ABSTRACT The effects of machinery traffic and cover crops on soil physical properties have been underexplored under no-till agricultural production in subtropical environments. The objective of this study was to quantify the soil water infiltration rate and related soil physical properties in response to tractor traffic levels (0, 2, 5, and 20 passes) and the presence or absence of cover crops in a Xanthic Hapludox soil over two growing seasons under no-till conditions. The experiment was carried out in a randomized block design arranged in a factorial scheme with four replications. The traffic factor was constituted by the number of passes with a 6 Mg weight tractor. The winter crop management practices factor consisted of the cover crops (i) black oat (Avena strigosa) in 2017 and turnip (Raphanus sativus var. oleiferus) in 2018 compared with (ii) fallow with spontaneous vegetation. The soil water infiltration rate increased with cover crops when compared to fallow. Regarding tractor traffic levels, shortly after soil compaction, there was a lower water infiltration rate at 20 passes, 45 mm h-1 lower than the absence of tractor traffic. The soil water infiltration rate was positively correlated with macroporosity and negatively correlated with soil bulk density. After 14 months of soil compaction caused by tractor traffic, an improvement in the soil physical properties and the water infiltration rate was found, which were enhanced by the inclusion of cover crops.

RESUMO O valor comercial dos tubérculos de batata é afetado pelos danos causados por Diabrotica speciosa, cujas larvas fazem orifícios na casca dos tubérculos e túneis internos. A estimativa dos danos aos tubérculos de batata é geralmente realizada avaliando os danos externos, em detrimento dos túneis de alimentação causados por larvas. Assim, propomos um método para estimar os danos de D. speciosa, considerando os aspectos externos e internos dos tubérculos separadamente. Para tanto, plantas de batata cv. Ágata foram cultivadas sob diferentes infestações de larvas, medindo-se a área ocupada pelos buracos e o volume dos túneis de alimentação internamente, relacionando esses dados com a área total e o volume do tubérculo. A metodologia utilizada permitiu caracterizar o aumento dos danos nos tubérculos com maior infestação de larvas. A correlação entre os danos internos e externos causados por larvas de D. speciosa não foi significativa, indicando que o dano externo por si só não é um parâmetro adequado para o diagnóstico da qualidade geral do tubérculo. No entanto, o método aqui proposto fornece informações sobre o volume de polpa consumido pelas larvas, a extensão das galerias formadas e o volume relativo de danos em relação ao tubérculo total. Além disso, o método aqui proposto contempla uma análise mais precisa da área externa danificada pela herbivoria em relação à área total do tubérculo, o que não é comumente considerado em estudos de estruturas de plantas subterrâneas.

ABSTRACT The marketable value of potato tubers is affected by damage caused by Diabrotica speciosa, whose larvae create holes on the tubers’ skin and internal feeding tunnels. The estimation of potato tuber damage is usually performed by assessing the external damage to the detriment of feeding tunnels caused by larvae. Thus, we propose a method to estimate the damage caused by D. speciosa larvae, considering the external and internal aspects of the tubers separately. For that, potato plants cv. Agata were grown under different infestations of larvae, measuring the area occupied by the holes and the volume of internal feeding tunnels, relating these data to the total area and volume of the tuber. The methodology used allowed us to characterize an increase in damage in tubers with the highest infestation of larvae. The correlation between internal and external damage caused by D. speciosa larvae was not significant, indicating that external damage alone is not an adequate parameter for the diagnosis of overall tuber quality. However, the method proposed here provides information regarding the volume of pulp consumed by the larvae, the extent of the galleries formed, and the relative volume of damage concerning the total tuber. Moreover, the method proposed here contemplates a more precise analysis of the external area damaged by herbivory relative to the total area of the tuber, which is not commonly considered in studies of underground plant structures.