Rural Industries Research & Development Corporation

Research Compendium 1993 - 1994

Research Project

SUSTAINABLE HORTICULTURE USING IN-SITU MULCHES

Objectives

To develop practical, sustainable vegetable production systems based on in-situ mulch crops and drip irrigation, incorporating the following specific goals:

• identifying the essential physiological, environmental and morphological characteristics of in-situ mulch crops which permit viable vegetable production and improve soil structure;
• characterising the efficacy of mulch crops in suppressing weed growth;
• determining the operating requirements for drip irrigation of mulch and vegetable crops; and
• determining the requirements for transplanting and direct seeding equipment for mulch and vegetable crops.

Background

Most vegetable production in Australia is irrigated and intensively cultivated. Severe overwatering occurs in almost all of the irrigated area. These combined pressures have led to severe soil structural decline which requires increased levels of inputs of water, fertiliser and soil ameliorants to maintain productivity.

Work at Sydney University has demonstrated that winter-grown legume crops which senesce in Spring leaving a protective in-situ mulch have great utility in maintaining and improving soil structure while maintaining crop yields. When the irrigation method is changed to drip irrigation, significant reductions in water and fertiliser usage occur. The marriage of the two systems promises the basis of a more sustainable system of vegetable production.

Research

Most of the experiments were conducted in the field, on a realistic commercial scale. The main areas investigated were the production levels of crops grown with and without in-situ mulches; effects of the mulches on soil properties; ability of the mulches to suppress weeds and irrigation requirements of crops grown with the mulches.

Outcome

In the well-watered clay loam used, by the researchers, the crops grown with subclover mulches generally grew about as well as those grown with zero tillage and cultivation. Ryegrass always showed a phytotoxic effect on the vegetable crops. The soil under subclover mulches showed a greater accumulation of organic matter and nitrogen than cultivated soil. Subclover appeared to be the best mulch for suppressing weeds, but had the potential to become a vigorous weed itself after vegetable crops. Wetting patterns were studied and effective placement of water from drip lines in the root zone was demonstrated.

Implications

Mulches certainly have a lot to offer in a marginal cropping system, where beneficial effects on soil structure and strength have been observed. On a well managed farm where the soil has good structure, this advantage is less important. The beneficial effects of non-chemical weed suppression, prevention of erosion and amelioration of extreme soil temperatures have to be balanced against the necessity for finely tuned management, the possibility of the mulch becoming a weed and a possible increase in soil-borne pathogens.

RIRDC Project No: US-18A

RESEARCHERS: Bruce Sutton Richard Stirzaker

ORGANISATIONS: Dept of Crop Sciences Centre for

The University of Sydney Environmental

PHONE: 02 351 2050 06 246 5646

Last updated: 10 October 1996
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