Research and Education Project, Region: North Central. The management of watermelon vine decline through sustainable management practices
The addition of biological treatments, BioYield or T22, at planting slowed down the early growth of vines in both field seasons. However, the same biological treatments either improved overall yield (2007) or didn’t affect yield (2008). In general, the biological treatments have had more effect on yields than the cover crop treatments. Fewer differences were observed in the elemental contents of leaves as a result of either cover crops or biological treatments in 2008 as compared to 2007. The only trend in element analysis that was consistent for both years was that zinc levels were statistically higher in the canola plots than in either of the other cover crop treatments in both 2007 and 2008. Although the vine collapse that occurred the field in 2007 did not occur in the field in 2008, a greenhouse experiment was performed in fall 2008 to test whether vine collapse is due to biological factors in the soil. The data supports the hypothesis that there is a biological factor involved in the observed collapse.
Changes in Watermelon Culture by Growers
As a result of the data supported by this grant, growers are more likely to try a cover crop in general and a brassica cover crop specifically. As a result of the greenhouse study reported here, growers are more likely to use longer crop rotations between watermelon crops.
More Sustainable Culture of Watermelon
Both the use of cover crops and the use of longer crop rotations are more sustainable practices. Crop rotation allows the crop residue to decay and thus disease pressure to lessen as well as helping the fertility and tilth of the soil. The use of cover crops helps add organic matter to the soil, helps reduce the disease pressure (in the case of brassica cover crops) and helps reduce erosion.
At the technical meeting of the Southwest Melon and Vegetable Growers Association, data from the two years of experiments was presented: “The Use of Cover Crops to Manage Soilborne Diseases of Watermelon”. 77 growers attended. Several questions were asked both during and immediately after the presentation as well as individuals who asked questions privately.
Impacts and Contributions/Outcomes
Information Growers can use to Avoid Mature Watermelon Vine Decline
The data from 2007 showed that there was less vine collapse in the canola cover crop treatment than the rye or bare ground treatments (significantly less than the rye treatment). Since the vine collapse did not occur in 2008, this result could not be tested again. The data from the greenhouse experiment suggests a biological factor in the soil causes vine collapse. Thus, growers may use crop rotation as a means to help minimize vine collapse. The 2007 data suggest that canola as a cover crop may help lessen the impact of vine decline symptoms.
The following is a discussion of the data for both seasons:
In general, early vine growth was better for untreated (control) vines than vines treated with either of the biological treatments at planting. It is interesting to note that on 5 August 2008, treatments that had been on bare ground yielded better when planted with BioYield or T22 than when no biological treatments were included at planting. This was not the case when either canola or rye had been the cover crops in those plots. (There was an interaction between cover crop and biological treatment on this harvest date-thus, the data was presented by individual treatment on this date.) Although biological treatments seem to have slowed early vine growth, in overall yield data, biological treatments increased yields in 2007 and had little affect on yield data in 2008. In general, biological treatments have had more influence on yields than cover crops.
In 2007, several elements (phosphorus, zinc, sulfur and copper) were significantly higher in canola plots than any other treatment. In 2008, potassium and zinc were higher in canola. Only zinc was consistently higher in canola plots both years. Biological treatments did not influence elemental analysis in either year.
In 2007, the bare ground treatment had a greater yield than the rye treatment. In 2008, there were no differences in yield due to cover crop .
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