Nutrient uptake by surface and subsurface drip irrigated cotton

Abstract

Field experiments to compare absorption of nutrients by cotton plant (Gossvpium hirsutum L. Var. Deltapine 62) and their distribution in soil under surface and subsurface drip systems were conducted in 1984 and 1985 at the Campus Agricultural Center, University of Arizona in Agua fine sandy loam soil (Typic Torriflvents). The mixed fertilizer solution with labeled nitrogen-source was injected into surface and subsurface drip treatments in equal amounts. There were no significant differences among surface and subsurface drip treatments detected with respect to total nitrogen, phosphorus, potassium and zinc uptake by plants because of equal availability of nitrogen under both drip systems and sufficient initial levels of the other nutrients were found in this soil. Fertilizer application significantly increased total nitrogen, phosphorus, potassium and zinc uptake by cotton plants because N promoted more vegetative growth and therefore more dry matter production was obtained. Under all drip treatments and both labeled nitrogen sources, plants growing on unfertilized rows absorbed nitrogen-15 fertilizer mainly because of the extension of roots and some lateral movement of nitrate to the unfertilized rows. Significant differencs among surface and subsurface drip treatments were not detected with respect to absorption of nitrogen-15 and percentage of fertilizer nitrogen in plants. Consistent differences among ammonium (N-16) and nitrate (N-15) labeled sources were not observed with respect to percentage of fertilizer nitrogen in plants. The plant recovery of applied nitrogen was higher with the difference method than with the tracer method because the nitrogen fertilizer produced effects in the soil or on the ability of the plants to obtain soil nitrogen that did not occur in the unfertilized rows. Consistent differences between drip treatments were not observed with respect to the final nitrate, ammonium, phosphorus, potassium, zinc levels and total soluble salts in the soil horizontally or vertically. The range of the residual fertilizer nitrogen in the soil after the first growing season was 7 to 28%.