The effect of increasing genetic diversity through the mixture of wheat cultivars on nitrogen efficiencies and water productivity

Agricultural ecosystems are a type of ecological systems where functions are organized in the direction of agricultural products and the characteristics of their production are determined based on the consumption of external inputs. In agricultural ecosystems, with monoculture of one cultivar and the excessive use of chemical inputs, crop yields are substantially increased. But the main challenge facing agriculture today is the environmental pollution caused by the use of chemicals and reduction of yield stability. Diversity in the selection of crop plant genotypes by farmers reduce production risk and annual yield fluctuations. Increasing genetic diversity through mixed cultivation of different cultivars or species with different morphological and physiological characteristics make possible use of the environment and resources. One of the ways to improve the quality and stability of wheat production is to increase the genetic diversity in the cultivation systems based on the mixed cultivation patterns. In Iran, excessive use of nitrogen fertilizers in agricultural ecosystems, especially in wheat production systems, is a problem, and it seems that increasing the efficiency of using this input is a very effective way to deal with this problem. The purpose of this research was to investigate the effect of increasing genetic diversity through intercropping of wheat cultivars on the efficiency of nitrogen and water use.

In order to evaluate the effect of increasing the genetic diversity of mixed cultivation of wheat cultivars on improving the efficiency of resource use, an experiment was carried out in the form of completely randomized block design with 3 replications in the research farm of Agriculture Faculty of Ferdowsi University of Mashhad in two crop years 2018-2019. Treatments included pure cultivation and double, triple and quadruple mixtures of four varieties of wheat, Heydari, Pishgam, Pishtaz and Falat, which were introduced in the 60s, 70s, 80s and 90s, respectively, and were in the same maturity group. The amount of absorbed nitrogen, absorption efficiency (NUpE), conversion efficiency (NUtE), nitrogen use efficiency (NUE) and water productivity. The data of the two-year test was compiled using Minitab software ver. 18.0 variance analysis was carried out and Excel software was used to draw graphs.

The results of the experiment showed that there was a significant differences in terms of water consumption efficiency, the amount of absorbed nitrogen, consumption efficiency and nitrogen absorption efficiency for pure and mixed cultivation of different wheat cultivars, but no significant difference observed for nitrogen conversion efficiency (p≤ 0.05). The highest amount of absorbed nitrogen, utilization efficiency, absorption efficiency and nitrogen conversion efficiency were observed for mixed cultivation of Pishtaz + Heydari cultivars (99.1 kg/ha, 34.5%, 69.3%, 49.8%), Pishtaz with Heydari and Falat (111.1 kg per hectare, 36.6%, 78.2%). While the highest water consumption efficiency was achieved for pure and mixed cultivars, respectively, Pishtaz (0.9 kg/m3 water), Pishtaz + Heydari (1.4 kg/m3 water), Pishtaz with Pishgam and Heidari (1.3 kg/m3 water). Water productivity showed a positive and significant correlation with absorption efficiency and nitrogen use efficiency (R2= 0.71, R2= 0.68). Thus, with the increase of nitrogen absorption and consumption efficiency, water consumption efficiency also increased, while no significant correlation was observed between water consumption efficiency and nitrogen conversion efficiency. According to the results of this research and the experiments result of other researchers, it can be said that through mixed cultivation and increasing the genetic diversity of wheat cultivars, the amount of absorption, the absorption efficiency and the efficiency of nitrogen consumption can be improved.

The results of this experiment showed that, by increasing genetic diversity through double and triple mixed cultivation of wheat cultivars, nitrogen efficiency and water consumption improved. In terms of water consumption efficiency, the amount of absorbed nitrogen, consumption efficiency and nitrogen absorption efficiency, there was a significant difference for the pure and mixed cultivation of different wheat cultivars, but no significant difference was observed for the nitrogen conversion efficiency. The highest amount of absorbed nitrogen, utilization efficiency, absorption efficiency and nitrogen conversion efficiency were belonged to the mixed cultivation of Pishtaz + Heidari cultivars, Pishtaz + Heidari + Falat. While the mixture of Pishtaz + Heidari, Pishtaz + Pishgam + Heidari had the highest water productivity.