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ARS Home » Plains Area » Akron, Colorado » Central Great Plains Resources Management Research » Research » Research Project #430157

Research Project: Develop Knowledge for the Efficacy of Using Cover Crops in Place of Summer Fallow in Dryland Wheat-fallow Cropping

Location: Central Great Plains Resources Management Research

Project Number: 3010-12210-004-01-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 1, 2016
End Date: Sep 30, 2019

The overall objective is to evaluate the impact of cropping system intensity on soil quality, nutrient cycling and yields in long-term established intensive dryland cropping systems to improve the long-term sustainability of dryland cropping systems in Eastern Colorado. Specific objectives are: 1) to evaluate and quantify the long-term effects of crop rotation intensity and alternative practices (e.g., summer cover crop mixtures) within existing wheat-based dryland cropping systems. Specifically we hope to quantify effects on soil quality/soil health, cover crop water use and effects on subsequent crops, weed community dynamics and quantify economic and biomass yields in these systems; 2) to calculate a nitrogen (N) balance of the long-term dryland cropping systems across the three locations and at each slope location; and 3) assess the carbon (C) sequestration and turnover of long-term dryland cropping systems across locations and slope position.

The CSU-ARS cooperative field experiments in Eastern Colorado will be utilized for the proposed research. The three locations were established in 1985 and have established replicated strips of wheat fallow (WF), wheat-corn-fallow (WCF), wheat-cover crop (WCc), and wheat forage crop-systems. In the WCc the cover crop replaces a portion of the traditional summer fallow. Each location also has replicated perennial grass strips that serve as a control treatment. These replicated strips are planted across a catena of a summit, side and toe slope sequence. This design provides a unique experimental design for evaluating a variety of dryland cropping systems. Updated soil quality assessements, a complete N balance across the catena of summit, side and toe slopes, and more mechanistic studies of C stabilization and turnover for the three sites have not been calculated. ARS and CSU will co-lead a team effort to conduct an N balance by quantifying total N in biomass and grain (e.g., nitrogen uptake, nitrogen use efficiencies) and changes in soil organic N, POM-N, MAO-N and soil inorganic N to assess the balance of the system and determine the magnitude of the N gains or losses for a given cropping system across the three locations and at each slope location. CSU and ARS will co-lead an effort to determine cover crops effects and long-term cropping systems on soil biology and health across each of the 9 unique soil types. ARS with CSU will collaborate in assessing long-term dryland cropping systems effects on C turnover and sequestration across the three locations and at each slope location. We will evaluate both potential changes in soil quality and yield at all sites and soils across the catena for another six years to complete the rotation cycles. Measurements to be evaluated and compared at each location and catena include total aboveground biomass, grain yields, water use, soil quality indicators of particulate organic matter carbon (POM-C), soil macrofauna abundance and diversity, soil structure, C mineralized in labortory incubations to estimate soil microbial biomass, and water soluble organic C and N (WSOC, WSON)). The data and knowledge gained in these studies will provide a quantitative understanding of how to best guide dryland producers in sustainable conservation management. Syntheses derived from these studies will be useful to help guide management practices for the implementation of dryland cropping strategies across a large gradient of climate and soil varibility.