Effects of Soil Amendment with Crab Shell on the Growth and Nodulation of Soybean Plants(Glycine max Merr.)

Abstract

Three pot experiments were conducted to investigate the effects of soil amendment with crab shell on (1) soybean (Glycine max Merr., cv. Akishirome) yield after 120 days outdoors, (2) soybean nodulation after 6 weeks in the greenhouse, and (3) soil chemical properties after 10 weeks in the greenhouse. The experimental treatments were addition of crab shell at rates of 0.1, 0.2, 0.3, 0.5, and 1% (w/w), standard fertilizer (NPK) treatment, and an untreated control with neither crab shell nor fertilizer application. The crab shell amendment treatment was applied either two months before seeding (incubated) or immediately before seeding (non-incubated). The soil used was a volcanic ash soil (Andosol) from Kakamigahara. Addition of crab shell just before seeding caused a significant increase in seed yield and 100-seed weight compared to the control, but similar yield to NPK treatment. However, seed yield and 100-seed weight did not differ with the crab shell application rate. Amendment by 0.1-0.3% crab shell without incubation lead to the formation of slightly more nodules than in the NPK and control treatments. Reduced numbers of nodules were observed in soil incubated at 0.5- 1%, and in non-incubated soil with 1% crab shell application. Nodule fresh weight and N₂-fixation plant^-1 were decreased in all incubation treatments and 0.3-1% non-incubation treatments as compared to the NPK treatment and the control. Both nodule fresh weight and N₂ fixation were lower in incubated soils than in non-incubated soils, at corresponding rates of crab shell treatment. Dry matter production of soybean plants in soil given the crab shell treatment, especially when incubation was used, was found to be reduced after 6 weeks of plant growth. EC, N, and P availability increased with the increasing rate of crab shell treatment. However, there was a gradual decrease of soil pH following the crab shell treatment. In conclusion, although soybean nodulation and N₂ fixation were not improved by crab shell application, seed yields were similar to those obtained with the NPK fertilizer.