Evaluation of Crop Rotation for High Value Cool Season Horticultural Crop Production in Organic and Sustainable Systems
The overarching objective of the study is to evaluate the profitability and production characteristics of two cool-season vegetable crop rotations. The research is being conducted at the Durham Horticulture Farm that has certified organic land.
Initially this project was to be run at two locations, the Vidalia Onion and Vegetable Research Center (VOVRC) in Lyons, GA and the Durham Horticulture Farm in Watkinsville, GA. Unfortunately due to poor site selection at the VOVRC this site was abandoned because of problems with poor drainage.
The experiment began in 2010 with two rotations that were started at different points in each rotation with a total of six treatments. In general, crops performed better in the second year (2011-12) than in the first year (2010-11) primarily due to better management and earlier planting. Strawberries were an exception. In year 2 an attempt was made to estimate the fertility that would be contributed from the previous crop. The amount of fertilizer was reduced accordingly, by approximately 45%. This highlights one of the problems with banking on the previous crop’s (southernpeas) contribution to fertility. It is difficult to assess this because of factors such as temperature, moisture, and time between crops.
Our yields were generally below the average conventional yields for the vegetables in the study. This was particularly true in year 1 with less management control and later planting dates. Lower yields in our organic plots could be anywhere from a third to 80% of the average yield. There were some notable exceptions. In the first year, one of the onion treatments and lettuce produced more than the average yield. In the second year, there were higher yields in our plots with onions, lettuce, and southernpeas. The improvement from year 1 to year 2 is not just notable in the yield data, but is borne out in the economic results.
Results are being shared with growers and other interested parties. We held an Organic Twilight Tour on 19 July 2012 at the Durham Horticulture Farm where current results were shared with attendees.
The site at the Vidalia Onion and Vegetable Research Center was abandoned due to poor drainage. We have continued the rotation as designed at the Durham Horticulture Farm. We have begun the third year of the study and have asked and received a no-cost extension for a fourth year. This will help us, by insuring that three years of good data are available.
A better understanding of nutrient budgeting from cover crops is anticipated from data from years 3 and 4. In addition, an additional year of data should help with completing the budgets.
Table 1 indicates the yields from the first and second years of the study. Yields were generally lower than average conventional yields with a few exceptions. Onions yielded better than the conventional yields in the second year. This was also true for lettuce and southernpeas. The performance improvement from year 1 to year 2 was primarily due to better oversight and earlier planting dates.
Table 2 depicts a summarized breakdown of key economic parameters extracted from the various enterprise budgets developed from the following organic rotation crops: broccoli, carrot, lettuce, onion, potato, strawberry, bush beans, and southernpeas, using field data collected by UGA Scientists at the Durham Horticulture Farm, Watkinsville, Georgia. The economic parameters include pre-harvest variable cost (P-HVC), total harvesting and marketing cost (THMC), total variable cost (TVC), total fixed cost (TFC), total revenue (TR) and net returns and/or profits (?). Amongst the crops in the 2011 (year 1) rotation, broccoli, bush beans and southernpeas were the least favored in terms of net returns. On the other hand, onions were the most favored with a net return of $16, 009. Lettuce and strawberry were the 2nd and 3rd favorites with net returns of $6,916 and $4,804, respectively.
Further, a summarized breakdown of the same key economic parameters is presented in table 3. Amongst the crops in the 2012 (year 2) rotation, only bush beans exhibited a negative net return of -$142 per acre. On the other hand, onions still maintained its lead position with a net return of $21,381. The net return for lettuce increased to $16,270 per acre, i.e. 2.4 times higher than year 1 whereas the net return for strawberry decreased to $17.
Impacts and Contributions/Outcomes
We held an Organic Twilight Tour at the Durham Horticulture Farm in July 2012, which attracted about 100 attendees. This field day highlighted the rotation experiment with a talk, poster, and attendees had the opportunity to visit the plots. In addition, preliminary results particularly on lettuce production were shared with attendees at the Georgia Fruit and Vegetable Grower Association Conference in Savannah, GA in January, 2013. This event has over 1,500 attendees and about 100 attended the specific session.
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