Author : Sem Savuth

Summary : Agricultural practices play an important role in increasing crop yields, but high crop yield is associated with high energy use. The study aimed to estimate the various energy use from farm-to-plate of lowland rice grown under four methods in Cambodia—namely, direct seeded rice (DSR), transplanted rice (TPR), system of rice intensification (SRI), and no-till rice cropping system (NTR). A total of 165 farmers and six rice millers were interviewed by using a pre-tested questionnaire in July 2017.

Results revealed that the total energy inputs in field production from highest to
lowest were 13,335.89 MJ ha-1 (NTR), 10,843.65 MJ ha-1 (TPR), 10,323.34 MJ ha-1 (DSR), and 7,051.61 MJ ha-1 (SRI), respectively. The energy used to produce a kilogram of paddy rice was highest in NTR (3.98 MJ kg-1) and lowest in SRI (2.08 MJ kg-1). The two main contributors of high energy costs in NTR were nitrogen application at 5,291.42 MJ ha-1 (40%) and Glyphosate herbicide use at 2,295.24 MJ ha-1 (17%). Nitrogen was the energy hotspot among the energy inputs, contributing 40–51 percent in the total energy input of NTR, DSR, and TPR, but not SRI. The energy hotspot of SRI was human labor, which required 24 percent in all rice crop stages. High energy footprint is associated with increasing energy inputs, especially nitrogen application. SRI had lower energy footprint (C0 emission) by 58 percent compared with DSR and TPR, while about 76 percent of energy footprint in DSR and TPR came from nitrogen application.

The total energy use of rice in Cambodia from farm-to-plate was 4.30 MJ kg-1 or about 0.09 Liter Diesel Oil Equivalent (LDOE) kg-1, wherein 69.30 percent was used in production, 26.28 percent in post-production (up to 280 km transport distance), and4.42 percent in cooking. The major contributor of the energy costs in post-production was transportation. When rice was milled and transported to up to 280 km-distance, the energy used in post-production increased by 2.05 times when compared to local consumption (5 km-distance).