Using frost‐sensitive cover crops for timely nitrogen mineralization and soil moisture management

Tom Storr,Jacqueline A Hannam,Robert W Simmons

doi:10.1111/sum.12619

Abstract

AbstractCover crops can be utilized to lower soil nitrate leaching. However, depending on the species grown and cover crop termination management, this may lead to nitrogen (N) immobilization and/or depletion of soil moisture available to the following cash crop, potentially impacting on crop yields. Cover crop management is also dependent on using herbicides to terminate growth prior to planting the next crop. We used an alternative method for cover crop termination by capitalizing on plant senescence by frost in a multi‐species cover crop established over winter between wheat and maize. The cover crops accumulated greater quantities of N than the control. However, upon cover crop senescence due to cold temperatures, the partially terminated cover crop significantly increased topsoil available N from December to late February. This available N in the topsoil could be susceptible to leaching although this was not observed in our study. Cover crops did not have a significant prolonged effect on soil moisture over winter and late spring. The following maize yields were not significantly different between the control and cover crop treatment. Frost‐sensitive cover crop species could not be reliably terminated under a temperate climate, but provided a continuous supply of soil available N as the plants senesced. Depending on the soil moisture and weather conditions in the spring, there could be a N leaching risk although this could be mitigated by establishing early spring crops.

Highlights

Cover crops are established between periods of cash crop growth when the ground is bare and can alleviate the effects of soil compaction (Chen & Weil, 2010), prevent soil erosion (Posthumus, Deeks, Rickson, & Quinton, 2015), suppress weeds (Brust, Claupein, & Gerhards, 2014) and sequester carbon (Poeplau & Don, 2015)
There were no significant differences between the cover crop and control for soil moisture content during the period of measurement, January–May (Figure 2)
Whilst leaching of N through the soil profile will be a concern following the senescence of the frost-sensitive cover crop, in wetter years, there could be benefits of frost termination with i) earlier N availability for the following cash crop aiding establishment and growth and ii) reduced reliance on herbicide or tillage as a means to terminate cover crop biomass, as some of the biomass is partially controlled by the cold temperatures

Summary

| INTRODUCTION

Cover crops are established between periods of cash crop growth when the ground is bare and can alleviate the effects of soil compaction (Chen & Weil, 2010), prevent soil erosion (Posthumus, Deeks, Rickson, & Quinton, 2015), suppress weeds (Brust, Claupein, & Gerhards, 2014) and sequester carbon (Poeplau & Don, 2015). Cultivations (plough) used as a method of cover crop termination showed decreased soil moisture at the time of maize establishment (Krstić et al, 2018) or had no effect on soil moisture (Snapp & Surapur, 2018). These studies indicated varied effects of cover crops on soil moisture available to the following crop. Aboveground biomass was determined from a 0.25 m2 quadrat, with one sample taken per plot and mean averaged across the cover crop treatment and control. Mean and mean minimum temperatures were recorded hourly but for ease of interpretation are shown in Figure 1 as weekly totals (rainfall) or averages of the mean and minimum temperature

| RESULTS

| DISCUSSION

Findings

| CONCLUSION