Effects of foliar application with effective microorganisms on leaf metabolism and seed yield in soybean.

Abstract

Photosynthesis and nitrogen metabolism are the most important physiological and biochemical processes in soybean plants. It is important to find agronomical practices to improve these metabolic processes in order to increase grain yield and quality. In this study, a field experiment was conducted using effective microorganisms (EM) to see whether EM can show the expected effects on soybean plants, with three treatments of EM spray concentrations, 0% (CK), 0.1%, and 0.5% at flowering (August 4) and podding (August 14) stages. Metabolic changes of soybean leaves were measured on August 8, August 19, August 29 and September 9 with the 16th, 18th, 18th, 21st functional leaves separately. Photosynthetic rate and stomatal conductance in functional leaves were increased by EM treatments. Nitrate reductase (NR) activities were improved by EM spray treatments. As a consequence, spraying EM increased seed protein and crude fat concentration and increased seed yield. Introduction Foliar applications of plant growth regulators or chemicals are widely used in crop and vegetable cultivation to promote plant growth and enhance yield especially under adverse environmental conditions such as nutrient deficiency and drought. Bio-products and microbial inoculants have been introduced to modern agriculture to produce food with good quality and safety in recent years. A microbial inoculant containing many kinds of naturally occurring beneficial microbes called Effective Microorganisms has been used widely in nature and organic farming (Xu, 2000a). Studies have shown that applying EM increase crop productivity and diseases resistance (Iwaishi, 2000; Mridha et al, 1999; Samy et al, 1995; Sangakara, 1995; Wang et al, 1999; Xu, 2000b; Yamada et al, 2000). However, the mechanism of the effect of EM was not clear in many aspects and there might exist some kinds of active substances in the fermented solution (Xu, 2000b). So far, we know little about whether EM affects seed yield and seed quality in soybean plants. In the present study, photosynthesis, stomatal conductance and nitrate reductase (NR) activity of functional leaves were measured, and seed yield and seed quality were analyzed in field-grown soybean plants with foliar application of diluted EM solutions. Materials Soybean plants (Gycine max cv Liaodou 10) were grown in plots each with an area of and Methods 5.0x3.0 m. The plots were in randomized block design with three replications. Plant density was 1.95x10 h with a 0.6-m row spacing and a 0.093-m plant spacing. Organic fertilizer and diammonium phosphate were applied at 15,000 kg h and 225 kg h, respectively. Foliar applications of EM diluted at 1:1000(0.1% EM) and at 1:500(0.5% EM) were conducted at flowering (August 4) and podding (August 14) stages. The control (C) was spraying water. Photosynthesis and stomatal conductance of leaves were measured using a LI-6200 Portable Photosynthesis System (LI-COR Inc NE USA) on a clear day during 10:00 12:00 am, with gentle wind and a photosynthetic photon fluxes over 1200 μmol m s. Nitrate reductase (NR) activity in leaves was measured using the live-tissue method. Results and Photosynthesis in functional leaves Discussion Photosynthesis is one of the most important factors that affects soybean seed yield. As shown in Table 1, photosynthesis was much higher in 0.1% EM than in C at the stages of August 19 (p Soybean plants treated with diluted EM solution (at 0.1% and 0.5%) produced more seed yield with higher protein and crude fat concentration. These were due to the higher nitrate reductase activity and photosynthetic capacity that benefited from higher leaf stomatal conductance in functional leaves during mid-growth period. Results of the present study suggest that EM can be used as a regulation substance to improve metabolisms of crop plants for yield promotion and quality improvement. References Iwaishi Shinji. 2000. Effect of organic fertilizer and effective microorganisms on growth, yield and quality of paddy-rice varieties. In:Hui-Lian Xu. James F. Parr and Huroshi Umemura (ed.), Nature Farming and Microbial Applications, 269-274. Mridha, M.A.U., H.U. Chowdhuary, H.L. Xu and H. Umemura. 1999. Influence of effective microorganisms on seed germination and growth of some crop p lants. In: Hui-Lian Xu (ed.), Nature Farming and Sustainable Environment 127-130. Sangakkara, U.R. 1995. Effects of EM on vegetable production in Sri Lanka: An economic analysis. In: Kyusei Nature Farming (Fourth International Conference), 217-222. Wang Ran, Hui-Lian Xu and M.A.U. Mridha. 1999. Effects of organic fertilization and EM inoculation on leaf photosynthesis and fruit yield and quality of tomato plants. In: Hui-Lian Xu (ed.), Nature Farming and Sustainable Environment 119-126 Samy, J., A. Xaviar, A.B. Rahman and H. A. H. Sharifuddin. 1995. Effect of EM on rice production and methane emission from paddy fields in Malaysia. In: Kyusei Nature Farming (Fourth International Conference), 208-210. Xu Hui-Lian. 2000a. Nature farming: History, principles and perspectives. Journal of Crop Production. 3 (1), 1-10. Xu Hui-Lian. 2000b. Effects of a microbial inoculant and oganic fertilizers on the growth, photosynthesis and yield of sweet corn. In:Hui-Lian Xu. James F. Parr and Huroshi Umemura (ed.), Nature Farming and Microbial Applications, 139-156. Yamada Kengo and Hui-Lian Xu. 2000. Properties and applications of an organic fertilizer inoculated with effective microorganisms. Journal of Crop Production. 3 (1), 255-268.

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