Manutenção de cafezal com adubação exclusivamente mineral

Abstract

O presente estudo foi executado com o objetivo de pesquisar a possibilidade de aumentar a produtividade de cafèzais velhos, sem emprêgo de matéria orgânica trazida de fora. Foram estudados N, P, K, micronutrientes (zinco, cobre e boro) e adubação verde. Utilizou-se um delineamento fatorial 32 X 22, em blocos de 18 canteiros com nove plantas cada um, com bordadura de uma planta entre os canteiros. O ensaio foi instalado na Estação Experimental de Ribeirão Prêto, em um cafèzal com mais de 40 anos de idade, em terra-roxa-legítima, e cuja produção média nos quatro anos anteriores foi de 24 sacos de café em côco por mil pés. Obteve-se grande aumento de produção com o emprêgo de nitrogênio, devido não só às quantidades aplicados, mais elevadas do que as até então recomendadas, mas principalmente à sua aplicação parcelada. Os aumentos devidos ao nitrogênio na dose de 360 g de N por planta, na forma de sulfato de amônio, corresponderam a 6, 11, 13, 16 e 34 sacos de café em côco por mil pés, nos anos de 1954 a 1958. A dose mínima de potássio empregada foi de 120 g de K20 por planta. A dose de 240 g de K20 por planta ainda proporcionou um aumento de produção de 9% em relação à anterior. Não houve reação ao fósforo nem à adubação verde. A aplicação de micronutrientes (zinco, boro e cobre) fêz desaparecer os sintomas de deficiência de zinco, mas resultou em decréscimo significativo da produção. A aplicação do nitrogênio melhorou a coloração e o desenvolvimento da folhagem. Não houve influência dos outros fatôres sôbre o aspecto vegetativo das plantas.It has been believed in Brazil that it is not possible to maintain coffee plantings profitably without the use of organic matter. Consequently it has been routine to recommend yearly applications of manure or compost. The present experiment was carried out to study the possibility of increasing the yield of a coffee planting and maintaining it at a high level by the exclusive use of mineral fertilizers. A coffee plantation of the "Bourbon vermelho" variety about 40 years old grown on "terra-roxa-legítima" soil was used. A factorial experiment 32 X 22 was installed in 1953 with 9 plants per plot. The treatments used were: ammonium sulphate 0 g, 600 g and 1800 g per plant, superphosphate 0 g, 500 g and 1500 g per plant and potassium chloride 200 g, 400 g and 800 g per plant, microelements (Zn, Bo, Cu) and green manure. Until 1957 the phosphate and the chloride were applied in furrows once a year and the ammonium sulphate was applied three times a year as top dressings. Starting in 1958 all the fertilizers were applied four times a year as top dressings. The microelements were applied as foliage spray of the following solution: zinc sulphate — 6 g, copper sulphate — 1 g and borax — 3 g per liter of water. Soybean was used as green manure until 1955 and jack bean (Canavalia ensiformis, D. C.) in the later years. The response to nitrogen application was highly significant and kept increasing every year as shown by the percentage of yield increases for the years 1954 through 1958. These were 8.4%, 60.7%, 30.9%, 50.3% and 63.1%. In previous experiments doses of KCI of up to 200 g per tree had already been used. For that reason in this experiment the minimum dose of that fertilizer used was 200 g per tree. An application of 8OO g per tree of KCI gave only 9% of yield increase in relation to the 200 g per tree application. No reaction was obtained to the application of phosphorus. The microelement spray cured the zinc deficiency symptoms which were evident prior to its application, but decreased the yield significantly, the highest decrease being 39% in 1955. No reaction was obtained to the use of green manure. The results obtained seem to show that it is possible to increase substantially the yield of a coffee plantation through the use of mineral fertilizers only.