Effect of irrigation regimes and phosphorus fertilization on water-use efficiency, phosphorus-agronomic efficiency and yield of grass pea (Lathyrus sativus L.) ecotypes

Grass pea (Lathyrus sativus L.) is a crop of immense economic significance. It is one of the most resilient to climate changes and to be survival food during drought-triggered famines.

In a field study split factorial experiment based on a randomized complete block design with 3 replications were used, effects of irrigation regimes (50, 75 and 100% evaporation of Pan class A) and different rates of phosphorous fertilizer (triple superphosphate 0, 60 and 120 kg/ha) on growth and yield of two grass pea ecotypes (Lalehzar and Sharekord) in Lalezar area (Kerman province, Iran) was carried out during 2018 and 2019.

The results showed that drought stress reduced grass pea seed yield (401 kg/ha¹) and biological yield (863 kg/ha¹) and this reduction was depended on the severity of stress. In the other side, application of phosphorous fertilizer (60 kg/ha¹) increased grass pea yield (2401 kg/ha¹). This means that phosphorus fertilizer could partiaiiy offset the effect of drought stress and had a significant effect on the water use efficiency and phosphorus agronomic efficiency. Finally, drought stress, either no-application phosphorus fertilizer, could decrease yield. Overally, Shahrekord ecotype showed the higher and most desirable grain yield (2401 kg/ha¹), biological yield (5612 kg/ha⁻¹), grain water use efficiency and biological water use efficiency, respectively, with (0.74 and 1.72 m³ water/ha⁻¹) and phosphorus agronomic efficiency (18.76 kg yield/kg P) to the applied treatments (75% irrigation+ triple superphosphate fertilizer 60 kg/ha).