In the advent of precision agriculture, applying fertilizer based on soil testing is a crucial tool to prescribe nutrient levels for crops, to increase nutrient use efficiency and production. A field experiment was conducted in a farmer's field in the Dindigul district, Southern agro-climatic zone of Tamil Nadu to ascertain the effect of artificial soil fertility gradient method on soil fertility, green fodder production of sorghum (Sorghum bicolor (L.) Moench) (var. CO 30) and nutrient absorption. A fertility gradient technique has been investigated to produce fertilizer recommendations for location-specific in red soils (Alfisols, Typic Rhodustalf).  The experimental field was separated into three equal strips: strip I, II, and III, which received applications of the three graded levels of ertilizer N0P0K0, N1P1K1, and N2P2K2, respectively. Urea, single super phosphate, and muriate of potash fertilizers, respectively, were used to apply NPK. As a gradient crop, S. bicolor  was raised. The N1 level was set based on the general fertilizer recommendation of feed sorghum, while the P1 and K1 values were set based on the soil’s ability to fix 100 kg ha-1 of phosphorus and 100 kg ha-1 of potassium, respectively. Plant samples were taken at harvest time, and their NPK content and nutrient uptake were determined. With addition of graded doses of nitrogen, phosphorus and potassium fertilizer in Strip I, II & III increased the soil's available N, P & K status substantially in the order of Strip I<II<III and minimize the heterogeneity in the soil population , management strategies employed, and prevailing climate conditions to induce fertility variations in the same field. The outcomes showed that sorghum crop yields for fodder (Strip III – 25.01 t ha-1) and NPK uptake were significantly impacted by the application of graded amounts of NPK fertilizers.

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Background: Barnyard millet is one of the significant small millets cultivated in India. It has provided a good source of nutrients. Its production is low in low fertile soil. For that study undertaken into supplying balanced nutrition to achieve maximum yield by following soil test crop response-based fertilizer prescription equation. Methods: The Inductive methodology adopted in the field experiment for developing a scientific basis of fertilizer prescription for barnyard millet was performed on Periyanaickenpalayam soil series of Inceptisol soil order of Tamil Nadu during 2019-2020. The initial soil available nutrient status, grain yield, total nutrient uptake by barnyard millet and fertilizer N, P2O5 and K2O and FYM applied were taken into account for calculating four basic parameters for developing fertilizer prescription equation viz., Nutrient Requirement (NR) to produce 100 kg of barnyard millet grains, the contribution of nutrients from soil (Cs), fertilizer (Cf) and FYM (Cfym). Result: The fertilizer prescription equations and ready reckoner were developed to prescribe fertilizer dosage for a range of soil test values for specific yield target of barnyard millet on Inceptisol. It can be adopted on the Periyanaickenpalayam soil series of Tamil Nadu and also in regions with allied soil types.