Effect of Biochar and Azosprillum lipoferum bacteria on Yield and Water Use Efficiency Indices of Tarom Hashemi Rice Cultivar under Flooded and Alternation Irrigation Regimes

Rice is a staple food source and the most important grain in developing countries, which is most commonly consumed by more than 90 percent of the world populations. Moreover, this plant is produced and consumed in Asia. However this major crop faces severe limitations such as water scarcity and other environmental stresses. Limited water resources along with climate change effects, have increased attention to methods which improve water use efficiency in crops such as rice cultivation. On the other hand, traditional irrigation methods for rice production often waste considerable fraction of irrigation water. Therefore, it is necessary to modify irrigation and other farming methods. Furthermore, using biochar and nitrogen fixing bacteria as organic biofertilizers can be effective methods to improve water use efficiency and yield attributes of rice plant. Therefore, the present research was conducted to investigate the effect of biochar and Azosprillum lipoferum rhizobacteria on yield and water use efficiency on Tarom Hashemi rice cultivar of under flooded and alternating irrigation regimes. 

This study was conducted at the research fields of the Sari Agricultural Sciences and Natural Resources University in 2017 and 2018. The experimental site is located at 36º 39ʹ42ʺ N latitude and 53º03´54ʺ E longitude with -11 m above sea level. Soil samples were taken from depths of 0-30 cm before land preparation. The experiment was done in factorial split-split plot arrangement with complete randomized blocks based design with three replications. Treatments included two irrigation management methods (flooding and irrigation regimes) in combination with nine fertilizers levels (100% of recommended nitrogen or N100, N100+ 10 ton biochar or biochar 10, N100+ biochar 20, N75, N75+ biochar 10, N100+ biochar 20, N50, n50+ biochar 10 and N100+ biochar 20) as main plots and seedling inoculation with Azospirillum lipoferum bacteria (without inoculation was also included as control) as sub plots.Plot ridges were covered by plastic sheets and inserted into the soil at 50 cm to prevent water flowing from one plot to the others. The plots were then leveled and 3-4 leaf seedlings stage. A specific number of seedlings were gently washed and placed for 30 minutes in a pan containing 10 L of water mixed with 1 L of bacterial inoculum. Carboxymethyl cellulose, 15 g, was added to increase adhesion of bacteria into the plant roots. Nitrogen, phosphorus and potassium fertilizers were applied according to the results of soil analysis. Weeds and pests were controlled mechanically or by hand and no herbicides or pesticides were used.

Results showed that biochar and nitrogen fertilizers, irrigation methods, and seedling inoculation with bacteria had significant effects on water use efficiency indices. Comparison of means of interaction effects showed that the highest paddy yield (5950.43 and 5330.78 kg/ha, respectively) were observed by flooding irrigation method in combination with N50 + biochar 20 treatment and inoculated by Azospirillum lipoferum bacteria and alternating irrigation management method which was along with N50 + biochar 20 without inoculation. Alternating irrigation plots experienced water shortage in some growth stages and therefore slightly lower paddy yield is acceptable. Application of biochar 20 and flooding or alternating methods which treated by N75 and N50, respectively showed 49.1% increase in economic efficiency index.

In general, application of 20 ton biachar along with 75% nitrogen fertilizers led to 42.8% increase in economic advantages in alternating irrigation method as compared to the flooding systems. These observation indicates beneficial effect of fertilizer in economic advantage enhancement in rice cultivation.