Investigation of the effect of fertilizer enhancers on some yield components of wheat yield in the last irrigation cut in the field conditions

In recent years, special attention has been paid to the consumption of plant growth stimulants such as amino acids and humic acids along with micronutrients to adjust the effects of abnormal environmental conditions such as untimely cold or salinity and drought stress in grain production programs. In order to investigate the effect of growth enhancers on compensating for the lack of transport assimilates from storage sources to grain during the last irrigation cut in two wheat cultivars in field conditions, an experiment was conducted as a split-plot in a randomized complete block design with three replications at the Kashmar Research Station during of 2019-2020. Two wheat cultivars were Sirvan and Rakhshan (a common cultivar of the region) in the main plots and growth enhancers included amino acid fertilizer, complete micronutrient, humic acid each one with 2:1000 concentration and control, were taken in a subplot. All these fertilizer nutrients with an 8 kg ha-1 concentration of solo potash were sprayed in two growth stages of tillering and spiking. The results showed that the highest plant height (63.8 cm) was obtained in the Rakhshan cultivar by foliar application of humic acid. The effect of amino acid foliar application on peduncle length and weight in Rakhshan cultivar was more than other fertilizer treatments. In the Sirvan cultivar, the use of amino acid fertilizer had the highest number of seeds per spike (30.2) and grain weight per spike (1.28 g). The most number and weight of spikes per unit area were obtained from the application of amino acid fertilizer. The highest dry weight per square meter belonged to Sirvan cultivar (161 g) and Rakhshan cultivar (131 g) using humic acid fertilizer treatment. The most seed weight per unit area (91.9 g m-2) was obtained from amino acid fertilizer treatment in the Sirvan cultivar. The highest amount of photosynthesis (13.6 mmolm-2s-1) and stomatal conductance (145 mmolm-2s-1) were obtained from amino acid fertilizer treatment. The correlation coefficients showed a positive and significant correlation between yield and spike weight per unit area (r = 0.94 **) and then with the number of spikes (r = 0.70 *). In general, foliar application of amino acids and humic acid in two stages of tillering and spiking can compensate for wheat yield reduction due to the last irrigation cut by changing the physiological and metabolic processes of the plant.