Cover Crops for Managing Stream Water Quantity and Improving Stream Water Quality of Non-Tile Drained Paired Watersheds

Gurbir Singh,Jon Schoonover,Karl Williard

doi:10.3390/w10040521

Abstract

In the Midwestern United States, cover crops are being promoted as a best management practice for managing nutrient and sediment losses from agricultural fields through surface and subsurface water movement. To date, the water quality benefits of cover crops have been inferred primarily from plot scale studies. This project is one of the first to analyze the impacts of cover crops on stream water quality at the watershed scale. The objective of this research was to evaluate nitrogen, phosphorus, and sediment loss in stream water from a no-till corn-soybean rotation planted with winter cover crops cereal rye (Secale cereale) and hairy vetch (Vicia villosa) in non-tile drained paired watersheds in Illinois, USA. The paired watersheds are under mixed land use (agriculture, forest, and pasture). The control watershed had 27 ha of row-crop agriculture, and the treatment watershed had 42 ha of row crop agriculture with cover crop treatment (CC-treatment). During a 4-year calibration period, 42 storm events were collected and Event Mean Concentrations (EMCs) for each storm event were calculated for total suspended solids (TSS), nitrate-N (NO3-N), ammonia-N (NH4-N), dissolved reactive phosphorus (DRP), and total discharge. Predictive regression equations developed from the calibration period were used for calculating TSS, NO3-N, NH4-N, and DRP losses of surface runoff for the CC-treatment watershed. The treatment period consisted of total 18 storm events, seven of which were collected during the cereal rye, eight in the hairy vetch cover crop season and three during cash crop season. Cover crops reduced TSS and discharge by 33% and 34%, respectively in the CC-treatment watershed during the treatment period. However, surprisingly, EMCs for NO3-N, NH4-N, and DRP did not decrease. Stream discharge from the paired-watersheds will continue to be monitored to determine if the current water quality results hold or new patterns emerge.

Highlights

Nutrient enrichment of runoff from agricultural fields is a significant problem in the MidwesternUnited States [1]
Cover crops do have the potential to reduce surface runoff and sediment loading to the streams when implemented at the watershed scale
Surface water quality in terms of nutrients was not improved by using cover crops after two years

Summary

Introduction

Nutrient enrichment of runoff from agricultural fields is a significant problem in the MidwesternUnited States [1]. The effectiveness of these BMPs in improving water quality at the plot to field scale varies from 100% to not effective [2,3,4,5,6]. Best management practices like cover crops, when planted at the plot or field scale, can reduce nitrate-N (NO3 -N), ammonia-N (NH4 -N), and dissolved reactive phosphorus (DRP) in soil leachate by. The benefits of using cover crops for nutrient reduction were realized in a relatively short period (two to three years) in most of these studies. Many watershed scale studies have reported no or little improvement in water quality with a combination of different conservation programs/BMPs over the last four decades [4,16,17,18]. Numerous factors can contribute towards failure of water quality improvement projects in large watersheds, such as insufficient participation of landowners, improper selection and installation of conservation practices, poor experimental design, unidentifiable pollution sources in watersheds, and inadequate distribution/design of BMPs in critical source areas within watersheds [19]

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Conclusion