QUANTIFYING THE EFFECT OF DIFFERENT SOWING DATES ON THE PRODUCTIVITY OF TWO ELITE SOYBEAN GENOTYPES PRODUCTIVITY IN THE FACE OF CLIMATE CHANGE

Abstract

Rainfall in Sub-Saharan Africa (SSA) would decrease by about 20%, making some agricultural land in SSA unsuitable for cultivation, resulting in yield losses. The extent of these yield losses is unclear, but some analysts predict they could be severe. Increasing climate variability could lead to declining soil moisture, increasing drought, salinization and groundwater depletion. Soybean is a thermophilic and photophilic crop and is therefore sensitive to seasonal weather patterns. Planting date is an agronomic measure to manage climatic impacts. It affects stand establishment, physiological parameters, and yield formation. We investigated the effects of five sowing dates on two improved soybean genotypes (Gyidie & Tundana) during the 2021 and 2022 cropping seasons. A 2 x 5 factorial design with five replications was used for this study. The genotypes, Gyidie & Tundana, were the first factor while sowing date was the second factor. Sowing commenced on the 1st of June in 2021 and on the 5th of April in 2022. The sowing dates tested were day 1 (1st June and 5th April, respectively), 5 days later, 10 days later, 15 days later, and 20 days later. The results showed significant (p≤0.05) vegetative and yield differences effects among genotypes. The genotype Tundana yielded 11.2% and 6.5% higher grain yields than Gyidie in both years. Day to maturity was shortened by 1 to 11 days as sowing days were delayed from 5 to 20 days. Rainwater harvesting efficiency was significantly higher in the early-sown crops, which had a significant (r = 0.99) effect on grain yield. Grain yield decreased by 5.1 - 6.7% after 5 days delay, 14.8 - 19.3% after 10 days delay, 22.8 - 24.3% after 15 days delay, and 28.4 - 29.3% after 20 days delay in 2021 and 2022. Grain quality (oil and protein content) was not affected by late sowing. The results suggest that farmers have a better chance of higher yields if they sow these genotypes early to take advantage of the early rains. In the worst-case scenario, farmers should not delay the sowing date of soybean more than 5 days to minimize yield losses.