Experimento de adubação em arroz de sequeiro.

Abstract

ABSTRACT 1: In the present work, the authors report the results obtained in a fertilizer experiment with rice, carried out af the Escola de Agronomia da Anmzônia, in a yellow Latosol. The best treatments were farm manure with mineral fertilizers and farm manure alone which gone yield of 2.220 and 1709 kg/ha respectively, representing increases of 138% and 83% over the control. However, considering the cost of fertilizers, both treatments would be uneconomical under present conditions.

ABSTRACT 2: The cemtral theme of the present work is photosynthesis and the author takes into consideration the primar/ productivity, biological productivity, and agricultural productivity of plants. The importance of total leaf area, efective assimilation rate, photosynthetic efficiency, relative growth rate, leaf area ratio, leaf arrangement (Plant architecture) and coordination of plant growth, is taken into consideration in order to arrive at conclusions concerning productivity in the tropics.

ABSTRACT 3: The increase in solubility of soil phosphorus and. pchassium, and the riss in pH, after' being flooded with water, was determined in lowland soils (várzea soils) of Guamá river Belém, Pará, Brazil, in a period of 120 days. In a soil sample taken under forest, it was found a rise from 14 ppm P2O5 in dry soil, to 98 ppm, within 40 days. The same kind of soil, under cultivation, showed a rise from 6 ppm, to 49 ppm, within 25 days. After reaching a peak PH remained practically unchanged too. The stabilization in a high levei of soluble phophorus irter a long time submergence is not in agreement with Pcnnamperuma's findings (Ponnamperuma, 1964). No change has been detected in potsssium solubility arher flooding.

ABSTRACT 4: The purpose of Ihis work was to find out a method for determining total, inorganic, and organic phosphorus content in soils containing a high content in free iron, as it commonly occurs in Amazonian soils. It was followed the method used by MEHTA et al, with a modification consisting in the elimination of cations through a changing resin strongly acid the washing of the extracting column with a 1% acetic acld solution, in order to separate the phosphorus retained by the resin particles and adsorved in silica from the sample, in the upper part of the column.