Agronomic performance of Pesticide Free Production under two crop rotations

Abstract

Pesticide Free Production (PFP) is a pesticide reduction system that removes in-crop pesticide use on a yearly basis. A longterm study was established in 2000 to investigate the effect of crop rotation and frequency of inclusion on the success of PFP, as well as the effect of PFP on subsequent crops in the rotation. The crop rotations being compared were linola-oat-canola-wheat and linola-oat-alfalfa-alfalfa. PFP occurred either once in the rotation (oat) or twice (linola-oat). Weed density and yield were measured in the crops that followed PFP. Oat was a more successful PFP crop than linola because it was better able to compete with weeds. Furthermore, PFP oat had a higher weed density when it followed PFP linola, but this did not influence PFP oat yield. Under the conditions of this study, PFP linola was more successful in the annual crop rotation. Inclusion of alfalfa hay crops in the crop rotation was not effective in lowering weed pressure and, in fact, may have contributed to an increase in weed density. It is concluded that weed species present influenced the effectiveness of alfalfa in facilitating PFP, because major weeds in the study are not effectively controlled by alfalfa. PFP did not have a negative effect on following crops in the rotation (i.e. canola-wheat or alfalfa), regardless of whether one or two consecutive years of PFP occurred in the rotation. No additional herbicide was necessary for weed control in the crops that followed PFP; however, alfalfa hay was weedier for the first year following PFP. This study indicates that PFP is a viable way to reduce herbicide use in a cropping system and that attention needs to be paid to PFP crop selection and crop rotation, particularly when the PFP crop is less competitive with weeds.

Preceding crop and weed management history affect denitrification and denitrifier community structure throughout the development of durum wheat

“…In each block, this rotation is repeated three times and subjected to different in-crop herbicide-use regimes including: (i) the control rotation (low seedbank density), where selective in-crop herbicides were applied to all annual crops, (ii) the same rotation where in-crop herbicides have not been applied to the oat crop (medium seedbank density) and (iii) the same rotation where in-crop herbicides have been omitted from each oat and flax crop (high seedbank density). These herbicide-use patterns have resulted in distinctly different above ground weed population densities (Schoofs et al, 2005). Over time, this shift is also reflected in weed seedbank populations where the lowest in-crop herbicideuse (2 in 4 years) has resulted in a more than 2-fold greater weed seedbank population density throughout all crops in rotation while the intermediate treatment (3 in-crop herbicides in 4 years) showed marked differences in seedbank densities following the flax crop when compared to the highest in-crop herbicide use intensities, but only an average increase of 30% over all crops in rotation (Gulden et al, 2011).…”

“…Part of the study consists of an annual crop rotation typical of the region at that time [flax (Linum usitatissimum L.) -oats (Avena sativa L.) -canola (Brassica napus L.) -wheat (Triticum aestivum L.)] managed using no-till methods (Schoofs et al, 2005). In each block, this rotation is repeated three times and subjected to different in-crop herbicide-use regimes including: (i) the control rotation (low seedbank density), where selective in-crop herbicides were applied to all annual crops, (ii) the same rotation where in-crop herbicides have not been applied to the oat crop (medium seedbank density) and (iii) the same rotation where in-crop herbicides have been omitted from each oat and flax crop (high seedbank density).…”

Seedbank–plant relationships for 19 weed taxa in spring barley–red clover cropping systems

“…In certifiable fields at the farm scale (71 farms, 120 fields), PFP resulted in 8 to 10% lower yields than the conventional average, with manageable weed densities in spite of the reduction in herbicide use (Nazarko et al 2003). Both on-farm and experimental data highlighted the importance of crop selection for the success of PFP Nazarko et al 2003;Schoofs et al 2005). The small-plot PFP experiment initiated in 2000 focused on incrop herbicide omissions and contained both a 4-yr annual grain crop rotation (flax/oats/canola/wheat) and an annual grain/perennial forage rotation (flax/oats/alfalfa/alfalfa).…”

“…In Manitoba, PFP was evaluated at the farm scale (2000 and 2001) (Nazarko et al 2003) and in a small-plot PFP experiment initiated in 2000 by the University of Manitoba (Schoofs et al 2005). In certifiable fields at the farm scale (71 farms, 120 fields), PFP resulted in 8 to 10% lower yields than the conventional average, with manageable weed densities in spite of the reduction in herbicide use (Nazarko et al 2003).…”

“…A regression analysis of weed biomass and crop yield was conducted for the flax and oat crops across the three rotations using averaged data collected from the first 4 yr of the study (Schoofs et al 2005). The relationship between weed biomass and crop yield was only significant in the flax crop (annual grain rotation R 2 ¼ 0.39, P , 0.074; annual grain/perennial forage rotation R 2 ¼ 0.82, P , 0.001), but was not significant for the oat crop in either rotation.…”