The effect of seeding rate, timing of nitrogen application and frequency of irrigation on wheat growth, yield and water use

Abstract

Wheat (Triticum aestivum cv. SST66) was planted in a 2 × 2 × 2 factorial field experiment. Factors investigated were seeding rate, timing of nitrogen application and frequency of irrigation. The two seeding rates were 85 and 170 kg ha⁻¹. The two N application times were 80 kg ha⁻¹ at planting and 120 kg ha⁻¹ at late tillering compared with 20 kg ha⁻¹ at planting and 60 kg ha⁻¹ each at the beginning of stem elongation, at ear appearance and at anthesis. Irrigation was applied when 70% (low frequency) and 30% (high frequency) of the plant available water was depleted. Seeding rate had no effect on either grain yield or water use, but both grain yield and water use efficiency were significantly affected by an interaction between nitrogen timing and irrigation frequency. When all N was applied early (at late tillering), low frequency irrigation resulted in 23% higher grain yield and 42% higher water use efficiency than high frequency irrigation. When N was applied in four instalments, frequency of irrigation had no effect on either grain yield or water use efficiency.