How to Build Soil Fertility? Main Sources of Crop Nutrients and Key Points of Fertility Management
Fertility management:To achieve the goal of sustainable agricultural production, so that nature cycles endlessly and life continues without cease. This is the ecological balance we need to achieve. The main significance of fertility management in sustainable agriculture lies in using natural substances that do not consume energy to supply crop nutrients, by improving the soil environment for crop growth and paying attention to fertility techniques. We not only speak of ecological environmental protection but also want to gain a harvest from it. This is what we want to see.
Sources of Crop Nutrients
Plant nutritionists have found that the nutrient elements required by most plants include 16 kinds: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, boron, copper, molybdenum, chlorine, and others. Among them, carbon, hydrogen, and oxygen can be fully supplied by air and water, so plants need not worry about scarcity. The remaining nutrients mainly come from soil minerals, soil organic matter, and fertilizers added by humans. Soil minerals and soil organic matter, through the physical, chemical, and biological processes of nature, release most of the nutrient elements needed by plants. However, if crops are cultivated for a long time without supplementing fertilizers, the nutrients released by the soil will be insufficient for crop needs, so fertilizers still need to be applied when cultivating crops.
Sustainable agriculture emphasizes soil conservation so that the plant nutrients contained in the soil can be effectively brought into play, and uses organic matter from the farm or outside the farm and natural ores containing plant nutrients as fertilizers to supplement crop nutrients. Common examples such as green manure crops, poultry and livestock manure, phosphate rock, and limestone are all usable materials. In fact, there are many more types. As long as they are natural substances that do not require large amounts of energy to purify or concentrate and do not risk polluting the soil, they can all be applied in the fertility management of sustainable agriculture.
Key Points of Fertility Management
1. Improve the soil environment and maintain the soil
There are many environmental factors affecting crop production, which can be divided into climate and soil aspects. If climate factors are not discussed, crop production is mainly affected by the soil environment. It can thus be seen that to achieve effective crop production, a good soil environment should first be created, that is, to harmonize the physical, chemical, and biological properties of the soil so that crops can effectively use soil nutrients and realize their potential. Among Taiwan, China's soil problems (Table 1), the six major problems of strongly acidic soil, poor drainage, soil compaction, lack of organic matter, excessive salinity, and heavy metal pollution occupy the largest area and are also the most important. Therefore, in the practices of fertility management for sustainable agriculture in Taiwan, China, countermeasures should first be sought for these problems in order to cultivate soil with high productivity and promote agricultural production.
Second, fertility management in sustainable agriculture should emphasize soil maintenance; for soil without the above shortcomings, because humans plant crops in fields year after year, the physical, chemical, and biological phases of the soil often deteriorate. Among these, the reduction of soil nutrients and the decrease of organic matter are the most serious. In response, soil fertility can usually be maintained through fallowing, applying organic fertilizers, planting green manure crops, and designing crop rotation systems.
2. Pay attention to fertility techniques
In addition to improving the soil environment and giving crops a suitable place to grow, although this can also allow the nutrients contained in the soil to be fully used by crops, fertilizers are still indispensable materials for crop production; the organic matter and natural ores used in sustainable agriculture are generally slow-acting, and because their sources differ, their plant nutrient contents (Table 2: Nutrient contents of various organic fertilizers) and decomposition rates vary. When applying them, they should be matched to the crop and soil properties and applied at the "appropriate time," in the "appropriate amount" (Table 3: General application rates of some organic fertilizers in Taiwan, China), and in the "appropriate location" to be effective; otherwise, they will either have no effect, produce toxicity, or cause environmental pollution.
In addition, in order to maintain the physical, chemical, and biological properties of the soil and the supply of nutrients, the organic materials applied should preferably be properly blended from two types of organic fertilizers: easily decomposable types (such as chicken manure, soybean meal, etc.) and difficult-to-decompose types (such as bark, rice straw, etc.); other matters such as the maturity of compost, heavy metal content, harmful phenolic compounds, and other harmful factors should also be noted during fertility management.