Sustainability Performance through Technology Adoption: A Case Study of Land Leveling in a Paddy Field

Abstract

Energy is required in all agricultural activities. Diagramming material flows needed by crop production systems supports the proper analysis of energy flows interactions within a system’s boundaries. The latter complemented with an economic analysis gives a clear view of how beneficial a new practice within a crop cycle is—in this case, the variable slope (VS) land leveling (LL) operation. VS is a global navigation satellite system (GNSS, with real time kinematics—RTK—accuracy) LL technique used to create a smooth continuous surface with a constant slope, by cutting and filling topsoil layers only in those points presenting “anomalies” of micro-relief which make the movement of water difficult. This operation is important for paddy production since: (i) it enables to crop during dry seasons by harnessing the water of rivers and wells, and (ii) improves the production during rainy seasons, by allowing the farmer to manage the drainage timely and homogeneously. The present study aims to analyze, from the energy perspective, the effects of the VS leveling implementation in a paddy field (located in the Costa Rican Pacific), throughout input (labor, gas oil, etc.) and output (yield and price) data of five consecutive years (2011–2015). A material flow diagram was created representing two scenarios: before and after leveling the land. The materials were converted into energy (MJ ha−1) data, used for the estimation of EROI (energy return on investment), EP (energy productivity) and EB (energy balance) indices, while looking for a clearer understanding of the LL impact on the use of energy within the agroecosystem. Moreover, in order to complement the energy perspective, an economic point of view was considered as well through a profitability analysis where the total gain obtained over the years with LL was compared with that obtained without LL. Results showed that the increase in energy consumed by incorporating VS leveling is compensated by the gradual increase of energy embodied in yield, increasing energy balance (EB) from 26,192 MJ ha−1 up to 91,166 MJ ha−1. Similarly, EROI and EP were duplicated with LL. Economic total gain after incorporating the VS increased from less than 500 USD ha−1 up to 1800 USD ha−1 in the third year after leveling. Yield is more affected under adverse weather conditions with irregular water supply, either limited or excessive; and effects are less pronounced when the yield limiting factor is associated with biotic stress unrelated to irrigation and drainage facts. An environmental positive impact should also be noted, since VS allowed the production benefits of having highly-efficient irrigation and drainage systems, while avoiding major damage to topsoil layers.