Temperate vegetable and nursery industries face significant challenges in managing Meloldogyne hapla, a plant-parasite for which few resistant cultivars and/or viable alternatives to methyl bromide exist. N-Viro Soil (R) (NVS), an alkaline-stabilized biosolid product, has soil nutrition enrichment capacity and potential for plant-parasitic nematode suppression In three sets of experiments, we investigated the effects of NVS on M hapla populations from Rhode Island (RI), Connecticut (CT), New York, Geneva (NYC) and Lyndon-ville (NYL), and Michigan (MI), and growth of tomato cv 'Rutgers' in five soils commonly used for vegetable and nursery crop production in the Great Lakes Region of the USA. Either 0 (control) or 600 eggs/100 cm(3) of soil per M. hapla population were added in all experiments In the first set, NVS was applied at rates of 0, 1, 2 and 4 g/100 cm(3) of sandy loam soil (pH 7) and resulted in variable responses on the numbers of nematodes recovered and plant growth at 30 and 90 days (25 +/- 2 degrees C), however, the 2 g NVS treatment consistently increased plant growth Either 0 or 2 NVS/100 cm(3) were applied to a coarse loamy (pH 4 5) and sandy loam (pH 8, second set of experiments), and muck (pH 5 5), loamy sand (pH 7 1) and sandy loam (pH 75, third set of experiments) soils and experiments terminated four weeks after nematode inoculation Across experiments, the effect of NVS on the M hapla populations varied. Generally nematode infection decreased plant growth. NVS increased soil pH the most in muck and the least in sandy loam soil The most consistent interaction effects of NVS*soil, NVS*M hapla, soil*M hapla and/or NVS*soil*M hapla across the experiments indicate that NVS affects M hapla populations in different ways in different soil types, suggesting that NVS application is likely to be site-specific These findings further provide basis that may potentially explain reports of variable effects of NVS on nematodes and how future studies may account in furthering our understanding of NVS activities for M hapla management (C) 2010 Elsevier Ltd All rights reserved.