Antonio Fernando Guerra

Manejo da adubação nitrogenada de tensões hídricas sobre a produção de matéria seca e índice de área foliar de Tifton 85 cultivado no Cerrado

This work was carried out to evaluate the influence of water tensions (35, 60, 100 and 500 kPa) and nitrogen levels (0 - Control, 45, 90, 180, 360 kg/ha) on the dry matter (DM) yield, the dry matter yield rate (DMYR) and the leaf area index (LAI) of Cynodon spp. cv. Tifton 85 bermudagrass. A randomized blocks design in a split splot scheme with three replications was used, split plots were represented by the water tensions were and the plots, by the nitrogen (N) levels. The dry matter yield was influenced by the nitrogen levels for all tensions, where the highest productivity (41.8 t/ha) was obtained at 35 kPa the tension and the maximum N level (360 kg/ha of N), while the smallest productivity (17.3 t/ha), at 100 kPa the tension without N addition. At the tensions of 60, 100 and 500 kPa there was limitation in the use of N at the highest doses, due to the deficit water. Higher DMAR were observed from 09/21 to 11/29, and the averages ranged from 73.4 to 194.6 kg/ha/day of DM, while from 05/26 to 08/09 the smallest averages were observed, that ranged from 44.9 to 55.2 kg/ha/day of DM. No effect of N levels was observed from 03/16 to 08/09. In the other periods, DMYR increased as N levels increased. There was no effect of the different water tensions on DMYR. LAI increased as N levels increased, from 09/21 to 01/10, with averages from 3.07 to 9.64. In the periods with low temperatures, N levels and did not affect LAI. Water tension did not affect LAI in all evaluated periods.

Soil phosphorus dynamics and availability and irrigated coffee yield

Resultados de pesquisa tem demonstrado que o cafeeiro demanda uma quantidade anual de fosforo semelhante a das culturas de ciclo curto. Nesse contexto, o objetivo deste trabalho foi avaliar o status do P no solo, em funcao da aplicacao anual de doses de P, por meio da quantificacao de fracoes de P labeis, moderadamente labeis, pouco labeis e P total, associando-as as produtividades do cafeeiro. O experimento foi instalado num Latossolo Vermelho distrofico tipico (LVd) cultivado com cafeeiros irrigados em producao, submetidos a adubacoes fosfatadas anuais de 0, 50, 100, 200 e 400 kg ha-1 de P2O5, como superfosfato triplo. Foram determinadas fracoes de fosforo no solo nas profundidades de 0-10 e 10-20 cm. Tambem foram avaliados teores foliares de fosforo e a producao dos cafeeiros em 2008. O cafeeiro irrigado respondeu a adubacao fosfatada em fase de producao, com incrementos de ate 138 % na produtividade com a aplicacao de 400 kg ha-1 de P2O5, na safra avaliada. Os teores foliares de P no cafeeiro aumentaram com o aumento das doses de P e se estabilizaram em torno de 1,98 g kg-1 a partir da dose de 270 kg ha-1 de P2O5. A aplicacao de fosforo ao solo promoveu, em geral, incrementos nas fracoes de P biodisponiveis, sendo estas o principal reservatorio de P do solo.

Regimes hídricos e doses de fósforo em cafeeiro

This work aimed to study the vegetative and reproductive growth and yield of coffee plants under three water regimes and four phosphorus fertilization doses, on second year after pruning on cerrado soil. The cultivar used was Catuai Rubi, MG 1192, Coffea arabica L. with 7,143 plants ha-1. Water regimes were: all year round irrigation (I); after June 24th, 2007, irrigation was stopped for 70 days (SI70) and for 109 days (SI109). Treatments SI70 e SI109 were interrupted with a rainfall of 12 mm (October 1st, 2007), which visually caused flowering initiation. The four phosphorus doses were: 0 (P0), 100 (P100), 200 (P200) e 400 (P400) kg of P2O5 ha-1. The experiment was arranged in randomized complete block design for water regime with phosphorus doses as split plot and three replications. The highest doses of phosphorus (P200) and (P400) provided increases in branch length, leaf area, number of fruits and grain yield. Water regimes SI70 and SI109 provided higher cherry fruit percentage and the highest and lowest grain yield, respectively.

BRS 180: cevada cervejeira para cultivo irrigado no Cerrado

Culturas alternativas de inverno com viabilidade tecnica e economica para integrar os sistemas de producao irrigados constituem-se na principal demanda dos agricultores da regiao do Cerrado. A cultivar de cevada BRS 180 obtida pela Embrapa-Centro Nacional de Pesquisa de Trigo e Embrapa-Centro de Pesquisa Agropecuaria dos Cerrados, lancada para o cultivo irrigado em 1999, representa a primeira cultivar adaptada para a regiao, potencializando essa cultura como uma nova opcao para o produtor. BRS 180 apresenta elevados indices de produtividade, resistencia ao acamamento e baixos teores de proteinas, o que vem atender as demandas agronomicas dos agricultores e aos padroes de qualidade da industria de malte cervejeiro. Em parcelas experimentais, BRS 180 apresentou rendimentos de graos de ate 8.920 kg/ha, atingindo ate 6.000 kg/ha em lavouras comerciais.

