Effect of Irrigation Intervals and Harvest Dates on Seed Yield and its Components of Alfalfa

Alfalfa, a key forage crop, thrives through growth stages like flowering and pod formation. Optimal irrigation intervals, especially during critical stages, improve water use efficiency and seed yield. Harvest date, such as at the yellow pod stage, enhances seed quality and quantity. Effective irrigation and harvest management boost productivity, particularly in arid regions. This study aims to improve these practices in Iraq to maximize seed yield under water scarce conditions.

The study investigated irrigation intervals and harvest dates on alfalfa seed yield in Baghdad, Iraq (33.3161N, 44.2129E) from Oct 2023 to Jul 2024. A randomized complete block design with a nested arrangement assessed four irrigation schedules synchronized with different growth stages and three harvest timings (6, 10, 14 days post last irrigation). Measured properties included stems per plant, pods per raceme, seed yield, biological yield and harvest index. Data were analyzed via ANOVA with LSD (p<0.05). Irrigation was regulated based on soil field capacity and fertilizers were applied at recommended rates.

Irrigation significantly affected alfalfa productive properties, with irrigation treatment synchronized with flowering/pod stages yielding the highest stem count (12.2 plant^-1), mature racemes (13.2 stem^-1), pods (10.7 raceme^-1) and seed yield (465.3 kg ha^-1). Fixed weekly irrigation underperformed due to mismatched timing. The harvest date 10 days after last irrigation improved pod/seed yields by allowing full maturation. Seed weight remained stable across irrigation but increased with delayed harvest (14 days after last irrigation). Irrigation treatment synchronized with flowering/pod stages also achieved the highest harvest index (9.47%), showing efficient reproductive growth, while fixed irrigation promoted excessive vegetation. Optimal irrigation timing and harvest synchronization maximize productivity.