SPRING 2002 13
Soil Fertility Projects
Developing Site Specific Management Zones
Raj Khosla, Robin Reich, and Dwayne Westfall
Managing in-field variability using the management zone approach will
lead to more efficient management of crop production inputs and reduce
the need for intensive soil sampling (grid sampling approach). This approach
may also optimize environmentally sensitive chemical application and enhance
overall farm profits. Variable rate precision farming technologies can
help develop and evaluate those in-field productivity level management
zones designed to optimize nutrient application, grain yield, and nitrogen
use efficiency. Low, medium and high potential productivity in-field management
zones were developed for center pivot and furrow irrigated cornfields
in NE Colorado. Treatments include: variable rate nitrogen (N) application
based on intensive gridsampling; variable rate N application based on
the management zone approach; and conventional uniform application of
N based on the currently recommended algorithm. Fertilizer rate was determined
by the farmer's discretion. Managing a field for inherent soil variability
can be done with GPS and GIS technologies without expensive and time-consuming
grid based techniques. By managing a field using productivity zones and
N treatments that account for spatial soil variability, biomass productivity,
N uptake, and N use efficiency is increased compared to conventional N
application treatments.
Root Characteristics of Colorado Crops as
Related to Efficient N Fertilizer Use
Parviz Soltanpour, Grant Cardon, Mary Schutter, and Abdullah Al-Sheikh
Using crop varieties that require less nitrogen (N) and other nutrient inputs will reduce the cost of these inputs to Colorado farmers and will reduce the potential pollution by farming in Colorado surface and ground water. Current experiments are testing if potato varieties with larger root surface areas associated with larger root volumes increase the uptake efficiency of N by measuring root surface area and N uptake rates for two varieties, one with a smaller root volume and top then the other. We are also trying to develop a faster and less expensive method for measuring root surface area. Results will potentially enable plant breeders to assess their lines for root characteristics that increase the nutrient uptake efficiency leading to a lower level of leachable nitrate and protection of water quality.
