Energy inputs – yield relationship and sensitivity analysis for tomato greenhouse production in Iran

This paper studies the energy balance between the input and the output energies per unit area for greenhouse tomato production. For this purpose, the data on 30 tomato production greenhouses in Isfahan province, Iran were collected and analyzed. The results indicated that a total specific input energy of 116,768.4 MJ ha-1 was consumed for tomato production. Diesel fuel (with 40%) and chemical fertilizers and manure (with 30%) were amongst the highest input energies for tomato production. The energy productivity was estimated to be 1.16 kg MJ-1. The ratio of output energy to input energy was approximately 0.92. 19% and 81% of total energy input was in renewable and non-renewable forms, respectively. The regression results revealed that the contribution of input energies on crop yield for human power, machinery, pesticides and electricity inputs was significant. The human power energy had the highest impact (1.45) among the other inputs in greenhouse tomato production. The marginal physical productivity of diesel fuel, seed and total chemical fertilizer with manure was negative. It can be because of applying the inputs more than required or improperly applying. The highest shares of expenses were found to be 34% and 21% for human power and total diesel fuel and machinery, respectively. Cost analysis revealed that total cost of production for 1 ha greenhouse tomato production was around US$34939. Accordingly, the benefit-cost ratio was estimated as 2.74. Results of greenhouse gas emission indicated that tomato production is mostly depended on diesel fuel sources. Diesel fuel had the highest share (2,719.98 kg CO2eq.ha-1) followed by electricity (729.6 kg CO2eq.ha-1) and nitrogen fertilizer (409.5 kg CO2eq.ha-1). Keywords: tomato, greenhouse, energy productivity, economic analysis, Cobb-Douglas functio