The effects of perennial groundcover on soil-water and nutrient dynamics in maize intercropping systems

Abstract

While conventional agriculture has accelerated crop productivity, it has come at a cost to both environmental degradation and nitrate leaching into waterways. Perennial groundcovers, cool-season grasses intercropped in the interrow spacing between maize, provide reduced erosion rates and nutrient leaching mitigation, at minimal cost to farmers. Our study assessed the compatibility of five grasses between maize rows - four Kentucky bluegrass (Poa pratensis L.) cultivars and one Bulbous bluegrass (Poa bulbosa L.) cultivar. We compared how each perennial groundcover species affects soil water and nutrient dynamics within the top 45 cm of the soil profile, including gravimetric water content, plant-available nitrate, ammonium and orthophosphate, soil pH, and leaching mitigation potential. Overall Kentucky bluegrass cultivars lowered potential nitrate losses, as assessed by suction lysimeter concentrations, by 76% compared to the control (maize without perennial groundcover). However, the grasses also decreased soil moisture by up to 5%, and ultimately decreased yield by approximately 34% compared to the control. Poa bulbosa decreased potential nitrate losses by 73% compared to the control, but unlike Kentucky bluegrass cultivars, did not decrease soil moisture or maize yields. Overall, my thesis shows Poa bulbosa is more compatible than Kentucky bluegrass when grown between maize and yet provides sought after ecosystem services – e.g. no or minimal effect on maize yield but decreases potential nitrate leaching.