In 2016 we established day-neutral strawberry cultivar Albion on raised beds with plastic mulch with and without low tunnels. All treatments were managed under organic certification standards. Strawberries were grown at the U of MN West Central Research and Outreach Center (WCROC), and the U of MN St. Paul campus (UMTC).
One of our objectives was to develop production recommendations for nitrogen fertilizer. The results of using different nitrogen rates in a low tunnel and non low tunnel are shown in the tables below.
To determine nitrogen rates we tested five nitrogen regimes on two soil types:
- 0 lb N/acre/week (0x)
- 5 lb N/acre/week (0.5x)
- 5 lb N/acre/week (1x)
- 5 lb N/acre/week (1.5x)
- 5 lb N/acre/week only until first harvest, then 0 lb N/acre/week for the rest of the season (1-0x). This treatment is to test a hypothesis that implies nitrogen application during harvest season can actually reduce cumulative yield.
Similar to our previous findings, day neutral production resulted in excellent yields regardless of fertility practice or low tunnel use. Since day neutral cultivars in this production system are treated as annuals, growers can enjoy the added economic benefit of yield in the first year, rather than the typical no yield ‘establishment year’ common to in June-bearing systems. Similarly, labor and other management costs are saved by eliminating the need to overwinter the plants. Day neutral cultivars managed with an annual system can be incorporated into crop rotations, reducing the potential buildup of soil pathogens.
Interestingly, fertility rate applications did not significantly affect average yield per plant, average yield per acre or average berry weight at either WCROC or UMTC research sites. The only significant difference in yield is between the two different treatments: low tunnel vs. no low tunnel.
At WCROC there was a difference in average yield per acre between the low tunnel and non-low tunnels. The low tunnel treatment had an average yield in lbs. per acre of 14,230 and the non-low tunnel was 16,596 lbs. per acre. This is the first year of the past four years of this trial that the non-low tunnel had higher yields per acre than the low tunnel at the WCROC site. Late in the picking season, around early to mid-September we noticed some strawberry plants in our WCROC low tunnel that started to look unhealthy and appeared to be dying. More detailed explanation concerning this issue is explained later in the report.
At St. Paul average yield in lbs. per acre was 20,369 lbs/acre under low tunnels and 14,526 lbs/acre without low tunnels. Thus our first year and second year of data implies that in environments without rich prairie soils (St. Paul site) low tunnels appear to offer some yield advantage. If low tunnels aren’t used in these environments some form of fertility should be applied, though the rate does not appear to be important if the crops are managed annually.