Effect of water stress on competition betweenMedicago truncatulaand wheat in15N labeled soil

Abstract

Crop mixtures that include legumes increase yield and restore soil fertility. These mixtures are limited by drought, which is frequent in Morocco due to lack of and poor distribution of rain. However, annual Medicago species are very important to forage production, and they have a tolerance to water stress. The effect of water stress on N2 fixation and N transfer by Medicago truncatula cv. Jemalong (medic), when mixed with wheat (Triticum durum cv. Karim), was investigated in three greenhouse experiments. Annual medic and wheat were seeded in 20‐L pots in pure and mixed stands. Three watering treatments were used: ‐0.9, ‐1.5, and ‐2.5 MPa in the first experiment; and ‐0.9, ‐2.5, and ‐3.5 MPa in the second and third experiments. Competition between medic and wheat was affected by hxdric treatments; the medic was more competitive for soil water than the wheat, especially under severe water stress. Shoot dry weight of wheat grown with medic was higher than that of wheat grown in pure stands. Medic alone took...