Efficacy of conservation tillage systems on soil quality in wheat-based cropping systems in dryland agroecosystems

Soil health is one of the main components to achieve the sustainable agricultural systems being adversely affected by agricultural operations such as tillage. Soil health can be quantified using the specific physical, chemical and biological parameters of the soil via specific quantitative soil quality methods. As a result, studying soil quality and fertility in different land management systems is essential to establish appropriate crop operations to achieve optimal production and sustainable cropping systems. Soil Management Assessment Framework (SMAF) is used as a powerful and reliable tool to assess the effect of different crop management on soil quality and health. This study aims to evaluate and quantify the effect of different tillage methods on soil quality using the SMAF algorithm.

The present study was conducted as a field experiment based on a randomized complete block design during two cropping years in 2016-2017 and 2017-2018, in four replications. Experimental treatments included tillage methods (no-tillage, reduced tillage, and no- tillage), and the areas were considered replication. Winter wheat (Triticum aestivum L.) was planted in the first year, followed by winter chickpea (Cicer arietinum L.) in the second year of crop rotation in farmers' fields. Soil sampling from a soil depth of 0-30 cm was taken in two stages, before planting wheat at the beginning and after harvesting chickpea in the second year. Important soil parameters were measured, including bulk density, phosphorus, potassium, acidity, electrical conductivity, soil organic carbon, carbon, microbial biomass, and microbial biomass nitrogen.

The results showed that implementing the conservation tillage methods improved some of the important soil parameters and soil quality index, indicating the positive effect of minimum soil disturbance and crop residue maintenance on soil quality. Although the physical and chemical properties of soil at the end of the second year did not change significantly compared to pre-treatment conditions, soil biological properties such as microbial biomass carbon and soil organic matter were positively affected by tillage systems. The laboratory-measured data of soil properties were well reflected in the SMAF algorithm. The results showed that at the end of experiment, soil quality index in the conventional plowing system was lower compared to conservation tillage methods. No-tillage had the highest value of soil quality index (0.65) at the end of the experiment. As stated in the quantitative description of soil properties, the higher quality index in the no-tillage method is mainly due to the improvement of soil biological conditions. Soil degradation due to excessive plowing, lack of residue preservation, and improper use of chemical fertilizers not only reduces soil organic matter but also degrades the physical properties of soil.

In general, the results showed that conservation tillage methods could improve soil quality and efficiency in dryland areas, and SMAF algorithm can be a useful tool to assess and monitor the soil quality of various cropping systems in dryland areas. However, citing the data of this study requires long-term results, and in order to evaluate the efficiency of soil ecosystem to provide ecosystem services, it is necessary to compare crop systems with more sustainable systems such as forests and pastures.