The use of iron hydroxide‐impregnated filter paper (Pi) strips as a collector for phosphorus (P) in soil suspension offers a new approach to soil testing for plant‐available P. To correlate the Pi test with crop response, four soils ranging in pH from 4.5 to 8.2 were incubated with three rates of P either as triple superphosphate (TSP) or central Florida phosphate rock (CFPR), and P was measured in these soils by the Pi, Bray 1, Bray 2, double acid, Olsen, water, and resin extraction methods. Two successive crops of maize (Zea mays L.) were grown on these soils in greenhouse pots, and the dry matter yield and P uptake by maize were correlated with the soil test values. The Pi gave highly significant correlation with crop response in all four soils. Across all soils, P source, rates of application and crops, Pi gave the best correlation (0.870) with P uptake and dry matter yield. The next best correlation with dry matter yield was that of Olsen extractable P. The Pi test showed potential as a tool for prediction of P fertilizer requirements in soils.
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Following resective extratemporal epilepsy surgery, AED can be successfully discontinued in only in a minority of patients. One-third of patients who recur fail to regain seizure control upon AED reintroduction. Longer duration of epilepsy prior to surgery, abnormal postoperative EEG, early postoperative seizures, and focal gliosis or dysplasia as substrate predispose to seizure recurrence. This information will be helpful in making rational decisions on AED withdrawal following extratemporal resective epilepsy surgery.
Quantitative estimation of the enhancement effect of water‐soluble P on P availability from phosphate rock (PR) has not been reported. The objective of this study was to use radioactive 32P as a tracer to distinguish P availability from soil, PR, and TSP so that P uptake by crops from PR in the presence of TSP could be estimated. Three sets of 4‐kg soil samples of an acid Hartsells silt loam (fine‐loamy, siliceous, thermic Typic Hapludult, pH 4.8) were mixed with the following treatments: (i) 32P solution and central Florida PR (CFPR), (ii) 32P‐tagged TSP, and (iii) 32P‐tagged TSP and CFPR at a P ratio of 50:50. The rates of P applied were 0, 12.5, 25, 50, 100, and 200 mg P kg−1. For treatment (iii), an additional rate of 400 mg P kg−1 was also prepared. Maize (Zea mays L.) and cowpea (Vigna unguiculata [L.] Walp. ssp. unguiculata) were planted and harvested at 42 d after planting for maize and 45 d for cowpea. The effectiveness of P sources in terms of increasing dry‐matter yield and P uptake followed the order of TSP >‐ (CFPR + TSP) > CFPR for maize and TSP = (CFPR + TSP) > CFPR for cowpea. Phosphorus uptake from CFPR in the presence of TSP was higher than P uptake from CFPR applied alone, indicating an enhancement effect of TSP on the effectiveness of CFPR. The increase in P uptake from CFPR due to TSP influence, across all the PR rates applied, was 3.48 mg P pot−1 for maize and 1.38 mg P pot−1 for cowpea. With respect to P uptake from CFPR applied alone, the corresponding relative increase in P uptake from CFPR due to TSP influence was 165% for maize and 72% for cowpea.
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