Introduction
The most powerful and yet most misunderstood tool for modern agriculture, particularly among smallholder farmers in Nigeria is soil testing. The soil careless application of fertilizers by many farmers has resulted in significant loss of money, and fruit yields because many may not know what their soil requires. The issue goes beyond the lack of soil tests, but rather from the common missteps with sampling, deciding on the interpretation, and deciding on which soil action to take. If soil tests are conducted improperly, they will yield false answers and the resulting soil reaction will bring about improper fertilization or over-fertilization. Through time, this imbalance will slowly affect productivity and soil health, lower microbial activity, and drive up production costs, and-yields will decline further. Once one has identified these silent errors by knowing what they are, one can identify them in the future and take appropriate corrective measures to ensure sustainable productivity. Here, we’ll examine each of eight common soil-testing pitfalls that gallops under your feet—and one of the ways you can avoid getting in the way of farming productivity.
In Nigeria, whether farmers are siting their farms in the savannah regions of the north or in the humid regions of the south, they use guesswork or systematic blind repetition of fertilizer programmes that they have previously adopted, usually from previous seasons. These practices may be convenient but they adopt a one size fits all approach to soils, even in the same farmland, which is far from realistic. Farmers often make errors in interpreting the soil test results, or do not get the right soil samples, which results in inaccurate fertilizer recommendations. One of the key factors that contributes to low use of fertilizer efficiency in many farming communities is this mismatch. Excessive fertilizer fertilizer applications can result in soil acidity, off-balance nutrient issues and sub-optimal crop development rather than increased yield. Conversely, crops with insufficient nutrient application are stunted, nutrient deficient and less productive. A properly conducted soil test can then be an asset to a farming operation that will save money and improve yields by letting farmers use just the right amount at the right time.
Eight mistakes when conducting a soil test
1. Sampling at the wrong time of the season.
A very common mistake that farmers are making is taking soil samples out of time! Fertilizer application, rainfall and harvest divert, significantly alter soil conditions. If the samples are collected right after fertilizer has been applied, the results may indicate high nutrient levels that could lead farmers into believing their soil is more productive than it does have the capacity to be. Likewise, when samples are taken under very dry or waterlogged conditions, nutrient readings can also be skewed. Soil sampling is best conducted when the soil is in a relatively stable condition in either a relatively organic state (after the crop) or in a relatively in-organic state (before land preparation for the next crop). In this stage nutrient distribution is more uniform and it is possible to evaluate Soil Health more accurately. Timing the recommendations allows the right advice to be given in relation to the nutrients in the soil and not in reaction to short-term changes as a result of farm activities.
2. Shooting the ball too deep or too shallow.
Another serious error is sampling depth which has a greater impact on soil test accuracy. Many farmers either do not till or have gone too far from the standard tillage. Nutrients are not uniformly available through the soil profile, and the greatest uptake of nutrients will occur within the top 15 to 30 cm of the soil profile. Selection of limited depths may cause an overestimate of nutrients if fertilizers or organic matter has been recently applied or added to the soils; selection of very deep depths may cause the nutrient content to be under-represented in the sample because of the presence of nutrient-poor subsoil. The best practice is to have one sampling depth for all the sampling stations in a field. This way, the results are representative of the location where the majority of the nutrients are acquired. Ideal depth is critical for determining the suitability of fertilizer recommendations, as use of the input is not as efficient and crop performance suffers if an incorrect recommendation is used.
3. Neglecting appropriate soil sample mixing.
Resampling of soil for different parts in a field is common, but mixing of the soils is not done adequately before sending them to the laboratory. This will give unrepresentative and inconsistent answers, as a sample of soil will not be representative of farmland unless it can be made composite. Any field is naturally not uniform, and the nutrient levels can vary widely between different areas of the field. Farmers need to take several subsamples at various points across a field, thoroughly combining them into a single sample to obtain reliable results. This method would take into account, not just points, but a more representative picture of the average soil condition. A failure to mix up properly will often lead to false recommendations that over-fertilize and under-fertilize parts of the farm field, and thus decrease yield uniformity over the field.
