A no-till farming system has been developed for horticultural production, utilizing permanent beds that are not cultivated after initial land preparation. While a previous HAL project (VG98050) developed the original system for horticultural crops grown in Bowen, Queensland, the present study has expanded the range of techniques which can be employed to address a wider range of crops and regions. By applying the most appropriate combination of practices to each production situation, this project broadens the relevance of previous work to Australian vegetable farmers, with an emphasis on implementation.

Cover crops are established on beds, grown to maturity, killed and then flattened into an organic mulch. Commercial crops are directly sown or transplanted into this cover crop residue. This system aims to increase sustainability in relevant horticultural industries through the long-term maintenance of soil health and stability, as well as eliminating reliance on plastic mulch, which is difficult to dispose of, in an environmentally responsible fashion.

The project aimed to identify appropriate cover crops for winter and summer growth in the tropical and temperate regions and implement the system on the farms of co-operating growers. Practices were developed for managing crop nutrition, planting, weed and pest control and irrigation, as well as the best techniques for killing the cover crop.

Forage sorghum is the most commonly used summer season cover crop. Nutrifeed, a hybrid Pennisetum, has shown potential as a sorghum replacement in some regions, with fine stems resulting in mulch which is easier to manage. Millet can be used to provide mulch for both winter crops in the tropics and summer crops in the subtropics, although the cover produced is much thinner than that of sorghum.

Winter cereals (wheat, oats and barley) as well as ryegrass grow well through the winter / spring period. Cereal rye produces very high quality mulch suitable for New South Wales and Victoria when sown at high density. Cereal growth in tropical areas can be relatively slow, leading to problems with weed management.

Legumes were evaluated as cover crops, alone and in combination with a cereal or forage crop. White lupins and field peas were selected for temperate sites and Caloona cowpea and soybeans were examined in the tropics. Competition with weeds was poor for all legume species tested, although further research is needed to measure soybean performance. White lupin and field pea growth was suppressed when sown with barley.

The best method for killing the cover crop was found to be an application of glyphosate, followed by rolling with a crimping roller within 7 days of herbicide application. Tank-mixing the glyphosate with a broadleaf herbicide was beneficial if legumes were present. Transplanting seedlings into cover crop residue requires access to no-till transplanters, such as the Canadian manufactured RJV-600. This type of transplanter was found to handle all conditions well, with the exception of wet mulch.

Maximum soil temperatures under organic mulch were found to be lower than those under plastic mulch, leading to slower crop maturation, although yields were found to be comparable in some instances. This effect provided benefits in some situations, such as the reduction of excessive temperatures experienced in the tropics. Protection of produce from soil moisture was an observed advantage of organic mulch, relative to bare soil production. Irrigation frequency should be increased when using organic mulch, especially during the establishment stage, as soil moisture retention is less than that which is provided by a plastic mulch.

Conventional farming and no-till farming systems were compared throughout the project. The previous HAL project which investigated the use of cover crop mulches in Bowen (VG98050) provided an economic comparison of no-till and conventional farming. With further development of this system and it’s application to a greater number of production types, a more comprehensive economic review is now required to establish potential returns for a range of situations.

Field days were held in Bowen and Giru, in North Queensland and articles were published in various publications, providing extension of project findings.