Elifas Nunes de Alcântara

Métodos de controle de plantas daninhas no cafeeiro afetam os atributos químicos do solo

In agricultural ecosystems under coffee cultivation, soil management is based on liming, fertilizers and weed control. Alternatives that preserve or increase soil organic matter content are considered when the sustainability is the goal. This study was conducted to evaluate the chemical attributes of a dystroferric Red Latosol (Oxisols) under coffee cultivation submitted to 15 years of weed control methods. Seven interrows coffee plant weed control methods were used; a mower (RC), tanden disk harrow (GR), rotative hoe (ER), pre-emergence herbicide (HPRE), post-emergence herbicide (HPOS), hand hoe (CM) and no interrows control (TEST). The P, K+, Ca2++ Mg2+, sum of bases (SB), base saturation (V), effective (t) and potential (T) cation exchange capacity (CEC) were determined in soil depth from 0-0.15m and 0.15-0.30m. TEST treatment affected positively the P, K+, Ca2+ + Mg2+ content, and effective and potential CEC and V values, while the HR inversely reduced analyzed variable values. Others interrows methods RC, GR, ER, HPOS e CM presented an intermediary conduct among the TEST and HPRE methods on soil fertility.

Alterações nos atributos químicos de um latossolo pelo manejo de plantas invasoras em cafeeiros

Weed control is one of the most intensive management practices in coffee plantations resulting in changes in soil chemical properties. The objectives of this study were: a) to assess the effects of weed management in a coffee plantation on the chemical properties of a Dystroferric Red Latosol (Oxisol) compared to soil under native forest; b) to verify the relationship between soil organic carbon content (COS) and the effective cation exchange capacity (effective CEC) and the cation exchange capacity at pH 7. This study was carried out on an experimental farm of the Agricultural Research Company of Minas Gerais (EPAMIG) at the Sao Sebastiao do Paraiso County, of Minas Gerais State. In the experimental area, coffee was planted and the experiment was installed in randomized blocks with three replications. The following weed plant managements were evaluated: without weed control (SCAP); hand weeding (CAPM); post-emergence herbicide (HPOS); mechanized mower (ROCA); rotary tiller (ENRT); coffee tandem disc harrow (GRAD) and pre- emergence herbicide (HPRE). Each one of these weed control systems had been performed in the preceding 30 years in three inter-rows (length 36 m). Five soil samples were collected in three layers (0-3, 10-13 and 25-28 cm) per plot between coffee rows, in December 2007. The following soil chemical analyses were performed: pH-water, exchangeable cations (Ca, Mg, K and Al), cation exchange capacity at natural pH (effective CEC) and cation exchange capacity at pH 7.0 (CEC potential. The results showed that the maintenance of weed plants between coffee rows in the treatment no weed control (SCAP) had positive effects on the chemical properties (exchangeable Ca, effective CEC and CEC at pH 7.0 in the three layers). Furthermore, the total soil organic carbon content at 0-3 cm depth increased and may contribute to the increase and maintenance of carbon stocks in coffee plantations. Thus, no weed control (SCAP) between coffee rows can be adopted for the improvement and maintenance of the chemical properties in coffee plantations. On the other hand, the constant long term-use (30 years) with HPRE management decreases the pH-water values in the layers 10-13 and 25-28 cm and the exchangeable Ca, Mg and effective CEC in the three layers studied in relation to other weed plant managements. The effective CEC of the soil was related with organic carbon content in 59, 60 and 47 % of the cases and CEC at pH 7 in 65, 55 and 46 % in the layers 0-3, 10-13 and 25-28 cm.

Métodos de controle de plantas daninhas e seus impactos na qualidade microbiana de solo sob cafeeiro

