Influence of nitrogen and row spacing on soybean [Glycine max (L.) Merrill)] yield, nitrogen, carbohydrate, protein content, and water use

Author

Wan Mohomad Kadir

Date of Award

12-1987

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant, Soil and Environmental Sciences

Major Professor

W. L. Parks

Committee Members

J. H. Reynolds, J. D. Wolt, J. B. McLaren

Abstract

The study, conducted over two years, attempted to measure the responses of two soybean [Glycine max (L.) Merrill] cultivars, namely 'Essex' and 'Asgrow 5474', grown under different rates of nitrogen (N) fertilization and row spacings with irrigation. Prilled ammonium nitrate at the rates of 0,56,112, and 224 kg ha^-1 was broadcast just before pod-filling stage. The plants grown at 51,38,25, and 13 cm row spacings. Tissue samples for N determination, consisting of the most recently matured trifoliates from experimental plots, were collected at about weekly intervals beginning at the time just before fertilizer application and continued until the plants reached physiological maturity in 1986. Similarly, tissue samples for water soluble carbohydrate determination, consisting of upper, middle, and lower trifoliates, were collected from plants subjected to 0 and 112 kg N ha^-1at four row spacings. Besides recording the bean yields, seed samples from individual plots were also taken to be analyzed for protein content. In relating water use efficiency of the crop, apparent evapotranspiration rates and leaf area index were measured and recorded from 'Asgrow 5474' soybean plants subjected to 0 and 112 kg N ha^-1 at four row spacings. These measurements were recorded commencing from four weeks after planting until the plants reached physiological maturity. The 1986 study with 'Essex' and 'Asgrow 5474' soybean cultivars showed that applying N fertilizer at the rates of 0, 56,112, and 224 kg ha^-1 and planting with the row spacings of 51,38,25, and 13 cm, did not have any significant effect on the N content of leaves. As plants reached physiological maturity, the leaf N content decreased rapidly beginning from R5 stage, i.e. when beans begin to develop at one of the four uppermost nodes with a completely unrolled leaf. Applying N at 0 and 112 kg ha^-1 with four spacings did not result in any significant effect on the water soluble carbohydrate content of upper, middle, and lower trifoliates of either soybean cultivar. However, the water soluble carbohydrate content in the leaves initially decreased starting from R4 (when the pod is 2 cm long at one of the four uppermost nodes with a completely unrolled leaf) to R6 (when the pod contains full size green beans at one of the four uppermost nodes with a completely unrolled leaf) stage and increased for two weeks, followed by a marked decline thereafter, until the plants reached physiological maturity. Significant yield increases were observed for both soybean varieties planted in narrow rows. Nitrogen fertilization did not have any significant effect on the yields. Seed protein contents were not affected by N fertilization or row spacing. Water use efficiency of 'Asgrow 5474' cultivar under 0 and 112 kg N ha^-1 increased as row spacings were narrowed. The average rate of soil moisture use by the plants for all row spacings was 0.71 cm d^-1 Peak moisture use occurred when maximum leaf area index was reached.

Recommended Citation

Kadir, Wan Mohomad, "Influence of nitrogen and row spacing on soybean [Glycine max (L.) Merrill)] yield, nitrogen, carbohydrate, protein content, and water use. " PhD diss., University of Tennessee, 1987.
https://trace.tennessee.edu/utk_graddiss/7786