November 28, 2016
Soil fertility and plant nutrient management is an important part of agroecosystems. Agroecological approaches to soil fertility and nutrient management begin with soil testing. A soil test will tell you soil pH. Soil pH affects the availability of nutrients to the plant. Soil pH should be adjusted to the optimal level for each crop before adding other fertilizers. A relatively new approach to fertilizer best management practices is to apply fertilizers considering the 4 Rs – Right Rate, Right Time, Right Place, Right Source.
The right rate will be determined by evaluating several factors and environmental conditions. Producers should always start with a soil test to determine current plant available nutrient levels in the soil. The UF/IFAS fertilizer recommendation will be based on the plant available nutrients in the soil and the plant nutrient demand. Producers should also consider the nutrient sources and their predicted use efficiencies. Lastly, producers should consider how nutrients will be removed or recycled on the farm. More nutrients are recycled on grazed pastures and more nutrients are removed on hay fields. Therefore hay fields will require more nutrient inputs to offset the nutrient outputs coming off the farm as hay.
Producers will consider the rate, source and place of application again when deciding when to apply fertilizers to hay fields or pastures. Nutrients should be applied when plants are actively taking up nutrients from the soil. This will be dependent on plant species, variety and planting date. Also, predictable weather patterns affect the timing of fertilizer applications. Periods of high rainfall should be avoided because nutrient leaching losses will be higher. Overall farm logistics also should be considered. Split applications of conventional sources are best to decrease nutrient losses but not always logistically and economically possible.
The source, rate and timing of application should be considered when deciding on placement of fertilizers on the farm. Also, producers should consider root depth, soil chemical reactions and tillage systems. For perennial pastures, fertilizers are applied on the soil surface rather than incorporated into the soil subsurface. This affects how the fertilizers become available to the plant and how the nutrients become susceptible to losses. The goal of fertilizing pastures and hay field should be to optimize that amount of nutrients that are available to the plant in the root zone but to decrease nutrient losses due to leaching.
Producers will need to consider desired rates, timing and place of applications when deciding what source of fertilizers to use. The goal is choosing a source that will provide plant available nutrients when the plants are actively taking up nutrients while decreasing nutrient losses to the environment. Nutrients include macronutrients and micronutrients. Producers should apply balance nutrients to meet the crop demands. Producers are forced to choose sources by what is commercially available to them. The main sources of nitrogen commercially available to producers in Northwest Florida currently are urea, controlled release fertilizers (polycoated ureas and inhibitor additives with urea) and slow release fertilizers (biosolids).
For more specific forage fertilization recommendations, download: