Growth and productivity of wheat (Triticum aestivum) as influenced by potassium application

A field experiment was conducted during winter (rabi) seasons of 2015–16 and 2016–17 at New Delhi to assess the effects of rate, methods, time and sources of potassium (K) fertilization on wheat (Triticum aestivum L.) growth, growth indices, yield and returns from investment on K. Application of 60 kg K₂O/ha in 2 splits, half basal and remaining half at spike initiation stage or 75% basal and remaining 25% at spike initiation stage increased the grain yield (5.5 t/ha) by 8.8% over applying entire dose as basal. The split application of recommended dose of K (RDK) also increased the growth parameters (plant height, dry-matter, leaf area index) and growth indices [crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR)] significantly over control. All the growth parameters and growth indices were recorded the highest with 75% RDK as basal + 25% at spike initiation + 2 foliar spray of 2.5% KNO₃ (68.8 kg K₂O/ha), whereas control recorded the lowest. A strong positive and significant correlation was observed between dry matter production and grain yield during 90 days after sowing (DAS) (R²=0.76) and 120 DAS (R²=0.74). Similarly, positive and significant correlation was also observed between LAI and grain yield during 90 DAS (R²=0.72) and 120 DAS (R²=0.71). The highest returns from investment on K fertilizer was obtained with 2 foliar spray of 2.5% KNO₃, whereas 150% RDK as basal gave the lowest returns. Application of 60 kg K₂O/ha in 2 splits (50:50 or 75:25 ratio) increased returns from investment on K 4 by over application of entire dose as basal. Thus, for wheat, application of 60 kg K₂O/ha in 2 equal splits (50% as basal + 50% at spike initiation) is recommended to realize maximum benefit from K fertilization.