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Nutrient Management and CRW

Situation:
Macronutrients such as nitrogen (N), phosphorus (P), and potassium (K) are important in the growth and development of crops. Deficiencies in these nutrients can affect root system development, tolerance of insect injury, and plant susceptibility to stress.
Nitrogen is an important component of proteins. Because the protection provided against insects in transgenic corn is based on Bt proteins, effects of nitrogen deficiencies on corn physiology and protein production may jeopardize plant protection. Nitrogen loss in wet springs or delayed breakdown of organic matter in cool summers, such as 2009, can limit nitrogen availability and increase plant susceptible to corn rootworm or caterpillar pests.
Phosphorus and potassium can be important early season, even in high testing soils, when limited root growth and poor soil mobility movement in the soil can lead to deficiencies. Starter fertilizer is an accepted practice that aids in nutrient uptake by placing a band of fertilizer close to the roots. This generally leads to faster early growth and larger plants which may be beneficial in tolerating corn rootworm infestations.

Fluctuations in nutrient prices have caused some producers to cut back on inputs. As farmers cut back in fertilizer application, they run the risk of nutritional deficiencies that may lead to poorer early-season root growth, reduced growth and vigor, and increased susceptibility to insect attack. The prevalence of macronutrient deficiencies on corn and its impact on corn rootworm populations and injury has become a more-important issue with the appearance of unexplained corn rootworm injury in 2009 to transgenic corn presumably resistant to corn rootworm.

Project Description: The role of macronutrients on corn and corn rootworm is the subject of two research projects:

Effect of hybrid traits and nitrogen management on nitrogen use efficiency (NUE): Improved NUE has been a major focus of corn breeding programs lately as the seed industry focuses on improving hybrid efficiencies, increasing yields, and reducing energy demands. This study focuses on determining differences in NUE from the trait for corn rootworm protection in two hybrids of differing maturities in continuous corn. Four corn hybrids representing two trait packages (with and without Bt-RW protection via the VT3 gene package) and two relative maturities (94 and 102 day relative maturity) were used in this study. These hybrids were grown on nitrogen rates of 0, 60, 120, 180, and 240 lbs of N per acre (pre-plant incorporated urea) to determine NUE for individual corn hybrids and the Bt-RW trait. The NUE study began in 2008 at UMORE Park (Rosemount) and is in the second year of data collection.

Impact of nutrients applied in starter fertilizer on rootworm damage: Two 100-day relative maturity hybrids (near isolines with and without the Bt-RW gene) are being compared with different combinations of N, P, and K applied as starter while planting. Research has shown benefits of N and P for increasing plant growth in the spring, but data for K is not as clearcut. Research trials in other states are looking at K nutrition and the incidence and severity of rootworm damage. Increased early growth increases nutrient uptake but the question is whether or not increased K uptake early is beneficial later in the season. Twelve locations will be studied between 2008 and 2010 across southern Minnesota along with three locations in northwest Minnesota.

Expected Outcomes:

  • Determine if differences exist between hybrids on NUE of corn
  • Examine if corn rootworm protection alters the NUE of corn and potentially optimal nitrogen rates
  • Determine if starter fertilizer can partially offset corn rootworm injury and the optimal starter composition for minimizing damage.
  • Investigate if, and how, N, P and K affect corn rootworm injury

Funding Sources:
The corn NUE study funding was provided by Monsanto and the Starter fertilizer work was funded through the Minnesota Corn Research and Promotion Council.

Kenneth Ostlie
Professor and Extension Entomologist
University of Minnesota
Department of Entomology
1980 Folwell Ave., Rm. 219
St. Paul, MN 55108-6125
Cell: (612) 750-0993
Office: (612) 624-7436
Fax: (612) 625-5299
Email questions on corn rootworm