Challenges of fertilization in reduced tillage systems
In reduced tillage systems, fertilization must be planned so that crops receive everything they need in the right form and at the right time. Simply spreading fertilizer โon the surfaceโ in no till farming does not deliver good results. Why? The lack of ploughing means that soil is loosened and mixed only to a limited extent and depth, which affects nutrient distribution โ nutrients remain in the top 5 cm of soil, where roots cannot effectively access them.
Important! In reduced tillage systems, it is essential to find a balance between pre-sowing and top-dressing fertilization and to make maximum use of available tillage operations for fertilizer application. Soil analysis is indispensable.
Pre-sowing and top-dressing fertilization โ when and what to apply?
Pre-sowing (base) fertilization is carried out before sowing and aims to build a nutrient โbaseโ in the soil. This is the best moment to supply nutrients that move slowly in the soil, mainly phosphorus and potassium. Both are essential from the very beginning of plant growth โ phosphorus stimulates root development, while potassium regulates water management. However, they must be placed at a certain depth to be available to plants, which is why they should be well mixed with the soil before sowing.
Pre-sowing fertilization also includes part of the nitrogen dose (as well as sulfur or magnesium) as a starter, adjusted to crop requirements and site conditions. It is important to consider the preceding crop โ for example, after legumes, winter cereals often do not require additional nitrogen in autumn, or only very small amounts.
Top-dressing fertilization is applied after crop emergence, during the growing season. Its main purpose is to supplement nutrient deficiencies at critical growth stages and to respond to the current needs of plants. Most often this concerns nitrogen, which is intensively absorbed during rapid growth. If necessary, potassium or magnesium can also be supplemented, and increasingly microelements (boron, zinc, copper, etc.) are applied via foliar fertilizers.
Example: In spring wheat, nitrogen is often split into two applications โ the first at the beginning of stem elongation and the second at the flag leaf stage.
However, for top-dressing fertilization to be effective, suitable conditions are required:
- Granular fertilizers should be applied to moist soil just before expected rainfall, which dissolves granules and moves nutrients into the root zone,
- During drought, nitrogen application should be postponed until rainfall,
- Foliar sprays should be planned for cooler parts of the day to avoid leaf scorch.
Important! Dividing fertilization into pre-sowing and top-dressing applications makes it possible to combine long-term soil nutrition with ongoing crop feeding. This approach increases fertilizer use efficiency โ nutrients applied at the right time are taken up by plants instead of being lost.
How to combine fertilization with tillage operations?
Combining agrotechnical operations is one of the key elements of reduced tillage โ it saves time and fuel and protects soil from unnecessary compaction.
One common practice is fertilizer application during stubble cultivation or pre-sowing tillage, so that in a single pass the soil is cultivated and fertilizers are spread or incorporated. Applying fertilizers immediately after harvest and mixing them with the soil during shallow stubble cultivation or the next pre-sowing operation allows nutrients to become available more quickly. In practice, seeds of the following crop (cover crops or winter crops) sown shortly afterwards can benefit from these nutrients from the very beginning.
In strip-till and generally no till farming, fertilization is often applied during sowing or deep loosening. Strip-till machines are equipped with applicators that place fertilizer precisely under the root zone โ nutrients are delivered exactly where roots will reach them, maximizing their uptake.
However, liming should not be combined with mineral nitrogen fertilization in a single pass, as this may cause nitrogen losses due to chemical reactions with lime.
Using soil analysis to optimize fertilizer rates
Soil analysis provides information on pH and the availability of phosphorus, potassium, magnesium, and other nutrients โ it is the foundation of rational fertilizer planning. Soil test results (discussed in more detail in e-book 1) make it possible to determine what the soil actually lacks for the planned crop and which nutrients are already present in sufficient amounts.
Important! Studies by the Institute of Soil Science and Plant Cultivation in Poland have shown that adjusting fertilizer rates to the actual soil nutrient status can reduce mineral fertilizer use by up to 30%, while simultaneously increasing yields by 15โ20%.
How to practically use soil analysis results?
First of all, soil pH should be regulated. Optimal pH is a prerequisite for effective fertilization โ if the soil is overly acidic, many nutrients (such as phosphorus) become unavailable to plants. The pH test result indicates whether liming is required (or not, which is rare, as around 60% of soils in Poland are too acidic). Liming often needs to be carried out before proper fertilization so that nutrients can be absorbed from the soil..
Important! Studies by the Institute of Soil Science and Plant Cultivation in Poland have shown that adjusting fertilizer rates to the actual soil nutrient status can reduce mineral fertilizer use by up to 30%, while simultaneously increasing yields by 15โ20%.
Nitrogen fertilization planning often also takes into account estimated soil nitrogen content. Knowing the mineral nitrogen level in the soil and the expected yield, it is possible to calculate the nitrogen dose using a formula.
Such calculations allow you to supply only the difference between crop demand and what the soil already provides, avoiding both deficiencies and over-fertilization.
Important! Determining soil nitrogen availability requires special sampling (from 30โ60 cm and even 60โ90 cm soil layers), because nitrogen moves quickly down the soil profile.
