Abstract
Farmers may be reluctant to adopt variable rate nitrogen (VRN) management because of uncertain profits. This study assessed field landscape, soil, and weather effects on optical sensing (OS)-based VRN on cotton (Gossypium hirsutum L.) N rates, yields, and net returns (NRs). Field data were collected from 21 locations in Louisiana, Mississippi, Missouri, and Tennessee, USA, between 2011 and 2014. Data included yields, N rates, and NRs for the farmer practice (FP), OS-based VRN, and OS-based VRN supplemented with other information. Production data were augmented with landscape, soils, and weather data, and ANOVA and logistic regressions were used to identify field conditions where VRN was profitable, provided risk management benefits, and improved N efficiency. Key findings indicate that NRs were improved with VRN by applying additional N on more erodible soils. Higher organic matter soils also benefited from VRN through enhanced yields and NRs. VRN may also have provided risk management benefits by providing a lower probability of NRs below NRs for the FP on soils associated with greater water-holding capacity, higher organic matter levels, or deeper profiles. Results from this study may help identify farm fields with similar characteristics for adoption of VRN management.
Highlights
Upland cotton (Gossypium hirsutum L.) is an important crop in the lower Mississippi River Basin (MRB)of the United States (US) that includes the states of Louisiana, Mississippi, Missouri, and Tennessee [1].Agronomy 2020, 10, 1858; doi:10.3390/agronomy10121858 www.mdpi.com/journal/agronomyCotton area planted in the four states was 700,405 ha in 2019 [2]
The soil, landscape, and weather factors associated with lint yields in the estimated mean difference regressions were silt soil texture (Pr ≤ 0.01), loam soil texture (Pr ≤ 0.05), elevation (Pr ≤ 0.01), organic matter (Pr ≤ 0.01), soil depth (Pr ≤ 0.01), soil erosion index (Pr ≤ 0.01), and growing degree days (GDD) (Pr ≤ 0.01) (Table 4)
Soils classified as having a silty or loamy texture relative to sand were negative in relation to variable rate nitrogen (VRN) yields when compared to farmer practice (FP)
Summary
Upland cotton (Gossypium hirsutum L.) is an important crop in the lower Mississippi River Basin (MRB)of the United States (US) that includes the states of Louisiana, Mississippi, Missouri, and Tennessee [1].Agronomy 2020, 10, 1858; doi:10.3390/agronomy10121858 www.mdpi.com/journal/agronomyCotton area planted in the four states was 700,405 ha in 2019 [2]. Upland cotton (Gossypium hirsutum L.) is an important crop in the lower Mississippi River Basin (MRB). Nitrogen is especially important for lint yield formation after the cotton plant’s first bloom [5]. Under application of fertilizer N reduces lint yield and profit. Over application of fertilizer N in cotton increases fertilizer costs and can cause excessive vegetative plant growth rather than increased production of cotton bolls that contribute to lint yield and profit [6]. Excessive vegetative growth can decrease lint yield due to boll rot and insects, reduce lint fiber quality, and cause increased expenses due to additional applications of pesticides and plant growth regulators to prevent lint yield losses [6]
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