NITROGEN AND POTASSIUM REQUIREMENT FOR TARGETED YIELD OF COTTON

A field experiment was conducted on medium black calcareous soil at Instructional Farm, Junagadh and second cluster of field experiment was conducted on farmer‟s field with medium black calcareous soils of different villages of Junagadh district to study the “Nitrogen and potassium requirement for targeted yield of cotton” during kharif 2003-04 and 2004-05. The object was to assess the effect of nitrogen and potassium levels on growth, content and uptake of nutrient, yield and yield attributes, quality of seed cotton, and nutrients (NPK) availability as well as to developed targeted yield equations and to verify different yield targets. Twenty one fertilization treatments from four levels of nitrogen (90, 120, 150 and 180 kg ha-1) and five levels of potassium (30, 60, 90, 120 and 150 kg ha-1) and one absolute control in triplicate were under investigation. The results of field experiment revealed that the dry yield (g plant-1) of leaves, shoot, root, total plant and CGR was increased with nitrogen levels and recorded maximum values under 180 kg N ha-1. Potassium did not influenced the growth parameters significantly. The concentration of nitrogen in leaves and shoot at 90, 120 and 150 days and that in stalk was significantly influenced by nitrogen levels while the concentration of K in the leaves and shoot at 30, 60, 90 and 120 days increased with potash levels. The uptake of nitrogen, phosphorus and potassium by leaves, shoot and root at different growth stages and nitrogen and potassium uptake by seed cotton and stalk was recorded higher under application of nitrogen @ 180 kg ha-1. Similarly, the maximum uptake of nitrogen and potassium was recorded at 150 kg K2O ha-1 due to higher seed cotton yield. Plant height, bolls per plant, seed cotton yield and total yield were obtained significantly higher at 180 kg N ha-1 which remained at par with 150 kg N ha-1 whereas the branches per plant, bolls per plant and seed cotton yield were recorded higher under 150 kg K2O ha-1. The quality parameters of seed cotton viz., lint index, oil content, fiber elongation and short fiber index (SFI) were significantly influenced by nitrogen while bundle strength (Tenacity) and fiber elongation were influenced by potassium levels. The interaction effect of N and K was not observed on yield and yield attributes but it affected the quality parameters viz., seed index, micronair and fiber elongation. In respect of the distribution of dry matter and nutrients, the relative dry weight of leaves contributed higher to total dry matter than shoot and root under nitrogen level, where as K application @ 150 kg ha-1 resulted in higher relative dry weight of shoot. The content of nitrogen was recorded higher in leaves (0.91-1.65 %) followed by shoot (0.630.87 %) and root (0.38-0.64 %) while content of K was higher in shoot (0.52-1.48 %) compared to root (0.47-1.07 %) and leaves (0.41-1.10 %) during growing period. In general, the concentration of nitrogen and potassium diminished with the age of plant. The requirement of nitrogen and potassium for producing one quintal seed cotton was 4.48 and 2.30 kg, respectively. Seed cotton yield were achieved within ± 0.96 to 6.38 per cent variation at different yield targets (18, 22, 26 and 30 q ha-1) from verified trials on basis of derived equation of N (FN = 16.95 x T-0.93 SN) and K (FK2O = 8.79 x T-0.42 SK). The additional seed cotton yield was obtained at 26 and 30 q ha-1 yield targets by 15.79 and 30.0 per cent, respectively, over general recommended dose of cotton.