Comparison of humic acid types on the concentration of macro nutrients elements in soil and leaves and yield components of pistachio trees in field conditions

The use of organic fertilizers in sustainable agriculture, in addition to increasing the support and activity of beneficial soil microorganisms in order to provide plant nutrients such as nitrogen, phosphorus and soluble potassium and also improves plant growth and yield are so necessary. In pistachio growing areas due to soil constraints such as salinity and sodium content of the soil, lack of proper structure in most areas, poor soil texture and long irrigation cycle, the use of auxiliary substances such as humic acid, can improve the situation and lead to increase nutrient uptake and increase growth and yield and sustainable production.

This experiment was carried out in a randomized complete block design with three replications in MahVelat. The main plot consisted of four types of humic acid (ordinary solid humic acid, Ferti Plus solid humic acid, Iranian liquid humic acid (all three products of Shimi Gol Feyz Khorasan Company) and American Liquid Humic Acid (HUMAX) and subplot including different application levels (0, first level for solid fertilizers 600 kg and liquid fertilizers 40 liters per hectare and second level for solid fertilizers 800 kg and liquid fertilizers 60 liters per hectare). The number of trees tested was 36 trees of 10-year-old almond cultivar. Solid fertilizer was applied once (March 2016) and liquid fertilizer twice (March 2016 and May 2017). Irrigation was drip (Babler) and studies were considered for one year. In August 2017, by random sampling of the leaves of each tree, the concentration of nitrogen, phosphorus, potassium, calcium and magnesium in the plant leaves and also by sampling the soil of the foot of each tree, some soil chemical properties, including pH, Organic carbon content, available nitrogen concentration and available phosphorus concentration in soil, potassium, calcium and magnesium in soil solution extract were measured. In September 2017, yield components (weight of 100 grains, ounce and emptiness percent) of each tree were measured by weight. The results were statistically analyzed using SAS software and the mean of the experimental data were compared with each other by Duncan's multiple range tests at 5% probability level.

The amount of organic carbon (71.42%), nitrogen (72.22%), and soil potassium (43.01%) with all types of humic acids showed a significant increase compared to the control, but no significant difference was observed between the consumed humic acids. The highest amount of available phosphorus (78/30%) in soil, calcium (54/90%) and magnesium (56.05%) was obtained from liquid ShimiGol and Humax. With increasing the amount of humic acid, electrical conductivity (13.71%) decreased but organic carbon (82.88%), nitrogen (55%), phosphorus (75.93%), potassium (23.97%), calcium (46.35%) and magnesium (58.82%) showed a significant increase and the highest amount of these properties was obtained in the highest amount of humic acid consumption. The interaction of humic acid type and its amount on the amount of organic carbon, phosphorus, potassium, calcium and magnesium in the soil was significant and the highest amount of calcium (57.03%) was obtained from the application of 60 liters per hectare of Humax. The highest leaf nitrogen concentrations were obtained from the application of liquid Humax (MAX:42.23%), liquid of Shimi Gol, solid Ferti Plus and ordinary solid ShimiGol, respectively. The highest concentrations of phosphorus (17.65%) and magnesium (16.96%) were obtained from Humax and the highest concentrations of calcium were obtained from three solid humic acids, Ferti Plus, liquid of ShimiGol and liquid of Humax with a significant difference with ordinary solid. The type of humic acid consumed was not significant on any of the yield components (weight of 100 grains (21.69%), ounces (27.45%) and emptiness percent (25.38%)). The amount of humic acid consumed was significant on all measured characteristics. So that the best yield components and the highest element concentration were obtained from the highest amount of humic acid consumption.Humic acid has direct and indirect effects on plants. Indirect effect is usually in the form of changes in environmental conditions such as modification of soil physical condition, enzymatic and hormonal effects and soil pH, improvement of soil structure, aeration, drainage, water holding capacity, soil temperature and direct effects includes increasing biomass and microbial population, antiviral activity and growth modulation, increasing plant resistance to salinity and drought stress. Humic acid increases nutrient uptake, increases germination and root growth, and improves yield quantitatively and qualitatively. Humic substances also dissolve calcium carbonate in the soil and replace calcium with sodium by activating sulfur oxidizing bacteria, as well as reduction of soil pH to improve nutrient uptake. Humic acid can directly release various elements from minerals, absorb them and deliver them to the roots at the right time. Because humic acid is a valuable source of macro and micro nutrients, it provides a good nutritional balance for the plant and leads to greater absorption of nutrients and specific functional responses in the plant.

Application of humic acids in liquid or solid form, domestically or externally produced, can increase the supply of nitrogen, potassium, phosphorus, calcium, magnesium, as well as the content of organic carbon in the soil and reduce pH, increase the concentration of elements in leaves and improve yield components. Of course, it should be noted that among the internal humic acids, the solid Ferty Plus, Shimi Gol were as well as Humax liquid. Relying on internal knowledge can prevent unnecessary outflow of currency.