Garlic- Spacing, Weed Flaming, Scape Removal and Drip Irrigation

2003

Introduction: During the 2003-2004 garlic growing season, we examined several different aspects of growing hard-necked garlic including various planting spacings, weeding techniques, irrigation techniques, and scape removal. Most garlic producers plant at a 6″ in-row spacing. We examined the effects of closer garlic spacing on garlic yields. Experience from our garlic experiment in 2003 had shown that flame weeding with a propane flamer is an effective weed control agent for organic and small farmers. We investigated whether the flaming had any effect on garlic yields compared to hand cultivation. Scape removal from garlic plants can be time consuming and costly in labor. We measured bulbs to see whether removing scapes from plants actually affect yields. Finally, we also examined the effect of two different irrigation rates using drip irrigation.

Null Hypotheses:

1. There will be no difference in garlic yields between the 3″, 4.5″, and 6″ spacing treatments.
2. There will be no difference in garlic yields between the flame weeded garlic and the hand cultivated garlic.
3. There will be no difference in garlic yields between garlic plants that have their scapes removed and those that do not have their scapes removed.
4. There will be no difference in garlic yields between the garlic beds with two lines of drip tape and the garlic beds with one line of drip tape.

Methods:

On November 10, 2003, the garlic variety Music was hand-planted on 30 inch beds in double rows at three different in-row spacings of 3, 4.5, and 6 inches.  Forty cloves were planted for each spacing treatment and there were three replications of each treatment. The experiment was repeated in the adjacent bed. One bed had one line of drip tape and the other had two lines of drip tape. We used Chapin drip tape which delivers 0.5 gal/min/100′.

Another three replicates per treatment of the variety Music were planted at 6″ spacings for a study to compare the effects of flame weeding on garlic yields.

Yet another three replicates per treatment were planted with the variety German Extra Hardy to examine the effects of removing the scapes from garlic plants on garlic yields. The garlic was covered with a single layer of floating row cover which was secured using pots of soil. The row cover stayed in place with this system even during the high winds that occur at the Horticulture Research Center. The row cover was removed on April 22, 2004.

The weather for 2004 was wetter than average with quite a bit of rain falling in the spring. See our ARDEC south Study Area Description for more information about the weather and soils. Approximately 5.7 inches of precipitation fell on the garlic, and we added 7.6 inches with supplemental drip irrigation (for one line of drip tape) for a total of 13.3 inches of precipitation and irrigation water. The garlic which had two lines of drip tape received 20.9 inches of precipitation and irrigation water. The graph below depicts the precipitation and added irrigation from one line of drip tape.

In the weeding experiment area, the garlic was flame-weeded and hand/hoe weeded on April 26, 2004 in the respective treatment areas. Large remaining weeds were hand weeded in all plots again on May 14, 2004. Scapes were removed by hand (snapping them off the plant) on May 24, 2004 at the curling stage.

	Garlic was harvested on June 28, 2004 during the Specialty Crops Program Field Day using a potato digger. The garlic was dried on wire racks under a hoop house with a shade-cloth structure for approximately two weeks. The bulbs were then cleaned, the roots trimmed, sized by diameter (extra small = <1.5 inches, small = 1.5 to 2.0 inches, medium = 2.0 to 2.25 inches, and large = >2.25 inches), and weighed.

Results:

The graphs below show the percentage of different sized bulbs for each of the experimental treatments under one line and two lines of drip tape respectively.

Conclusions:

1. The spacing data revealed that there was a significant statistical difference (P < 0.05) between the three inch and six inch spacings with the six inch spacing producing significantly more large, marketable bulbs than the three inch spacing for the variety Music.
2. It takes almost three times as much time to hand- and hoe-weed garlic as it does to flame-weed it. We found that it took an average of 1.4 (standard error of 0.1) minutes to hand/hoe weed a 10 foot section of a 30 inch wide bed whereas it only took 0.5 minutes to flame weed the same size section of a garlic planting. Costs of fuel of course need to be accounted for. There was no significant difference in yield between the flame-weeded and hand/hoe weeded garlic.
3. There were no significant statistical differences in garlic yield between the plants with scapes removed and the plants with scapes left on. There was a trend however for the garlic plants with the scapes removed to have a larger bulb size. We may not have found a statistically significant difference due to our small sample size.
4. The only significant differences that occurred between the single line and double lines of drip tape were in the spacing experiment. The garlic planted at 3″ and 4.5″ spacings had larger bulbs with two lines of drip tape than with one line. Since it was a very wet year, the garlic with one line of drip tape was not as stressed as it normally would have been. We suspect that in a drier year, more significant differences would be seen.

Recommendations:

1. In our clay soils, it appears that at least a 6″ clove planting spacing is required for optimal yields.
2. Flame weeding is faster and more effective than hand weeding or hoeing. The economic efficiency of flame weeding may depend on the price of fuel, however, it is likely to be a better alternative to labor intensive hand weeding.
3. Removing scapes takes extra labor time and may not result in appreciable yield differences, however selling the edible scapes may offset the cost and generate extra income.
4. Garlic performs better and yields more if sufficient irrigation water is provided. Our initial findings (2003 and 2004) suggest that yields are negatively impacted when less than 12″ combined precipitation and irrigation are received.