In 2011, we established a research plot in a commercial ginseng field near Turkey Point to test different straw mulch treatments (Figure 1). The treatments included straw of rye, oat and wheat. For all of these treatments, any grains contained in the straw were allowed to grow for the fall of 2011. Those that survived the winter (rye and wheat) were killed off in April 2012 with a glyphosate application. Not much wheat sprouted in some of the wheat straw treatments. In an additional treatment with wheat straw, glyphosate was applied shortly after the wheat sprouted in the fall of 2011 to prevent growth. The straw was applied by hand to approximate the depth of straw used in the commercial field. Oat straw formed a denser mat than wheat or rye straw at the same depth and as a result it was more difficult for seeds to emerge through the straw layer the following year. Fewer differences were observed between the rye and wheat straw treatments. In fall 2013, all of the plots were topped up with wheat straw.
Figure 1. Straw mulch trial in April of 2012. Bare plots are oat straw or wheat straw with glyphosate applied in the fall of 2011. Plots containing plants are wheat and rye straw treatments.
A full harvest assessment was done initially in the seedling year and again after three years of growth. After one year of growth the wheat straw treatment with no glyphosate application had the highest yield and the least damage from root lesion nematodes (Figure 2). Plant stand was also about 10% higher initially in both wheat straw treatments compared to the oat and rye straw treatments. This difference could partially be due to differences in the ability of the seedlings to penetrate the straw layer.
Figure 2. Constrictions on seedling roots, probably caused by root lesion nematodes. These symptoms were more prevalent in the rye and oat straw treatments.
A final harvest assessment was completed in September 2014. The results followed the same trends as the seedling year, but with larger differences among treatments (Table 1). Total and marketable root yield on a fresh weight basis was higher in the wheat straw treatment than the oat and rye straw treatments. The yield of the wheat treatment with glyphosate applied in the fall was intermediate between the other treatments. Plant stand results followed the same trend as the seedling year, except that the stand in the oat straw was much lower than all other treatments. It is possible that the denser straw layer in this treatment resulted in weaker seedlings that were more prone to dying in later years.
Most of the differences among the treatments in the seedling year appeared to be due to root lesion nematode damage. It is unknown why this effect occurred, but it is possible that the oat and rye that sprouted in the fall of 2011 were more susceptible to root lesion nematodes and allowed populations to build up. It is also possible that another soil pathogen can cause similar symptoms to those of root lesion nematodes and this pathogen could have been introduced on the oat or rye straw. While the same pattern of damage occurred in the final harvest assessment, there were no significant differences among treatments. Certain straws can also produce chemicals that can inhibit the growth of other crops, and this may also account for some of the differences in yield among treatments.
Table 1. Effect of straw mulch on stand, total and marketable weight per plot and percentage of undamaged roots for 3-yr old ginseng grown near Turkey Point, Ontario.
|Treatment||Stand/plot||Total Weight (g)||Marketable Weight (g)||% of plants without damage|
|Wheat (fall glyphosate)||105 a||1530 ab||1310 ab||50 a|
|Wheat||97 a||1610 a||1440 a||59 a|
|Rye||91 ab||1200 bc||930 b||42 a|
|Oat||64 b||1050 c||970 b||47 a|
1 Numbers in a column followed by the same letter are not significantly different at P=0.05, Fisher’s Protected LSD Test.
The results of one research trial do not provide sufficient evidence to suggest growers should switch completely to wheat straw. It is possible that the results were influenced by the source of the straw and the cultivar of the grain from which the straw was collected. Results may also differ in different soil types. However, given the yield increase from the wheat straw in this experiment, growers may want to conduct their own side-by-side trials.
This trial was originally funded through an Ontario Farm Innovation Program grant to C&R Atkinson Farms Ltd. The trial was continued with support from OMAFRA, OGGA and C&R Atkinson Farms Ltd.