When soils are left bare or sprayed with a herbicide, nature is designed to bring up various weeds to cover and protect the soil. All over the world farmers are losing the war on weeds and in some countries, certain weeds can no longer be controlled.
Weeds ‘herbs’ are designed to bring the soil back into balance and each has a certain gesture of what exactly it is trying to achieve. Copper levels are generally quite low in Australian soils which is why you’ll see Heliotrope (potato weed) accumulate.
An issue in a few crops is Nut Grass. It grows in low calcium, low phosphorus, high potassium and high magnesium soils. The carbon levels are quite low with very low biology. So instead of working on correcting the soil physiology and biology, we kill the messenger.
Conventional herbicide use is a short-term solution which can create long-term problems.
One of the biggest problems is the reduction of beneficial microbes in the soil. A reduction in the overall soil biology is a calling card for diseases to enter the system through the root zone in tree and small crops.
Tree farmers are trained to keep their orchard looking like a golf course with single species, interrow grass mowed very short with 1 to 2-metre bare soil either side of the trees. Bare soils dry out very quickly, runoff during rain and root exposure can cause serious damage to the ecosystem.
What are some options conventional, biological and organic farms can use in tree crops?
Turn weeds into green manure. Allow weeds to come up and then mulch them on top of the soil as they start to flower. This ensures that many mineral deficiencies are rectified by the weeds that nature chooses to grow. For example, cobblers peg. Regular herbicide sprays will encourage an even stronger and taller plant. After cutting these weeds back and let nature take care of the cobblers peg, they will start reducing in size and a small billy goat weed will replace the cobbler pegs after a while.
Under tree and interrow planting. Choosing specific grasses, legumes and cereals which increase soil carbon by increasing the diversity of species in the orchard. Every living plant is photosynthesizing during the day and sends their sugars down to the root zone to feed the biology. The more diverse species of plants, weeds and grasses are present the more diverse the soil biology. Let the interrows grow to about knee height then slash them directly under the tree line. I encourage farmers in tree crops to slash every 2nd row during the off season so to still can provide beneficial insects a home. Lucent with its long taproot can go deep down into the soil and breaks even hardpans open. When slashed it will work like green manure and is a great boron collector.
Under tree mulch. This will require some investment and time to apply the mulch around every tree. Depending on where the mulch comes from the chance is that there could be some weed seeds imported which are not desirable. It will keep moisture around the root zone and protects valuable soil biology.
Correcting and balancing soil nutrition. Taking a soil test is only one part of the entire equation. Finding and applying the proper nutrients and applying these at the right time to benefit the crop and at the same time correcting, the soil profile is an art and will take some planning.
Looking at weeds from a different point of view and working with them instead of against them should be the long-term goal of every farmer. It will require a change in management and long-term planning but can provide a significant return in investment.