INTERACTIVE EFFECTS OF ZINC APPLICATION METHODS AND PHOSPHORUS SOURCES ON GROWTH YIELD AND QUALITY OF FINE AND COARSE RICE CULTIVARS

Abstract

Investigating how zinc application methods interact with phosphorus source types represents a crucial strategy for refining rice yield and grain quality in nutrient-impoverished soils. This field experiment was executed across two consecutive rice-growing seasons (2015–2016) rice season in Tibba Hamid Shah Bhakkar District, Punjab, Pakistan. The study sought to quantify the cumulative effects of three Zn application methods, soil application at 15 kg Zn ha⁻¹, a 1.5% foliar spray, and 1.5% seed priming with three P sources, diammonium phosphate, single super phosphate and nitrophos across two rice cultivars, Basmati-515 (fine grain) and IRRI-6 (coarse grain). A split-plot arrangement with four replicates was employed. Measurements encompassed leaf emergence and tiller emergence rates, days to heading, and allometric variables including leaf area index, leaf area duration, crop growth rate, and net assimilation rate. Yield determinants such as plant height, total tiller count, number of panicles bearing tillers, kernel count per panicle, 1000-kernel weight, grain and straw yield, and harvest index were recorded. The study further evaluated panicle sterility, kernel protein concentration, and Zn concentration in both grains and leaves, thereby correlating nutrient management strategies with both quantitative and qualitative yield outcomes. The study documented that soil-applied Zn at 15 kg ha⁻¹ combined with DAP as the P component markedly enhanced physiological, agronomic, and quality metrics relative to all alternative treatments. Basmati-515 consistently exceeded IRRI-6 regarding LAI, CGR, final yield, and Zn concentration in the grain. The Zn soil placement augmented yield through increased tiller number, stature, and visible radiation use efficiency, diminished panicle sterility and elevated both grain protein and Zn levels. Foliar applications delivered moderate yield response while seed priming principally fostered seedling vigor and advanced maturity by a few days.