I. M. R. Guedes

Effect of Soil Compaction Alleviation on Quality and Yield of Potato

Soils of tropical environments are exposed to the process of degradation when the natural ecosystems are converted to unsustainable agro-ecosystems. Soil compaction, which is part of that degradation process, is widely found in Brazilian cultivated areas, especially in the potato fields in which the intensive soil revolving operations promote the disruption of aggregates. Furthermore, potato is very sensitive to the problems associated to the soil compaction, such as the low development of roots and the diseases that are favored by high humidity in the tuber. In this way, a tillage system based on deep alleviation of soil compaction for the potato crop is presented in this chapter. This system, named “deep soil loosening” was evaluated in two Brazilian producing regions in Bahia and Sao Paulo States and provided higher yields, which were associated to the improvement of soil physical attributes. Thus, the “deep soil loosening” system is suggested as an alternative to improve potato production in compacted areas and, also, as a tool for promote the recuperation of soils damaged by compaction.

Efeito da adubação química na infestação do ácaro rajado e na produção do morangueiro

Effect of chemical fertilization on two-spotted-spider mite infestation and strawberry yield The effect of N:K relationship was evaluated when applied through fertigation, on two-spotted-spider mite, Tetranychus urticae, infestation and on the yield of two strawberry cultivars. Strawberry plants received weekly doses of N and K (g/plant) by drip irrigation: 0.27 and 0.13; 0.27 and 0.50; 0.27 and 0.76 and control (water+micronutrients). Fruits were collected twenty two times during crop cycle. Marketable, non-marketable fruits and other yield parameters were evaluated. Leaf nutrient content analysis was performed to determine the nutritional condition of the plants. Population density of T. urticae was evaluated weekly. A significant interaction between K doses and pest population was observed. Higher doses of the nutrient reduced the number of eggs and active forms of the pest population and the cultivar Diamante showed the smallest pest density. K and P showed negative correlation with both variables, but N showed a positive one. No effects were observed of fertilization on yield parameters due, probably, to the high mite infestation (>40 individuals per leaflet) in all treatments during most of the crop cycle. Solely the use of different N:K ratios on the strawberry fertilization management at this specific experimental condition, was not sufficient to control two-spotted spider mite nor to reduce losses caused by that pest.