ABSTRACT: The spatial variability of soil organic matter, plant water availability, and soil nitrogen (N) availability are drivers of crop response to mineral N fertilizer. The complex interaction of these factors is responsible for within-field corn and wheat yield variability. The hairy vetch (HV) cover crop is an economic, environmentally friendly, and efficient N source capable of conciliating crop yield and soil health. Nevertheless, the HV effects to mitigate yield gap of management zone (MZ) have not yet been documented. This study evaluated the effects of HV and mineral N fertilization, in single or combined input, on alleviating crop yield gap. The study was carried out in two croplands southern Brazil. The experimental design was a complete randomized block in a split plot having MZ (high, medium, and low yield) and N fertilizer rates. Wheat and corn N uptake and grain yield had a quadratic adjustment with N fertilizer input, but there was a significant MZ effect, where low yield zone (LYZ) was less responsive. Consequently, mineral N fertilization as a single input to mitigate the yield gap in this MZ was not efficient. On the other hand, HV increased corn N uptake and grain yield mainly in LYZ compared to MYZ and HYZ. HV fully mitigated the yield gap between MYZ and HYZ. The combined use of HV and mineral N fertilization rate adjusted according to N legume credit and MZ was an efficient strategy to boost yield, favoring soil health and environmental protection.

ABSTRACT Vermicomposted vegetal and animal residues are rich in nutrients and humic substances and thus can be applied to the soil as a source of functionalized organic matter (OM) and as an alternative to chemical fertilizers. In Southern Brazil, many animal and vegetal residues are easily accessible. Therefore, this study aimed to evaluate alterations in soil chemical properties and OM chemical composition in response to the application of local vermicomposted residues. The vermicomposts of: cattle manure (CM), sheep manure (SM), rice parboiling sludge (PS), CM+PS; SM+PS; CM+food waste (FW); SM+FW; CM+fruit waste (FRW); and SM+FRW were mixed with Acrisol (Argissolo) samples collected at 0.00-0.20 m layer, and the samples were incubated in plastic bags for 182 days. Soil samples without vermicomposts were also incubated (control). Overall, vermicomposts increased soil pH(H2O), exchangeable Ca and available P and K contents. The treatments with CM or SM with FW promoted carbon accumulation in the soil compared to the control, especially as humin. The humic acids of SM and PS were more oxygenated than the others, and oxygenation was apparently associated with aromatic structures. Fulvic acids of CM+PS showed the greatest oxygenation and aliphatic character. The relationship between vermicompost origin (animal or vegetal) and soil properties or OM composition was not clear. Aromaticity degree (H/C) and C/N ratio were similar in fulvic and humic acids, and oxygenation degree (O/C) as well as polarity index [(O+N)/C] were more efficient parameters to distinguish these humic fractions. We concluded that vermicomposts derived from cheap and easily available vegetal and animal residues in Southern Brazil have great potential as alternative fertilizers as well as sources of functionalized OM when applied to the soil, especially vermicomposts of rice parboiling sludge and cattle or sheep manure mixed with food waste.

Resumo O objetivo deste trabalho foi avaliar as relações da condutividade elétrica aparente (CEa), determinada por sensoriamento em tempo real, com os atributos do solo e com a produção vegetal, além de espacializar de forma indireta e em alta resolução os componentes da acidez de um Latossolo Vermelho distrófico no Sul do Brasil. O sensoriamento do solo foi realizado em duas áreas agrícolas, com o sensor Veris 3100. O solo foi amostrado à profundidade de 0,00-0,15 m, com trado calador. Avaliou-se o índice de vigor do milho (IV) com um sensor óptico, e a produtividade com sensores de produtividade e umidade. A associação dos atributos da acidez do solo com a produtividade do milho e com a CEa foi determinada por meio de análises de correlação e de componentes principais. A CEa relacionou-se ao IV e à produtividade de milho. Além disso, na área com qualidade química inferior, a CEa apresentou relação positiva com os conteúdos de Ca2+, Mg2+, com pH em água, saturação e soma de bases, e com a capacidade de troca catiônica; e negativa com os valores de Al3+, saturação por alumínio e de H+Al3+. Na área com melhor qualidade química, a CEa apresentou relação com Ca2+, Mg2+, matéria orgânica do solo e teor de argila.

Abstract The objective of this work was to evaluate the relationships between the apparent electric conductivity (ECa), measured by on-the-go sensing, with soil attributes and plant production, besides indirectly mapping with high resolution, the main acidity attributes of an Oxisol in South Brazil. Soil sensing was performed in two crop fields using the Veris 3100 sensor. Soil was sampled at the 0.00-0.15-m soil depth using a hand auger. The corn vigor index (VI) was measured with an optical sensor, and yield was determined using grain yield and moisture sensors. The association of soil acidity attributes with corn yield and ECa was determined with correlation and principal component analyses. ECa was associated with the VI and corn yield. Moreover, in the area with low chemical quality, ECa had a positive relationship with Ca2+ and Mg2+ contents, pH in water, base saturation, sum of bases, and cation exchange capacity; and a negative relationship with Al3+, aluminum saturation, and H+Al3+ values. In the area with better chemical quality, ECa was related to Ca2+ and Mg2+ contents, soil organic matter, and clay content.