The Effect of Different Levels of Pistachio Harvesting Wastes Biochar on Growth and Water Productivity of Maize (Zea mays L.)

The application of biochar in the soil in order to improve soil quality and also waste management, has received considerable interest in recent years. Success of such management requires expert knowledge about the impact of a given biochar on soil and plant properties, before its field application. For this purpose, the effect of five different levels of biochar (0, 1, 2, 3 and 5% w/w), produced from residual of pistachio, on growth and water productivity of maize plants in a sandy and a silt loam soil was investigated. The study was performed in 2018 as a greenhouse experiment with a completely randomized design. The results showed that the effect of biochar on plant growth is strongly soil dependent. The biochar application had a negative effect on the growth of maize in the sandy soil. Root and shoot dry biomass as well water productivity were reduced more than 90% by application of 2 and 3% of biochar as compared to the control (0%), and the plant growth was hindered by further increase of biochar (at 5%). Consequently, water productivity was also reduced significantly. This negative effect of biochar application in sandy soil was attributed to an induced salinity as a result of biochar application and the low water holding capacity of the soil. In contrast, the effect of biochar on salinity of silty loam soil was not remarkable and only at application rate of 5%, it was increased significantly as compared to the control. Although the application of biochar in silty loam soil did not show a significant effect on root biomass, plant height, and chlorophyl index but shoot biomass and water productivity were increased till the application rate of 2% compared to the control. In conclusion, the results showed that i) one should be cautious with application of biochar (originated from pistachio residual) in coarse-textured soils, ii) and also the efficient application rate of each biochar should be determined in each soil before its application.