The effect of different humic acid applications on cotton yield, nutrient uptake and fiber quality properties

This study was carried out to determine the effect of different humic acid application methods on cotton yield, yield components, nutrient uptake and fiber technological characteristics. The study was conducted at Siirt University Faculty of Agriculture Department of Field Crops experimental area as randomized complete block design with four replications in 2016. Stoneville 468 cotton variety and TKI Humas humic acid were used as material. Seven different humic acid applications were performed as Control, To Soil, Seeds, Leaves at Pre-Flowering Stage, Leaves at Flowering Stage, Soil + Leaves at Pre-Flowering Stage and Seeds + Leaves at Flowering Stage. The results of variance analysis showed that seed cotton yield, fiber yield, number of boll per plant and seed yield weight per boll significantly affected from different humic acid applications. On the other hand, days of flowering, first opening days of bolls, plant height, monopodial branches, sympodial branches, the number of first vegetative branche's node, number of nodes, height / node rates, boll weight, 100 seeds weight, ginning percentage, first harvest percentage, leaf chlorophyll content (SPAD Values), GreenSeeker (NDVI values) and fiber technological characteristics were not affected from different humic acid applications. The results of leaf analysis showed that the leaf content of potassium, calcium, sodium, magnesium, zinc and copper affected from different applications, while nitrogen, iron and manganese were not. The different application of humic acid significantly affected the soil content of phosphorus, potassium, calcium, sodium, magnesium, iron, zinc and copper, but not nitrogen. It was determined that seed cotton yield, fiber yield, number of boll per plant; nitrogen, calcium and magnesium content of leaves; phosphorus and sodium content of soil increased by different humic acid applications. Sodium and zinc content of leaves increased by soil application of humic acid, while copper content decreased. Potassium, iron and manganese content of soil increased by humic acid applications to the seeds. Additionally, at pre-flowering stage application of humic acid to the leaves and seeds increased the content of calcium, magnesium and copper in soil. It was concluded that application of humic acid at pre-flowering stage to green parts of plants is more suitable than other applications in cotton.