Colorado Corn Cultivating Opportunities

Overview – Root Architecture study at the Irrigation Research Farm
The Colorado Corn Growers (CCGA) and the Irrigation Research Foundation (IRF) joined forces in 2008 to evaluate differences in corn rooting patterns. At the farm north of Yuma, Colorado, The study was designed to initiate research in three key areas of study, each addressing a significant question related to root development of corn hybrids known to be good performers in low water conditions for the Northeast Colorado region:

Rooting study 
Key question addressed: Do different varieties exhibit significant differences in rooting architecture?

• Each variety’s root profile volume, depth, and number of main roots will be analyzed and documented.
• Digs will be performed at 25, 55, and 100 days after planting to physically examine and attribute the rooting architecture.

Results

YES. Deep, modified, and shallow types were recognized among the eight varieties tested. Their mature plant profiles are shown indicating noticeably different characteristics that could warrant different management techniques in order to maximize water and nutrient uptake. The depth scale noting feet below ground surface.

• Deep profiles were roughly 2X the depth penetration of the shallow type.
• There appeared to be consistency between varieties of the same type.
• Generally, we believe these differences to be worth considering in variety selection, deficit irrigation water conditions, and breeding considerations.
• Worth repeating with same and different varieties to increase confidence, and to address whether the recognized differences are the result of genetic or environmental factors.

Yield study
Key question addressed: What varieties promoted as "drought-tolerant" are best performers in 50% and 85% consumptive use environments?

• Examine yields of the same recognized "drought-tolerant" hybrids at two levels of limited irrigation, 50% and 85% of normal consumptive use. (planned water deficits to occur during vegetative stages)
• Evaluate at three population levels for each irrigation level.

Results
There was a significant difference among recognized drought tolerant varieties from different companies.

Populations matter, but vary by variety and flex vs. semi-determinant vs. fixed ear characteristics. In some instances, the lower populations out-yielded the higher populations of the same variety. Rooting architecture differences may be a key factor in predicting population responses. Further study is warranted.

Observations based on rooting profiles: Varieties with Type I (deeper rooting) root characteristics generally out yielded the shallower rooting varieties.

• While the sample size was relatively small, (eight varieties) there was a recognizable difference.
• Due to unusually heavy natural rainfall, water availability was not as “limited” as planned. However, visual drought stress symptoms were allowed to develop during the earlier vegetative stages.
• Applied water rates were 5.75 inches and 9.5 inches.
• This part of the study is worth repeating with same and different varieties to increase confidence under varying environmental conditions.

Nitrogen study
Key question addressed: When producing corn with limited water, are traditional N fertilization methods appropriate?

• Designed to evaluate viability of typical nitrogen fertigation practices in limited water environments.
• Track movement and availability of N applied through center pivot in limited applications.

Results:

• Methods used in this study included 10% applied through strip till unit at 6 and 10 inch levels below ground surface, 16% applied as starter (2 x 2), and 74% applied through pivot sprinkler from Jun 23 to July 24, but pre-tassel. Total nitrogen applied was 190 lbs/acre to all plots.
• Evidence from this year’s work indicates a portion of applied N escaped the lower limits of the root zone due to deep percolation, but heavy June rains were a factor. Increasing the percentage of N applied pre-tassel through the pivot system could help insure against N movement beyond the root zone. There is good evidence outside of this research that foliar application of slow release N products have value to enhance late kernel development just prior to pollen shed. This method may be needed to be evaluated.
• There is also evidence we may be able to reduce N amounts, but use the same application methods.
• We also learned to recognize the general shape and depth of the 3 root architecture types at 50 and 100 days after emergence. This information may prove valuable to understanding varietal response differences to various nutrient and population differences and water application placement methods.