Effects of coralline lime, in combination with 3 kg Cu ha-1 plus 3 kg Zn ha-1, on yield and nutrient uptake by peanut (Arachis hypogea) were studied at three locations in Western Samoa. Coarse (0-10 mm) coralline lime material containing 3 I. 1% Ca and 1.7% Mg was used as lime at 0, 555, 2222 and 5000 kg ha -1 . In the Togitogiga soil, which had the lowest level of exchangeable Ca, peanut yield increased by 6 fold after liming with 555 kg ha -1 , relative to the unamended control. This yield increase was associated with reduced Mn toxicity as well as reduced Ca deficiency. The alleviation of Mn toxicity was not likely due to decreased Mn solubility because the lime application (555 kg ha -l) increased soil pH by < 0.1 unit. Rather it was the increased Ca availability which reduced the Mn toxicity through a Ca/Mn antagonism. The critical range of exchangeable Ca for peanut growth was found to be about 1.5-1.6 cmot ½Ca 2+ kg -t . A Ca/Mn-ratio >80 was required for a desirable Ca/Mn balance in peanut tissue. On the other two locations (with exchangeable Ca levels of 1.5-1.6 cmol ½Ca 2+ kg-I), liming increased peanut yields by 15-20%. Additions of Cu plus Zn also increased the yields, although the increases were small (7%) and not significant at the 95% probability level.
Liming values of calcium carbonate (CaCO3) and cowpea green manure were evaluated on an acid Oxisol (Typic Acrorthox, Togitogiga series), based on seed yield and tissue composition of sweet corn (Zea mays), and soil chemical properties. Application rates were 0, 5, and 10 Mg/ha for CaCO 3 and 0, 7.5, and 15 Mg/ha for the green manure, factorially arranged. Treatments with commercial NPK fertilizers were included for comparison. Growth and yield of sweet corn showed that soil acidity can be corrected by either lime or green manure additions. Both lime and manure raised soil pH and (modified Truog) extractable phosphorus (P), which were partially responsible for yield increases. Green manuring significantly increased plant P and potassium (K) concentrations, which explain why the manure was more effective than lime in increasing corn yield. Ear leaves sampled at tasseling required at least 0.25% P and 2.4% K to attain >90% of the maximum seed yield.
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