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Title: SOIL ACIDITY EFFECTS ON GROWTH AND NUTRITION OF CACAO

Author
item Baligar, Virupax
item FAGERIA, N - EMBRAPA, BRAZIL

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/22/2004
Publication Date: 8/5/2004
Citation: Baligar, V.C., Fageria, N.K. 2004. Soil acidity effects on growth and nutrition of cacao[abstract]. 6th International Symposium Soil-Plant Interactions at Low Ph - Sendai, Japan.

Interpretive Summary:

Technical Abstract: Cacao (Theobroma cacao L) is grown from 18 degrees N to 15 degrees S of the equator on a wide range of soils. Abiotic (soil moisture, soil acidity, Al toxicity, deficiencies of essential nutrients) and biotic (diseases/pests) stresses are largely responsible for low yields of cacao. Research was undertaken in a climatically controlled growth room (28 degrees C day/28 degrees C night, 75% RH, PPFD of 350 micro moles/m2/s light, for 14h), to evaluate the effects of three levels (0.2, 21, and 31%) of soil Al saturations on growth, relative growth rate, net assimilation rate, and nutrient uptake parameters of cacao. Decreasing soil Al saturation increased shoot and root dry weight, root length, stem height, relative growth rate, leaf mass/unit leaf area and net assimilation rate. However, decreasing soil Al saturation decreased leaf area, specific leaf area, and leaf area ratio. With few exceptions, overall decreasing soil Al saturation increased uptake, influx, and transport for N, P, K, Ca, Mg, Cu, and Fe, and decreased uptake, influx and transport for Na, B, Mn, and Zn. Increasing soil Al saturation increased nutrient use efficiency ratio (ER) for Ca and Mg, and decreased ER for other elements under consideration. Reduction of soil acidity constraints, with the addition of lime and maintenance of adequate levels of essential nutrients, appear to be key factors in improving cacao yields in tropical soils.