Nutrição mineral de seringueira: IX. alumínio no substrato afetando o desenvolvimento, a sintomatologia de toxicidade e a concentração em seringueira (Hevea spp)

Abstract

RESUMO: Com o propósito de comparar os efeitos de doses crescentes de alumínio sobre o desenvolvimento de plantas de seringueira e distinguir o grau de tolerân-cia do grau de toxicidade desse elemento sobre a planta, conduziu-se um experimento usando-se separadamente solução nutritiva de BOLLE-JONES (1957) e soluções de doses de alumínio que se constituíram de 0, 5, 10, 15, 20 e 25ppm de alumínio, em que as plantas passaram vinte e quatro horas na solução nutritiva (sem alumínio) e vinte e quatro horas nas soluções de alumínio correspondentes aos tratamentos acima. As plantas foram coletadas e separadas em raíz, caule, folhas dos vertici¬ los inferiores e folhas do último verticilo. Determinaram-se os acúmulos de alumínio e as concentrações em função das doses de alumínio em cada parte da planta. Os sintomas visuais de toxicidade de alumínio foram identificados e descritos. Concluiu-se que: -o desenvolvimento de plantas de seringueira é afetado a partir

Nutrient management of immature rubber plantations. A review

“…Use of nitrogen-fixing legume species as a cover crop is by far the best soil management technique with respect to nutrient management during the immature phase. Broughton (1977) made a comprehensive review of work carried out in Malaysia between the 1950s and the 1970s on the effect of legume cover crops on rubber tree growth and soil fertility compared to other types of soil cover (grass and natural cover). More recently, Clermont-Dauphin et al (2016) conducted a similar study with additional measurements to assess N transfer from Pueraria phaseolides to the rubber trees using the natural abundance of 15 N. The legume cover crop strongly increased tree girth from 11 to 29% in 4-to 6-year-old plantations compared with natural cover (Broughton 1977;Watson et al 1964a;Clermont-Dauphin et al 2016).…”

“…Three years after establishment of the cover crop, Clermont-Dauphin et al (2016) observed significantly higher nutrient contents in rubber tree leaves in plots with intercropped legumes in the inter-row (2.66% N, 0.19% P, and 1.62% K) than in plots with bare soil (1.69% N, 0.15% P, and 1.18% K). Broughton (1977) concluded that a legume cover crops act as a "bank" of nutrients because of its capacity to rapidly accumulate nutrients, mainly N, and to make it available to the rubber trees though the degradation of its litter. He assumed that the legume cover crop stimulates the proliferation of the rubber tree roots, thereby boosting nutrient recycling.…”

“…Cover crops produce a considerable amount of biomass, especially in the first 2 years after establishment, from 5 Mg ha −1 year −1 for grass cover to 10 Mg ha −1 year −1 for Pueraria phaseoloides (Clermont-Dauphin et al 2016;Watson et al 1964a). Legumes, often P. phaseoloides, begin to fix atmospheric nitrogen after the first two to 3 weeks of growth, and litter fall begins about 6 months later (Broughton 1977). Canopy closure in rubber plantations leads to the gradual death of the Pueraria (flux 2b; Fig.…”

“…The second year after planting, Watson et al (1964a) showed that legumes contained 340 kg N ha −1 , 22 kg P ha −1 , and 80 K ha −1 by summing the amounts in the litter on the soil surface and in plant biomass. Legumes (a mixture of P. phaseoloides, Centrosema pubescens, and Calopogonium mucunoides) are likely to supply larger amounts of nutrients than non-fixing plants (a mixture of Axonopus compressus and Paspalum) + 151 kg ha −1 year −1 for N, + 10 kg ha −1 year −1 for P, and + 20 kg ha −1 year −1 for K in Broughton (1977). More recently, Clermont-Dauphin et al (2016) showed that P. phaseoloides accumulated 250 kg N ha −1 , 10 kg P ha −1 , and 170 kg K ha −1 the first year after their establishment.…”

“…Aweto (1987) in Nigeria and Zhang et al (2007) in China observed a significant decrease in soil pH (between 0.5 and 1.0 units) and a depletion of exchangeable cations in the topsoil. Zhang et al (2007) also found an increase in soil exchangeable Al, which could impair rubber tree growth (Bueno et al 1988). Moreover, export (Shigematsu et al 2011) or burning (Yew 2001) of tree biomass after clearcutting of old plantations before replanting may worsen the long-term soil nutrient depletion.…”