirect energy was observed for triticale and forage mustard (57.1%), followed by forage safflower (46.7%) and faba bean (46.3%). Non-renewable energy showed a much higher share than renewable energy. The highest share of renewable energy belonged to the forage pea with an average of 14.3%, followed by vetch (11.4%) and faba bean (10.7%). While, the crops of mustard, berseem clover and forage safflower showed the largest share of non-renewable energy with the averages of 98.3%, 96.4%, and 95.7%, respectively. Fuel and N fertilizer played the most important role in increasing the share of non-renewable energy in the experiment. The energy output varied in the range of 151551 MJ ha-1 for intercropping of triticale + vetch to 72450 MJ ha-1 for forage safflower. Based on the results, intercropping of triticale + vetch had the highest energy use efficiency (7.64). The vetch with the averages of 7.57 was also ranked next. The lowest energy use efficiency (3.21) was related to forage mustard. The intercropping of triticale + vetch, berseem clover and barley with energy productivity (0.65 kg MJ-1), (0.49 kg MJ-1) and (0.45 kg MJ-1) were ranked first to third, respectively. While, forage mustard with an average of 0.26 kg MJ-1 had the lowest energy productivity. The results of the mean comparison showed that the highest specific energy allocated to forage mustard with an average of 3.81 MJ kg-1, which was separately classified in group a. Intercropping of triticale + vetch with an average of 1.54 MJ kg-1, had also the lowest specific energy. Based on the results, intercropping of triticale + vetch had the maximum net energy (131719 MJ ha-1). The vetch with the averages of 118866 MJ ha1 was ranked next. Among the various energy inputs, fuel and N fertilizer play the greatest role in total GHG emissions for all forage crops.

Conclusions

The results indicated that the triticale and forage mustard had the highest energy input and GHG emissions. The lowest GHG emissions was related to forage pea and vetch, respectively. The intercropping of triticale + vetch had the highest energy use efficiency, energy productivity and net energy. Based on the results of this study, the fuel and N fertilizer showed higher share percentages in energy inputs and GHG emissions. Therefore, decrease fuel consumption, optimal management of N fertilizer and cultivation of forage legumes can help increase energy efficiency and reduce GHG emissions from fodder production in paddy fields of Guilan Province.
Keywords
Input energy
Net energy
Energy productivity
Energy use efficiency
Global warming
Subjects
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