ABSTRACT. Intensive weed management is one of the most common practices in coffee cultivation areas. Consequently, some problems, such as soil degradation and the selection of herbicide resistant weed, have increased over time, but, if properly managed, weeds at coffee planting inter-rows can offer benefits of erosion control, nutrient recycling and crop sustainability. The aim of this study is to evaluate the effect of different weed management strategies on the productivity and coffee grain size, i.e., quality. The experiment is installed onto a resprouting Coffea arabica L. site, four years after it was established. Treatments are implanted at planting inter-row Urochloa ruziziensis, Pueraria phaseoloides, and spontaneous vegetation maintained by mowing, herbicides, and weeding. To measure dry matter accumulation, samples are taken with a 0.25 m2 square template at plots maintained by mowing and herbicide application. To evaluate the yield and granulometry, coffee fruits are harvested, processed and classified in a set of 14 sieves (grouped in flat or “moca” shapes). The methods of controlling herbicide and weeding show significance in relation to grain production, with the production of grains having a higher market value standing out, when compared with the other treatments. The accumulation of dry matter above soil, in treatments with herbicides and spontaneous vegetation positively influenced the early coffee productivity (2018), and with U. ruziziensis and spontaneous vegetation, positively influenced the productivity of late harvest (2019). The accumulation of dry matter on the soil tends to be positively linked to coffee productivity, especially in periods when there is a shortage of rain in the region under study; however, it cannot be stated that this influence relationship (causality) has a direct positive effect between dry matter mass production and productivity of future coffee plantations.

RESUMO Atividade rizosférica de espécies fitorremediadoras em solo contaminado com picloram Algumas espécies de planta têm a capacidade de estimular a atividade da microbiota na rizosfera e, com isso, aumentar a degradação de herbicida no solo. Objetivou-se avaliar a atividade microbiana de solos contaminados com picloram e pré-cultivados com espécies fitorremediadoras. O delineamento experimental utilizado foi inteiramente casualizado, com três repetições. Os tratamentos foram organizados em esquema fatorial 5 x 2, sendo o primeiro fator constituído por tipos de cultivo (solo sem cultivo autoclavado e não autoclavado e solo da rizosfera de Urochloa brizantha, Panicum maximum e Zea mays) e o segundo consistindo da ausência ou presença (240 g ha-1) de picloram. Estimaram-se o C-CO2 evoluído, o carbono da biomassa microbiana e o quociente metabólico. O herbicida alterou o C-CO2 evoluído, mas não alterou o carbono da biomassa microbiana e o quociente metabólico nos solos rizosféricos das espécies. O cultivo de Zea mays aumentou a atividade da rizosfera. As três espécies de planta afetam a atividade microbiana do solo, no entanto, o cultivo de Panicum maximum e Urochloa brizantha causam menor perturbação na população microbiana, em comparação a Zea mays. A aplicação de picloran não afeta a qualidade biológica dos solos estudados.

ABSTRACT Some plant species have the ability to stimulate the microbiota activity in the rhizosphere and thereby increase the herbicide degradation in the soil. This study aimed at evaluating the microbial activity of soils contaminated with picloram and pre-cultivated with phytoremediation species. The experimental design was completely randomized, with three replicates. The treatments were organized in a 5 x 2 factorial scheme, with the first factor being the types of cultivation (autoclaved and non-autoclaved soil without cultivation and soil from the rhizosphere of Urochloa brizantha, Panicum maximum and Zea mays) and the second factor referring to the absence or presence (240 g ha-1) of picloram. The evolved C-CO2, microbial biomass carbon and metabolic quotient were estimated. The herbicide altered the evolved C-CO2, however, it did not affect the microbial biomass carbon and the metabolic quotient in the rhizospheric soils of the species. The cultivation of Zea mays increased the rhizosphere activity. The three plant species affect the soil microbial activity, however, the cultivation of Panicum maximum and Urochloa brizantha cause a lower disturbance on the microbial population, if compared to Zea mays. The picloran application does not affect the biological quality of the soils studied.

