Improving Resource Use Efficiency Through Strip Tillage, Cover Cropping, and Deep Fertilizer Placement

View the project final report

Commodities

• Vegetables: sweet corn

Practices

• Crop Production: conservation tillage
• Education and Training: on-farm/ranch research
• Natural Resources/Environment: carbon sequestration, soil stabilization
• Production Systems: general crop production
• Soil Management: green manures, nutrient mineralization, organic matter, soil quality/health

This project seeks to demonstrate improved agronomic nitrogen use efficiency (NUE) and sweet corn yield per unit N applied through a combination of deep fertilizer banding, strip tillage, and cover cropping. Improved NUE will increase sweet corn profitability and reduce N losses to the environment. Short-term outcomes of this project include an increased awareness of strip tillage and deep N banding as a viable option for sweet corn production in the North Central region; intermediate-term outcomes include increased adoption of reduced tillage, cover cropping, and deep banding of N by sweet corn growers region-wide; reduced N and herbicide use; reduced tractor use and fuel purchases; increased profitability; and reduced N leaching and nitrous oxide (N2O) release. We will compare sweet corn yield, quality, and profitability, as well as N loss to the environment from leaching and N2O flux in two treatments: one with broadcast fertilizer incorporated with conventional, full-width tillage and the other with deep-banded fertilizer and strip tillage. Cover crops are used in both treatments. We hypothesize that deep-banded fertilizer, compared to broadcast applications, will be more accessible to sweet corn roots and less accessible to weeds emerging near the soil surface, increasing crop growth and yield and improving weed management. Increased uptake by the sweet corn plant will result in higher yields and in less N lost through leaching and as N2O. Trials on collaborators’ farms will allow us to examine these practices in production systems and analyze profitability by creating partial enterprise budgets with farmers’ input costs and revenues for their standard practice and with deep-banded N fertilizer and strip tillage. Profitability analysis and on-farm demonstrations will increase grower awareness of these practices and hopefully lead to increased adoption.

Introduction:

Nitrogen (N) is an essential element for crop growth and N fertilizers are often over-applied to ensure optimal yields. When N is applied in excess to crop demand, however, it can be lost from the agroecosystem. Two common N loss pathways include nitrate (NO3-) leaching and nitrous oxide (N2O) flux as a result of partial denitrification. The latter typically represents only a small fraction of N loss, but is important because nitrous oxide is a potent greenhouse gas. In addition to causing environmental problems, N that is applied in fertilizers but is lost to either leaching or via nitrous oxide flux represents a direct cost to growers in wasted resources. Thus, agricultural practices that can mitigate nitrate leaching and nitrous oxide flux are beneficial to both growers and to society as well.

Reducing nitrogen application rates while maintaining yields and profits is a challenge that can be addressed by improving the agronomic nitrogen use efficiency (NUE) of a cropping system—getting more harvestable yield per unit nitrogen applied (Robertson and Vitousek 2009). NUE can be improved in part by placing nitrogen closer the developing plant roots, thereby increasing the likelihood that it will be taken up by the crop rather than lost to the environment. Strip tillage (ST) is a form of reduced tillage that offers a convenient way to band fertilizers at depths of 6” or more. In ST, strips are tilled only where the crop will be planted while the rest of the soil remains undisturbed. Yield of many crops, including sweet corn (Luna and Staben, 2002), is either similar or higher in ST compared to conventional, full-width tillage (FWT). ST offers other benefits as well, including lower cost because primary and secondary tillage is accomplished in one pass (Luna and Staben 2002). Improved NUE through banding and deep placement of N sources may also have important benefits for weed management—an ongoing challenge for sweet corn producers. Since many weeds are highly responsive to N fertility, deep-banding fertilizer may enhance weed suppression by placing resources beyond the reach of weeds emerging close to the soil surface.

This experiment compared sweet corn yield and profitability, weed management, and N loss to the environment from leaching and N2O flux in two tillage systems: one with broadcast fertilizer incorporated with FWT and the other with deep-banded fertilizer and ST. We hypothesized that deep-banded fertilizer, compared to broadcast applications, would be more accessible to sweet corn roots and less accessible to weeds emerging near the soil surface, thereby increasing crop growth and yield and improving weed management. Increased uptake by the sweet corn plant was expected to result in higher yields and in less N lost through leaching and as N2O.

The primary objectives of this experiment were to evaluate the impact of ST with deep N fertilizer banding on:

1. sweet corn yield and profitability
2. N losses via leaching and partial denitrification to nitrous oxide
3. weed management efficacy with herbicides.  

We also used this experiment to address a secondary objective: to evaluate the impact of relative strip placement on yield.  Consultation with growers led to the development of this secondary objective as they were interested in knowing how strip placement from year to year would affect crop yield.