Dealing with Spatial Variability in Nutrient Management
eKonomics News Team
Growers nationwide continue to note the benefits of 4R nutrient stewardship. The 4Rs are based on selecting the ‘right’ fertilizer source and applying it at the right rate, at the right time and in the right place. What is ‘right’ for a given field depends on site-specific factors, including the degree of spatial variability.
Spatial variability describes a soil’s capacity to supply nutrients and how crop nutrient demand varies across a field. Failing to consider spatial variability when making nutrient management decisions can result in decreased fertilizer use efficiency and poor return on investment.
Productivity and profitability can be improved by applying fertilizer at the right rate and in the right place within the field. Understanding how requirements vary spatially in a field allows the grower to use variable-rate application technology to distribute fertilizer accordingly. This enables growers to avoid missing out on additional yield in under-fertilized areas and enhances profitability where fertilizer is less needed.
Managing nutrient inputs at smaller spatial scales across a field can also improve environmental quality and cropping system sustainability. Understanding variables that influence spatial variability – such as soil type, water and nutrient-holding capacity, slope and topsoil thickness – can aid growers and advisers in selecting appropriate best management practices (BMPs) for each field. These BMPs may go beyond nutrient inputs and impact a grower’s decisions such as seeding rate and perhaps even hybrid/variety.
Technology that takes spatial variability information to form an action plan is readily available. Harvest yield monitors, mapping software and variable-rate fertilizer applicators were all developed based on the premise that not all areas of a field possess the same yield potential or nutrient-supplying capacity. Therefore, the areas of a field do not necessarily have the same nutrient requirements.
Precision agriculture technology currently provides the tools needed to identify, diagnose and treat spatial variability. Continued investigation into the effects of variability on fertilizer management is leading to refined approaches and additional technological advances for enhancing a grower’s return on fertilizer investment.