Nitrogen Consumption and Productivity of Cotton under Sensor‐based Variable‐rate Nitrogen Fertilization

Abstract

Precision N management based on crop reflectance can be used to reduce over‐ and under‐application of N fertilizer to cotton (Gossypium hirsutum L.). The objective of this study was to evaluate the effects of variable‐rate nitrogen management systems (VNMS) based on optical sensing of crop canopy relative to a farmer's uniform‐rate nitrogen application system (FUNS) on N fertilizer consumption, post‐harvest soil N level, and cotton productivity. Eight field strip‐plot trials were conducted on cotton across West Tennessee during 2012 to 2014. Four sensor‐based VNMS were compared with FUNS in a randomized complete block design with three replicates. Two VNMS were based on optical sensing of canopy alone with different algorithms, while the other two were developed from optical sensing and crop yield maps of previous years but differed in algorithms. The variable and uniform fertilizer application systems had similar leaf N concentrations between early bloom and mid‐bloom and similar canopy normalized difference vegetation index (NDVI) values at mid‐bloom. The VNMS produced similar lint yield as FUNS. The VNMS reduced N consumption by 10.3 to 16.9% and improved nitrogen use efficiency (NUE) by 8.3 to 11.0% compared with FUNS. Both VNMS and FUNS had similar post‐harvest N levels in soil profile. Benefits from incorporating yield maps into sensor‐based VNMS were not noticeable. Thus, the in‐season sensor‐based VNMS are reliable in precision N management for cotton resulting in comparable lint yield, less N consumption, and higher NUE, which could lead to environmental and economic benefits. Core Ideas Leaf N concentration and canopy normalized difference vegetation index were comparable under variable‐rate N management systems relative to a farmer's uniform‐rate N application system. Variable‐rate N management systems produced similar lint yield but better fiber quality compared with a farmer's uniform‐rate N application system. Variable‐rate N management systems reduced N use by 10.3 to 16.9% but increased nitrogen use efficiency by 8.3 to 11.0% over a farmer's uniform‐rate N application system. No effect of variable‐rate N management systems was observed on post‐harvest soil N level relative to a farmer's uniform‐rate N application system. Benefits with incorporating yield maps into sensor‐based variable‐rate N management systems were not noticeable.

A vision of precision agriculture: Balance between agricultural sustainability and environmental stewardship

“…PA can also reduce nitrogen use and increase nitrogen use efficiency (NUE) by matching nitrogen inputs with crop requirements. For example, a study conducted by Yu et al (2019) reported that variable-rate nitrogen management systems reduced nitrogen consumption by 10.3%-16.9% and improved NUE by 8.3% to 11.0% compared with farmer's uniform-rate nitrogen application system. In another study conducted in China, precision nitrogen management reduced nitrous oxide emissions by 33% compared to conventional nitrogen management practices (Zhang et al, 2018).…”

Environmental impacts of cotton and opportunities for improvement

“…It is critical that nutrient availability synchronize with plant growth requirements 82 . Potential solutions to improved synchronization include controlled-release fertilizers 90 , split application 91 , fertigation 92 and precision fertilization 93 . It is also important for growers to determine site-specific nutrient budgets and efficiency targets.…”

Research on the Effects of Drying Temperature for the Detection of Soil Nitrogen by Near-Infrared Spectroscopy

“…Hence, a close study of soil nitrogen can determine the degree of soil fertility and offer a scientific basis for plant cultivation, which can provide guiding suggestions for precise fertilization. It also facilitates the protection of the environment and prevents overfertilization and contamination of the soil [ 5 , 6 , 7 , 8 , 9 ]. Accordingly, the rapid and accurate acquisition of nitrogen content is of great significance to agricultural production and environmental protection [ 10 ].…”