Nematode communities in soils of four farm cropping management systems

Nematode community composition was compared for four farm cropping manageme nt systems near Ithaca, Nebraska, USA. Management systems differed in their source of nutrients and pest management, and were designated as manure onl y (O), mineral fertilizer only (F), mineral fertilizer plus herbicides (KF) , and mineral fertilizer, herbicides plus insecticides (HFI). All farming s ystems were cultivated annually and planted to annual crops either in rotat ion (O, F, HF systems) or continuous corn (HFI system), Eleven nematode com munity (plant-parasites and free-living) and four microbial biomass indices were measured in 1993, 18 years after establishment of management practice s. Numbers of bacterivores and plant-parasites and maturity index (PPI and PPI:MI) values were greater, and MI1-5 values smaller, with manure than min eral fertilizer applications, MI2-5 values decreased with additions of herb icides and/or insecticides but were not sensitive to source of nutrients. T otal fungal biomass and active bacterial biomass were associated positively with application of insecticides. Numbers of Pratylenchus increased and Ce phalobus decreased with applications of manure compared to mineral fertiliz ers. Numbers of Helicotylenchus decreased with additions of mineral fertili zer, herbicides and insecticides but Monhystera and Mylonchulus abundance i ncreased with insecticide applications. This study demonstrates differentia l effects of pesticides and nutrient source on nematode community compositi on.