weed science
BP-10-11
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • DEPARTMENT OF BOTANY AND PLANT PATHOLOGY LILLY HALL OF LIFE SCIENCES • WEST LAFAYETTE, INDIANA 47907
WEED PROBLEMS IN REDUCED AND NO-TILL PRODUCTION T. N. Jordan, T. T. Bauman, and J. L. Williams, Jr., Extension Weed Specialists

The rising cost of producing corn and soybeans has greatly influenced the rapid increase in minimum and no-tillage farming in Indiana and other states in the north central section of the Nation. Hhile some success has been seen with reduced tillage practices, failures with these systems has been high. There is no question that reduced or no-tillage crop production has been beneficial in the preservation and development of the soil and conservation of water, energy, sod equipment. However, the lack of weed control limits the use of reduced tillage practices or in many cases totally prevents the use of these systems, bosses in soybean production caused by weeds are greater than those for all other pests combined. The excessive cost is due largely to the complexity of the weed control problem and the lack of techniques that permit farmers to control weeds effectively.

The need to control weeds is a ma-jor factor in determining the amount of tillage needed for crop production, without tillage, successful weed control depends entirely upon a satisfactory herbicide program. If the herbicide program fails, then a no-till program becomes a disaster. Proper herbicide management is much more critical with reduced tillage than with conventional tillage. Likewise, agronomic managerial
decisions are more critical as tillage is reduced. In most cases, no tillage or reduced tillage combined with narrow row spacing is successful for a few years; then a buildup of weeds forces the return to wide rows and intensive tillage to clean up the fields. Available herbicides provide more opportunity for no tillage in corn production than in soybean production. Season-long weed control in no-till soybeans is extremely difficult to achieve. Before considering a reduced or no-tillage program in a particular field, determine the weeds in that field by scouting and mapping the weeds in the crop preceeding the year that no-till is to be used. This will establish the types and severity of the weed problem and will indicate the feasibility of no-till in that location. It will also help in selecting the right herbicide program for that particular situation. If the weed population is such that cultivation is the best control measure, then no-till would not be the best program.

Weeds which compete with a crop for the first 4 to 8 weeks have the most influence on yields. This is particularly true for soybeans. Weeds which emerge 8 to ID weeks after crop emergence have little effect on yields per se but can reduce grade and harvest efficiency to the point that the benefits gained from

Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S, Department of Agriculture Cooperating. H.G. Diesslin, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue at all persons shall have equal opportunity and access to its programs and facilities without regard to race, religion, color, sex or national origin.