| Article Index |
|---|
| Fertility options for organic and transitional growers |
| Soil organic matter: start with the basics |
| Soil nutrient balance |
| Fertiliser options |
| Problem Solving |
| All Pages |
In some ways even more surprising than the rush of new growers to certified organic production, is the rate at which conventional growers are adopting organic practices, especially the use of compost, organic fertilisers and soil fertility products.
Almost all fertility problems can now be confidently solved with organic methods. The one remaining serious issue is phosphorus fertility in alkaline soils. Furthermore, as some of the more unsustainable growing areas progress down the path of declining organic matter, compaction and accumulation of salt, herbicide and pesticide residues, conventional products have ceased to deliver economic returns. Without enough organic matter in soils to support the vital soil ecosystem, conventional growers are forced to confront the failure of the conventional NPK fertilisers. In horticulture production areas such as Virginia and Two Wells, in the previously highly productive northern Adelaide Plains, all the better growers are now spending more money on organic inputs than they spend on conventional fertilisers. They have adequate N, P and K in their soils but still can’t produce the yields they need to remain viable. This trend is also observable in intensive horticulture areas in the other states.
The prevalence of organic products in broadacre cropping and dairy farming regions is even more indicative of change. Even a decade ago, the conventional wisdom was that organic fertility solutions might work in high value horticulture, but could not be economically delivered to broadacre crops. Now there are many manufacturers and purveyors of certified (and ‘certifiable’) inputs in all farming regions. So much so, that the old problem of “how can I obtain organic fertilisers at a reasonable cost” has been replaced with the dilemma of “which one”?
So what are the options available to organic producers, or to anyone else in the transitional area between fully conventional and fully organic, and, faced with so many new products, how do or should producers chose between these products?
Soil analysis
Any commercial grower starting out on new land or contemplating conversion to organic should attempt to understand as much as possible about the particular soil characteristics where they will farm. It is fundamental to organic management to identify, as soon as possible, the ‘limiting factors’. This is best done with an Albrecht style analysis and report; that includes all the major, minor and trace elements, pH and CEC. It may be worth seeking out an independent laboratory, so that the recommendations are free of direct commercial interest. If you do choose to use a fertiliser supplier’s analysis, you may still be able to get a comment on the recommendations from an independent consultant.
It is very important that growers understand how to take soil samples. The following recommendations will help, but also heed advice from the laboratory.
- sample very different soil types (or history of use) independently
- if possible, sample at the time of year when crop nutrition is most critical, this will vary depending on the crop
- walk an “S” pattern path, from corner to corner of the paddock or portion to be sampled
- take an even core down to about 15cm in depth (i.e. if not using a soil probe, which makes correct sampling easy, try not to bias the sample in favour of surface or subsurface layers
- use a clean spade or sampling tool and bucket
- take at least 10 sub-samples. 20 is better. Mix them thoroughly at the end and send off the required amount as a sample of the batch
- ALWAYS test in roughly the same location and at the same time of year – otherwise your results will not be directly comparable
Some organic growers sample different paddocks frequently and use the information obtained to constantly tweak their soil fertility. Many of these growers find this fascinating and it can become as significant to them as other basic farming operation such as machinery maintenance or routine stock management. For most growers, it is only necessary to test soils annually for a few years. Based on the first report, major soil deficiencies and imbalances are corrected. For the next few years growers can test soil to confirm that the initial adjustments and maintenance fertility-replacement is delivering the required results. Thereafter, testing can be much more infrequent, to check up on nutrient and soil-balance conditions. The frequency of on-going testing will probably be determined by the economic return of the crop, but three to five years may well be appropriate.
The recommendations
Independent laboratories make generic recommendations, but they may also report on acceptable products to fulfil the requirement. The qualifications, skills and experience of the person making the recommendations is critical. Like any professionals, soil consultants should be prepared to reveal their background and commercial affiliations and provide details of previous satisfied clients. Knowledge of your particular region and enterprise is also important. The consultant should be able to give a good account of why each material is required and why the particular product recommended is the best for the job.
