ABSTRACT Various attributes are often required to build soil quality indicators. However, determining these attributes is time-consuming and requires several specific devices. Thus, it is desirable to develop indexes that express soil quality based on easily determined attributes. The objective of this study was to investigate the spatial variability of the S index and its correlation with other physical and chemical soil attributes to generate a pedotransfer function for estimating the S index. A georeferenced sampling mesh covering 1.4 ha and employing 71 points was installed. The soil samples were collected in 0.00–0.15 m and 0.15–0.30 m deep layers to determine the physical and chemical attributes. The results indicated that the S index was correlated with porosity, carbon stocks, cation exchange capacity, and particle size fractions. However, macroporosity, microporosity, and sand content were the most suitable attributes for the construction of pedotransfer functions. A principal component analysis indicated that the S index was representative of 9.4% and 11.5% of the total variability in the dataset in the respective soil layers. Spherical semivariogram models showed that the S index was spatially dependent and ranged between 84–188 m. The S index maps estimated by the pedotransfer function resemble the observed S values; therefore, the function can be applied in spatial variability studies.

RESUMO A utilização de bactérias promotoras de crescimento pode promover incrementos de produtividade e qualidade de sementes de diversas culturas anuais, como a soja. Com base no exposto, com o presente estudo objetivou-se avaliar os efeitos da inoculação de estirpes de Bacillus subtilis no tratamento de sementes avaliando-se a produtividade e qualidade de sementes de duas cultivares de soja. O experimento foi conduzido em sistema convencional, num Latossolo Vermelho Distrófico de textura argilosa, em cultivo irrigado por aspersão. O delineamento experimental utilizado foi em blocos ao acaso dispostos em parcelas subdivididas com quatro repetições. Os tratamentos foram compostos, nas parcelas, por duas cultivares de soja: M7110 IPRO e Brasmax Desafio RR. Dentro dos níveis de subparcelas, os tratamentos foram constituídos de inoculação e doses de inoculante: Bacillus subtilis estirpe Pant001 nas doses de 0, 2, 3, 4 e 5 mL kg-1, e estirpe QST713, na dose recomendada de 2 mL kg-1. A inoculação com as estirpes Pant001 e QST713 proporcionou incrementos de produtividade em ambas cultivares de soja testadas, além de melhorar a qualidade das sementes em função do aumento na concentração de proteínas totais de reserva, porcentagem de emergência de plântulas e vigor de sementes pelo teste de envelhecimento acelerado.

ABSTRACT The use of growth-promoting bacteria can increase the yield and quality of seeds of several annual crops, such as soybean. Based on that, the present study aimed to evaluate the effects of the inoculation of Bacillus subtilis strains on seed treatment, evaluating the yield and quality of seeds of two soybean cultivars. The experiment was conducted in a conventional system, in an Oxisol of clayey texture, in a crop under sprinkler irrigation. The experimental design was randomized blocks, arranged in split plots with four repetitions. Treatments were composed, in the plots, of two soybean cultivars: M7110 IPRO and Brasmax Desafio RR. Within the levels of subplots, the treatments consisted of inoculation and doses of inoculant: Bacillus subtilis Pant001 strain at doses of 0, 2, 3, 4 and 5 mL kg-1, and QST713 strain at the recommended dose of 2 mL kg-1. Inoculation with the strains Pant001 and QST713 increased the yield of both soybean cultivars tested, besides improving seed quality due to the increase in the concentration of total storage proteins, seedling emergence percentage and seed vigor by the accelerated aging test.

