Assessing soil structural quality as an indicator of productivity under semi-arid climate

Abstract

A near real-time evaluation of the management system's impact on soil conditions requires a quick and straightforward framework to help farmers with a reliable on-farm assessment. The visual soil evaluation methods can potentially be used as a reliable on-farm approach for assessing soil physical quality. This research aims to better understand the importance of visual soil evaluation for productivity in semi-arid climates. The objectives were to evaluate the ability of Visual Evaluation of Soil Structure (VESS) and Double Spade (DS) under agricultural systems in a semi-arid region and to assess the relationship between soil structural quality and crop yield. Forty arable sites under rain-fed and irrigated farming with crop rotation and mono-cropping systems were studied, and twenty-one physical and bio-chemical soil properties were determined at two depths (0–20 cm and 20–40 cm). VESS and DS were conducted at each farm. The reliability of visual approaches was evaluated using measured soil properties and their capability to detect the impact of management systems. Soil quantitative measurements and crop yield information were deployed to assess soil productivity and its relationship with soil physical quality. The overall assessment of soil properties indicated a better soil condition for irrigated farming with crop rotation. The visual scores were in a range of 1.5–3.4 for VESS and a range of 1.9–3.5 for DS. The mean scores of VESS and DS were different between rain-fed and irrigated farms (P < 0.05), and visual methods were able to differentiate between mono-cropping and crop rotation (P < 0.05). The best soil structural quality was associated with the highest level of crop yield, and visual approaches were able to detect the differences in wheat yield levels (P < 0.05). The scores of VESS and DS were significantly correlated with soil properties (r > 0.6). Both VESS and DS indicated good efficiency for a practical on-farm assessment of soil conditions under agricultural management in northwest Iran and similar ecosystems. A close relationship between crop yield and soil structural quality was obtained, which indicated that the optimum soil structural condition plays an important role in the sustainability of crop production in semi-arid cultivation.