RESUMO O tráfego intenso das máquinas nos solos cultivados aplica diferentes tensões que combinadas com altos valores de umidade desses

The continuous use of tillage equipment without variation of the work depth can lead to soil compression problems. This study aimed to evaluate the spatial variability of soil resistance to penetration (RP) in a yellow ultisol profile in different tillage systems and tractor-equipment speeds. The experiment was carried out at the Agricultural Sciences Campus – UNIVASF, Petrolina- PE, Brazil, in randomized blocks with split plot with four repetitions. The treatments consisted of five tillage systems applied to the plots: without the first soil preparation, tandem grid and moldboard plow, 0.56 m off-set grid discs, 0.61 m off-set grid disc plus tandem grid and chisel plow. For the subplots, the speeds of the tractor-equipment used were: 2.45 km h‑1 (L1), 3.88 km h-1 (L2), 5.72 km h-1 (L3) and 6.50 km h-1 (H1). For the soil data collection and the RP determination, an electronic penetrometer was used, determining the sample profile moisture. Data analysis was carried out based on geostatistics and isoline maps. It can be verified the operationarea of the active organs of the equipment, the zoning of compacted areas (RP) and the RP levels of the studied profile. The lower RP was obtained when the tandem grid plus the chisel plow was used.

RESUMO:Os sistemas de preparo do solo afetam a quantidade de resíduo vegetal sobre a superfície do solo e, consequentemente, sua umidade e temperatura. Objetivou-se avaliar a temperatura e a umidade do Argissolo Amarelo em estádios de desenvolvimento da cultura do milho sob sistemas de preparo mecanizado. O experimento foi conduzido no delineamento em blocos inteiramente casualizados, com quatro repetições, em Petrolina -PE. Os sistemas de preparo do solo foram: sem preparo primário, grade off-set de discos de 0,56 m, grade off-set de discos de 0,61 m, escarificador e arado de aivecas. As leituras de umidade e temperatura foram realizadas ao longo do dia, nos horários de 6; 9; 12; 15 e 18 h, nos estádios de desenvolvimento V3, V8, R3 e R6 do milho. A umidade do solo foi avaliada na camada de 0,00-0,05 m utilizando-se do método gravimétrico, e a temperatura do solo na superfície, utilizando-se de termômetro infravermelho. Os sistemas de preparo do solo e os horários de leitura influenciaram na umidade e na temperatura do solo. Os maiores valores de umidade ocorreram no período da manhã, enquanto a maior temperatura do solo ocorreu na parte da tarde. PALAVRAS-CHAVE:mecanização agrícola, Semiárido Nordestino, variação térmica. SOIL MOISTURE CONTENT AND SURFACE TEMPERATURE IN TILLAGE SYSTEMS AND STAGES OF DEVELOPMENT OF MAIZE CROP ABSTRACT:The tillage systems affect the amount of crop residue on the soil surface, and hence its temperature and moisture content. To evaluate the variation of moisture content and soil temperature in systems of tillage on maize growth stages, an experiment was conducted in Ultisol.The experiment was conducted with randomized complete block with four replications in Petrolina -PE, Brazil. The treatments consisted of five tillage systems applied to the plots -unprepared primary, off-set disc harrow of 0.56 m, off-set disc harrow of 0.61 m, chisel plow and moldboard plow. The soil moisture and temperature readings were taken at 6, 9, 12, 15 and 18 h for the different maize stages V3, V8, R3 and R6. Soil moisture was measured in the layer between 0.00-0.05 m by means of deformed samples by using gravimetric method and soil temperature at the surface with infrared thermometer. Systems of soil tillage and hours of reading influenced the moisture and soil temperature. The highest values of soil moisture content occur in the morning, while the highest temperature of the soil in the afternoon.

Plant cocktails used as cover crop present a significant multifunctional resource compared to monoculture, which may increase functional diversity within crop rotation and is particularly effective for designing mixtures with characteristics that increase the multifunctionality and sustainability of the agroecosystem. The objective was to evaluate sustainable agroecosystems models that improve the efficiency of nutrient cycling for crops. The treatments were arranged in four blocks in a split-plot design with two soil management (tillage and no-till) systems and three cropping systems (2 plant cocktails [PCs] and 1 natural vegetation [NV]). C/N ratio, lignin content, dry biomass (DB) production and decomposition, nutrients accumulation and mineralization by PCs and NV were evaluated. Decomposition and release of nutrients were monitored by the litterbag-method. PCs had a DB production twice higher than NV, essential for the adoption of no-tillage systems. The order of nutrient release was K> N> Ca> P> Mg. PCs as cover crops and green manure, with or without predominance of legumes and use of a no-tillage system, could be a technological strategy in agroecosystems for nutrients cycling in semi-arid regions.