ISHS Acta Horticulturae 627: XXVI International Horticultural Congress: Toward Ecologically Sound Fertilization Strategies for Field Vegetable Production
NOVEL TECHNIQUES TO REDUCE ENVIRONMENTAL N POLLUTION FROM HIGH NITROGEN CONTENT CROP RESIDUES |
| Authors: | C.R. Rahn, G.D. Bending, R.D. Lillywhite, M.K. Turner |
| Keywords: | sugar beet, Brassica, leaching, composting, paperwaste |
| Abstract:
Return of high-N content crop residues, such as from vegetable brassicas to soil, particularly in autumn, can result in considerable environmental pollution. This can arise both from NO3- leaching to water courses, and the generation of nitrous oxides, which are implicated in global warming. Improved management of such residues can reduce losses following harvest and increase cycling of N between crops, particularly in nitrate sensitive areas. Two novel management techniques were investigated to assess their potential to reduce N pollution following the return of high- N content sugar beet crop residues to soil. In the first, sugar beet residues were co-incorporated with a range of biodegradable amendment materials to manipulate the release of N. In the second, residues were removed from the field in the autumn and ensiled with a similar range of amendment materials before being returned to the field the next spring. The amendment materials included paper waste, cereal straw, composted green waste and molasses. The most effective material at reducing N losses to the environment, compactor waste, was derived from the recycling of cardboard. Co-incorporating compactor waste into field soils at a rate equivalent to 3.75 t/ha of carbon, together with sugar beet residues had a significant effect in reducing both autumn soil mineral N levels and subsequent N losses by leaching and denitrification. This material was also effective in reducing N losses where crop residues were ensiled prior to being spread back onto the field. However, in both cases the grain yield of a following spring barley crop was reduced compared to a control with just sugar beet residues. These yield losses, following application of ensiled mixtures, could be mitigated by field application of 60 kg/ha fertiliser N. The use of biodegradable amendment materials also reduces the amount of biodegradable materials being sent to landfill which is becoming more expensive. | |
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