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Fertilizer Recommendations Based on Soil Test – Soil Testing Patterns & Choosing Fertilizers 

Soil testing is the only way to determine the available nutrient status of a field and get specific fertilizer recommendations. The use of efficiencies of nitrogen, potassium, and phosphorous can certainly increase and decrease the cost of cultivation. In the past few decades, the use of fertilizers to increase food production has increased a lot. If it exceeds the crop requirements, it often causes environmental pollution and other detrimental effects. The imbalanced use of inorganic fertilizers results in a negative balance of nutrients. Without the proper understanding of the fertilizer recommendations based on soil tests, it’s easy to cause imbalanced fertilization. This disturbs nutrient availability, leading to a reduction in soil productivity that has long-term effects.

Apart from that, the increasing fertilizer price and their availability is one of the main hurdles in planning for balanced fertilization. Excessive chemical fertilizer application has caused deficiencies of secondary and micro-nutrients in different soils. Also, inadequate nutrition of crops worsens the situation when it comes to soil fertility. Organic matters (OM) are one of the most crucial sources of nutrients, but their sole application is not enough to meet the nutrient requirements of high-yielding varieties, and it often results in poor crop yields. Furthermore, using a generally recommended dose (GRD) of fertilizer cannot help in maintaining the economic returns of the crops due to the fatigue in soil health, and this needs refinement for balanced crop nutrition.

Therefore, using an appropriate combination of OM and chemical fertilizers based on the soil fertility status is a crucial step forward in offering balanced fertilization to crops. Integrated nutrient management (INM) can increase the income of farmers. The continuous application of GRD of fertilizer along with farmyard manure increases rice grain yields and sustainability. Soil sampling and testing are essential in determining the soil fertility levels and soil properties to ensure good management decisions about fertilizer, lime application, and manure rates. Proper nutrient and amendment applications can increase crop yield, reduce environmental impact, and reduce input costs.

Soil Sampling Patterns

To understand the fertilizer recommendations based on soil tests, it is crucial to know the different soil sampling patterns.

1. Traditional Composite Random Sampling

15-20 cores are collected throughout the field, mixed thoroughly, subsampled, and then sent to the lab as a single sample. In simple terms, a soil core is a vertical view of everything below the ground in a long and clear tube. The core tube contains the soil that is removed from a hole drilled in the ground. Each core is usually several feet in length.

The representative sampling areas must also be sampled when using traditional composite random sampling. For the hilly areas with knolls, depressions, or slopes, it is better to take samples from mid-slope positions to get the average results. The level fields are easy to sample. Avoid sampling the obvious areas of unusual variability. These include saline areas, eroded knolls, burn piles, manure piles, haystacks, fence rows, corrals, and old farmsteads, on headlands within 50 feet of field borders or shelterbelts and 150 feet of built-up roads.

fertilizer recommendations based on soil test

2. Benchmark Soil Sampling

When it comes to fertilizer recommendations based on soil tests, benchmark soil sampling is yet another form of soil sampling where a small area is selected as typifying the field or most of the soil type within the field. In this benchmark area, 15-20 samples are collected randomly and mixed. In this technique, it is assumed that the benchmark area is less variable than the complete field because it is smaller. The same area is sampled for quite a long time, and it reduces the chances of errors. Choosing the benchmark area is crucial. The representative sites can be selected through close crop observation (especially during the early growth stages when the fertility differences are highly evident), past grower experience, yield maps, soil surveys, and remote sensed images.

3. Grid Soil Sampling

This technique uses a systematic method for revealing fertility patterns and assumes there is no logical reason for fertility patterns to vary within the field. The field is divided into blocks or areas. The sample location within the block, which is mostly at the center of the grid point, is sampled 3-10 times. Modifications to the grid point sample might be done to avoid repeat sampling of regular spaced patterns within the fields. These are fertilizer overlaps, tillage, or tile damage. Using grid sampling for fertilizer recommendations based on soil tests could be costly based on the grid size selected. The sampling density of one sample per acre is needed to ensure accurate information for variable rate fertilization. The sampling of larger areas might still offer useful information on the magnitude of field variability.

4. Remote Soil Sensing

Using remote soil sensing techniques is a highly accurate method of soil testing that is very effective for creating fertilizer recommendations based on soil tests. This method entails using remote sensing technologies like sensors and satellites to measure and monitor the soil with precision, typically combining that dataset with traditional core samples to provide growers and farmers with high density soil models to base fertilizer recommendations off of. By combining multiple technologies and datasets, this allows for less labour intensive and typically more cost-effective results that is scalable in different field sizes and soil types.

Choosing Fertilizers Bases on Soil Test Results

When it comes to fertilizer recommendations based on soil test results, the fertilizer labels display three numbers to show the percentage weight of nitrogen (N), phosphate (P), and potash (K) in that order (N-P-K). To choose a fertilizer based on the soil test results, do the following:
1. Look at the pounds of N-P-K recommendations in the soil test result.

2. Find a fertilizer that has the same ratio of those numbers.

3. If the result suggests adding N, base the amount needed on N.

4. If the result doesn’t suggest adding N, then base the amount on any nutrient the test results suggest adding. Add the amounts as needed. For instance, if the soil test recommends 8lb of N, find the amount of fertilizer that offers 4lb of N and multiply it by 2.

Harnessing the potential yields of high-yielding varieties of crops requires the application of optimal doses of nutrients. Therefore, a comprehensive approach that includes soil tests and field research can be employed to add profitability throughout fertilizer use. If you are in search of the most effective organization to avail the best fertilizer recommendations based on soil tests, get in touch with SoilOptix® today! Visit for details.