Improvement of leaf area index andleaf chlorophyll concentration (SPAD) soybean by Fe, Zn and Mn nano-chelates foliar application under limited irrigation conditions

Maintaining the balance of nutrients leads to increase yield so the essential elements should be available enough in the process of plant nutrition. This experiment was performed by foliar application of iron, zinc, and manganese nano-clates under limited irrigation conditions to improving leaf area index and leaf chlorophyll concentration.

The two years experiment was conducted (2016-2017). The main plot included four levels of irrigation: full irrigation, irrigation withhold at flowering stage, podding stage, and grain filling period. The subplot included eight levels of foliar application with Fe, Zn, Mn, Fe+Zn, Fe+Mn, Zn+Mn, Fe+Zn+Mn nano-chelates, and distilled water (control).

Drought stress reduced leaf area index significantly. The highest reduction was obtained from the interaction of control treatment and cessation of irrigation in the pod stage, which was 31.5% less than the full irrigation treatment. Foliar application of Zn+Mn was more successful in modulating drought stress and increased leaf area index by 49.4% compared to the control. Irrigation cessation in flowering stage increased chlorophyll concentration by 11.2% and decreased it by 16.5% in pod stage. With the application of Fe+Zn nano-chelate increased on leaf chlorophyll concentration in the pod stage and grain formation by 38.8% and 39.1% compared to the control and was recognized as the best treatment.

In limited irrigation conditions, foliar feeding of Fe, Zn and Mn nano-chlates is a suitable solution and compatible with water crisis and can improve soybean yield by modifying drought stress and improving leaf area index and leaf chlorophyll concentration.