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Chemical composition of garden bean plant and the uptake of nutrients from the stage of blooming to maturity

The purpose of this investigation was to gain information on the rate of dry matter production and nutrient absorption of bean plants. Samples of fertilized and unfertilized bean plants, grown on «terra-roxa-misturada» type of soil at Campinas and under field conditions, were taken at various stages of growth. They were divided in roots, stems, leaves and fruits and have been analyzed for N, P, K, Ca, Mg, and S. At maturity the seeds were separated from the pods and analyzed separately. With the exception of calcium in the leaves, the percentage of all mineral elements tended to reach a maximum in the various plant parts at about blooming and pod-forming stage. The total seeds and pods contained more nitrogen and phosphorus, and less calcium, magnesium and sulphur throughout the season. The percentages of potassium, calcium and magnesium in leaves were higher than in other plant parts. Total sulphur content was higher in the roots than in leaves, stems or pods plus seeds. Nitrogen and potassium were absorbed in greater total amount than phosphorus and other elements. The unfertilized mature plants contained 29 and 23 kg of nitrogen and potassium respectively per hectare. Phosphorus was absorbed in a smaller amount than any other nutrient studied. The maximum absorption rate changed according to the element and was modified by treatment. In fertilized plants the maximum rate of uptake of calcium and magnesium from the soil ocurred during the interval 33 to 44 days from sowing; potassium, 44 to 53 days; and nitrogen, phosphorus and sulphur, 53 to 65 days, the period of growth of seed in the pod. Table 7 shows the distribution of total nutrient in roots, stems, leaves, and pods plus seeds in the mature plant. Data presented in the foregoing pages suggest certain practical considerations of interest. Environmental conditions during the early growth stages were generally favorable, but a deficiency in precipitation that occurred in the period of pod formation and seed development depressed the yield. However, fertilization promoted an increase in the uptake of nutrients, dry matter production, and in yield of bean. Since only the level of phosphorus was higher in the plant of the fertilized plot, it is assumed that phosphate fertilization induced such increase. Analytical results indicate that relatively large quantities of bases will be removed from the land if the entire bean plant is harvested, whereas if seeds alone are harvested only nitrogen and phosphorus are removed in relatively large amounts. The soil becomes most impoverished by the removal of potassium, nitrogen being less affected due to a partial supply from fixation of atmospheric nitrogen. The results showing that nitrogen absorption rate is maximum at the time the seeds are developed suggest that a delayed nitrogen application for beans might be desirable since the plant needs at this stage may not be satisfied by nitrogen fixation alone. This late nitrogen application would not interfere with the early steps of the symbiotic process.


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