RESUMO O uso de microrganismos na agricultura como Azospirillum brasilense e o cultivo de plantas de cobertura na entressafra, juntamente com a adubação nitrogenada, podem ser alternativas interessantes para aumentar a produtividade das culturas. Este estudo teve por objetivo avaliar os componentes de crescimento e de produção e o teor de nitrogênio do milho cultivado em sucessão ao cultivo de plantas de cobertura e suas interações com a inoculação de A. brasilense e a adubação mineral de N em cobertura. O experimento foi conduzido em Latossolo Vermelho-Amarelo no delineamento de blocos casualizados em parcelas sub-subdivididas com quatro repetições. As parcelas foram constituídas por quatro plantas de cobertura: feijão-de-porco (Canavalia ensiformis), feijão guandu anão (Cajanus cajan), crotalária (Crotalaria spectabilis) e vegetação espontânea. Nas subparcelas, com ou sem inoculação de A. brasilense nas sementes de milho e, nas sub-subparcelas: com ou sem adubação nitrogenada em cobertura. Verificou-se que o feijão-de-porco pode gerar incrementos de até 8,3% em grãos por espiga, 6,9% em comprimento de espiga e 15,2% em massa de cem grãos. Consequentemente, a produtividade de grãos foi maior neste tratamento (18%). A inoculação com A. brasilense e a adubação nitrogenada em cobertura não geraram incrementos significativos nos componentes produtivos do milho, como observado para plantas de cobertura.

ABSTRACT The use of microorganisms in agriculture such as Azospirillum brasilense and the cultivation of cover crops in the off season, together with nitrogen fertilization, may be interesting alternatives to increase crop yield. The objective of this study was to evaluate the growth, production and nitrogen concentration of maize grown in succession to cover crops and their interactions with A. brasilense inoculation and topdressing mineral N fertilization. The experiment was conducted on Oxisol, in randomized block design in split-split-plot scheme with four repetitions. The plots consisted of four cover crops: jackbean (Canavalia ensiformis), dwarf pigeon pea (Cajanus cajan), crotalaria (Crotalaria spectabilis) and spontaneous vegetation. In the subplots, with or without inoculation of A. brasilense in maize seeds, and in the sub-subplots: with or without topdressing N fertilization. It was verified that jackbean can generate increments of up to 8.3% in grains per ear, 6.9% in length of ear and 15.2% in mass of one hundred grains. Consequently, the grain yield was higher in this treatment (18%). The inoculation with A. brasilense and topdressing N fertilization did not generate significant increments in maize production components, as observed for cover crops.

ABSTRACT The least limiting water range (LLWR) is a soil physical quality indicator that receives much attention. It has been criticized and put to the test regarding mathematical models that compose it since they describe the behavior of soil physical attributes in a simplified way. This study aimed to assess the efficiency of some pedofunctions proposed in the literature and artificial neural networks on the accuracy in predicting soil water retention at potentials equivalent to field capacity (θFC) and permanent wilting point (θPWP). In other words, to apply the best models to LLWR of two soil types (Oxisol and Ultisol) and verify changes in their structure. The results indicated that pedofunctions using sand, silt, clay, bulk density, and soil organic matter contents are more efficient in estimating θFC and θPWP. However, the use of multiple linear regression models to predict θFC values below 0.20 m3 m−3 may present a slight tendency to overestimate it, which is not observed in the neural networks. As in R2, equations from neural networks were more efficient in estimating θFC and θPWP. Pedofunctions used to calculate LLWR differ in the establishment of the critical soil bulk density, exposing the limitations of the model.

ABSTRACT Assess the physical quality of agricultural soils it is important to establish the management more adequate for plant growth. In this study, the soil water retention curve and S index as indicators of soil physical quality were evaluated in five integrated production systems in the following forestry arrangements: Eucalyptus in a single line, double line and triple line (Eucalyptus I, II and III respectively), Balsa in triple line and Teak triple line. The density and arrangement of forest trees influence the soil physical properties. Less soil water retention was observed in the Teak and Balsa wood systems in the layers 0-0.10 and 0.10-0.20 m. The field capacity, permanent wilting point, and available water were lower under the projection from the treetops, providing less soil water retention at this site. This position suffers more influence of the animal's footstep, having greater alterations on the soil structure. Integrated production systems showed poor soil structural quality based on the S index, averaging 0.034 and 0.035 for layers 0-0.10 and 0.10-0.20 m respectively.