**E** ff**ects of Landscape, Soils, and Weather on Yields, Nitrogen Use, and Profitability with Sensor-Based Variable Rate Nitrogen Management in Cotton**

**James A. Larson 1,\* , Melissa Stefanini 1, Xinhua Yin 2, Christopher N. Boyer 1 , Dayton M. Lambert 3, Xia Vivian Zhou 1, Brenda S. Tubaña 4, Peter Scharf 5, Jac J. Varco 6 , David J. Dunn 5, Hubert J. Savoy 7 and Michael J. Buschermohle 7**


Received: 15 October 2020; Accepted: 20 November 2020; Published: 25 November 2020

**Abstract:** Farmers may be reluctant to adopt variable rate nitrogen (VRN) managemen<sup>t</sup> because of uncertain profits. This study assessed field landscape, soil, and weather e ffects 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 managemen<sup>t</sup> 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 managemen<sup>t</sup> 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.

**Keywords:** economics; normalized di fference vegetation index (NDVI); on-the-go sensors; site-specific nutrient managemen<sup>t</sup>
