SEED COTTON YIELD AND NUTRIENT CONCENTRATIONS AS INFLUENCED BY LIGNITIC COAL DERIVED HUMIC ACID IN SALT-AFFECTED SOILS

Humic acid (HA) can supplement the chemical fertilizers to reduce the input cost of agricultural production. Field experiments on increasing cotton [Gossipium hirsutum L, cv. CIM-473] crop yield through HA were conducted in salt-affected soil of Kohat division, NWFP, Pakistan, during Kharif 2005 at two sites being irrigated with tube-well saline waters. Four levels of humic acid (0, 0.5, 1.0 and 2.0 kg ha^-1) were applied alone or with recommended dose of NPK (90:60:30 kg N:P2O5:K2O ha^-1). Results showed that seed cotton yield (seed+cotton fiber) significantly (P 0.05) responded to both HA and NPK levels at both sites. When averaged across levels of NPK, application of 0.5, 1.0 and 2.0 kg ha^-1 HA increased seed cotton yield by 10.5, 15.6 and 13.5 at site 1 and 12.2, 17.7 and 21.2 % at site 2 as compared to control while such increases reached to 30.5, 42.5 and 35.3 % at site 1 and 23.4, 37.7 and 31.1 % at site 2 when the same HA levels were applied with NPK. Combine application of 0.5, 1.0 and 2.0 kg HA ha^-1 plus NPK enhanced seed cotton yields by 9.01, 19.03 and 13.02 % at site 1 and 5.02, 17.18 and 11.51 %, in site 2, respectively as compared to plots receiving NPK (90:60:30 kg ha^-1) alone. The seed cotton yield increased by 19.69 at site 1 and 17.52 % with NPK as compared with control. The results suggested that addition of 1.0 kg ha^-1 could supplement NPK fertilizer and enhance farmer’s income by increasing yield in arid zone salt affected soils.