Nutrient management is the key to having a sustainable high yielding crop without any damage to the plant, environment, and soil productivity. Even when the operation is organic or conventional, the nutrient requirement of the crop must be met to ensure a satisfactory yield. One crucial challenge is the multiple cropping systems that they implement. Most small farms focus on special markets with numerous crops and multiple crop management. Fertilizers are applied to meet the crop requirements, and the application of fertilizers are based on soil fertility test, plant tissue nutrient test and crop yields.
The materials applied as fertilizer or added as a supplemental nutrient source must have a known nutrient value. The materials applied must have a known, researched crop nutrient value seen frequently in green manures. A fertilizer recommendation is a research-based set of guidelines or management practices to supply fertilizers to the crops to achieve yield and quality goals in such a way that reduces nutrient losses to the environment.
A typical soil test fertilizer recommendation includes guidelines for:
- The fertilizer rate: Specifying how much fertilizer is needed to supplement the nutrients.
- The types of forms of fertilizer to be used: This includes dry granular, soluble, fluid, controlled release, and more.
- Fertilizer sources to supply specific nutrients: These include nitrogen to be supplied from urea, calcium nitrate, ammonium sulphate, ammonium nitrate and more.
- Placement method – Whether it is ground or foliar, pre-plant, broadcast or band, side-dressing in the season
- Timing: The soil test fertilizer recommendations include timing based on specific growth cycles or growth stages in the season.
- Managing the irrigation system: Soil test fertilizer recommendations include recommendations for managing the irrigation system so that the water and nutrients stay in the root zone.
Specific Soil Test Recommendation Components:
Economic :
Fertilizer includes 10% of the total production costs for most vehicles. There is no denying that fertilizer costs have increased sharply in the early 2020s. The fertilizer expenses on the farm are controlled by paying close attention to science-based recommendations and the best management practices. The nutrients that are applied but unused by the crop represent the lost money and profits.
Irrigation Management :
Irrigation is the most important management tool for managing fertilizers properly. Optimum irrigation management is a crucial part of the soil test fertilizer recommendation so that the nutrients are not leached. Irrigation management and fertilizer application must be done in the right balance to ensure enough water and nutrients in the root zone. Irrigation must be planned with the knowledge of the root zone of the crop, and the leaching potential of the soil is reduced. The goal of the irrigation program is to keep the water and nutrients in the root zone till the nutrients are absorbed by the plant. Irrigation frequency and run-time are scheduled so that water and nutrients don’t move below the root zone. Soil moisture monitoring is crucial for optimal irrigation management, and there are many new technologies available.
Fertilization Rate:
For most of the crop production areas, the fertilizer nutrients have two specific categories – those that are highly mobile in the soil and those that are not highly mobile. Growers get a nitrogen recommendation based on the field research that determined the crop nitrogen requirement. Potassium is mobile in sandy soils and for some crops like potatoes.
For vegetables, the potassium recommendations are based on the soil test till the research disapproves the need for a soil test. Soil testing can be used for determining the fertilizer needs for the nutrients, like phosphorous, that are not mobile in the soil. For mobile nutrients like nitrate-nitrogen, the fertilizer rates are recommended based on the Crop Nutrient Requirement (CNR), which is based on the fertilizer rate field trials.