K. Scholte et M. Lootsma, EFFECT OF FARMYARD MANURE AND GREEN MANURE CROPS ON POPULATIONS OF MYCOPHAGOUS SOIL FAUNA AND RHIZOCTONIA STEM CANKER OF POTATO, Pedobiologia, 42(3), 1998, pp. 223-231
Effects of organic soil amendments on populations of mycophagous sprin
gtails and nematodes and on Rhizoctonia solani stem canker of potato w
ere investigated in two field experiments each lasting two years. The
organic amendments consisted of three green manure crops (white mustar
d, forage rape and oats), and farmyard manure (FYM, alone or in combin
ation with white mustard). In Year 1, before the application of soil a
mendments, experimental fields were infested with R, solani by growing
a potato crop from seed tubers severely infested with black scurf. In
the next year potato was grown again as test crop. In Experiment 1, t
here was a moderate degree of Rhizoctonia stem infection in the test c
rop. Organic amendments reduced the disease severity and increased pop
ulations of mycophagous soil organisms. The greatest reduction in dise
ase severity was found when FYM application was combined with white mu
stard or when oats was grown as green manure crop. In Experiment 2, Rh
izoctonia stem infection was so severe that emergence of potatoes in t
he test crop was reduced. Again, soil fauna populations were increased
by farmyard manure combined with mustard and also when oats was grown
as green manure crop. The disease severity was only slightly reduced
by the former treatment, and significantly by the latter one. FYM+whit
e mustard increased the springtail populations and hed no effect on my
cophagous nematodes, whereas oats increased the numbers of mycophagous
nematodes tenfold. The results from both experiments support the hypo
thesis that stimulating the populations of mycophagous soil mesofauna
can contribute to a reduction in Rhizoctonia disease severity in potat
o.