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Effect of Defoliation on Photosynthesis, Dry Matter Production and Yield in Soybean

Dr. Md. Tariqul Islam
Principal Scientific Officer and Head
Crop Physiology Division, Bangladesh Institute of Nuclear Agriculture, BAU Campus, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

Two pot experiments were conducted to assess the effect of various degree of defoliation on photosynthesis, dry matter production and yield in soybean. Defoliation significantly increased rate of photosynthesis and transpiration and leaf conductance of the soybean genotypes however, it decreased dry matter production and yield.

Keywords: Defoliation, Dry matter, Photosynthesis, Soybean yield

Location: BINA, Mymensingh

Start Date: 01-01-2010

End Date: 30-05-2011

Program Area: Crop-Soil-Water Management

Commodity: Soybean

Objectives:

The objective of the study was to investigate the effect of the magnitude and positions of leaf removal during the beginning of reproductive phase on photosynthesis, dry matter production, yield attributes and yield in soybean.

Methodology:

Two experiments were conducted at the pot yard of Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh (24⁰8´ N 90⁰0´ E), Bangladesh during January-May, 2010 and 2011. Four soybean genotypes viz., BARI Soybean-5, BAU Soybean-109, AVRDC Soybean-78 and BAU Soybean-147 were subjected to different defoliation treatments viz., control (undefoliated), 50% basal leaf defoliation, 100% defoliation, 50% defoliation of top leaves, defoliation of top four leaves, defoliation of top three leaves, defoliation of top two leaves and defoliation of top one leaf. The experiment was laid out in complete randomized design with four replications. Additional 24 pots were taken to grow six plants of each genotype for leaf area calculation. Several seeds were sown in plastic pots containing 8 kg soils (Silty loam, organic matter 1.05%, total N 0.07%, available P 14.3 ppm, exchangeable K 0.25 meq. per 100g soil, available S 13.2 and soil pH 6.67). Finally one plant was allowed to grow in each pot. Urea, triple superphosphate and muriate of potash were used as a source of nitrogen, phosphorus and potassium at the rate of 1.66, 2.82 and 1.16 g pot^-1, respectively, corresponding dose of 50, 85 and 35 kg ha^-1, respectively, at the time of final pot preparation. Leaf area of top one compound leaf represented about 6-10% of the total leaf area plant^-1measured in automatic leaf area meter. Cultural practices were done as and when required. Defoliation treatments were imposed at 53 DAS. Data on photosynthetic parameters were measured at 60 DAS using Portable Photosynthesis System. Dry mass and yield attributes were taken at maturity. All data were analyzed statistically as per the used design following the analysis of variance (ANOVA) technique and the mean differences were adjusted with Duncan’s Multiple Range Test (DMRT) using the statistical computer package program, MSTAT-C.

Source of Information: Bangladesh J. Bot. 43(3): 261-265, 2014 (December)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Defoliation treatments decreased yield in soybean in following order as 100% defoliation, 50% defoliation of top leaves, defoliation of top 4 leaves, defoliation of top 3 leaves, 50% defoliation of basal leaves and defoliation of top 1 or 2 leaves did not affect yield. With defoliation of either 1 or 2 top leaves, yield production remained same as compared to undefoliated control. This indicates that physiological mechanisms might have rejuvenalized just after defoliation by defoliation of either 1 or 2 top leaves threshold level by initiating new leaves and could be one of the reasons that compensated this leaf loss.

Knowledge Management: Journal