Site-specific fertilizer nitrogen management in Bt cotton using chlorophyll meter

Abstract

Field experiments were conducted to standardize protocols for site-specific fertilizer nitrogen (N) management in Bt cotton using Soil Plant Analysis Development (SPAD) chlorophyll meter. Performance of different SPAD-based site-specific N management scenarios was evaluated vis-à-vis blanket fertilizer N recommendation. The N treatments comprised a no-N (control), four fixed-time and fixed N doses (60, 90, 120, and 150 kg N ha-1) including the recommended dose (150 kg ha-1), and eight fixed-time and adjustable N doses based on critical SPAD readings of 45 and 41 at first flowering and boll formation stages, respectively. The results revealed that by applying 45 or 60 kg N ha-1 at thinning stage of the crop and critical SPAD value-guided dose of 45 or 30 kg N ha-1 at first flowering stage resulted in yields similar to that recorded by applying the recommended dose of 150 kg N ha-1. However, significantly higher N use efficiency as well as 30–40% less total fertilizer N use was recorded with site-specific N management. Applying 30 kg N ha-1 at thinning and SPAD meter-guided 45 kg N ha-1 at first flowering were not enough and required additional SPAD meter-guided 45 kg N ha-1 at boll formation for sustaining yield levels equivalent to those observed by following blanket recommendation but resulted in 20% less fertilizer N application. Our data revealed that SPAD meter-based site-specific N management in Bt cotton results in optimum yield with dynamic adjustment of fertilizer N doses at first flowering and boll formation stages. The total amount of N fertilizer following site-specific management strategies was substantially less than the blanket recommendation of 150 kg N ha-1, but the extent may vary in different fields.

Fruits-Based Critical Nitrogen Dilution Curve for Diagnosing Nitrogen Status in Cotton

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Enhancement of nitrogen use efficiency through agronomic and molecular based approaches in cotton

“…Quantifying the spatial variability of soil properties and crop yield is important for decision-making in site-specific crop management because the spatial variability of soil and crop growth is the critical factor for determining variable-rate inputs of fertilizers and other chemicals. Improving the synchrony between demand and supply of N in the crop from all sources, that is, fertilizer application throughout the growing season, improves crop NUE ( Cassman et al, 2003 ; Shankar et al, 2020 ; Ali et al, 2022b ). However, site-specific N management is only possible following spatial variations.…”

Resistance identification and nitrogen management of wheat under late spring coldness

“…Remarkably, the nitrogen utilization rate for wheat production in China ranges from 21.2% to 35.9%, significantly lower than the international standard of 40%–60% (Ladha et al., 2005). Such excessive and inappropriate fertilizer management practice not only diminish fertilizer use efficiency but also exert great ecological pressure (Shankar et al., 2020). A well‐executed fertilizer approach plays a pivotal role in fostering an optimal population structure, thereby facilitating the synchronized development of yield‐related components.…”