Effect of Sowing Time and Plant Density on Growth and Yield of Crops: A Review

Abstract

Sowing time and plant density are two of the most fundamental, low-cost agronomic decisions a farmer makes, yet their combined influence on crop growth and final yield is frequently underestimated relative to inputs such as fertilizer or irrigation. This review synthesizes recent experimental evidence on the effects of sowing time and plant density, individually and in interaction, on the growth and yield of a diverse range of field, fibre, pulse and specialty crops, including wheat, rice, maize, cotton, soybean, lentil, guar and roselle. Across crops, delayed sowing consistently shortened the vegetative growth period, reduced light and thermal resource capture, and lowered yield-forming components: cotton lint yield fell by roughly 21% and soybean seed yield by 29.1% when sowing was delayed beyond the optimal window, while wheat, rice, lentil and roselle each showed a similar pattern of yield decline with sowing delay, mediated through reduced tillering, panicle number, pod number or flowering duration. Plant density effects followed a more universal inverted-U response: yield per unit area typically peaked at an intermediate, crop- and environment-specific optimum density, with cotton lint yield 13% higher at moderate density than at high density, while maize yield gains from increased density depended on simultaneous optimization of row spacing and nutrient supply. Importantly, sowing time and plant density did not act independently: in wheat, sowing date consistently overrode the effect of density, and yield losses from late sowing could not be fully compensated by adjusting seeding rate; in cotton and soybean, the optimal density shifted depending on sowing date, with moderate-to-high density favoured under late sowing and lower density favoured under early sowing. These findings indicate that sowing time and plant density recommendations cannot be developed in isolation, and that agronomic guidance must specify density targets conditional on realistic sowing windows, and vice versa, to achieve consistent yield gains across seasons and environments.