INFLUENCE OF PHOSPHATE FERTILIZER ON GROWTH, YIELD, COMPOSITION OF ROOTS AND CHARACTERISTICS OF STARCH IN CASSAVA CULTIVATED BY TWO VEGETATIVE CYCLES

Abstract

Brazil is a country with a natural vocation for agribusiness due to its characteristics and diversities, mainly found in the favorable climate, soil, water, relief and luminosity. Cassava is a tuberous root grown in all Brazilian states and the second largest source of commercial starch in the country. In Brazil most cassava crops grown for industrial purposes have been harvested with two vegetative cycles and adequate plant nutrition is one of the essential factors to increase cassava growth and biomass accumulation. Phosphorus (P) has been a nutrient that promotes pronounced and frequent responses in cassava, and plays an important role in the synthesis of starch in plants. Starch due to its physic-chemical and functional properties has great importance in the most diverse food and non-food industrial sectors. The starch consumer and productive market has constantly sought starches with properties that meet the most diverse requirements, however, the interference of cassava growing conditions on starch properties has still been little explored, justifying the importance of research that integrates knowledge of the growth conditions and technology of starch. This work has as objectives: to evaluate the growth, productivity and accumulation of phosphorus and starch in cassava cultivated under different levels of phosphate fertilization, to study the effect of the stage of development of the cassava plant on the structural and physicochemical characteristics of starches and finally to evaluate the interference of fertilization rates on the structural and physicochemical characteristics of cassava starch. In order to reach the objectives, an experiment will be carried out with cassava cultivar IAC 14 in randomized blocks and in a subdivided plot scheme, with four replications. The plots consist of four levels of phosphorus (P) supply and the subplots are formed by five plant harvest times during the cycles. The variables that will be evaluated are: A) leaf diagnosis; B) number, length, diameter and average weight of tuberous roots; C) accumulation of dry matter (DM) in leaves, stems, strains and tuberous roots; D) MS accumulation rate; E) partition of assimilates; F) content, accumulation and export of P; G) content and accumulation of starch; H) final population of plants; I) yield of tuberous roots. Starch extraction will also be performed at the six root harvest times and the starches will be analyzed for crystallinity, granule shape and size, phosphorus content, amylose, swelling power, solubility, pasting and thermal. The obtained data will be submitted to analysis of variance. The means of the treatments with P levels will be compared by the t test (DMS) (p <0.05), while the effects of the plant harvest times will be evaluated by regression analysis. The results obtained will be divulged through participation in events and publication of articles in scientific journals. (AU)