Soil testing is the only way to determine the available nutrient status in soil or soil-less media and the only way a farmer can develop specific fertilizer recommendations. Periodic soil testing combined with a good record-keeping system for each field (including information on prior soil tests, fertilizer and manure applications, and crop yields) serves as a gauge to indicate whether soil fertility is increasing, decreasing, or remaining constant. An effective fertility testing program is one in which every field is properly sampled and tested on a regular basis.Soil testing can be good and effective for cost minimization; can contribute for higher yield is completely unknown to our farming community.
Due to time and the cost of soil analysis many farmers do not soil test but instead use standard fertilizer rates which are often given on fertilizer bags or that used by other farmers. Many farmers do not have a clear understanding of soil testing. The confusion revolves around the fact that the nutrient content of soil seldom is important in testing for fertilizer recommendations because of many chemical forms of nutrients in soil. The preliminary conception of our farmer about soil testing is negative; he thinks it is costly and would not give him any extra benefits, but his thinking changes after trial results, appreciating the importance of soil testing in farming to increase farm profitability.It is in fact a method of fertility evaluation – to understand the capacity of the soil for crop production – helps for the efficient and economic use of fertilizers as per actual requirement of the soil – helps for increased production of crops – to maintain the soil health in a sustainable manner – helps for adopting integrated nutrient management system for increased crop production and soil health.
Soil and climate can greatly influence the reliability of fertilizer recommendations based on a soil test. For example, a recommendation that is satisfactory in semi-arid areas, where alkaline, calcareous soils are common, may not be satisfactory for other parts of the country where soil and climate are very different. Therefore, once a test has been selected, it must be related to field conditions for individual crops.
This involves growing crops on fields treated with the nutrient being evaluated. Nutrient rates range from zero to more than adequate for maximum yields. By conducting a series of experiments, on a wide range of soils, it is possible to relate the laboratory soil test value to actual field yields and rates of fertilizer necessary to achieve maximum yields. Because crops have different growth habits and nutrient requirements, the same procedure must be followed for each important crop in an area.The difference between rich, fertile soil and poor, infertile soil is essentially the mineral composition of the soil.
The farmers can save time, money and help the environment when they use soil tests to determine the proper amounts of soil amendments for their needs. Time and money are wasted when the farmer over-applies soil amendments such as fertilizer and herbicides. In addition to wastage of money the environment is harmed when fertilizers are over applied. Over-applied fertilizer is a major source of pollution that damages rivers by encouraging excessive algae growth among other things.
The excessive use of fertilizers adversely affects the nutrient balance of soils. It results in the depletion of soil fertility. The nitrogen in nitrogenous fertilizers may get stagnated in the soil or get volatalised as ammonia. It may escape into atmosphere increasing its nitrogen content.The nitrogenoxide may cause the depletion of ozone layer. The run off nitrogen from nitrogenous fertilizers into rivers and canals increases nitrate levels in water.
It is harmful to animal and human beings. Basic soil tests look for the amount of Nitrogen, Phosphorus and Potassium (NPK) as well as soil pH (acidity/alkalinity). The flavor and nutrition in fruit, grains, and vegetables are based on the soil minerals available, not the amount or type of organic matter.
If a needed mineral is missing, it is just that, missing, and no amount of organic matter will make up for it. No amount or combination of the air elements Carbon, Oxygen, and Hydrogen will add Zinc to our soil, and all plants and animals need Zinc.
Plants also need Copper and Iron and Manganese, Calcium and Magnesium and Phosphorus, and at least seven other essential minerals, and they need them in an available and balanced form. Rotting organic matter may release growth stimulants like Nitrogen and Potassium, but the other minerals are what create sweetness and flavor and nutrition in food. Without these other minerals we may achieve high production, but we will not be able to achieve the highest quality.The goal of soil testing is to provide an accurate assessment of the soil’s fertility status that can be used to make fertilizer recommendations.
With the increasing awareness of fertilizer effects on environmental quality, soil tests can also be used to determine where fertilizers or manure should not be applied. Farmers should use soil testing as a management tool for making scientifically sound management decisions about their soil fertility program. A fertility management program based on soil testing benefits the farmer in many ways.
Soil testing is based upon years of scientific study of sampling procedures, crop yield responses to fertilizer application, and interactions of plant nutrients with other production factors. Scientists have proven that soil tests provide the information necessary to make intelligent decisions on the amounts and composition needed to achieve a selected yield goal for a specific soil-climate- management system. Soil testing helps identify the variability of nutrient content within a field and among different fields on a farm.
The continuous increase of input cost and similar decrease in land productivity has made the farmers reluctant to continue crop cultivation because the profits are so frustrating. To maximize return on every Rupee spent on fertilizer, it is important that the right combination and rates of fertilizer materials be used for the crop to be grown. Yield and economic return can be optimized when fertilizer rates accurately address the needs of a crop.
Potential soil and water pollution can be minimized when nutrient application is geared to the needs of a particular crop. Soil test information along with a realistic yield goal is essential to making the decisions on fertilizer needs.
Without soil tests it is impossible to determine which nutrients are in short supply and which ones are adequate for the crop. Total fertilizer costs are sometimes reduced through use of soil tests, but even more important, the money spent on fertilizer is invested in the nutrients most needed by the crop. Fertilizer application according to soil test results assures the proper combination of nutrients for most efficient utilization by the crop. Potassium fertilizer, for example, can increase the efficiency of nitrogen utilization. As potassium application is increased, the most profitable level of nitrogen application is also increased. Without knowing the potassium soil test level, it is impossible to determine the most efficient rate of nitrogen.Since nutrient levels in soil, plant tissue and water cannot visually be seen, only a professional analysis will expose potential problems. By knowing our crops’ requirements and using a fertility testing program, we will save time, money and labor. Growing comes with experience and knowledge!
By Shaukat Masood Zafar