Growth and Nitrogen Fixation and Uptake in Dhaincha/Sorghum Intercropping System Under Saline and Non‐saline Conditions

Abstract

Two field experiments on dhaincha (Sesbania aculeata Pers.) and sorghum (Sorghum bicolor L.) grown in monocropping and intercropping systems was conducted under non‐saline and saline conditions to evaluate dry matter production, total nitrogen (N) yield, land equivalent ratio (LER), soil N uptake and N2‐fixation using 15N isotope dilution method. The first experiment was conducted under non‐saline conditions, three different combinations of sesbania (ses) and sorghum (sor) were investigated in the intercropping system (2ses:1sor; 1ses:1sor, and 1ses:2sor, row ratio). Whereas, in the second experiment, only one combination (1ses:1sor row ratio) was tested under saline conditions. Results of the first experiment showed that dry matter yield of sole sorghum was higher than that of sole sesbania, and was similar to that produced by the intercropping treatments; however, its total N uptake was the lowest, with no significant differences being found between sole sesbania and intercropping treatments. The LERs in 2ses:1sor and 1ses:2sor treatments were higher than one, reflecting a greater advantage of intercropping system in terms of land use efficiency. In the second experiment, dry matter yield of a sole crop of sesbania was significantly higher than that of a sole sorghum or a mixed treatment. Total N uptake in sesbania grown alone was four times higher than that of sole sorghum; whereas, the mixed cropping was 260% greater that of the sole sorghum. In both experiments, percentages of N2 fixed by the sesbania in the intercropping system were considerably enhanced relative to sole cropping of sesbania. On the other hand, the magnitude of intraspecific competition for soil N uptake was affected by the different arrangement of crops in the mixture, and it was considerably reduced in the 2ses:1sor row ratio. Results on the relative growth of plants on saline soil compared with that on non‐saline soil clearly demonstrated that sesbania was more salt tolerant than the sorghum. Amounts of N2‐fixed by sesbania grown in saline soil were close or even higher than those grown under non‐saline conditions. The use of intercropping systems of legumes and non‐legumes would be a promising agricultural practice for rehabilitation of saline wasted lands, after a careful selection of appropriate tolerant genotypes to the prevailing saline conditions.