UTILIZATION OF "N-UREA BY RATOON SUGAR-CANE IN THE COASTAL PLAINS OF PERNAM3UC0

SUMMARY

A field experiment was established at Goiana-PE, on a Red-yellow Podzoitc soil. Treatments, replicated four times, were: 1} no nitrogen;

2) 60 kg/ha of N at planting time and after plant crop harvest; and 3 ) 20 kg/ha of N at planting and after plant crop harvest plus 40 kg/ha of N three months after each of these applications. Each plot had 9 rows, 10 m long and 1,25 nt apart. Three subplots 1,25 m

by 1,25 m were established at each N receiving plot and were limited fcy a plastic film from the surface down to 80 cm depth. Two of these subplots were fertilized at planting time, with urea labelled with

90

-I SN at 10.2 atm " excess and after plant harvest one received no N and the other received common urea. The third subplot was fertilized with common urea at planting time and with l*N labelled urea after plant harvest. Plant cane was harvested 16 months after planting and ratoon cane 12 months later. There were no significant differences among treatments either in terms of ratoon cane production (100 t/ha) or in ratoon N content in the different plant parts (total = 200 kg/ha).

These values were lower than those obtained for plant cane (130 t/ha of cane and 250 kg of N ) . Ratoon fertilizer utilization were 42: and 46$ for split and single fertilizer application, respectively; similar to those obtained with plot cane (44 and 39',). From the ISN applied at planting time, fertilized ratoon recovered 4.7" and unfertilized ratoon 6.6%.

ESTUDO DAS PERDAS POR VOLATILIZAÇAO DO ISN-UR£1A E ISN-SUIFATO DE AKÕNIO NUM ENTESSOLO CALCICO DA PARTE CENTRAL DA REGIÃO COSTEIRA DO PERU1

URQUIAGA C , S.2; VICTORIA, R.L.J; BRUITON, F . \ CHAVEZ N., J.s

RESUMO

A presente pesquisa foi desenvolvida em casa de vegetação da Universidade Nacional Agrária, La Molina, Lima, usando-se amostras de um Entessoio representativo da parte central da região costeira üc Peru. O solo í de textura media, pobre em N-total (0,089.Í) e matéria orgânica (1,58*,) de reação básica (pH 7,5), com média CTC (12 meq/100g) e com 4,85, de CaCOj. Estudou-se as perdas por volátilização do

N-fertilizante aplicado COÍBO cobertura na cultura de milho (Zea nays, L.). utilizou-se uréia (10.191% átomos liH) e sulfato de amorno

(7,801% átomos de 1 5N) na dose de 150 mg N por vaso (1,50 kg de terra) aplicados aos 15 dias após a germinação das plantas, em quatro

diferentes formas de localização: aplicação na superfície de solo seco, na superfície de solo unido, na superfície de solo seco c<m irrigação imediata e enterrado a quatro cm de profundidade em solo ünrido. Apôs a aplicação dos adubos continuou-se a irrigação por mais 12 horas. As perdas do N-fertilizante por volatilização foram avaliadas através do balanço de massa do N aplicado, considerando-se o N-fertilizante extraído pelas plantas e o residual no solo no final do experimento

(45 DAG). Os resultados indicaram que: a) A adubação com N duplicou a produção de matéria seca da cultura e os maiores valores ocorreram quando a adubação foi feita na superfície do solo seco, ou enterrada em solo úmido; b) Na eficiência de utilização do N-fertilizante pela cultura, a uréia (64,83) superou sensivelmente ao sulfato de amõnio

(522), e os valores foram mais altos quando os adubos foram aplicados na superfície do solo seco ou enterrado em solo úmido; c) A maior perda de N por volatilização ocorreu com sulfato de amônio (38,3*.), que

superou sensivelmente uréia (23,622); d) As perdas de N quando os adubos foram aplicados na superfície de solo (23,43) ouenterrado em^solo úmido

(22%) foram sensivelmente menores que as aplicações na superfície de solo úmido (41,7%) e superfície de solo seco com irrigação imediata(36,8).

'Contribuição do CENA/USP e UNA, La Molina, Lima, Peru.

2Prof. Assoc. UNA, La Molina, Lima. Atualmente Consultor EMBRAPA/UAPNPBS, Km.47, Seropédica, 23,460-Rio de Janeiro, Brasil,

'Pesquisador - CENA/USP, Caixa Postal 96, 13.400-Piracicaba, SP.,Brasil.

•"Pesquisador do Centro Internacional de La Papa, Lima, Peru,

92

-STUDY OF LOSS DUE TO V O L A T I L I Z A T I O N OF ' ' ? i ifRFA AííD X'H AMMONIUM SULPHATE I N A C A L C I C E.NTISOL OF THE CENTRAL I'ART OF THE PERUVIAN COAST

SUMMARY

The present research work was carried out in the greenhouse at Universidad Nacional Agraria, La Molina, Limo, Peru using samples of an entisol representative of the central part of the Peruvian coast.

The soil is of medium texture, poor in total-N (0.089') and in organic matter (1.58K), basic reaction (pH 7.5), medium CEC (12 meq/100 g) and 4.85fi CaCOs. Losses due to volatilization of fertilizer-N broadcast applied to a maize (Zea mays, L.) crop were studied. Urea (10.1912

X*N atom) and ammonium sulphate (7.301::: !5N atom) were used at a rate of 150 mg N/pot (1.50 kg soil) applied 15 days after germination, in four different forms: on dry soil surface, on humid soil surface, on dry soil surface followed by immediate irrigation and at 4 cm depth in humid soil. Irrigation continued for 12 h after fertilization. Losses of fertilizer-N due to volatilization were evaluated by the mass balance of the applied N, considering the fertilizer-N extracted from the plants and the soil residue at the end of the experiment (45 DAG). Results indicated that: a) fertilization doubled the crop dry matter production and the greatest values occurred when the fertilizer was applied on dry soil surface or at depth in humid soil; b) As for efficient utilization of the fertilizer-N by the plant, urea (64.83) was markedly better than ammonium sulphate (52^), and the values were higher when the fertilizer was applied on dry soil surface or at depth in huniid soil; c) The greatest N loss due to volatilization occurred with ammonium sulphate

(38.3%) which exceeded urea by far (23.623); d) N losses when fertilizer was applied on dry soil surface (23.4*4) or at depth in humid soil (223) were rather smaller than applications on humid soil surface (41.7?») and dry soil surface followed by immediate irrigation (38.8*).

EFEITOS OA APLICAÇÃO FOLIAR DE URÉIA E OA ADUBAÇAO NO SOLO DE SULFATO