Microbiological properties and oxidizable organic carbon fractions of an oxisol under coffee with split phosphorus applications and irrigation regimes

Phosphorus fertilization and irrigation increase coffee production, but little is known about the effect of these practices on soil organic matter and soil microbiota in the Cerrado. The objective of this study was to evaluate the microbiological and oxidizable organic carbon fractions of a dystrophic Red Latossol under coffee and split phosphorus (P) applications and different irrigation regimes. The experiment was arranged in a randomized block design in a 3 x 2 factorial design with three split P applications (P1: 300 kg ha-1 P2O5, recommended for the crop year, of which two thirds were applied in September and the third part in December; P2: 600 kg ha-1 P2O5, applied at planting and then every two years, and P3: 1,800 kg ha-1 P2O5, the requirement for six years, applied at once at planting), two irrigation regimes (rainfed and year-round irrigation), with three replications. The layers 0-5 and 5-10 cm were sampled to determine microbial biomass carbon (MBC), basal respiration (BR), enzyme activity of acid phosphatase, the oxidizable organic carbon fractions (F1, F2, F3, and F4), and total organic carbon (TOC). The irrigation regimes increased the levels of MBC, microbial activity and acid phosphatase, TOC and oxidizable fractions of soil organic matter under coffee. In general, the form of dividing P had little influence on the soil microbial properties and OC. Only P3 under irrigation increased the levels of MBC and acid phosphatase activity.

Dynamics of Forms of Inorganic Phosphorus in Soil under Coffee Plants as a Function of Successive Annual Additions of the Nutrient

Phosphorus (P) dynamics and availability in soils are influenced by P fertilization. This paper aimed to evaluate inorganic P fractions bonded to calcium (Ca), iron (Fe), and aluminum (Al), associating them with soil mineralogy. The experiment was carried out using an acidic kaolinitic–oxidic soil, located in an irrigated area cultivated with coffee plants (Coffee arabica L.), submitted to successive annual fertilizations with triple superphosphate doses of 0, 50, 100 200, and 400 kg ha−1 phosphorus pentoxide (P2O5) in randomized blocks with three replications. Phosphorus fractions were determined in soil samples collected at two depths, 0–10 and 10–20 cm, according to the methodology used by Chang and Jackson (1957). The inorganic P fractions presented the following sequence: P-Al > P-Fe > P-Ca. The dynamics of forms of inorganic P showed that P-Al is controlling the P bioavailability as a result of an acidic pH and a very simple and thermodynamically stable clay mineralogy, typical of very weathered and old tropical soils.

Ajuste do modelo Chistiansen-Hargreaves para estimativa da evapotranspiração do feijão no cerrado

Bean producers from the Brazilian Cerrado region have only one technology for the irrigation management: the measurement of the water tension in the soil through the use of tensiometers. Although this methodology has high potential, it has not been widely adopted by the producers. Thus, the utilization of models to estimate evapotranspiration estimate has shown to be applicable to the Cerrado region. So, this paper aims to evaluate the performance of the Chistiansen-Hargreaves model to estimate evapotranspiration of black bean crop in the dry season of the Brazilian Cerrado region. It also aims to provide producers an the adjusted model to estimate evapotranspiration which permit an efficient management for the agricultural irrigated system of the Cerrado region. The evapotranspiration of the black bean crop was measured with the use of a weighing lysimeter. The experiment was carried in the Brazilian Agricultural Research Corporation (Embrapa Cerrados), located in Planaltina, DF, Brazil. When calculated with crop coefficient, determined in the research and tested with adjusted energetic term (S0=0.5), the Chistiansen-Hargreaves model presented an excellent performance and may be used in irrigation management.

Qualidade físico-hídrica de um latossolo sob irrigação e braquiária em lavoura de café no cerrado

The objective of this study was to evaluate the effect of irrigation and cultivation of brachiaria among coffee trees lines on physical-hydric Oxisol quality at Brazilian central plateau. The experiment was carried out in five randomized blocks in a factorial design 2 x 2, with two water treatments, irrigated and rainfed systems, and two management systems, with and without brachiaria between coffee trees lines. The research strategy was based on studying soil water storage based on porosity distribution due to the behavior of physical parameters in different water and management treatments. Soil samples were collected in duplicate in each plot at depths from 0.0 to 0.05, 0.05 to 0.10, 0.10 and 0.20 m. The irrigation regime increased soil bulk density in the surface layer without reducing its readily available water that, due to presence of brachiaria was increased by 18%. In general, irrigated brachiaria had a positive effect on the physical-hydric soil characteristics of the soil and promoted an increase in readly available soil microporosity from the redistribution of pore diameter characterized by increasing retention curve amplitude in the soil water tension range corresponding to the readily-available water.