Agronomic and Economic Assessment of Variable Rate
Determine the agronomic information required to choose the optimum nutrient rates and assess the economic the benefits of variable rate fertilization.
IPNI-1995-CAN-SK17
31 Aug 2001
Methodology
- In the first year of the proposed project, two test sites (wheat, canola) will be located in the Black soil zone. At each site distinctive management units will be determined using extensive soil sampling and nutrient testing. These management units will be at a size which is practical for varying the rates using the existing technology, and will be distinctive units in terms of nutrient requirements and moisture conditions. Clearly it is not practical to carry out this level of assessment at all sites in Saskatchewan, and we will use existing information technology at the Department of Soil Science to extend the Soil Survey data base for the province to the quarter-section scale mapping required for this project.
In the second year, the optimum rates of N and P required for the management units will be determined from the response of the wheat and canola to different rates of N and P fertilizers. Rates of N will be from 0 to 2 times the recommended rates at 0.25 increments; rates of P at 0, 0.5, and recommended rate. At each site four adjacent 3-5 ha blocks will be developed. The first block will be used to establish the optimum rates of N and P in year two; two blocks will be used for application of the variable rate inputs in years three and four; and in the final block N and P will be added at a constant rate in all years of the trial. The treatments will be established in long strips which contain at least 10 spatially independent replicates of each of the management units.
Extensive soil sampling (to 60 cm in two 30 cm increments) of each of the management units present at each site will be carried out over the field season. At the conclusion of the trials the minimum number of samples required to obtain reliable soil fertility levels for each management unit will be determined.
Yield data will be determined at harvest for each management unit, and grain samples will be analyzed for protein, moisture and quality.
The soil and yield data assessed in year two will allow us to develop a yield response model for N and P in each management unit. This model, coupled with spring moisture levels, will be used to develop a variable rate fertilizer program for the study sites in years three and four. The results from the variable rate sites will be compared to the adjacent control site (with constant N and P at the recommended rate) to determine the economic benefit of variable rate fertilizer technology.
The yield data and the known levels of inputs are the major inputs into the economic assessment of the benefits of the variable rate technology. The assessment will be further refined by factoring in the time required for the field operations and the standard assessments of the equipment costs. We will work with both economists from the Agricultural Economics Department and with the farm cooperators to achieve a realistic, comprehensive assessments of the economic benefits of the variable rate technology.