MODELLING ENERGY INPUTS, OUTPUTS AND CONSUMPTION PATTERNS OF SELECTED CROPS IN NIGERIA

Abstract

ABSTRACT Energy consumption in agriculture has increased year by year while more intensive energy use has led to some environmental problems such as natural resources depletion and climate change. Such problems can be ameliorated by effective use of energy resources in crop production.However, in Nigeria, there is scarcity of information on energy expenditure and returns in crop production. This study was designed to determine the energy inputs and consumption patterns of three common staple crops: (rice, maize and yam) in Nigeria. The study was undertaken across five states: Ondo and Ekiti for rice; Oyo and Ogun for maize and Benue for yam production. For each crop, nine established farms were purposively selected and categorised into small (< 2 ha), medium (2 - 10 ha) and large (> 10 ha) farms. Energy inputs in the production of each crop for 2012 and 2013 growing seasons were investigated based on unit operations. Energy related data such as human labour ( x_1), fuel (x_2), machinery (x_3), biological (x_4), N.P.K fertiliser (x_5,x_6,x_7) and herbicide (x_8) were obtained through field surveys, direct measurements, interviews with farmers and structured questionnaires. Efficiencies of energy utilised were determined using standard methods. The relationship between the different input and output energy sources were modelled using Cobb-Douglas production function and validated following Durbin-Watson procedure. Data were analysed using ANOVA at〖 α〗_0.05. Total energy input for rice production on small, medium and large farms were 15107.39±106.0, 14842.52±164.0 and 14396.62±61.9 MJ/ha, respectively. The corresponding energy inputs for maize production were 10084.5±42.0, 9999.5±148.1, 9445.87±36.0 MJ/ha and yam production were 19895.0±67.0, 19392.1±61.5, 19024.3±40.2 MJ/ha, respectively. The net energy for rice production were 81838.11±4046.9, 90693.2±2975.4, 93854.14±1751.9 MJ/ha and for maize production were 30977.45± 1153.6, 39564.0±460.3, 40558.4±1133.7 MJ/ha and yam production were 37535.7±1725.7, 39814.9±919.8, 41209.1±1597.3 MJ/ha on small, medium and large farms, respectively. The average energy efficiencies for rice production on small, medium and large farms were 7.5±0.2, 7.2±0.1 and 7.7±0.1, respectively. The corresponding maize and yam production average efficiencies were 4.0±0.1, 4.9±0.1, 5.2±0.1 and 2.9±0, 3.0±1, 3.5±0, respectively, indicating that energy were efficiently utilised. For rice production, chemical energy accounted for 72.2±0.8, 73.6±0.9 and 75.14±1.6% of the total energy consumed on small, medium and large farms, respectively. Chemical energy constituted 49.4±0.7, 49.6±0.3, 48.34±0.2% in maize production and constituted 48.99±0.9, 48.38±0.1, 48.0±0.1% in yam production. The model equations for rice, maize and yam production were: ln⁡〖y_i 〗=0.02684lnx_1+0.05082lnx_2+0.08157lnx_3+0.13891lnx_4+0.86125x_5+0.44623lnx_6-0.64041lnx_7+ 0.00344lnx_8 (R2 = 0.98), ln⁡〖y_i 〗=0.59171lnx_1-2.14991lnx_2+ 6.72003lnx_3-0.84842lnx_4-2.50803lnx_5+0.17059lnx_6+0.12608lnx_7+ 0.05759lnx_(8 ) (R^2 = 0.98)and ln⁡〖y_i 〗=- 0.14937lnx_1+ 0.08818lnx_2+0.15034lnx_3+0.16875lnx_4+0.03868lnx_5+0.6038lnx_6-0.11359lnx_7+ 0.59838lnx_8 (R2 = 0.98), respectively. The energy resources thatare significant for rice production were chemical, biological, manual, and mechanical energy. The corresponding energy resources that are significant for maize and yam production were manual, thermal, mechanical, chemical energy and chemical, thermal, and manual energy, respectively. The results obtained from Durbin-Watson procedure showed that the developed models were capable of predicting energy output at different inputs. Energy inputs and patterns of energy consumption in rice, maize and yam production were modelled. The models adequately predicted the input and output energies for the selected crops. Keywords: Crop production, Crop energy utilisation, Energy efficiency, Energy model