No abstract

Losses of soil and nutrients affect a large part of agricultural areas in tropical regions, regardless of the level of technology adopted. This study evaluated the physical attributes and erosivity indices associated with rainfall patterns and return periods in the region of Formosa, State of Goiás, Brazil. Using series of pluviographic (2002-2008) and pluviometric (1975-1998) data from a station located at municipality of Formosa, the erosive potential (EI30 and KE>25), rainfall patterns (advanced, intermediate and delayed) and the erosivity associated with the rainfall return periods were determined. The average annual rainfall of the region was 1,391.6 mm with 87.4% of the rains concentrated in October to March. The average annual values of EI30 and KE>25 corresponded to 8,041.6 MJ mm ha-1 h-1 year-1 and 125.7 MJ ha-1 year-1, respectively. The months of the year did not differ based on rainfall pattern. The advanced hydrological pattern had the highest frequency of occurrence, followed by the delayed and intermediate patterns. The highest EI30 and KE>25 indices for individual rainfall seasons occurred under the intermediate and the advanced patterns in February and under the intermediate pattern in October for the index KE>25. The average annual erosivity index (R factor of USLE) (8041.6 MJ mm ha-1 h-1 year-1) is expected to occur at least once every 1.89 years, corresponding to a probability of occurrence of 52.84%. The average annual values of EI30 estimated for the return periods of 2, 5, 10, 25, 50 and 100 years were 8,230, 10,225, 10,889, 11,222, 11,421 and 11,488 MJ mm ha-1 h-1 year-1, respectively.

Lowlands represent a significant portion of agricultural areas in the world. Thus, understanding the spatial variability of the chemical and granulometric characteristics of hydromorphic soils can contribute to improving soil management and fertility. The objective of this work was to characterize spatial dependence, spatialized chemical attributes, granulometry, and the ideal number of samples in irrigated hydromorphic soil. Soil sampling was conducted in a grid of 10x10 m, in the layers of 0–0.1 and 0.1–0.2 m, totalling 432 composite samples. The evaluated attributes are as follows: pH in water, H+Al, SOM, Ca, Mg, Al, P, K, CTC, V%, Cu, Fe, Zn, Mn, clay, silt, and sand. The texture of the area was classified as loamy–sandy and free in the 0–0.1 and 0.1–0.2 m layers, respectively. The coefficient of variation of the attributes ranged from 2.71% (0–0.1m) to 149.07% (0.1–0.2m). All the attributes studied exhibited moderate to strong spatial dependence. The sample grid with a sampling interval of 20 m referring to the 0–0.1 m layer proved to be adequate. The ideal number of simple samples per composite is 19 for granulometry and macronutrients, and 28 for the micronutrients in the 0–0.1 m layer.

As características físicas do solo podem variam de acordo com o tipo de uso e cultivo ao qual o mesmo é submetido, e algumas práticas de manejo provocam efeitos negativos nas propriedades físicas do solo, podendo comprometer o desenvolvimento das culturas. Assim, este trabalho teve como objetivo avaliar, em três profundidades, as propriedades físicas de um Latossolo Vermelho-Amarelo Distrófico localizado no município de Anápolis, Goiás, sob diferentes sistemas de manejo. Foi adotado o delineamento inteiramente casualizado, fator único, sendo os tratamentos constituídos dos seguintes sistemas de manejo: Pastagem, Pomar, Plantio Direto e Plantio Convencional, com quatro pontos de amostragem por tratamento, em cada profundidade. Verificou-se que os diferentes sistemas de manejo e profundidades provocam pouca ou nenhuma alteração na densidade do solo, densidade de partículas, porosidade e umidade. A pastagem proporcionou o maior aporte de matéria orgânica em relação aos demais sistemas. O pomar apresentou os melhores resultados de capacidade de água disponível. A resistência a penetração foi maior na camada de 0,20-0,30 m do solo e diferiu significativamente entre os tratamentos avaliados. Na área de pomar observouse os menores valores de resistência à penetração e, na pastagem, os maiores. Palavras-chave: Manejo conservacionista, Qualidade física do solo, Retenção de água pelo solo.