Nematode-Suppressive Potential of Digestates to Meloidogyne incognita and Heterodera schachtii .

Management of plant-parasitic nematodes uses host plant resistance, crop rotation, cultural methods and nematicide applications. Host plant resistance is tedious to develop, crop rotation and cultural methods are challenging to use. Environmental and human health concerns render sole reliance on chemical nematode suppression non-sustainable. Previously, digestate from anaerobically fermented maize silage suppressed Heterodera schachtii in Beta vulgaris subsp. crops. Here, seven digestates were investigated for nematode suppressive potential: liquid dairy manure digestate (LDMD), liquid dairy manure digestate with ammonia removed (LDMDA-), food waste digestate (FWD), liquid food waste digestate with ammonia removed (LFWDA-), liquid food waste digestate (LFWD), food waste hydrolysate from the Renewable Energy Anaerobic Digester (HREAD), and food waste hydrolysate from the South Area Transfer Station in Sacramento (HSATS). In a red radish, Raphanus sativus, bioassay with H. schachtii, digestates were amended at rates of 0.02, 0.11, 0.57 and 2.86 ml/100 cm3 of soil. At a rate of 2.86 ml, all amendments except LDMDA- and LFWDA- significantly reduced juvenile root penetration compared to the infested control. In a greenhouse watermelon, Citrullus lanatus, bioassay with Meloidogyne incognita, amendments FWD, LFWD, HREAD and HSATS as well as LDMD (less effectively), at 2.86 ml and 5.76 ml per 100 cm3 soil significantly reduced egg masses per root system compared to the non-treated, nematode-infested control. In a microplot experiment with M. incognita and red radish, in the treatment amended with LFWD at 2.37 ml/100 cm3 soil marketable yields were improved by ~50% over the non-treated control and were comparable to those in the treatment with the nematicide Reklemel. In a second microplot experiment with M. incognita and watermelon, treatments that contained LFWD at rates of 3.55 ml/100 cm3 of soil had transient numerical effects of initial nematode suppression that were not maintained throughout the three-month growth period. The results of these studies demonstrated that digestates FWD and LFWD consistently expressed some nematode-suppressive capacity.