Weed biomass and density in a long-term conservation agriculture experiment in Mexico

Weed management can be one of the main challenges when adopting conservation agriculture. Although all three components of conservation agriculture (minimal tillage, permanent soil cover and crop diversification) can have a reducing effect on weed populations, these effects may only become apparent in the medium to long term. This study evaluated weed biomass, density and diversity with and without control by herbicides in a long-term trial that was initiated in 1991 in the Mexican Highlands to evaluate all three components of conservation agriculture. The experiment was located in the experiment station of the International Maize and Wheat Improvement Center (CIMMYT) at El Batan, Texcoco, in the state of Mexico (2240 masl; 19.318N, 98.508W). The climate was semi-arid, with a mean annual temperature of 14°C, and 616 mm average annual rainfall between 1995 and 2015, of which on average 567 mm fell during the growing season (May–October). The soil was a Haplic Phaeozem (clayic). Data were collected in 16 treatments, which consisted of the full factorial combination between the factors of tillage, soil cover and crop rotation, including continuous wheat or maize, and wheat and maize rotations, with both phases of the double crop rotation included each year; keeping all residue on the field or removing all residue for fodder (R) and conventional tillage or zero tillage with direct seeding. The data set contains weed density data collected in 2004, 2013, 2014 and 2015 and weed biomass data collected in 2005, 2013, 2014 and 2015.