Site-specific Crop Nutrient Management for Precision Agriculture – A Review

Present irrational crop and nutrient management practices have raised several concerns of high merit. The concerns include low factor productivity or nutrient use efficiency (NUE), declining crop productivity, farmer’s profitability, impaired soil health and ecological contamination. Site-specific nutrient management (SSNM), after considering indigenous nutrient supplying capacity of soil using plant and soil analysis, can feed the crop in synchrony with its nutrient requirement in different physiological growth stages. Besides, several modern geospatial techniques viz. remote sensing techniques, geographic information system (GIS), global positioning system (GPS), proximal sensing; information and communication technologies (ICTs) including decision support system, smartphone apps and web services can also assist in diagnosis of soil and crop nutrient status, fertilizer recommendation and its dissemination to users. Optical and thermal remote sensing can effectively detect crop stress including nitrogen (N) deficiency through several vegetation indices especially normalized difference vegetation index (NDVI). GIS techniques with spatial data acquired by GPS, can create spatial variability map and management zone (MZ) for precise farm operations including variable rate fertilization. Proximal crop sensors viz. chlorophyll meter and Green Seeker can also recognize crop nitrogen status and promote fertilizer N use efficiency by synchronizing fertilizer N supply with crop requirement. Even proximal soil sensing using electromagnetic radiation and contact electrode can estimate soil properties like soil pH, electrical conductivity, major and micronutrient content. Several decision support systems such as QUEFTS based model, crop manager, nutrient expert® and smartphone apps like ‘crop doctor’ can suggest for precise application of agro-inputs to rural youths and farmers. Yield monitoring and mapping tool can generate historical GIS database for spatial variability of crop yield under farmers’ crop management practices and assessment of nutrient uptake. Variable rate machinery based on variability map and sensor technologies can also be used for fertilization under different management zones. Therefore, SSNM technologies can enhance NUE; improve and sustain crop productivity, profitability; avoid nutrient wastage; maintain good soil health and environmental safety.