Yield and diseases of potato as affected by deep soil tillage and crop succession with grass types

Resumo

Yield and disease incidence were evaluated in potato (Solanum tuberosum cv. Atlantic) after six years of cultivation in succession with corn (Zea mays cv. ‘AG 6080’) under conventional tillage (CT, depth of tillage: 0.20 m) or in succession with three grass types [Guinea grass (Panicum maximum cv. Tanzânia), Palisade grass (Brachiaria brizantha cv. Marandu) and corn] under deep tillage (DT, depth of tillage: 0.70 m). Total tuber yield was higher in DT in average 36% the value obtained in CT (17.76 t ha^-1), with no effect of the grass type. Common scab (Streptomyces scabies) incidence was influenced by treatments, the highest (16.9%) and the lowest (9.5%) values being obtained in succession with corn and Guinea grass (Panicum maximum cv. Tanzania), respectively, both under DT. The lowest incidence of tuber greening at field (2.58%) was also recorded in Guinea DT, significantly lower than obtained in Corn CT (6.33%), possibly due to a more efficient ridging operation. Grass types showed different values of aboveground dry matter production. Guinea grass (26.56 Mg ha^-1) was the most and Corn under CT and DT (5.72 and 5.56 Mg.ha^-1, respectively, without ears) were the least productive ones. Soil density, macroporosity and resistance to penetration indices were significantly better with DT, the grass type affecting them in a minor degree. The deep tillage system is therefore recommended for potato cultivation regardless the grass type used for crop sucesssion.