Crop responses to sulfonylurea residues in soils of the subtropical grain region of Australia

Abstract

Crop response following applications of sulfonylurea herbicides can vary considerably across the grain region of subtropical Australia. The aim of the study was to develop recommendations for safe re-cropping following chlorsulfuron, triasulfuron, and metsulfuron-methyl specific for the different soils and climates of this region. Seedling dry matter (SDM) and grain yield were measured at 17 sites over 4 seasons. Soils were ferrosols (pH 5.5–6.8), sodosols (pH 6.6–7.1), and vertosols (pH 7.8–9.0). Sorghum and sunflower were sown at plant-backs between 2 and 20 months, and chickpea at 10–13 months, after applications of sulfonylurea herbicides. Seedling response of the summer crops to these herbicides was substantially different for the 3 soils. Crop response in theferrosols was largely unaffected by plant-back, soil, or climatic factors after a minimum of 2–3 months. In contrast, response of summer crops in the vertosols and sodosols was strongly affected by plant-backs for up to 10 months, and SDM was more affected in sodosols than in vertosols. Predictive relationships between SDM and plant-back, cumulative temperature, and measured chlorsulfuron residues were developed for sowing summer crops in these soils. In ferrosols and vertosols, chickpea was unaffected by any treatment following plant-back of 10–12 months. These findings indicate that shorter re-cropping is possible in this region than currently recommended. However, the decision should be based not only on plant-back, but on soil type, cumulative temperature, and possibly even residue level in soil. These more specific recommendations will improve the safety and flexibility of re-cropping following applications of sulfonylurea herbicides in this region.

Improved management of Avena ludoviciana and Phalaris paradoxa with more densely sown wheat and less herbicide

“…These were artificially infested with P. paradoxa in Expt 1 and with both P. paradoxa and A. ludoviciana as individual treatments in the other experiments. Soils were heavy textured vertosols with 63% clay at Dalby and 71% clay at Toowoomba (Walker et al ., 2000). A month before sowing of crops, P. paradoxa (≈ 800 seeds m −2 ) was hand‐broadcast to designated plots in all experiments and A. ludoviciana (≈ 400 seeds m −2 ) to separate plots in Expts 2–4.…”

Weed species richness, density and relative abundance on farms in the subtropical grain region of Australia

“…Some herbicides have residual properties so, in order to ensure that future cropping choices are not restricted, herbicides have to be chosen carefully and with the aim of avoiding potential phytotoxic conflicts in subsequent crops (Jettner et al 1999;Walker et al 2000). A further concern with the increased reliance on herbicides to manage weeds both in the fallow and in-crop is the rising incidence of herbicide resistant weed populations in the region (Adkins et al 1997;Storrie and Walker 1999;O'Donnell et al 2002).…”

Occurrence of Summer Fallow Weeds within the Grain Belt Region of Southwestern Australia

“…Herbicides are the primary choice for weed management in Australia, although other tools such as grazing and cultivation are also used (Felton et al 1994;Osten et al 2007). Residual herbicides (i.e., acetolactate synthase herbicides) are effective in controlling weeds in summer fallows, but may cause potential phytotoxic effects in subsequent crops (Walker et al 2000). Herbicide applications to each weed cohort (i.e., glyphosate mixed with 2,4-D) are also effective (Fromm and Grieger 2004) but become expensive if there are several rainfall events that stimulate germination.…”