Abstract
Knowledge about the fate of fertilizer nitrogen in agricultural systems is essential for the improvement of management practices in order to maximize nitrogen (N) recovery by the crop and reduce N losses from the system to a minimum. This study involves fertilizer management practices using the 15N isotope label applied in a single rate to determine the fertilizer-N balance in a particular soil-coffee-atmosphere system and to deepen the understanding of N plant dynamics. Five replicates consisting of plots of about 120 plants each were randomly defined within a 0.2 ha coffee plantation planted in 2001, in Piracicaba, SP, Brazil. Nine plants of each plot were separated in sub-plots for the 15N balance studies and treated with N rates of 280 and 350 kg ha-1 during 2003/2004 and 2004/2005, respectively, both of them as ammonium sulfate enriched to a 15N abundance of 2.072 atom %. Plant shoots were considered as separate parts: the orthotropic central branch, productive branches, leaves of productive branches, vegetative branches, leaves of vegetative branches and fruit. Litter, consisting of dead leaves accumulated below the plant canopy, was measured by the difference between leaves at harvest and at the beginning of the following flowering. Roots and soil were sampled down to a depth of 1.0 at intervals of 0.2 m. Samples from the isotopic sub-plots were used to evaluate total N and 15N, and plants outside sub-plots were used to evaluate dry matter. Volatilization losses of NH3 were estimated using special collectors. Leaching of fertilizer-N was estimated from deep drainage water fluxes and 15N concentrations of the soil solution at 1 m soil depth. At the end of the 2-year evaluation, the recovery of 15N applied as ammonium sulfate was 19.1 % in aerial plant parts, 9.4 % in the roots, 23.8 % in the litter, 26.3 % in the fruit and 12.6 % remaining in the 0_1.0 m soil profile. Annual leaching and volatilization losses were very small (2.0 % and 0.9 %, respectively). After two years, only 6.2 % N were missing in the balance (100 %) which can be attributed to other non-estimated compartments and experimental errors. Results show that an enrichment of only 2 % atom 15N allows the study of the partition of fertilizer-N in a perennial crop such as coffee during a period of two years.
Highlights
Coffee, cultivated in more than 50 countries and on several continents, is worldwide an important agribusiness
The purpose of this study was to improve the understanding of N dynamics in a soil-coffee-atmosphere system, in order to help in the establishment of efficient fertilizer management practices that maximize the use of fertilizer N by the coffee crop
This study focuses on the fate of N from the fertilizer only in the labeled treatment T2, the treatments T0, T1 and T2 were compared (Table 1) in terms of plant height (PH) and coffee bean dry matter yield (Y), at both harvest times
Summary
Coffee, cultivated in more than 50 countries and on several continents, is worldwide an important agribusiness. Colombia and Vietnam are responsible for more than half of the total global coffee production. In Brazil, coffee is the most important cash crop, grown on an area of about 3 million hectares with an annual production of 2 million tons of coffee beans worth 700 million US dollars (FNP, 2004). After potassium (K), nitrogen (N) is the nutrient most required by coffee plants, since it is a constituent of protein molecules, enzymes, co-enzymes, nucleic acids and cytochromes, as well as part of the chlorophyll molecule. It is responsible for substantial yield increases in coffee. Missmanagement of N fertilization is characterized by the inadequately timed application of either too low or too high fertilizer rates, contributing to high N losses from the system due to low plant uptake at the time of application (Prado & Nascimento, 2003)
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