HARVEST AND NITROGEN MANANGEMENT OF WINTER CEREAL RYE AS FORAGE AND COVER CROP

Author

Kelsey Jo Vaughn, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2022

Degree Name

Master of Science

Department

Plant and Soil Science

First Advisor

Sadeghpour, Amir

Abstract

Sustainability of dairy production depends on their production of feed and finding ways to increase profitability through dairy production or even carbon (C) crediting and adding C inputs into the soil to sequester C. To increase farm profitability, dairy producers in Illinois, has intensified their feed production through integrating winter cereals such as winter cereal rye (Secale cereale) (WCR) into single season corn for silage (double cropping). Intensified cropping system allows for increased feed production, covering the soil year-round, and adding C inputs while minimizing nutrient loss mainly through runoff or leaching. Two management practices that improve the sustainability of corn silage – WCR double crop are harvesting date and nitrogen (N) management during the WCR phase of the production. This thesis has two main chapters. Chapter 1 evaluates the effect of harvesting date (five weekly harvest from late-March to early-May) with and without optimum N addition (0 vs. 47 kg N ha-1). Our objective was to evaluate harvesting date and spring N fertilization effect on WCR morphology, forage yield, nutrient removal, and quality. A quadratic model best explained an increase in WCR biomass in response to GDD (growing degree days) accumulation (R2 = 0.81). Increase in GDD linearly decreased WCR relative forage quality (RFQ). Benchmarking RFQ at 150 for dairy milk production indicates that WCR should be harvested at a GDD of 543 at which WCR plant height was 31.8 cm and dry matter (DM) biomass was 0.77 Mg ha-1. Benchmarking RFQ at 125 for heifer production indicated that harvest should occur at a GDD of 668 at which the WCR was 71 cm tall and its DM yield was 2.25 Mg ha-1. Nitrogen balances were negative at the no-N control treatment indicating a need for some N to maximize WCR yield. We found that a rate between 21 and 42 kg N ha-1 maximizes yields reflecting on slightly positive balances. Our results suggest that harvesting date can be predicted by GDD and should be adjusted for RFQ. We conclude that smaller than 42 kg N ha-1 N fertilizer is required for WCR production in soils with manure history and high soil organic matter (>30 g kg-1). Chapter 2 hypothesized that N fertilization of WCR as cover crop can increase nutrient recycling and C sequestration which offers C trading benefits to growers. We evaluated the effects of N fertilizer application in fall (0 vs. 56 kg N ha-1), and N fertilizer rates in spring (0, 23, 47, and 71 kg ha-1) on WCR dry matter (DM) biomass and cover crop quality. Results indicated that fall N fertilization had no effect on WCR biomass or quality reflecting on loss of applied N in the fall. Spring N application did not affect WCR biomass yield but increased N, P, and K concentrations, their uptake, C concentration, and decreased C:N and lignin:N ratios. We concluded that only spring N fertilization improves WCR cover crop benefits. Overall, we suggest that for high-quality forage, (RFQ at 150) WCR should be harvested at a GDD of 543 at which WCR plant height was 31.8 cm and dry matter (DM) biomass was 0.77 Mg ha-1. For RFQ of 125 (for heifer production), harvest should occur at a GDD of 668 at which the WCR was 71 cm tall and its DM yield was 2.25 Mg ha-1. Neither in fall nor in spring, N fertilization increase WCR C accumulation. Spring N fertilization reduces WCR C:N and lignin:N which are desirable for crop production.