Effect of Application of Nitrogen Doses Along with Biochar and Zinc Nanoparticles on Quantitative and Qualitative Characteristics of Rice (Oryza sativa L.)

Among the various nutrients, nitrogen (N) is the limiting element for crop yield, which application of the optimum doses of this fertilizer in addition to increasing the yield components and grain yield in paddy fields, enhances the profits of rice cultivation in the region. One of the sustainable soil management techniques in paddy fields is the application of rice husk biochar. Biochar improves rice yield by improving soil chemical properties, increasing nutrient storage capacity, and also reducing soil acidity. Zinc deficiency can be the most important limiting factor of rice yield after N, P, and K. Therefore, the application of zinc fertilizer in the form of nanoparticles can be an effective technique to increase the quantitative and qualitative characteristics of rice. Therefore, the present study was conducted to investigate the effects of nitrogen doses along with the application of biochar and also zinc fertilizer in the form of nanoparticles on the quantitative and qualitative characteristics of rice.

The field experiment was carried out as a split-plot based on a randomized complete block design with three replications at the farmer's field located in Amol (North of Iran) in cropping season of 2019-2020. In this study, the doses of nitrogen applied at four levels of 0, 25, 50, and 75 kg.ha-1 as the main factor and application of fertilizers at four levels of control or no application of biochar and zinc nanoparticles, application of biochar, foliar application of zinc nanoparticles and combined application of biochar and zinc nanoparticles as the sub-factor were considered. The fertilizers of biochar and zinc nanoparticles at 40 ton.ha-1 and 50 mg.l-1 were used in this experiment, respectively. At harvest time, the yield components, yield, and N and Zn concentrations in grain were measured. Analysis of variance was performed using SAS software (ver. 9.2) and mean comparisons based on the least significant difference (LSD) test at the level of 5% probability.

The results showed that the simple effects of experimental treatments were significant on all morphological traits, yield components, and grain yield except the number of filled grains per panicle. The grain N concentration was not affected by biochar and zinc, while grain Zn concentration was significant under this treatment. Also, the impact of N application was significant on N and Zn concentrations in grain. The interaction between experimental treatments was not significant on the studied traits except for the number of fertile tillers per hill. The maximum fertile tillers number per hill (17.66 tillers) was obtained by using a combination of biochar + zinc nanoparticles + 50 kg N ha-1, which indicates the positive impacts of simultaneous application of these fertilizers. The application of N fertilizer at the amounts of 50 and 75 kg.ha-1, respectively, resulted in maximum grain yield (4340 kg.ha-1) and production of the highest grain N concentration (1.30%). Although the use of each of the biochar and zinc oxide nanoparticles improved the yield components, yield, and nutrient concentrations in rice grain, the combined application of biochar and zinc nanoparticles significantly increased the quantitative and qualitative characteristics of rice, so that the highest grain yield (4062 kg.ha-1) and greatest Zn concentration in grain (28.5 mg.kg-1) was observed under the simultaneous application of biochar + nanoparticles.

According to the results of the present study, N application at the rate of 50 kg.ha-1 and simultaneous application of rice husk biochar + zinc nanoparticles are introduced as the optimal dose of N and the ideal fertilizer option to increase crop yield and enrich rice grains.