CORN
Crop Observation and Recommendation Network

October 1 to October 7, 2001
C.O.R.N. 2001-33

In This Issue:

A) Phosphorus and Potash Recommendations for Corn and Soybeans
B) Weather Effects on Corn Silage
C) Multicolored Asian Lady Beetle

A) Phosphorus and Potash Recommendations for Corn and Soybeans (Ed Lentz) CORN Questions

Since phosphorus and potash are relatively immobile in the soil, what a crop does not remove will accumulate (build-up) for future use. Producers that have followed a good nutrient program may already have adequate P and K soil levels for the 2002 cropping year. A soil test is the best way to estimate if P and K levels are in excess, adequate or deficient. The following discussion provides some guidelines for soil test values:

Soil P levels above 40 ppm (80 lb) would not need additional amounts for corn or soybeans. Phosphorus applications should match crop removal if soil levels are 15-30 ppm (30-60 lb). For corn, crop removal equals the yield goal multiplied by 0.35; for soybeans, crop removal equals the yield goal multiplied by 0.83. Between 30-40 ppm, amounts less than crop removal would be recommended depending on yield goals. If soil levels are below 15 ppm, then applications would include crop removal and a build up program. For example, if soil P levels were 10 ppm (20 lb), then a 160 bu/A corn crop would require 85 lb/A P and a 50 bu/A soybean crop would require 65 lb/A.

Potash (K) recommendations follow the same philosophy as P except consideration is given for soil cation exchange capacity (CEC). Since applied potash may be held more tightly by soils with high CEC, potash rates increase as the soil CEC increases. Regardless of CEC and yield goals, corn and soybean yields would not respond to additional K at soil K levels above 200 ppm (400 lb). Corn and soybeans grown on soils that have a CEC < 10 would not respond to additional K when the soil test level > 150 ppm (300 lb). Tables on page 14 in the Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat & Alfalfa guide provide potash rates for corn and soybeans at various yield goals and soil CEC. Many private soil testing laboratories have the capability to make recommendations from this guide upon request. If you are not sure whether a private lab follows these recommendations, a computer program using the Tri-State recommendations may be downloaded from the Internet at http://ohioline.osu.edu/lines/farm.html#SWARE This program, labeled Ohio Soil Test, can use soil test values for P and K from most private labs to develop Tri-State recommendations.

In summary, by understanding your soil tests, P and K rates may be reduced without lowering corn and soybean yields. This may be one way to lower input costs when prospects for corn and soybean prices are low.

More details on soil fertility may be obtained in Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa, Bulletin E-2567, available through your county Extension Office. Recommendations from this publication incorporate over 40 years of data from field calibration and correlation studies.

B) Weather Effects on Corn Silage (Greg Roth, Corn Management , September 28, 2001 Pennsylvania State University Field Crops Newsletter) CORN Questions

The variation in our weather from year to year and location to location has a substantial impact on corn silage quality in our region. This variation causes dairy producers and nutritionists the need to adjust rations to maintain high milk production levels. The table above summarizes some of the effects of weather on yield and several forage quality traits of corn. Most of these data were adapted from a summary by Coors and Lauer (2001) from studies in the Netherlands and New York, but our data from Pennsylvania studies would support them as well.

Higher temperatures can increase DM yield, but cause more respiration to occur late in the season and reduce grain fill. High light intensity (lack of cloudy days) promotes good grain fill that has positive effects on whole plant digestibility. As plant densities increase, yields often increase, but reduced sugars and starch in the silage may lead to slightly lower whole plant digestibility. Delaying harvest tends to reduce dry matter slightly, decrease digestibility, and here in Pennsylvania, often decreases the fiber content and fiber digestibility. Drought generally reduces yield, and grain content. This increases the fiber content but this is often accompanied by lower lignin production that increases the fiber digestibility. In seasons where the drought comes at the end of the season, sometimes the grain content is reduced but the stalks are large and well lignified, so the fiber digestibility is not increased.

C) Multicolored Asian Lady Beetle (Bruce Eisley) CORN Questions

There continues to be a lot of interest in the Multicolored Asian Lady Beetle and what might happen in the next few weeks as they move from fields into their overwintering sites. The OSU IPM program has held four meetings throughout the state in the last three weeks talking with people about the beetle and the problems that it causes. Information presented at the meetings, including biology of the beetle, suggested management techniques and pesticides that might be used to control them, can be found under lady beetle information the on the OSU IPM website at: http://www.ag.ohio-state.edu/~ipm/

Readers can subscribe electronically to this newsletter by sending an e-mail message to: corn-out-on@postoffice.ag.ohio-state.edu. A successful subscription message will receive by an automatic reply from the listserv. Contact your local Ohio State University Extension Office or e-mail labarge.1@osu.edu if you have problems subscribing.

Past versions of C.O.R.N. can be found on the World Wide Web at: http:/www.ag.ohio-state.edu/~corn/archive/

C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

Editor: Barry Ward        Web Editor: Tom Rosati

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

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