Edson Patto Pacheco

Compressibilidade, resistência a penetração e intervalo hídrico ótimo de um Argissolo Amarelo cultivado com cana-de-açúcar nos Tabuleiros Costeiros de Alagoas

The intensive traffic of agricultural machinery of cultivation and harvesting operations of sugarcane can promote soil compaction and affect crop yield and longevity. One of the ways to evaluate soil degradation due to compaction is by analyses of soil compressibility and least limiting water range. The objective of this study was to evaluate the effect of sugarcane cultivation on pre-compaction pressure (sp), laboratory-determined soil penetration resistance (LPS) and on the least limiting water range (LLWR) of a cohesive Yellow Ultisol of the coastal tablelands of Alagoas. The study was conducted on the Fazenda Progresso, of the Usina Coruripe, where five sugarcane areas were selected, representing different use periods and crop systems: four years under winter cropping (4 year W), 14 years under winter cropping (14 year W), 14 years under summer cropping (14 year S), thirty years under winter cropping (30 year W), and 30 years under summer cropping (30 year S). A native subperennial forest fragment (Forest) was also included in this study as a reference area. To determine the effect of sugarcane cultivation on soil compaction, sp, LPS and LLWR were determined in soil samples from the layers 00,20 m, 0,200,40 m and 0,400,60 m, corresponding to the horizons A (Forest) or Ap (agricultural areas), AB and Bt. Sugarcane cultivation increased the σp and LPS of the Ap, AB and Bt horizons of the Yellow Ultisol, however, in the Ap horizon of the soil of the agricultural areas the LPS did not reach the value considered critical for root development, and the LLWR was higher than in the surface horizon of native forest. The mechanized operations for sugarcane cultivation increased LPS to critical levels for root development, even at moisture contents near field capacity, which decreased LLWR of AB and Bt horizons in the agricultural areas. Pre-compaction pressure can be used as an indicator of load support capacity in the strategic planning of machinery operations in sugarcane fields, in order to avoid further soil compaction in the subsurface horizons of cohesive Yellow Ultisol.

Avaliação de espécies leguminosas na formação de cafezais no segmento da agricultura familiar no Acre

Leguminosas quando consorciadas com o cafe e usadas como adubacao verde podem contribuir fornecendo nitrogenio e protecao ao solo pela adicao de materia orgânica. O trabalho foi conduzido com o objetivo de avaliar o efeito do uso de leguminosas no sistema de producao de cafe, no segmento de agricultura familiar, visando promover a implantacao e a manutencao dos cafezais de forma tecnica e economicamente sustentavel. O experimento foi conduzido no periodo de novembro de 2000 a abril de 2003, em delineamento experimental de blocos ao acaso em esquema de parcelas subdivididas, com quatro repeticoes. Os tratamentos utilizados nas parcelas foram as leguminosas (Stizolobium atterrimum, Cajanus cajan, Canavalia endiformis e Flemingia congesta) e a testemunha (sem leguminosa) e, nas subparcelas, duas doses de N (0 e 22 g de N por cova). A Flemingia congesta e a Mucuna aterrima foram as leguminosas que mais influenciaram positivamente a produtividade dos cafeeiros, independente da adubacao nitrogenada. Em relacao a testemunha, o aumento em producao foi de 109% quando utilizou-se a Flemingia congesta e 52% com a Mucuna aterrima. A Flemingia congesta foi tambem a leguminosa que melhor controlou as invasoras, dado o volume de fitomassa produzida e a possibilidade de 2 cortes durante um periodo de doze meses, evidenciando o potencial desta leguminosa na formacao de novos cafezais no Acre. Por outro lado, a Canavalia ensiformis, leguminosa que e normalmente utilizada nas entrelinhas dos cafeeiros pelos cafeicultores, do Acre e de outras regioes produtoras, neste trabalho influenciou negativamente a altura das plantas, diâmetro da copa e crescimento dos cafeeiros.

Characterisation of the optimal hydric interval for a Yellow Argisol cultivated with sugarcane on the coastal plains of Alagoas, Brazil

This work had as its objective to study the optimum water range (OWR) of a Yellow Argisol of the coastal plains, planted with sugarcane, when subjected to different levels of compaction. For the laboratory tests soil samples with a non-preserved structure were used, removed from depths of from 0.20 m to 0.40 m and 0.40 m to 0.60 m, representing the AB and Bt horizons respectively. The treatments consisted of different soil densities represented by specimens contained in volumetric rings. The critical densities of the AB and Bt horizons for samples of upturned soil, were 1.84 and 1.63 Mg m -3 respectively. In undisturbed soil a critical density of 1.63 and 1.64 Mg m -3 was observed for the same horizons. However, the soil density at which root development begins to be restricted was 1.61 Mg m -3 for samples of upturned soil, and 1.50 Mg m -3 for samples of undisturbed soil at a depth of from 0.20 to 0.40 m. From 0.40 to 0.60 m the critical density was 1.45 and 1.18 Mg m -3 for samples of upturned and undisturbed soil respectively. It can be concluded that upturning the soil increased the IHO of the AB and Bt horizons of the Yellow Argisol, compared to the undisturbed soil cultivated with sugarcane. The subsurface movement of the studied Argisol increases the IHO at higher densities, due to the increase in the critical density of the AB and Bt horizons, improving their hydro-mechanical behavior.

Ocorrência da mosca-do-sorgo Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae) em genótipos de sorgo em Rio Branco, AC, Brasil

The first occurrence of Stenodiplosis sorghicola (Coq.) and the incidence of this pest on different sorghum genotypes were related in the State of Acre, Brazil. Panicles were collected ten days after the beginning of the blooming stage, and placed in emergence boxes. S. sorghicola ocurred on sorghum for forage and grain, with greater incidence on the first one. The genotype 698005 was the most atacked. The presence of S. sorghicola on sorghum in Acre revealed that this insect occurs in the region surviving, probably, on other Sorghum species.