Organic fertilisers

I sometimes hear garden experts say that organic fertilisers are not as high in nutrients as chemical fertilisers, so you have to use more of them. This is simply not true.
The American Association for the Advancement of Science (AAAS) reported in February, 2009 that hundreds of studies have shown that “incrementally higher levels of fertilizer negatively impact the density of certain nutrients in harvested foodstuffs.” They also reported that the complex way in which nitrogen is absorbed in organic cultivation results in more efficient assimilation of the nutrient, allowing organically grown plants more energy to produce antioxidants, and the formation of less nitrates. Nitrates in food can form carcinogenic nitrosamines in the digestive tract.
AAAS Conclusions

Excess use of nitrogen fertilisers (including uncomposted manures and manure teas) promotes bursts of soft, sappy growth that is much loved by chewing and sap-sucking garden pests. Overuse of a particular nutrient can block the absorption of other nutrients. Nitrogen and phosphorus compete for absorption. Overuse of chemical nitrogen fertilisers can also result in deficiency of the less mobile phosphorus.
Organic fertilisers don’t need to be as high in nutrients. Organic fertilisers made from a variety of recycled organic matter will contain a full range of major nutrients and trace elements. Organic fertilisers in the form of compost, castings from worm farms, animal manures, leaf mould, and broken down green manure crops and organic mulch add humus to soil, but chemical fertilisers do not.
Humus, the most stable form of organic matter, consists of electrically charged particles called ions. Nutrient elements also carry a weak electrical charge. Humus has a large surface area and many charged sites to hold nutrient elements through electrostatic force where they are easily accessible to plants, and regulate their absorption so that nutrients are not absorbed by plants in toxic quantities. Humus also provides a habitat for a group of beneficial fungi that assist nutrition in a wide range of perennial plant families. Some chemical fertilisers, such as superphosphate, suppress the activity of these fungi and other beneficial soil organisms.
Although clay particles in soil also carry an electrical charge and are capable of holding some nutrients, without humus in soil, phosphorus can become locked up with iron, manganese or aluminium, and unavailable to plants, and nitrogen and sulphur can leach from soil.
A suitable soil pH plays an important role in efficient absorption of a full range of nutrients. Adding extra fertiliser when soil is too acid or alkaline for particular species of plants will not help their growth. Humus in soil assists in maintaining a suitable pH. See:Changing soil pH

Although we tend to worry about plants getting enough fertiliser, fertiliser plays a relatively small, but essential, part in plant growth. The major contributors to plant energy are water and carbon dioxide. In the presence of sunlight, the green parts of plants can convert these into carbohydrates, which form the cell structure of plants. You could say, in fact, that plants are solar powered.

Worm farming

compworms.jpg My husband has been busy with his chain saw carpentry again. He rescued a shower base bathtub from the local tip to make a small worm farm that could be set up in a shady spot near the house. This makes it easier for me to collect worm castings for my seedlings and pot plants. Worm farms are a wonderful way to recycle food scraps and household waste into fabulous 100 % organic complete fertiliser with a neutral pH.
Old bathtubs are hard to come by in our area, as they are popular for recycling as water troughs for horses. However, this tub was missing the plug rim and unsuitable for use as a water trough, so it was a lucky find.
Using his trusty chain saw, Brian built a simple frame for the tub, using scrap hard wood pieces from around the farm. The cover consists of recycled hardwood planks, placed side by side, across the top of the farm. Only the two end planks are attached to the frame. The loose planks allow me to expose as much, or as little, of the worm farm surface as I want when adding food or collecting castings. A large square of fly screen was placed across the base of the tub before filling to prevent the worms and castings falling through the drainage hole. A bucket is positioned under the drainage hole of the tub to catch the liquid that drains from the worm farm.

chnsaw.jpg wormfarm.jpg

A layer of edible bedding is needed across the bottom of the farm container for to keep the worms damp and protect them from temperature fluctuations. I added some of the digested matter from our main worm farm for bedding as this contained both worms and worm eggs to ensure that numbers in the new worm farm will build up more quickly. However, for new worm farmers, bedding can be shredded and soaked coconut husk fibre (Coco peat), or damp, aged cow or horse manure, and the starter worms are placed over the bedding where you want them to feed. I added some chopped scraps (in a 2-cm layer) to one half of the surface of the farm, so that the worms would be concentrated in that area. The surface of the farm was then covered with wet newspaper and the cover planks over the top of the farm. (A temporary plastic cover goes on when heavy rain is predicted.) Food is replaced as often as necessary. If your worm farm is new, don’t give them too much food at first or it will be a while before they eat all the food, and it will start to smell. But, if you don’t give your worms enough to eat, their growth and reproduction will be slow.

As worm numbers increase, they will be able to process larger quantities of waste. Once the worms have turned the food and bedding in their area into castings, I start putting food at the other end of the farm. This allows me to collect castings more easily from the other half and pour water through the processed bedding to collect some liquid for my plants. It is not recommended to pour water through undigested food in worm farms in case the food has been affected by fungal or bacterial disease. However, using common sense and following the organic principle of “feed the soil, not the plant”, avoids problems with liquid fertilisers.