Effects of organic amendments, fertilisers and fenamiphos on parasitic and free-living nematodes, tomato growth and yield

Abstract

The effects of various organic amendments, fertilisers and fenamiphos on the growth of tomatoes were compared in pots containing soil naturally infested with the plant parasitic nematodes Meloidogyne javanica, Paratrichodorus sp. and Criconemella xenoplax and free living nematodes. Organic amendments (at 3.2-14 t Dry Matter/ha, or 10,270 l molasses/ha) were added to the soil six weeks before transplanting tomato cv. Grosse Lisse. Soils amended with grassy weed residues, barley residues, lucerne pellets, molasses, two commercial organic fertilisers, or with complete fertiliser stimulated stem growth of tomato plants. Root growth was stimulated in plants grown in soil amended with molasses; this was correlated with an increased root gall index, but M. javanica densities in soil and roots were not elevated. Root gall index was also increased in plants grown with complete fertiliser. Fruit yield was stimulated in plants grown in soil amended or treated with grassy weed residues, lucerne pellets, complete fertiliser or fenamiphos; yields were 740% higher in plants grown in soil amended with grassy weed residues than in plants grown in unamended soil with an equivalent rate of urea. Shredded paper and potato peel caused N deficiency and poor growth, and sudden collapse was observed in plants growing in soil amended with potato peel, due to infection of stem bases by Pythium sp. Pea straw was resistant to breakdown, and inhibited plant growth. Lucerne pellets, a pig manure-based organic fertiliser, and fenamiphos reduced densities of M. javanica in soil; lucerne pellets, composted green waste and fenamiphos reduced densities of M. javanica on tomato roots. Densities of Paratrichodorus sp. were reduced in soil amended with all solid organic materials, or with molasses. Criconemella xenoplax densities remained low in all treatments. Of soil amendments and treatments that did not inhibit plant growth, only grassy weed residues, lucerne pellets and poultry manure maintained elevated densities of freeliving nematodes in soil up to harvest. Grassy weed residues and lucerne pellets have potential for stimulating tomato growth, and/or reducing M. javanica densities, while increasing densities of free-living nematodes.