Green Manuring 2

Because of the failure of the early summer green manure crop of Millet in late October, I decided to plant another crop and do it correct this time. I miscalculated the seed volume by a factor of ten, and in turn had a very lousy outcome. In essence it just meant I could wipe out one more generation of weeds without much effort, and there was little rain in that period so no erosion!

I chose to put another crop of Japanese Millet in late February, it is advisable not to sow until the soil temperature is above 14°C, which in February is no issue, Millet does not tolerate frost, and the frosts will not be here until late June/July, last year we only had two or three mild occurrences.

The recommended sowing rates vary according to the situation – as a guide, 12 kg/ha for lighter/poorer soils and up to 20-25 kg/ha for heavier, more fertile soils. These are the suggested rates from the NSW DPI. I put in the higher rate as I am after bulk, green matter. It will also allow me to slash, have regrowth and then plant the winter crop with legumes.

Regrowth of millet following slashing is very good if soil moisture and nitrogen levels are sufficient. I have been watering regularly and put 100Kg/1000m2 of certified Terra Firma pellets. The growth has been outstanding and goes to show that weed supression, good growth and positive outcomes can be attained without Glyphosate or DAP.

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Orchard Weed Management

What would the world be, once bereft
Of wet and wildness? Let them be left,
Oh let them be left, wildness and wet;
Long live the weeds and the wildness yet.

Gerard Manley Hopkins

What is a weed?

There are many reasons why certain plants are or become weeds in orchards or organic farming operations.

Conventional methods of broad scale systemic or selective weed suppression can have many undesirable effects on soil microbes and healthy soils.

Plants are commonly defined as ‘weeds’ if they exhibit one or more of the following characteristics:

• compete with plants for water (most plants);
• compete with plants for nutrients (most plants, especially non-legumes);
• interfere with water distribution from low-level sprinklers (most plants);
• poison livestock;
• harbour or encourage non-beneficial pests;
• produce spiky seeds/thorns that may injure workers or contaminate produce;
• interfere with harvest or other orchard operations;
• compete with more desirable cover crops;
• have the potential to invade neighbouring properties where they can exert their undesirable qualities;
• Are noxious or declared by the local Rural Lands Board / Council

When weeds are not weeds…

The real vs. perceived status of a weed can vary from grower to grower. Many agricultural weeds have been defined as such because of their negative impact in pasture and grain cropping systems and/or livestock, the dominant form of agriculture in Australia. E.g., grasses are often encouraged in cool climate orchards/vineyards on fertile soils where their competition for nitrogen is used to reduce excess vigour. On naturally poor soils of some hot, dry regions however, summer grasses tend to be discouraged, because they compete for water and nutrients – major issues for some regions. Summer ground cover does however help reduce soil temperatures and dust.

Beneficial ‘weeds’

Some ‘weeds’ provide benefits of value to organic systems, and these benefits need to be weighed against any negative characteristics of the weeds. Some benefits of weeds are listed below:

• Soil protection – Most plants protect otherwise bare soil from the effects of sun, wind and rain (erosion).
• Food source for beneficial insects – Many flowering plants produce pollen or nectar that is a useful food source for beneficial insects such as hover flies and lacewing insects (predators of mealybugs, scales and other pests) and predatory mites. They also provide a haven for bees and other pollen spreading insects, which is particularly important in an orchard setting.
• Other plants, like thistles, support aphids which provide a food source for beneficial insects and help maintain populations of those beneficial species.
• Nutrient recycling – Deep-rooted plants play a useful role in nutrient recycling by absorbing nutrients from lower in the soil profile and redistributing them when the plants decompose.
• Weed suppression – heavy growth of some ‘weeds’ like grasses, can suppress the establishment and growth of less desirable weeds.

Next I will look at weed control methods that i have used in the orchard, and some trialing of a certified weed supressant.

References:

Organic Farming: Vineyard Weed Management (2007), David Madge,
Department Of Primary Industries, Victoria, ISSN – 1329-8062
web site: http://www.dpi.vic.gov.au/notes

Soil Management for Orchards and Vineyards (1993), G O’Conner, J Strawhorn, K Orr, AGMEDIA – Department Of Agriculture, Victoria, ISBN – 0 7306 3018 8

Green Manuring

Over the next few posts, I will slowly describe the Organic principles that I have always believed in and the approach that we have taken to start on the quest for Organic Certification.

Organic farming can be described as farming sustainably without the addition of artificial chemicals, farming in a manner that respects the environment, and having a whole farm approach that treats it as a living and growing organism.

At the heart of this process is the soil;

From the outset we have used green manuring to improve the soil, and to prepare the soil for the plantings, given our soil was a little acidic, and had low organic material I set out to improve the ground using cover crops and re-mineralisation

Below is a brief description of these processes

Green Manure / Cover Crop

Green manure crops play a valuable role in agriculture, and especially organic farming practices because of the many benefits they provide to the soil, the ease of addition and to the cropping system.

Green manures are crops grown specifically to improve soil condition and nutrition. They can be used instead of heavy chemical fertilisers and inorganic farming practices, chemical fertilisers supply nutrients but no organic matter. Suppression of weeds and soil-borne diseases are additional benefits of particular green manures.

Instead of being harvested, green manure crops are incorporated back into the soil, usually while they are still lush and green and before they go to seed. At this stage of growth the plants have a relatively high nitrogen and moisture content, and provide an ideal food source for soil microbes and other organisms like earthworms. Under favorable conditions these organisms decompose the green manure reasonably quickly. During this process, organic matter and nutrients are released into the soil where they become available for use by other organisms including crop plants.

Some benefits of green manures

Organic materials:
Organic matter is provided by root growth and mechanical mulching. Soil organisms then decompose this organic matter into humus and other organic compounds. Improving the organic matter level and biological activity of soil is one of the fundamental objectives of organic agriculture, and green manure cropping helps growers achieve this

Weed control and Erosion
Weeds are suppressed by the competition that dense, green manure crops exert for water, light and nutrients. Soil improvement is also achieved by decreased erosion from heavy rains. Soil compaction can also be prevented with the use of a green cover crop.

Nitrogen Fixing
Soil nitrogen levels are increased by leguminous green manures through their association with nitrogen-fixing Rhizobium bacteria. The Rhizobia can take nitrogen (N2) from the air and convert it to the form plants normally obtain from the soil. This process is called nitrogen fixation. When leguminous plants decompose, the nitrogen is released for use by other crops.

Biological tillage
Biological tillage (cultivation) is the term used to describe plants loosening the soil as their roots grow and as they dry out the soil and it cracks. This can help in soil improvement by breaking down the hardpan in heavily compacted soils.

Below are some images of Oats and Dunn Peas that are a winter cover crops that we have used.