Department of Agronomy

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Browsing Department of Agronomy by Author "Bilbe, Sara Ann"

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    The relationship between soybean (Glycine Max (L.) Merrill) seed quality and the response to molybdenum seed treatment
    (Stellenbosch : Stellenbosch University, 2000-12) Bilbe, Sara Ann; Pieterse, P. J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.
    ENGLISH ABSTRACT: Experi!11entsin KwaZulu-Natal showed that seed treatment with molybdenum (Mo) could double the yield and increase the protein content by 1.9% of soybeans grown on acidic soils. However, it was also found that soybean yield at five of the localities was reduced on average by 8% after Mo seed treatment. It was surmised that the yield reductions observed after Mo seed treatment were connected to the quality of the seed used for planting. The aim of this project was to assess the relationship between seed quality and Mo seed treatment and find a fast, easy quality assessment test that could be used to adapt Mo treatments according to seed quality. The first investigation entailed assessing the quality of the seed obtained, from various seed lots, for planting. A number of different seed quality testing techniques were performed and they included the accelerated ageing test, tetrazolium test, conductivity test, standard germination test and an emergence . test planted at different depths with incubation at different temperatures. All the test results were compared with the accelerated ageing test results, to find the test most closely correlated to the accelerated ageing test, which is regarded as the most accurate indicator of soybean seed vigour. It was found that the emergence test where the seeds where planted at 10 cm presented a close correlation with the accelerated ageing test. An assessment of seed quality revealed that the four different seed lots provided seed of three significantly different levels of quality, which could be used for further investigations. The second investigation was concerned with the reaction of the seed of different quality levels to Mo seed treatment. Firstly, seeds from four different seed lots were treated with five different concentrations of Mo and planted under acidic conditions. The establishment was monitored up until six weeks, at which point the experiment was terminated. In the second planting, seeds from the four different seed lots were treated with six different concentrations of Mo and planted under optimum pH conditions. Emergence was monitored and after thinning out the remaining plants were left to mature and produce seed. The emergence percentage results from both of these two plantings did not reveal the alleged positive effect Mo seed treatment has produced in the field and no definite relationship between seed quality and Mo seed treatment was observed. The third investigation was concerned with the effect that osmoconditioning had on the reaction of seed to Mo seed treatment. Seeds from two seed lots, one of very poor quality and the other of good quality, were pre-treated with four different levels of poly-ethylene glycol (PEG 6000) and then treated with four concentrations of Mo. They were planted under optimum pH conditions and establishment was monitored. After being thinned out the remaining plants were allowed to mature and produce seed. The emergence percentage results revealed that the PEG pre-treatments greatly improved emergence percentages, especially in the poor quality seed. There were some positive effects of Mo seed treatment observed where the lower concentrations of Mo were used, but again, no definite relationship between seed quality and Mo seed treatment was found. PEG pre-treatment appeared to help make the seeds more "resistant" to the harmful effects of Mo.