ABSTRACT Phytostimulation plays a key role in the process of rhizodegradation of herbicides in soil. Additionally, bio-enhancement associated with phytoremediation may increase the efficiency of the decontamination process of soils with herbicides. Therefore, the objective of this study was to evaluate the biomass and microbial activity of soil contaminated with sulfentrazone and cultivated with phytoremediator species plus a bacterial consortium. The experiment was conducted in a greenhouse, carried out with a 2 × 4 × 4 completely randomized factorial design with 4 replications. The first factor consisted of the presence or absence of bio-enhancement with a bacterial consortium composed of Pseudomonas bacteria; the second factor consisted of a monoculture or mixed cultivation of 2 phytoremediator species Canavalia ensiformis and Helianthus annuus, besides the absence of cultivation; the third factor was made up by the bio-remediation time (25, 45, 65, and 85 days after thinning). Uncultivated soils displayed low values of microbial biomass carbon and microbial quotient as well as high values of metabolic quotient throughout the bio-remediation time, indicating the importance of cultivating phytoremediator species for the stimulation of soil microbiota. Bio-enhancement with the bacterial consortium, in general, promoted an increase in the microbial biomass and activity of soil contaminated with sulfentrazone. In the presence of the bacterial consortium, Canavalia ensiformis stimulated a greater activity of associated microbiota and supported a higher microbial biomass. Phytoremediation associated with microbial bio-enhancement are thus promising techniques for the bio-remediation for soils contaminated with sulfentrazone. This technique enhances the biomass and activity of soil microorganisms.

O sucesso de um programa de melhoramento de milho visando à obtenção de híbridos está intimamente ligado à identificação da população mais promissora para a extração de linhagens. O presente trabalho objetivou identificar procedimentos para a escolha dessas populações. Para isso, foram obtidas populações segregantes S0, S1 e 196 famílias S0:1 de cada um dos quatro materiais comerciais avaliados: híbridos simples (C 333B e Z 8392), duplo (AG 1051) e variedade (BR-105). Os experimentos foram conduzidos na safra agrícola 98/99 em duas localidades na região sul do Estado de Minas Gerais: Lavras e Ijaci. Na avaliação das 196 famílias S0:1 de cada população foi empregado o delineamento látice simples 14 x 14. Adicionalmente foi instalado um experimento em blocos casualizados, com 4 repetições, para avaliação simultânea das gerações F1, S0 e S1 A partir dos dados de produtividade de espigas despalhadas (kg por parcela) das gerações F1, S0 e S1, foram obtidas as estimativas da contribuição dos locos em homozigose (m + a) e em heterozigose (d). Foram também foram estimados os parâmetros genéticos e fenotípicos com os experimentos das famílias S0:1. Constatou-se que houve boa associação (r = 0,81) entre a estimativa de (m + a) e a média das famílias S0:1 e que população com maior potencial para a extração de linhagens, maior (m + a), foi a AG 1051. A correlação entre as estimativas de (d) e h² foi baixa, indicando que a estimativa da contribuição dos locos em heterozigose não foi bom indicador da variabilidade potencial da população.

The identification of the population with greatest potential for inbred line extraction is directly linked to the success of a maize hybrid breeding program. This study was carried out to identify procedures for selecting these populations. Segregant S0, S1 populations and 196 S0:1 families were obtained from each of four commercial cultivars assessed: single hybrids (C 333B and Z8392), double hybrid (AG 1051) and variety (BR-105). The experiments were carried out during the 1998/99 season, in two locations in the southern region of Minas Gerais State, Brazil: Lavras and Ijaci. A 14 x 14 simple lattice design was used in the assessment of the 196 S0:1 families from each population. A randomized complete blocks design with four replications experiment was also set up to assess, simultaneously, the F1, S0 and S1 generations. The husked ear yield (kg/plot) of the F1, S0 and S1 generations was obtained and the contribution of the homozygous locos (m + a) and heterozygous locos (d) were estimated. The genetic and phenotypic parameters were also estimated using the S0:1 family experiments. A high correlation (r = 0.81) between the (m + a) estimate and the S0:1 family mean was observed. The AG 1051 population showed the greatest potential for line extraction, i.e., greatest (m + a) value. The correlation between the d and h² estimates was low, indicating that the estimate of the contribution of the heterozygous locos was not a good indicator of the potential variability of the population.