Weed communities changes in wheat crops resulting from management improvements in the Rolling Pampa, Argentina

POGGIO, S. L.; CARREIRA, ANALÍA M

Praga

Congreso; 7th International Weed Science Congress; 2016

International Weed Science Society

Species diversity and composition of weed communities shift in response to technological transformations in agriculture. In the Pampas of Argentina, agricultural systems have been profoundly transformed since the 1990s, especially due to the rapid adoption of no-tillage and herbicide tolerant, genetically modified soybean varieties. These changes have also promoted modifications in wheat cropping systems, particularly due to double cropping with soybean. The objective of this research was to characterise the changes in the weed communities of wheat crops after recent transformations in cropping systems in the Rolling Pampa. Study of changes in species diversity and compositions was based on three sets of weed surveys carried out in 1996-1997, 2003-2004, and 2009-2010. Mean species richness decreased during the study period (S1996-1997= 13, SEM= 0.8, S2003-2004= 7, SEM= 0.6 and S2009-2010= 4, SEM= 0.4). Numbers of abundant species (exponential Shannon index: eH?1996-1997= 9, SEM= 0.7, eH?2003-2004= 4, SEM= 0.4, and eH?2009-2010= 3, SEM= 0.2) and dominant species (reciprocal Simpson index: 1/D= 1996-1997= 7, SEM= 0.6, 1/D2003-2004= 3, SEM= 0.2, and 1/D2009-2010= 2, SEM= 0.2) also decreased. Floristic composition tended to be more similar during the study period, particularly due to the loss of rare species. Mean wheat yields increased in ca. 45% during the period (1991-1995: 2973 kg ha-1, SEM= 91.2; 2006-2009: 4291 kg ha-1 SEM= 100.7). While no-tillage was used to sow only 7% of wheat crops in 1996-1997, all crops were sown with this practice in the remaining two surveys. No-tillage allowed the earlier sowing wheat varieties with longer cycles, whose length increased in about four weeks. Weed control was almost exclusively based on a single post-emergent, herbicide formulation (Dicamba+Metsulphuron Methil A), while glyphosate applications in fallows began since no-tillage adoption. This research contributes to understand the changes in weed community assembly due to rapid technological transformations in agricultural systems.