Study of millet (Panicum miliaceum) response to humic acid, silicon and mycorrhiza application under saline-sodic irrigation water stress

Salinity and sodicity stresses are the major problems in the production of crops under arid and semi-arid regions. Sustainable management by using water and soil resources, under conditions of salinity and sodicity, is considered as a management strategies, also application of mycorrhizal fungi along/or organic matter such as humic acid addition are the major causes in reclamation of the environment and also increases the stability of agro-systems by reducing the use of chemical fertilizers. Among other ways to overcome the negative effects of salinity on the growth and yield of the plant, application of ordinary silicon and silicon nanoparticles have prior importance. This research was conducted to evaluate the effect of humic acid, mycorrhiza and silicon (ordinary and nano) on yield and nutrient content of millet under saline-sodic irrigation water.

A field experiment was conducted as split plot factorial in a randomized complete block design with three replications in summer 2015. The study area is located in Tabas city, South Khorasan province (Iran) with longitude 56o 53' and latitude 33o 34'. The main plots consisted of saline-sodic irrigation water (S) at two levels (S1= EC: 2.1 dSm-1, SAR:11.5 and S2= EC: 5.04 dSm-1, SAR: 20.8) and a combination of sub factors including three treatments of silicon salts (SI): (control (Si0), silicon nanoparticles, 10KgSiha-1 (NSi) and ordinary silicon (by using sodium silicate salt) 10KgSiha-1 (Si)) and three levels of mycorrhiza and Humic acid (MH): (control (MH0), inoculation with Glomus mosseae mycorrhizal fungi (M) and humic acid 10Kgha-1 (H)) as The factorial was placed in the main plots.

The results showed that increasing salinity-sodicity of irrigation water decreased grain yield, straw yield, number of panicles per square meter and plant height and its effect on 1000 seed weight and grain number per spike were not significant. Increasing salinity-sodicity of irrigation water decreased the grain yield by reducing the number of panicles per square meter, reduction of the straw yield due to its negative impact in plant height. The application of silicon nanoparticles treatment increased the grain yield compared to non-silicon treatment, but ordinary silicon (sodium silicate) had no effect. Mycorrhizal inoculation increased grain yield, straw yield and panicle per square meter and application of humic acid also increased grain yield, number of panicles per square meter. Mean grain yield at S1 level increased with the use of humic acid and mycorrhiza and in S2 level, mean grain yield increased only with the use of humic acid. Saline-Sodic irrigation water reduced the concentrations of nitrogen, phosphorus, potassium and K/Na ratio, and increased sodium concentration in millet. Application of silicon had no significant effect on nitrogen, phosphorus, potassium, sodium and K/Na ratio in the plant, but mycorrhiza and humic acid increased plant phosphorus and K/Na ratio and decreased sodium content of the plant.

According to our results, it can be concluded that the use of silicon nanoparticles in comparison with ordinary silicon (sodium silicate) could increase the yield of millet. Also the application of humic acid or mycorrhiza can be improved the yield of millet by increasing the amount of phosphorus and K/Na ratio and decreasing sodium content in millet and thus the enhancement of resistance of the plant and the reduction of the effects of salinity-sodicity of water irrigation, and in this regard, the effect of humic acid was much superior to mycorrhiza impact.