Recuperação de pastagens de Brachiaria decumbensdegradada com introdução de Stylosanthes e adubação fosfatada1

RESUMO Objetivou-se avaliar a possibilidade de recuperação deumapastagem degradada, deBrachiaria decumbens, com a introdução da leguminosaStylosanthes e adubação fosfatada. O experimento constou de distintos métodos de introdução em um delineamento experimental em blocos casualizados com parcelas subdivididas (adubado com e sem fósforo), com quatro repetições e compostos pelos tratamentos: testemunha Brachiaria decumbens; dessecação parcial com 1,5L ha-1 de glifosato; dessecação total com 3,0L ha-1 de glifosato; plantio direto; escarificação do solo; gradagem rome e aração mais gradagem. Nos tratamentos gradagem rome e aração mais gradagem a semeadura da leguminosa foi feita a lanço e os demais na forma de semeadura direta. Foram realizados seis cortes para separação dos componentes morfológicos da forragem e composição botânica. Os maiores acúmulos de massa seca total foram encontrados para dessecação parcial com 1,5L ha-1 de glifosato, gradagem rome, aração mais gradagem e dessecação total com 3,0L ha-1 de glifosato em relação aos tratamentos plantio direto da leguminosa e testemunha. A composição bromatológica foi melhor na estação da primavera, PB e FDA apresentaram diferenças significativas entre todos os tratamentos (P<0,05). O adubo fosfatado teve efeito para FDA nas estações da primavera e outono. A introdução da leguminosa, por meio de gradageme aração + gradagem,promoveu a maior produtividade na biomassa total e a dessecação parcial e totalaumentaram a participação da leguminosa. A adubação fosfatada somente apresentou resultados positivos na produtividade e participação da leguminosa durante a época de verão

Improvement of dry tropical rangelands in Hainan Island, China. 1. Evaluation of pasture legumes.

During 1981-83, we studied some legumes for potential improvement of dry tropical (1,001 mm annual rainfall) rangelands in Hainan Island, China. The productivity and persistence of 16 pasture legumes were tested on sandy ( 1 plant/m2 on 1 or both soils, but only 5 perennial stylos (Stylosanthes), siratro [Macroptilium atropurpureum (D.C.) Urban], and centro (Centrosema pubescens Benth) (loam soil only) persisted through 2 dry seasons and yielded more than 0.5 metric tonne (t)/ha in 3-year-old swards. S. guianensis (Aubl.) Sw. cv Cook yielded best on both soils, but proved less tolerant to fire than cv Graham, which is the common stylo recommended by this study as a companion for siratro for improvement of loam soil rangeland. Siratro was the only non-stylo to produce > 2 t/ha and show relative stability with sward age, but careful grazing management and regular fertilization are needed to maintain siratro content above 40% in commercial sowings. Tolerance to fire, low P requirement, and high yield in 2- and 3-year-old stands makes S. scabra Vog. cv Seca the most suitable legume for sandy soil, but since it is slow to establish, a mixture of S. scabra and S. hamata (L.) Taub. cv Verano which is noted for its quick establishment and prolific seed production is recommended for range improvement of low P soils

Improvement of dry tropical rangelands on Hainen Island, China. 3. Legume response to initial fertilizers.

During 1981-83, we identified nutrient requirements and fertilizer strategies for the development of legume-based pastures in dry tropical rangelands of Hainan Island, China. Nutrient requirements for pastures grown on sandy and red loam soils were established using soil tests and missing element experiments with 3 test legumes. An acute P deficiency ( 20 mg kg-1. In contrast, application of P fertilizer proved both profitable and essential for development of legume-based pastures on P-deficient sandy soils. It is recommended that a rate of about 40 kg of P ha-1 should be applied at establishment of stylo pastures on sandy soil. At this rate both legume yield and P content of tops should be maintained at levels needed to sustain a beef production enterprise and return about $1.5 per dollar invested in fertilizer

Improvement of dry tropical rangelands in Hainan Island, China. 2. Evaluation of pasture grasses.

During 1981-83, we studied 19 grasses for potential improvement of dry tropical (1,001 mm annual rainfall) rangelands in Hainan Island, China. The productivity and persistence of the grasses were tested on sandy ( 5 plants/m2), but only 6 cultivars produced yields > 1.5 metric tonne (t)/ha. Melinis minutiflora Beauv., Brachiaria decumbens Stapf. and Chloris gayana Kunth. yielded more than 1.5 t/ha in 3-year-old swards on both soils, whereas Panicum maximum Jacq. and Setaria sphacelata (Schum.) Stapf. ex Massey only performed well on fertile loam soil. Grass establishment was superior on sandy soil, but plant density did not correlate well with production which was higher on red loam soil due to better waterholding capacity and nutrient status. Compatibility of these successful grasses with companion legumes was low with legumes contributing 4 t/ha. S. sphacelata was the only grass to form a stable mixture with companion legumes. [Macroptilium atropurpurem (D.C.) Urban and Stylosanthes guianensis (Aubl.) Sw.], which yielded more than 1.1 t/ha in 3-year-old swards on loam soil. This combination was recommended for improvement of loam soil rangelands. It is concluded from this study that range improvement with perennial grasses is confined to fertile soils, while direct broadcast of Stylosanthes legumes only into grazed native pastures is the practice recommended for improvement of infertile sandy soil until persistent low P tolerant grasses are found for the dry tropics