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The experiment was conducted with the aim to evaluate the effects of biofertilizers with phosphate and potash rocks and soluble fertilizers (Triple super phosphate and potassium chloride) in chemical attributes of a Brazilian tableland soil grown with sugarcane. The experiment was arranged in a completely randomized factorial design 2 × 4 × 3 + 1, with four replicates. Two varieties of sugarcane, three sources of P and K mixture (natural apatite + natural biotite; P + K biofertilizers with Acidithiobacillus and P + K chemical fertilizers) were applied in four levels. A control treatment with no P and K fertilization (P 0 K 0 ) was added for comparative purposes. Significant differences between varieties were observed in all analyzed parameters, with better results when applied the recommended levels of biofertilizers and chemical fertilizers. Stalk fresh matter increased with fertilizers and biofertilizers applications, especially when applied in levels near recommendation. Total N, total P and total K in stalk dry matter increased significantly when biofertilizers were applied. The results indicate potential use of biofertilizers that may be used as P source; however, long-term studies are necessary due to soil pH reductions and its possible adverse effects.

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Free living diazotrophic bacteria are known to enrich nitrogen of organic matter sources. In this paper we report of experiments using rock biofertilizers mixed with two types of organic matter (earthworm compound and ice cream waste) inoculated with free living diazotrophic bacteria. The earthworm compound and P and K biofertilizers were mixed to form substrates S 1 (earthworm compound 3 dm 3 ? PK biofertilizer 1 dm 3 and waste ice cream 1 dm 3 ); S 2 (earthworm compound 2.5 dm 3 ? PK biofertilizer 1.5 dm 3 and waste ice cream 1 dm 3 L) and S 3 earthworm compound 2.0 dm 3 ? PK biofertilizer 2.0 dm 3 and waste ice cream 1 dm 3 ), and subsequently inoculated (100 mL pot -1 ) with 3 free living diazotrophic bacteria isolated from different Brazilian soils. The control was an uninoculated earthworm compound. Samples were collected at various incubation time (0; 15; 30 and 45 days) and analyzed for total N. Total N concentrations were highest in S 1 , S 2 and S 3 substrates at 34, 27 and 29 days, respectively. The isolate NFB 1001 increased total N in all substrates and the best results were obtained at 34 days in S 1 substrate which contained the highest amount of earthworm compound. The isolates promoted a decline in N content after 30 days of growth, indicating the best time to produce the organic biofertilizer. The organic biofertilizer enriched in nitrogen by free living diazotrophic bacteria is of relevance to organic agriculture.

The aim of this study was to evaluate the effectiveness of a mixed biofertilizer with phosphate and potash rocks (PK biofertilizer) combined with an earthworm compound inoculated with free living diazotrophic bacteria and Cunninghamella elegans, fungi that produces chitosan, on cowpea nodulation, biomass yield and nutrient uptake. The effects of some chemical attributes from an acidic soil of the Brazilian Northeast were also studied. The treatments were as follows: a) biofertilizer enriched in N by free living diazotrophic bacteria(NPKB), applying crustaceous chitosan (ChCru) at a rate 2 mg mL -1 ; b) NPKB and ChCru at a rate 4 mg mL -1 ; c) NPKB and ChCru at a rate 6 mg mL -1 ; d) NPKB and fungi chitosan (ChFu, 2 mg mL -1); e) NPKB+C. elegans (NPKP); f) NPKB without chitosan; g) mineral fertilizers (NPKF); and h) control without NPK fertilizer and chitosan. Biofertilizer treatments increased cowpea nodules biomass, shoot biomass, and total N, P, and K in the shoots. The largest increase was obtained with ChCru, and the highest rate was obtained with NPKP. Furthermore, biofertilizers reduced soil pH and increased the total N and available P and K. These results reveal the potential of rock biofertilizer mixed with earthworm compound inoculated with free living diazotrophic bacteria and C. elegans (fungi chitosan) for plant production and nutrient uptake. The biofertilizer may be an alternative for NPK fertilization that slows the release of nutrients, favoring longterm soil fertility.

RESUMORealizou-se um experimento em casa de vegetação para avaliar a atuação do enxofre (S) inoculado com Acidithiobacillus na disponibilidade de fósforo (P) de fosfato natural (FN), em diferentes modos de aplicação do fertilizante, em um Espodossolo Ferrocárbico Órtico, do tabuleiro costeiro da Zona da Mata de Pernambuco, cultivado com jacatupé (Pachyrhizus erosus). As plantas foram inoculadas com rizóbio (NFB 747 e NFB 748) e adicionado tratamento-controle sem inoculação com rizóbio. Os tratamentos com P foram: (1) FN revestindo o enxofre inoculado com Acidithiobacillus (FN S*), (2) FN revestido com S e com Acidithiobacillus (S* FN), (3) mistura FN com S e com Acidithiobacillus (FN + S*), (4) mistura FN com S e sem Acidithiobacillus (FN + S), (5) superfosfato triplo (ST) e (6) sem aplicação de fósforo (P 0 ). Os tratamentos foram aplicados: (a) na superfície, (b) em sulco 10 cm abaixo da semente, e (c) em sulco 10 cm abaixo e ao lado da semente. A biomassa nodular foi maior no tratamento (FN + S*) com melhor efeito quando aplicado ao lado e abaixo das sementes. O (FN + S*) também aumentou a altura das plantas, a biomassa da parte aérea e das túberas e o N total da parte aérea, especialmente quando aplicado 10 cm abaixo das sementes. O P total da parte aérea foi mais elevado com (S* FN) aplicado 10 cm abaixo das sementes. Os melhores teores de P no solo foram obtidos com (FN + S*) e (S* FN), com efeito mais evidente quando aplicados 10 cm abaixo das sementes.Termos de indexação: biofertilizantes, fosfato reativo, Gafsa, localização do fertilizante.(1) Recebido para publicação em junho de 2002 e aprovado em novembro de 2003.(2) Professor Titular do