Soil Systems Farm

Strategies for orchards and vineyards

Weed control in organic orchards and vineyards is one of the most important management practices carried out by the farmer. Depending on the strategy and climatic region, it sets the foundation for yield potential and quality of fruit to be produced. Failure to get on top of weeds leads to significant yield losses of up to 80%. The best Australian organic & biodynamic producers always come back to the basics in one form or another; namely farm design, choose the best machinery, humus and mineral rich nutrition, timeliness of operation and measurement of every activity.

Here are some of their tips….

Site preparation prior to orchard or vineyard establishment

When selecting a site for an orchard or vineyard N/S orientation generally gives the best yields and quality. It maximises light absorption by the crop and inter-row pasture sward throughout the year. While walking across the paddock, farmers should initially take with them a shovel or preferably a garden fork. They should occasionally stop and examine the soil for compaction, observe where the pasture is rich in white feeder roots and where the problem weeds occur. Depending on the state of the paddock, this should be followed up with ripping or chisel ploughing to loosen up the compacted areas as many weeds prefer compacted soils.

A soil test should be taken to see what nutrients are deficient in each soil type across the farm. This is particularly important as we push organic farming onto more marginal soils in Australia. I prefer farmers purchase for themselves a simple GPS device (around $300) so that all future monitoring is done by themselves and comes from the same soil sampling sites. Sample at a number of different sites across the same soil type. Again I prefer to use an old manual soil tube (37mm wide with a point width of 30mm to avoid problems in heavy clay soils). This tube is hammered into the soil to 100cms, 0-30cms collected for one sample and 70-100cm into another. The deeper soil sample is useful in dryer areas where where constraints to root development may be an underlying issue.

The next step is for farmers to get into quality compost production and to add the deficient nutrients. This provides all the necessary nutrients for the growing plants. In essence you are introducing into this ancient landscape a European pasture and crop. It thrives on high humus and mineral rich soils like the ancient deltas of the Nile and Tigress. By focussing on quality compost production and nutrition you help the inter-row pasture sward establish a niche and outcompete weeds. The poorer the nutrition, the easier it is for the weeds to get control of the inter-row sward area of the orchard or vineyard.

When sowing the new orchard down to a pasture sward make sure you have a good mixture of grasses, herbs and legumes. The wider the selection of species the healthier the sward. Remember each pasture species puts into the root zone (rhizosphere) a number of exudates that dissolve minerals and provides a food source for beneficial microbes. These are the building blocks of stable humus and all future profit comes from these simple choices. Make sure also that all the legumes are inoculated with the correct Rhizobia.

Weed control in young orchards or vineyards

The difficulty for many producers entering organic production is control of weeds during the early development phase. There are a number of different methods employed and include the following; soil cultivation, mulching, flame weeding, steam weeding and certified sprays.

Soil cultivation is the most common method employed for weed control within the row. Here all plants are cultivated leaving bare soil under the young plants. Banded compost and nutrients can be incorporated in each pass. It gives the young plant an opportunity to grow without competition and control certain insect pests but does pose a risk from erosion.

Mulching is another method employed by many producers. Here higher C:N ratio hay, leaves or green waste is layered under the plants providing a barrier against weeds. Depending on the C:N ratio of the mulch, this layer of protection can last from 8 months to many years. It is ideal where moisture conservation is critical. The main disadvantage is the cost but this can be amortized across the life of the orchard or vineyard. Normally mulching can increase tree or vine growth by 50-150% depending on the climatic zone.

Flame and steam weeding have been adopted by organic producers with varying degrees of success. The key issues here are the selection of the right equipment, timing of operation and the cost of the fuel. Technology plays a big part here and I have seen successful operation make significant improvements in weed control using these techniques.

Certified sprays try to mimic the actions of conventional herbicides without ecological damage. They are generally expensive and efficacy is limited so I never recommend them. Further, the application of a “certified” ingredient may have a long term effect on soil health, there just has n´t been enough research on this method despite the advertising. Remember the long term goal of an orchardist is to build a humus rich soil with a diversified inter and intra row pasture sward once the plants are established.

Correct mulching in established orchards or vineyards

Once the orchard or vineyard is established, mulching with the annual application of compost/minerals/biology is an excellent way to build a healthy ecosystem. One method is to ensure that the inter-row pasture sward is slashed at different heights to protect the pollen source for the predators.

These nutritional and physical practices not only reduce weed pressure but also provide an ideal environment for the production of beneficial soil compounds like amino acids and vitamins – the foundation of quality food.

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