Yield losses in maize (Zea mays) infested with parthenium weed (Parthenium hysterophorus L.)

• The yield response of maize (Zea mays L.) to varying densities of the invasive weed Parthenium hysterophorus L. was tested during autumn seasons of two consecutive years.
• Increasing densities of P. hysterophorus (0, 5, 10, 15 and 20 plants m−2) increased P. hysterophorus dry weight, relative competition index; and uptake of N, P and K up to 433, 145, 336, 180 and 295%, respectively.
• Five or more parthenium weed plants per m2 decreased grain yield, biological yield, 100-grain weight, grain weight per cob and harvest index of maize.
• Maize grain yield losses varied between 21 and 50% with P. hysterophorus density ranging from 5 to 20 plants m−2.
• The economic threshold of P. hysterophorus as determined by prediction model was 1.2 and 1.0 plants m−2 during year 2012 and 2013 indicating that parthenium weed in maize should be controlled at these density levels.

For cost-effective control of a weed, it is essential to know about its economic threshold level in a specific crop. The yield response of maize (Zea mays L.) to varying densities of the invasive weed Parthenium hysterophorus L. was tested during autumn seasons of two consecutive years 2012 and 2013. Increasing densities of P. hysterophorus (0, 5, 10, 15 and 20 plants m−2) increased P. hysterophorus dry weight up to 433% and relative competition index up to 145%. Corresponding increases in the uptake of N (up to 336%), P (up to 180%) and K (up to 295%) were also recorded. Maize plant height and number of grains per cob were reduced at parthenium weed densities beyond 10 plants per m2. Five or more parthenium weed plants per m2 decreased grain yield, biological yield, 100-grain weight, grain weight per cob and harvest index of maize. Maize grain yield losses varied between 21 and 50% with P. hysterophorus density ranging from 5 to 20 plants m−2. Maximum N, P, and K uptake by P. hysterophorus was 78.0, 9.0 and 64.0 kg ha−1, respectively. The economic threshold of P. hysterophorus as determined by prediction model was 1.2 and 1.0 plants m−2 during year 2012 and 2013 indicating that parthenium weed in maize should be controlled at these density levels.