4. Eliminating fertilizer contaminated areas
One serious, but commonly made error is taking soils from spots that are polluted with manure piles, compost piles, fertilizer during storage, and animal resting areas. These areas will not be indicative of the actual nutrient level and can greatly over represent the nutrient level of the field. Many farmers take samples without realizing it from such places, due to its accessibility or its perceived fertility. This means fertilizer recommendations are “off track” resulting in under fertilization of the other area of the field. Farmers need to make a conscious effort to stay out of these areas and concentrate on representative areas where little disturbance is occurring on the farm. To correctly analyze the soil, the field must be selected correctly and be aware of the sources of contamination. Farmers may also find resources such as avoiding fertilizer-contaminated spots, during handling and store’ useful for more detailed advice on the prevention of contamination during the handling and storage of fertilizers, and the implications this can have on the accuracy of nutrients and soil testing results.
5. Incorrect interpretation of Soil pH results.
One of the key soil parameters that affects soil health is its pH which is often misinterpreted. A soil pH provided by many farmers is for a specific purpose and they do not know the significance of it to nutrient availability. Water pH is important for determining whether crops can access essential nutrients, such as Nitrogen, Phosphorus and Potassium. For instance, phosphorus in very acid soils (low pH) may be bound to plants even if abundant. However, excessively alkaline soils may result in iron and zinc deficiencies. The interpretation of these results is often misinterpreted, causing farmers to use more fertilizers when soil pH imbalance can be remedied with adjustments in pH through lime and/or organic amendments. The importance of understanding the pH is because it plays an important role in the use of fertilizer, as it will either be effective or lost. However, if they are unaware, the farmers will experience poor yields despite the rise in input prices.
6. Not considering NPK balance in soil reports
A common mistake is concentrating solely on one nutrient (typically nitrogen) and overlooking the balanced nutrients (NPK). It is a common fallacy of many farmers that they give more nitrogen fertiliser and will always produce more crops. There is a need for balanced application of nitrogen, phosphorous and potassium for the good growth of crops. Soil test reports contain a wealth of information on the concentrations of plant nutrients, but are often overlooked or misunderstood. Plants suffer when one nutrient is used excessively with deficient others present, resulting in poor growth and decreased production. If nitrogen is supplied in excess without a means to utilize it, such as potassium, for fruit or grain production, lush foliage can be produced with reduced fruit or grain production. With NPK balance, farmers can construct a more effective fertilizer scheme usually including all steps in the development of the crops; not only vegetative growth.
7. Using local testing methods without calibration or verification.
In many rural areas, farmers either rely on informal soil testing practices, or on local unchecked kits that may give inaccurate results. Some inexpensive tools can provide some information, but they may not be adequate to make correct recommendations. When samples are taken to a lab, results may be unreliable when the lab is unaccredited or equipped improperly. Proper soil testing demands uniformity of method, standardization of equipment, and experienced hand trained in the chemistry of soils in agriculture. Farmers should select certified or reputable local laboratories which make use of established testing protocols. While soil testing first cost might appear high, the use of dependable tests allows for significant reductions in fertilizer use and productivities when you are caused to consider soil testing.
8. Not following soil test recommendations.
The last and often most devastating error is not prepared to apply or not fully apply soil test recommendations. Soil test information can be used effectively, but many farmers take the time to test their soils but still use dated fertilizer practices when applying inputs. This will ultimately make the whole test point null and void. The rationale for Soil test results is to be used for precise nutrient management; Soil test results are only useful if these are adopted and followed; If Soil test results are ignored farmers are repeating the same inefficiencies that will lead to reduced yields. Some of the farmers also adjust recommendations without knowing the implications, which may result in imbalances in nutrients and crop performance. For meaningful results, farmers need to view soil test recommendations as a farming guide, not as recommended anyway. The only way to improve soil health, lower input costs, and improve yield stability from year to year is through consistent application of scientifically based thoughts, knowledge, and practices.
Conclusion:
Soil testing isn’t a technical process, it’s a strategy of the finances. Far too many losses in African farming are not due to inadequate fertilizers, but to misapplied fertilizers according to false soils information.
Make sure that you avoid issues of incorrect sampling depth, contamination, mixing, and not considering pH to have a significant impact on accuracy. Discussions that enrich a farmer’s own testing results with the proper interpretation allow them to cease guessing and begin a data-driven approach to selection.
Soil testing in the long run allows significant savings on costs, better crop health and more productivity. Farmers who incorporate good sampling practices into good agricultural operations, and are accustomed to trusted laboratories, will always work ahead of farmers who are more “hopeful” than hopeful (“ho’oho”).
The bottom line is to test first, fertilize precisely.