Minas Gerais destaca-se como o Estado que mais produz cafe no Brasil. Essa cultura e extremamente suscetivel a presenca de plantas daninhas, que podem ser manejadas por meio de metodos manuais, mecanizados e, ou, quimicos, com impacto nos custos da producao e qualidade do solo. Objetivou-se com este trabalho avaliar o efeito exercido por diferentes metodos de controle de plantas daninhas na linha e entrelinha de cafeeiro, sobre a microbiota do solo e seus processos, que destacadamente tem sido utilizados em virtude de sua extrema sensibilidade e baixo custo. Para isto, amostras de solo foram retiradas em abril de 2010, em Latossolo Roxo distrofico da fazenda experimental da Empresa de Pesquisa Agropecuaria de Minas Gerais (EPAMIG), em Sao Sebastiao do Paraiso, MG, na profundidade de 0-10 cm, no centro da rua (entrelinha) do cafe, e a 20 cm do caule da planta do cafe (linha), para determinar os atributos: densidade de bacterias e fungos totais, solubilizadores de fosfato, celuloliticos, amonificantes, bacterias diazotroficas nao simbioticas, carbono da biomassa e atividade microbianas, quociente metabolico (qCO2) e atividade enzimatica pela hidrolise de diacetato de fluoresceina. O cafeeiro foi submetido a sete metodos de controle de plantas daninhas: rocadora, grade, enxada rotativa, herbicida pos-emergencia, herbicida pre-emergencia, capina manual e sem capina. Os resultados evidenciaram a complexidade dos efeitos desses diferentes metodos na microbiota do solo e seus processos, com menores impactos para capina manual e enxada rotativa. Os impactos dos metodos rocadora, grade, sem capina e aplicacao de herbicidas de pre-emergencia foram considerados intermediarios, enquanto a aplicacao de herbicidas de pos-emergencia, na entrelinha do cafeeiro, promoveu os maiores impactos negativos nos atributos avaliados. Esses impactos devem ser considerados quando houver avaliacao e escolha do metodo a ser empregado para o controle de plantas daninhas em cafeeiro.

Interrelationships Among Weed Management in Coffee Plantation and Soil Physical Quality

Cezar Francisco Araujo-Junior1, Moacir de Souza Dias Junior2, Elifas Nunes de Alcântara3, Paulo Tacito Gontijo Guimaraes3 and Ayodele Ebenezer Ajayi4 1Agronomic Institute of Parana – IAPAR, Rodovia Celso Garcia Cid, Londrina, State of Parana, 2Department of Soil Science, Federal University of Lavras, Lavras, State of Minas Gerais, 3Minas Gerais State Corporation for Agriculture and Livestock Research, EPAMIG, CTSM 4Soil Water and Environment Section, Department of Agricultural Engineering, Federal University of Technology Akure Ondo State, 1,2,3Brazil 4Nigeria

Water retention and s index of an oxisol subjected to weed control methods in a coffee crop

O controle das plantas daninhas nos diferentes cultivos influenciam atributos quimicos, fisicos e biologicos do solo e consequentemente sua qualidade estrutural. O objetivo deste trabalho foi avaliar, por meio da retencao de agua e do indice S, a qualidade fisica de um Latossolo Vermelho-Amarelo (LVAd) submetido a metodos de controle de plantas invasoras na cultura do cafe. Foram avaliados os seguintes metodos de controle de plantas invasoras: grade, rocadora, trincha, capina manual, herbicida de pos-emergencia, herbicida de pre-emergencia, emanutencao da cobertura do solo com amendoim-forrageiro, capim-braquiaria e vegetacao espontânea (tratamento sem capina). Para a caracterizacao fisica do solo foram determinados os seguintes atributos do solo: densidade do solo, porosidade total, macroporosidade, microporosidade, retencao de agua e o indice S. Os metodos de controle das plantas invasoras afetaram significativamente os atributos fisicos e a retencao de agua das camadas superficial e subsuperficial do Latossolo Vermelho-Amarelo. Densidade do solo, porosidade total, macroporosidade e microporosidade correlacionaram-se significativamente com o indice S. De acordo com o indice S, a qualidade fisica do solo foi classificada como muito boa para os diversos metodos de controle empregados.

AGREGAÇÃO DE UM LATOSSOLO VERMELHO-AMARELO SUBMETIDO A MÉTODOS DE CONTROLE DE PLANTAS INVASORAS NA CULTURA DO CAFÉ

Weed management in the coffee crop has a pronounced effect on soil physical quality, affecting its structural stability, among other properties. The aim of the present study was to assess the state of aggregation of primary particles of a Latossolo Vermelho-Amarelo (LVA) [Oxisol] planted with coffee when subjected to various weed control methods. The weed control methods evaluated were biological control with Arachis pintoi L. (a forage crop close to the peanut) and Brachiaria decumbens; mechanical control with a disk harrow, brush cutter, brush shredder, and manual weeding; chemical control using herbicides in post- and pre-emergence; and no weed control between rows. A split-plot randomized block experimental design was used in a 9 × 2 factorial arrangement, composed of nine treatments and two sampling depths (0-15 and 15-30 cm), with three replicates. The stability of aggregates in water (expressed by geometric mean diameter), the dispersive potential of the clay fraction (estimated by the water dispersible clay content and the flocculation index), and the soil organic matter content were determined. The properties evaluated were affected by the different weed control methods; however, this was not dependent on the soil layers sampled. Continued use of a harrow and pre-emergence herbicide for weed control in the coffee crop decreased aggregation of soil particles, as seen through the lower values of geometric mean diameter. Biological weed control methods maintained a better state of soil particle aggregation. The state of soil particle aggregation showed no association with the dispersibility of the clay fraction in the soil.