Evaluation on the development of soil fertility gradients with nutrient exhaustive crop (Sorghum bicolor) regard to N, P, and K in Inceptisols in semi-arid regions of Tamil Nadu

Soil test crop response (STCR's) soil fertility gradient approach is based on the idea that complex treatments are superimposed in a field to obtain crop responses for correlating with soil test values that are artificially created by differential fertiliser treatments prior to conducting the regular experiment, thereby providing a scientific basis for balanced fertilisation between applied and available forms of nutrients. The present study aimed to develop the fertility gradient with sorghum as test crop in the field concerning N, P, and K and also to evaluate its impact on sorghum nutrient uptake, and soil fertility. The experimental field was split into three equal strips. Strips I, II, and III each received three graded levels of fertiliser N (nitrogen), P2O5 (phosphorus pentoxide), and K2O (potassium oxide) as urea, single super phosphate, and muriate of potash, respectively. The green fodder yield of sorghum recorded at harvest in strip I, II & III was 16.4, 23.4 and 28.2 t ha-1, respectively. Whereas post-harvest soil available nitrogen in strip I, II & III was 155, 190 & 214 kg ha-1 respectively, for available phosphorus 12.5, 23.2 & 31.8 kg ha-1 respectively and for available potassium it is 332, 370 & 396 kg ha-1 respectively. Wide variations in green fodder yield and soil fertility were observed among the strips, establishing the influence of graded amounts of fertiliser treatment on these parameters and the formation of a soil fertility gradient.