Effect of Cover Crops On Nitrogen Dynamics in Ridge Tillage Systems.

Utilizing cover crops has been proposed as a way for growers to improve nitrogen efficiency by reducing losses while also providing biologically sourced nitrogen to cropping systems. However, spring incorporation of cover crop residues often results in an initial nitrogen immobilization event, followed by rapid mineralization, resulting in a flux of soluble nitrogen that is often poorly synchronized with crop demand. Improving the synchrony of the supply of cover crop nitrogen while mitigating the negative effects of residue inputs is important to improving the effectiveness of cover crops and increasing adoption.

Ridge tillage systems may help growers manage cover crops and their effects on nitrogen cycling by giving them a degree of control over when and where residues are processed. By relocating cover crop residues from the ridge to the furrow at planting, growers may be able to relocate the site of immobilization to the between-row space, reducing losses while not adversely affecting crop growth. Residues are then mineralized in the between-row space, supplying nitrogen or readily mineralizable nitrogen that can be relocated to plants at re-ridging.

In this study we assessed the spatial variability of soluble nitrogen and potentially mineralizable nitrogen across the row/inter-row space of a corn-based cropping system. The study was established in 2011 and includes two main tillage treatments (ridge tillage and chisel plow), arranged in a randomized complete block design, and one split-plot factor of cover crop/no cover crop. Sampling was conducted in zero-fertilizer sub-plots using ion exchange resins and soil cores at three positions: in-row, shoulder (7.5 inches from row), and furrow. We then analyzed data to assess how turnover dynamics and patterns of nitrogen availability differed between treatments throughout the season.