In Organic Farming good productive pastures come from healthy soils, and the nitrogen cycle is very much part of this achieving this.
The nitrogen cycle
Here, nitrogen in the atmosphere is transferred into the soil where it is used up by Rhizobia bacteria, which live in the root nodules of legumes. These nodules convert atmospheric N it into nitrate and after they die, grass plants use the nitrate.
Grazing animals eat the clover and return a high proportion of the fixed nitrogen to the soil in dung and urine. Nitrogen also returns through dead and decay of plant material. The nitrogen returned to the soil in this way adds to the system and becomes available to the grasses through the action of microorganisms.
Exploit variety in pastures.
Pastures are made up of grasses, clovers, and weeds. Stock like a varied diet therefore a multi-species pasture can provide a balanced diet for the animal.
Over the last decade the trend has been to go for simple, monocultural pasture mixtures that respond to high rates of artificial fertiliser. The trend for organic farmers and many conventional is to plant seed mixtures with more varied species, including herbs such as chicory and plantain. Beware, are the species suited for your particular climate and topography.
As a result of a run of dry summers, deeper rooting species such as tall fescue, cocksfoot, phalaris and chicory are becoming more acceptable. Experience has shown that some of the modern high-producing cultivars require large inputs of artificial fertilisers to sustain their production. You need to take a proactive approach to find suitable cultivars that will adapt to your organic production system.
Avoiding pugging damage
Careful management of soils is required, especially in wet weather when pugging can occur. Pugging is now known to do long-term damage to the soil structure. It smears the delicate crumb structure of the soil, which can take years to repair. Some damage may literally never repair.
Pugging opens up pastures for weeds to gain entry. The bare areas of soil left between recovering plants will allow erosion caused by rain batter.
Here are some points to consider:
- Be aware when damage is most likely to occur.
- Be aware of wet trouble spots and fence them off.
- Be very vigilant in times of heavy rain.
- Use on/off grazing strategies.
- Build permanent feed pads for holding stock off pastures.
- Bedding materials on pads must not be of treated shavings or sawdust.
- Bring stock off pastures over long feed.
- Provide enough water troughs.
- Speed up the grazing round.
- Keep drains clean to prevent flooding.
Hay is considered by organic farmers to be an essential part of the diet of ruminants to help maintain a “balanced” diet. This is especially the case with cattle. The content of hay is important and it should contain a variety of plants - grasses, clovers and some herbs and weeds. It should have been grown with approved organic fertilisers.
Hay brought in to an organic property must have been grown under organic conditions. Under emergency situations, you can get approval from the organic certification body to use up to 10% of an animal’s daily intake from a non-organic source.
Silage likewise must have been grown using approved organic fertilisers. The use of additives or inoculents in the fermentation process is not allowed.
These must be grown from organically certified or untreated seed, and be free from any genetic modification (GM). Crops are best grown in a clearly worked out rotation where root crops follow leaf crops and so on. Monoculture cropping - ie the same crop year after year is discouraged under organic farming. Even under conventional systems it’s now causing major farming challenges.
To establish a successful crop, preparation is the key. Fertility levels may need improving before planting and weeds will have to be managed. Green manures crops can be planted to help improve soil structure, add Nitrogen and help build up OM in the soil. Burning crop residues inhibits soil structure and destroys a potential source of OM. To a large degree the success of the crop depends on managing and preparing the soil prior to planting.
Use cultivation techniques that prevent soil compaction, ie not cultivating wet soils and avoid using heavy machinery were not necessary. Cultivation that aerates the soil and incorporates organic matter are to be encouraged.
Information provided by:
Mr Denis Cadwallader, Organic Farming Specialist. 22 May Avenue, Napier, New Zealand
Mr Cadwallader is guest tutor in Organic Farming at the Waikato Polytechnic.
Phone (07) 834-8806 for further information on courses.