The effect of conservation agriculture practices on soil health in dryland crop production

Abstract

The impacts of conservation agricultural practices as well as hydrogel application on soil edaphic factors and, more importantly, soil biological properties in rainfed ecosystems are still unclear. To address this knowledge gap, I first evaluated the impact of no-tillage and no-tillage with mulch or crop residue retention on soil organic matter and biological factors as key proxies of soil health and grain yield using a meta-analytical approach. Secondly, I conducted a full factorial experimental study in a growth chamber to examine the effect of five different crop rotations (fallow-wheat (control), alfalfa-wheat, canola-wheat, pea-wheat, and wheat-wheat) in combination with hydrogel under two watering regimes (well-watered and water-deficit) on soil biochemical properties and wheat biomass production. The meta-analysis showed that no-tillage and no-tillage with mulch or crop residue retention can significantly increase soil organic matter, soil microbial biomass, and maize yield compared to conventional tillage. These positive impacts are most likely attributed to reduced disturbance and increased resource availability. There were no significant differences between conservation and conventional farming managements on wheat grain yield, which is important in that a reduction in yield would discourage the application of no-till practices. The growth chamber experiment demonstrated that alfalfa and field pea cover crops as well as fallow resulted in greater wheat total biomass production compared to canola-wheat and wheat-wheat when hydrogel was not applied. There were no significant differences in soil total carbon (C) and nitrogen (N) across all treatments (except for wheat-wheat with hydrogel), whereas crop rotations (e.g., alfalfa-wheat) positively influenced soil inorganic N and soil microbial biomass under ambient rainfall and following water-deficit. However, hydrogel resulted in a significant positive effect on wheat biomass production when grown as a monoculture, although it had no significant impact on wheat biomass production in the other crop rotations. While it is not clear what caused this effect, hydrogel is a promising tool to improve wheat yield in dryland systems. Taken together, the findings suggest that conservation agricultural practices regardless of soil organic amendment can enhance soil health and crop productivity even under drought conditions if the cover crops are selected properly based on the type of climate, soil, and cash crop. In addition, by changing from conventional tillage to conservation agriculture practices growers can develop food production according to global demand while conserving natural resources.

Date of Award	2022
Original language	English