Under trellis mowing component of this trial - 2013 Summary

A.Wise CCE-SC grape program

Traditionally, the area under the grapevine trellis has been managed with herbicides. In recent years growers have been implementing alternative strategies such as under vine mowing. For many growers, this reflects an overall desire to reduce pesticide use. Also, green growth may help to reduce excessive vine vigor. Several Long Island vineyards have purchased under vine mowers. To increase efficiency, the under vine mowing heads are mounted on the sides or a deck mower that simultaneously mows row middles. Under vine mowing is best suited to laser planted vineyards with relatively straight trunks. When vines are planted unevenly or when trunks protrude, damage is much more likely. In the Cornell research vineyard, we use a single sided unit from Edwards Equipment Co., Yakima, WA. Mowing with this unit is slow, it takes approximately 3 hours to mow one acre.  Single sided mowers are suitable for small vineyards but larger operations need two sided mowers.

We have maintained an under vine mowing trial in a Merlot block since 2008. There are four treatments: T1 - season long mowing (4 times); T2 - glyphosate only (2x); T3- mowing (2x) plus glyphosate late June; and T4 - mowing (3x) plus glyphosate late July. The glyphosate treatment reduced weed competition at bloom and veraison while the mowing + late June glyphosate did so only at veraison. Mowing + late July glyphosate eliminated tall weeds at harvest time, an issue in the other three treatments.

We have noted small differences in vine pruning weight, a gauge of the season’s growth. In both 2011 and 2012, vines maintained with glyphosate (T2) had higher pruning weights than those with season long mowing or mowing for most of the season (T1 &T4). We anticipate a similar result when we prune vines in early 2014. There were no significant differences in shoot length or in shoot diameter. Differences in pruning weight are likely related to increases in late season shoot growth and enhanced growth of lateral shoots (originating from the leaf axil of green shoots). The difference in lateral shoot growth has been visually evident. Because vines are VSP trained, repeated hedging trims lateral shoot growth to maintain good light and air flow through the canopy. However, this makes it difficult to capture any data on lateral shoot growth.

To assess vine nutrition, petioles were collected twice for analysis. There were no meaningful differences between treatments. All treatments were slightly deficient in nitrogen, likely a reflection of the severe drought during the second half of the season. Similarly, there were no differences between treatments in soil analysis results (data not presented).

There were no differences in yield components or fruit ripeness at harvest. Fruit set in this block was not optimal in 2013, likely due to 10” of rainfall in June during bloom. In recent years, this block has also suffered from crop loss due to frost and animal depredation. Consequently, it has been difficult to determine treatment effects on cluster architecture or on yield components.

In order to assess nitrate leaching, lysimeters were installed in April, 2013. Lysimeters are devices for collecting water from the pore spaces of soils in order to determine the soluble constituents in the sample water (definition from www.soilmoisture.com).  There are various types of lysimeters. We use 4 ft. PVC tubes with a ceramic cup at the base. A pump is used to pressurize the tube; we then extract a sample 24 hrs later. We collected five samples in May and June. We attempted to collect samples another five times but were unsuccessful. This was undoubtedly due to drought conditions which started late June and persisted through October. Despite limited sampling, ppm of nitrate-N was highest in glyphosate only plots. We did not statistically analyze this data. We look forward to another few seasons collecting this data.

For more information, see the full report on our website: http://ccesuffolk.org/viticulture.

 Table 1. Under trellis mowing trial: vine shoot measurements, cv. Merlot

Treatments		2012 season				2013 season
		Shoot length2 cm -5.22	Shoot length 6.4	Shoot length 6.19	Shoot diameter, cm – 8.8	Shoot length 6.5	Shoot length 6.10	Shoot length 6.17	Shoot diam. 8.12
T1	Mow 4x	26.1	57.7	89.5	9.2	39.1	52.3	67.4	8.80
T2	Glyphosate 2x	28.1	63.9	94.7	9.5	40.2	52.2	71.4	8.92
T3	Mow 2x +6-30 glyph	27.9	60.7	88.3	9.1	38.7	49.9	68.3	8.86
T4	Mow 3x + 8-3 glyph	28.4	64.5	88.5	9.2	38.5	51.9	69.2	8.86
Significance1		ns	ns	ns	ns	ns	ns	ns	ns

1 – Values followed by the same letter are not significantly different at p=0.05; ns – no significant difference.

Table 2. Under trellis mowing trial: vine pruning weights, cv. Merlot

Treatments		2011		2012		20132
		Vine pr. wt. lbs 2.15.12	Vine pr. wt. lbs./ foot row	Vine pr. wt. lbs – 2.13.13	Vine pr. wt. lbs./ foot row	Vine pr. wt. lbs.	Vine pr. wt. lbs./ foot row
T1	Mow 4x	2.29	0.38	2.16  b	0.36
T2	Glyphosate 2x	2.60	0.43	2.51 a	0.42
T3	Mow 2x + 6-30 glyph	2.64	0.44	2.33ab	0.39
T4	Mow 3x + 8-3.glyph	2.49	0.42	2.18 b	0.36
Significance1		ns	--	0.0079	--		--

1 – Values followed by the same letter are not significantly different, p=0.05. ns – no significant difference.  2 – Vines not yet pruned as of 1-13-14.

 Table 3. Under trellis mowing trial: fruit ripeness and yield components, cv. Merlot, 10.15.13

Treatments		Brix	TA, g/l	pH	Berry wt. –g.	Berry no./clust.	Clust.no/ vine	Crop wt./ vine-lbs.	Avg. clust. wt.-lbs.
T1	Mow 4x	21.4	6.2	3.47	1.87	86.4	20.3	4.5  b	0.24
T2	Glyphosate 2x	21.3	6.0	3.51	1.85	90.5	18.2	4.9 ab	0.28
T3	Mow + 6-30 glyph	21.3	6.1	3.50	1.82	90.1	19.6	5.1 ab	0.25
T4	Mow + 8-3 glyph	21.7	6.2	3.51	1.82	99.3	19.7	5.8 a	0.28
Significance1		ns	ns	ns	ns	ns	ns	0.0237	ns

1 – Values followed by the same letter are not significantly different at p=0.05; ns – no significant difference.

 Table 4. Under trellis mowing trial: ppm nitrate-nitrogen from lysimeters, cv. Merlot, 2013

Treatment		5.13.13	5.21.13	6.5.13	6.11.13	7.2.13
T1	Mow 4x	0.15	0.17	0.24	5.47	5.44
T2	Glyphosate 2x	0.15	0.25	0.32	8.27	9.99
T3	Mow 2x + 6-30 glyph	0.05	0.08	0.20	0.45	0.22
T4	Mow 3x + 8-3 glyph	0.05	0.10	0.11	1.54	0.64
% of lysimeters providing a sample		60%	100%	87%	100%	100%

Each number represents the average of four lysimeters though not all yielded samples on 5.13 and 6.5. Unsuccessful attempts to sample lysimeters - 6/24, 7/23, 7/30, 8/22, 8/30.