Is more compost always a good thing?
When it comes to soil, for the organic gardening movement, it’s all about organic matter. Most proponents tell that enough compost and adding lime according to the ph is all you need to grow a great crop on about every soil. I myself used this approach for years with some success, but my cabbages did not head and most embarrassingly, my beetroots did not form properly.
Surprisingly, there’s something like too much compost. Compost is a concentration of organic matter, usually collected from locally available ingredients. Your compost reflects the mineral contents of local soils, the deficiencies and the excess. Don’t get me wrong, compost is important, but too much can throw your soil out of balance.
Healthy people grow on healthy soils
Still in the WWII era, most food people ate was grown locally. William Albrecht, Chairman of the Soils Department at the University of Missouri saw a link between soil quality, food quality and human health. Back then, people who were raised on good soils were significantly healthier than people living on poor soils. For him, not only the sufficient quantity of certain minerals in the soil was important, but the ratio of the cations to each other. While this theory has a lot of followers, many agronomists disagree with the notion that the ratios are important.
No matter whether or not you agree with Albrecht, to grow a good crop you need more than compost and a bit of lime, unless you garden on a perfectly balanced soil, which is unlikely. The healthiest people of the past did not live on soils with most organic matter; they lived on soils with plenty of the right minerals. Most agricultural soils today are depleted due to excessive ploughing and synthetic fertilizers.
More than just compost and lime:
In case you grow a substantial part of your food, it is important for your health that your soil is well balanced with minerals. If you don’t it is much easier to grow in a well-balanced soil.
Talking about fertilizers seems a bit like leaving the organic camp and going the way of the much despised chemical agriculture. But there are many soil amendments approved for organic agriculture. No amount of organic matter makes up for missing phosphorus or boron. A thriving microbial life only makes those nutrients available which are already in the soil.
I agree, that you can do some conclusions with a ph-test kit alone, since most nutrients are more of less available according to the ph. But it neither tells you weather you have too much or too little of a nutrient. That can only be done by conducting a proper soil test by a lab. It is not cheap worth every cent.