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University of KwaZulu-Natal (2015)

Agronomic studies on edamame (vegetable soybean) in KwaZulu-Natal.

Arathoon, Arthur James

Titre : Agronomic studies on edamame (vegetable soybean) in KwaZulu-Natal.

Auteur : Arathoon, Arthur James.

Université de soutenance : University of KwaZulu-Natal

Grade : Master of Science in Agriculture 2015

Résumé
Vegetable soybean (Glycine max (L.) Merrill), also known as edamame, originated in China, but is now grown in many parts of the world, where its high protein content and beneficial health benefits are being recognized as a valuable food source for human consumption. The green pods are picked at the R6 growth stage when the beans have filled 80 - 90% of the pod. The pods are shelled and the beans are eaten, usually as a snack or included in salads, stir-fries and soups. _ Vegetable soybean is poorly known in South Africa. However, as in South East Asia, the crop could be economically viable for small-scale and commercial farmer production. As minimal previous research had been conducted on vegetable soybean in South Africa, the objectives of this study were to identify the best performing cultivars for KwaZulu-Natal, determine the most suitable seeding rate, determine the crop‟s phosphorus and potassium requirements, to evaluate the effect of seed coatings with fungicides and Bradyrhizobium japonicum Kirchner inoculants on plant population, nodulation and yield, and to estimate the costs and profitability of producing and marketing the crop. The research trials were conducted primarily on the Cedara Research Station (latitude 29°32’S ; longitude 30°16’E ; altitude 1051 m), but also on the Dundee Research Station (latitude 28°13’S ; longitude 30°31’E ; altitude 1219 m), of the KwaZulu-Natal Department of Agriculture and Rural Development, South Africa. _ Two medium-season cultivars (AGS 353 and AGS 354) and two long-season cultivars (AGS 352 and Lightning) were evaluated at the Cedara Research Station at seeding rates of 200 000, 300 000, 400 000 and 500 000 seeds ha-1 in four plantings from 2005 to 2008. No significant differences in mean seed yield were measured between the seeding rates. However, a significant interaction was measured for seed yield between the cultivars and seasons. AGS 354 produced significantly greater yields in the higher production seasons, 2007/08 (1) and 2005/06, and produced a significantly higher mean yield than AGS 352 and Lightning. Lightning produced the highest yields in the low production seasons, 2006/07 and 2007/08 (2), and the lowest yields in the high production seasons. AGS 352 produced the lowest yields in the lower production seasons. Similarly, at seeding rates from 50 000 to 250 000 seeds ha-1, no significant differences in mean seed yield were measured between the seeding rates for AGS 353, AGS 354, Lightning and the short-season cultivar, AGS 292, when evaluated in the 2012/13 and 2013/14 seasons. However, AGS 292, which was only evaluated in the 2013/14 season, yielded significantly better from 150 000 to 250 000 seeds ha-1 than from 50 to 100 000 seed ha-1. Due to the short plant height of AGS 292, the plants did not canopy in the 0.75 m wide rows and weeds competed with the crop, resulting in a low mean yield of 1.9 t ha-1 compared to the mean yield of 3.5 t ha-1 for the other three cultivars. Although significantly more branches plant-1 were produced by AGS 292 at the lower seeding rates, no significant differences in the number of pods plant-1 were measured. In both experiments, plant population was not significantly correlated to yield. Overall, as seeding rate decreased, plant height and bottom pod height decreased significantly, whilst significantly more branches containing more pods were produced per plant, but significantly fewer pods per hectare were produced. Seed size decreased significantly as the seeding rate increased from 200 000 to 500 00 seeds ha-1, but not at seeding rates from 50 000 to 250 000 seeds ha-1. At seeding rates from 200 000 to 500 000 seeds ha-1, no significant differences in the percentage export marketable pods were measured between the seeding rates. However, at seeding rates from 50 000 to 250 000 seeds ha-1, significantly higher percentages of export marketable pods were measured from 50 000 to 150 000 seeds ha-1 than from 200 000 to 250 000 seeds ha

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