Evaluating methods to predict potassium levels for optimum greenhouse tomato production (Lycopersicum escolentum Mill. var. Tropic)
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Date
1976
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Abstract
Two techniques were evaluated to predict the potassium (K) status of greenhouse tomatoes produced on a Lakeland loamy sand, "with a deficiency in K", "with an adequate K" and "with K accumulating in the soil". The three different L fertility levels were obtained by fertilizing a leached Lakeloand loamy sand with rates of 1.82, 3.65 and 7.30 kg K/ha/day. Also, two hydroponic cultures with different K fertilizer treatments (150 and 300 ppm K) were utilized to monitor fluctuations due to seasonal changes in the immature and mature petiole K concentrations, petiole weight ratios (fresh weight to oven-dried weight) and petiole lengths. In both soil and hydroponic cultures, fruit yields were significantly increased with the high K fertilizer rates. On the soil culture, 1.82, 3.65 and 7.30 kg K/ha/day produced these yields, 9.16, 10.13 and 10.79 kg fruit/plant, respectively. On the hydroponic culture, 150 and 300 pm K produced 8.79 and 9.35 kg fruit/plant, respectively. Soil analyses for K were made with two K extractants, H₂O and 1.2 N NH₄OAc adjusted to pH 4.2 with HCl. At the higher fertilizer rate (7.30 kg K/ha/day), both extractants showed an exponential accumulation of K on the Lakeland loamy sand. After the exponential accumulation of K in the soil, the K concentration in the mature petiole increased 28 days later..
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Tomatoes, Soil Chemistry