Change in energy budgets of the pampean wheat production system during the last four decades

J. DE PAEPE, R. ÁLVAREZ, S. NJAKOU DJOMO AND R. CEULEMANS

Conferencia; 19th ISTRO Conference; 2012

Energy budget analysis for agricultural production can be used to determine the evolution of technological improvements and its influence on productivity. This study was conducted in the Argentina Pampas across a hydric transect with annual precipitation going from 600 mm to 1100 mm, including a soil gradient from coarse to fine textured soils. The main objectives were to determine how the energy balance of the wheat agroecosystem is affected by adjustments in tillage systems and to analyze the changes in its efficiency. Energy analysis method was used and inputs were calculated with national statistics of supply use affected by recently published energy coefficients. Average situations were estimated by Pampean subregion and per decade, from 1967-1976 to 1997-2006. Average total energy input to the agroecosystems increased from 6.3 GJ ha-1 to 9.9 GJ ha-1, and average energy output increased from 23.6 GJ ha-1 to 44.2 GJ ha-1. Through the four decades, energy input contribution of soil tillage (64% of total input energy) was replaced by fertilizer use (50% of total input). Average energy efficiency improved, starting at 3.7 during the first decade and ending with 4.5 during the last decade. Total input into the production of a kilogram of average Pampean wheat grain, was estimated to range from 4.7 GJ kg-1 at the beginning reaching a value of 3.9 GJ kg-1. Energy balances became greater: the average balance was 17.3 GJ ha-1 and increased until 34.3 GJ ha-1. The balance was greater in a Pampean subregion were humid weather predominates in combination with fertile soils. The regional energy budged changed in time and a switch in input variable contribution was observed explained by the replacement of conventional tillage (more fuel consumption) with the no-till production system (more fertilizer and chemical use). Regional total energy balance increased and is related to environmental conditions.