Revista Raízes e Amidos Tropicais

7

Authors: Manuel Alberto Gutiérrez Cuenca, José Henrique de Albuquerque Rangel, Edivilson Silva Castro Filho

The objective of this study was to analyze the evolution of cassava productivity in Alagoas state and to evaluate the impact of such evolution over the PGV Percentage Variation Tax (TXV% of PGV), in different biennium, over the whole period, and in three sub-periods between 1977 and 2009. Data encompassing the 1977 – 1998 period were collected from the Basic Statistic (IBGE, 1997), and data relative to the period from 1990 to 2009, collected from SIDRA (IBGE, 2011). Data were updated to December 2010 by the Prices General Index of Getulio Vargas Foundation (FGV, 2011). Cassava TXV% of PGV and the effect of productivity were calculated from the annual productivity. The TXV% of PGV was calculated for each season to check the oscillations of cassava PGV and TXV% of PGV growing sources inside those periods. The prices obtained by cassava producers, the harvested area, the production, and the PGV of cassava in Alagoas during the analyzed had negative variation of respectively 87%,55%, and 38% causing a PGV reduction of 92%. Means of productivity, and PGV obtained by cassava growers in Alagoas between 1977 and 2009 were respectively 11.37 t ha-1 and R$ 162.6 million. The maximum productivity of 14.38 t ha-1 was observed in 1989 and the maximum PGV of R$ 725.6 million at 1977. The lowest productivity of 8.67 t ha-1 happen in 1987 and the minimum PGV (R$ 30.8 million occurred in 2007. The percentage and direction of productivity and PGV variations were divergent in the majority of the biennium. Such behavior is a consequence that variations in area or prices or even in both annul or compensated the possible impact of the productivity over the PGV.

8

Authors: Amarilis Beraldo Rós

Cassava crop extracts large amounts of nutrients from the soil, especially potassium. This work aimed to evaluate the height of cassava plants, cultivar IAC 576-70, and the roots yield in function of different doses of topdressing potassium fertilization. The experimental design was randomized blocks with six replications. The treatments were potassium doses: 0, 20, 40 and 60 kg K2O ha-1 (KCl) divided in until three topdressing fertilizations and four periods of height evaluation: 110, 140, 170 and 200 days after planting. The harvesting of the roots occurred eight months after planting. There was rise in plants height with increasing of doses of potassium added to soil, but roots yield was not affected by the addition of the nutrient, it probably because the soil had adequate amounts of this nutrient to the plants. Thus, the topdressing potassium fertilization does not increase the cassava yield in soils with adequate content of this nutrient.

10

Authors: Manuel Alberto Gutiérrez Cuenca, José Henrique de Albuquerque Rangel, Helber Rodrigues de Araújo

The aim of this study was to analyze the variation in the productivity of cassava roots in Pernambuco, and to evaluate the impact of this variation over the PGV Percentage Variation Tax (TXV% of PGV), in different biennium, for the total period, and for three sub-periods between 1977 and 2009. The historical series of cassava productivity, harvested area and prices obtained by producers in Pernambuco between 1977 and 2009 was considered. Data encompassing the 1977 – 1998 period were collected from the Basic Statistic (IBGE, 1997), and data relative to the period from 1990 to 2009, obtained from IBGE Automatic Recovering (SIDRA, IBGE, 2011). Data were processed for calculation of medium, maximum, and minimum values PGV and TX% of PGV. Data were updated to December 2010 by the Prices General Index of Getulio Vargas Foundation (FGV, 2011). The “Shift-share” model was used for decomposition of VBP variation Taxes in function of the effects of area, productivity, and price factors. Considered the total period 1977 – 2009, the factors price, harvested area, and production of cassava in Pernambuco decreased respectively 59%, 71%, and 68%, leading to a PGV reduction of 87%. An increasing of 9% in productivity softened only partially the negative effect of the others factors over the cassava PGV in the state. Means of productivity and PGV obtained by cassava growers of Pernambuco between 1977 and 2009 were respectively 9.78 t ha-1 and R$ 397.1 million. The maximum productivity of 11.5 t ha-1 occurred in 2005 and the maximum PGV (R$ 1,167.3 million) occurred in 1980. The lowest productivity of 8.10 t ha-1 was verified in 1998, while the lowest PGV of R$ 49.4 million was registered in 2001. Variation of productivity and PGV were divergent in most the biennium. Such behavior is attributed to the fact of variations of harvest area or prices, or even either of them annuls or compensated the effect of the productivity over the PGV.