PHENOTYPIC VARIATION IN MAIZE GROWTH AND YIELD ATTRIBUTES UNDER SOIL TEST-BASED NUTRIENT MANAGEMENT IN TROPICAL ALFISOLS

Abstract

Maize growth and yield attributes are measurable phenotypic traits that may respond to nutrient availability in heterogeneous tropical Alfisols. This study assessed phenotypic responses and productivity under farmers’ practice (FP), soil test-based nutrient management (STB) and the recommended fertilizer dose (RDF) in seven farmer fields during each of Kharif 2020 and Rabi 2020-21. Plant height, kernel weight per cob, grains per cob and 100-grain weight were evaluated alongside grain yield, nutrient uptake and economic returns. Available soil nitrogen was generally low, while phosphorus, potassium and zinc varied among fields. STB recorded the highest plant height (167.4 and 173.3 cm), kernel weight per cob (120.8 and 123.0 g), and 100-grain weight (29.2 and 29.4 g) in Kharif and Rabi, respectively. Differences in grains per cob were non-significant. Grain yields under STB were 6,856 and 8,570 kg ha⁻¹, approximately 22.2% and 22.3% higher than FP, respectively. The first two principal components of four standardized traits accounted for 84.6% of variation in Kharif and 88.8% in Rabi. These observations describe management-associated phenotypic responses, not genetic variation. Because fertilizer nitrogen rates differed among treatments, the effect of soil testing cannot be isolated from the complete fertilizer package.