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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%.

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The effect of the plant regulator Mepiquat chloride (PIXᵀᴹ) (1,1-dimethyl-piperidinium chloride), in the early flowering stage, and combinations with soil and foliar application of fertilizers was investigated through seven field experiments conducted in 1982 and 1983 at three University of Arizona experimental locations. Three upland cotton cultivars (Gossypium hirsutum L.), 'Deltapine 55', '61' and '62' were used. Cotton yield, boll properties, fiber properties, leaf chlorophyll content, plant height, plant partitioning and maturity were investigated. Petiole nitrate, leaf area index (LAI) and LAI interrelationship with yield were also included in this study. The use of PIX resulted in an increase in seed cotton yield and boll weight in one of the experiments, while fiber properties did not show any significant response to either PIX or fertilizers. PIX, however, had the tendency to enhance maturity by about 1 week. Use of PIX reduced plant height in all tested cultivars at all locations. The reduction in plant height ranged from 7 to 28% depending on the cultivar, location and the amount of PIX applied. The chlorophyll a and b content of leaves increased significantly as a result of PIX application in two of four tests, while their ratio decreased. Leaf area index between treatments were not significantly different except at one sampling date. In a regression study, however, yield was found to be related positively to LAI when soil and foliar application of fertilizer were added, while it was negative when PIX was applied. Neither PIX nor BALANCEᵀᴹ (1:18:18:1) application affected plant partitioning nor petiole nitrate concentration at most of the sampling dates.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

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