Effect of combination of the humic acid and nano-Potassium fertilizer on yield, yield components and protein percentage of cowpea (Vigna unguiculata L.)

Cowpea (Vigna unguiculata L.) as one of the important beans, has 20-25% protein and is a protein supplier that is needed by humans and plays an important role in this regard. Increasing yield per unit area is one of the most important factors for increasing production. Humic acid is a natural organic polymer compound that results from the decay of soil organic matter, peat, lignin, etc., which can be used to increase the product and its quality. One of the important benefits of using humic acid is the ability to chelate various nutrients such as potassium and magnesium and other elements to overcome the lack of nutrients. Humic acid also creates more space for water to penetrate through physical modification and improved soil granulation. Nanotechnology as a leading science in solving problems and issues of agriculture has well proven its place in agricultural sciences and related industries. Potassium is the most suitable cation with a capacity to activate plant enzymes because in addition to its high concentration in the cell and its amount in nature, this cation has an extraordinary mobility inside the plant. Therefore, the present study was conducted to investigate the effect of combining humic acid and potassium nano-chelate fertilizer on the characteristics of cowpea in Ahvaz.
 
In order to evaluate the effect of compilation of the humic acid and nano-potassium fertilizer on physiological, morphological and yield characteristics of cowpea (Vigna sp.) in Ahvaz, a factorial study was conducted in Ahvaz city in the year 2020 based on a randomized complete block design with four replications. Experimental factors included humic acid at three levels: zero (control), 2 and 4 liters per hectare and levels of potassium nano-chelate fertilizer as soil application at 3 levels including: zero (control), 2 and 4 kg ha-1 in Ahvaz region. Field preparation included plowing, disks and leveling. After preparation of the field, nitrogen and phosphate fertilizers were mixed with the disk machine at a depth of 15 cm. Nitrogen from the source of urea (46%) was 50 kg nitrogen per hectare and phosphorus fertilizer from the source of triple superphosphate at a rate of 80 kg/ha P (48%) was used. Statistical analysis was performed using SAS 9.2 and comparing of the means was based on LSD method at 5% probability level.
 
The experimental results showed that the effect of different levels of potassium and humic acid nanoclate on grain yield, number of seeds per pod, number of pods per plant, 100-seed weight, biological yield and protein percentage were effective and affected these traits. The highest grain yield of 4 kg/ha potassium nanoclate and 4 liters/ha of humic acid at the rate of 226.29 g/m2 (which was not statistically significant with the treatment of 4 kg/ha potassium nanoclate and 2 liters/ha of humic acid) It was found that compared to the non-application of humic acid and potassium nanochlate, it showed a 25% increase. In general, application of 2 liters per hectare of humic acid and 4 kg per hectare of potassium nanoclate can be recommended to increase the yield and percentage of protein in cowpea plant. Due to the persistence of photosynthetic tissues, humic acid increased plant yield and also increased plant yield through positive physiological effects such as the effect on plant cell metabolism and increasing leaf chlorophyll concentration. Potassium nano-chelate leads to improved plant growth conditions and cell division and the production of hydrocarbons and proteins and its rapid transfer to the grain, which increases grain weight and thus increases grain yield.
 
According to the results of this study, it was found that the application of two factors, humic acid and potassium, in plants do not have an inhibitory effect on each other, grain yield and protein percentage. Therefore, these two factors together increase the functional components. Therefore, due to the lack of potassium in the arable soils of Khuzestan, it seems that the use of nano-chelate potassium and humic acid at the rate of 4 kg per hectare and 2 liters per hectare, respectively, is a suitable solution to increase the yield and protein content of cowpea with suggested paying attention to the reduction of environmental pollution caused by the application of fertilizers in the soil.