Optimizing Water and Nitrogen Requirements with Cover Crops for Sustainable and Profitable Irrigated Cropping Systems

Commodities

Practices

Problem description: Corn is the major crop in the US and mostly produced in Midwest or Corn-belts states such as Nebraska, particularly in semi-arid regions of Western Nebraska with limited rainfall(10-12 inches/year). Therefore, irrigation is very crucial in addition to sufficient nitrogen to maximize yields and farm profits. However, excess water
(W) and nitrogen applications have compromised groundwater quality and quantity in Ogallala aquifer. Incorporating cover crops (CCs) in these irrigated cropping systems could be a potential solution to optimize inputs since soil water storage and nutrient retention at root zone can be increased depending on CC type with varied biomass accumulation and C:N ratio (i.e., cover crops with low C:N can easily release N). Moreover, farmers in Western Nebraska are asking about W x N requirements and use with CCs to avoid yield losses or increase their profits. However, there is limited knowledge on optimum requirements in CC systems since most studies have isolated both inputs and also independently studied to understand water use, N released by the CCs, and impacts on nitrate losses. This project aims to understand the effect of CCs on W x N requirements in irrigated corn and their optimal rates to either increase or maintain yields while improving efficiency, profitability, and water conservation and limiting nitrate
losses. Project outcomes expect to provide recommendations/guidelines on W x N requirements and use in irrigated corn with CCs.

Methodology: The project proposes a combination of small-research plot experiments at two research farms and on-farm trials at five farmer fields. Water and nitrogen requirements are evaluated under continuous use of CC types and different termination timings and management levels of both inputs from 0% to 125% of the recommended full
requirement. Project will prioritize farmer participation through on-farm trials and established producer fields days. Optimum requirements will be derived from developed production response curves from research plots and after tested on farmer fields. Yields, irrigation and nitrogen amounts, and achieved profits will be quantified in plots with and
without cover crops.

Expected Outcomes: Producer Field Days. Recommendations for optimum rates of water and nitrogen with continuous use of cover crops (CCs) in irrigated corn in Western Nebraska. Research and extension publications on input guidelines for different CC species. Producer awareness about CC benefits and best management practices to avoid yield penalties.

Assess different cover crop types (monoculture versus mixes) and their termination timing on accumulated biomass relative to available soil water and nitrogen supply

Determine in-season application rates and timings of water and inorganic nitrogen fertilizer for maximizing yields and profits with efficiency while increasing water savings and reducing nitrate losses, and developing response curves to achieve optimum rates for each CC type

Conduct on-farm research with five recruited producers to test optimal rates developed from research experiments to evaluate yields and profitability, resource use efficiency, and nitrate leaching

Establish producer field days at farms with trials and showcase plots at research center to share findings to facilitate peer-to-peer and experiential learning experiences