First, look at the possibility of obtaining lime for calcium. This is often available free or very inexpensively. Finely ground coral materials are also an excellent source of calcium? This is very often available near the coasts, it often is not recognized as important or used by people, and it provides the foundation for good plant nutrition – usually without any financial cost.
Next, growing seedlings – even without commercial fertilizers – but in a clean soil mix and protected from bugs, diseases, and the harsh elements, can greatly increase your productivity. It is work, and until you see the results, you may feel some resistance, since it requires daily attention. Make a clean compost pile of grasses, etc. and use them – preferably after composting for about 2 years – as potting soil for seedlings. In the meantime, underneath trees and shrubs, often there will be accumulations of leaf mold that work very well for the same thing. Ground-up coconut husks and many other organic materials can also be used.
The use of manure – even human materials if necessary – can also enhance plants’ nutrition. Manure tea can be used to grow seedlings quite successfully. We usually do not recommend manure be used directly on plants, for several reasons, including the introduction of weeds, bugs, and diseases. Also, fresh manure can burn plants, and any manure used in seedling soil mixes may cause germination problems. However, once the seedling has sprouted, manure tea can be used as a constant-feed solution.
After nutrition and healthy seedling production, the importance of proper seed-bed preparation and maintenance of a weed-free growing area are also important. Particularly in those situations where plant nutrition is already compromised due to a lack of supplemental organic or mineral nutrients, every weed is in competition with the vegetable plant for the scarce nutrition. In addition, weeds provide a haven and breeding place for bugs and diseases. Rather substantial increases in production can often be seen just from the careful application of these two principles, the need for which are universal anyway.
In many places, rains are sufficient to keep plants growing, and people do not think they need to water their plants. We have found, however, that fast-growing vegetables need constant moisture, and their yields will often be greatly increased if you will pay attention to providing adequate water to the plant roots. The level, raised, ridged soil-beds are ideal for this, since very little water is required, and all of it goes right to the root zone with no waste. Again, a little more work is required, but the resulting increase in yields can be substantial.
Even simple things like proper spacing of plants and proper placement (and pruning?) to assure full sunlight all day long sometimes are ignored, and will adversely affect crop yields.