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Alan N. Lakso, Robert M. Pool, Richard Dunst, and Andy Fendinger

Cover crops are of increasing interest in fruit plantings. Previous studies indicated that, in unirrigated New York vineyards, effects of row middle cover crops is primarily competition for soil water. Row middle management trials in `Concord' vineyards compared cover crops (orchardgrass, bluegrass, vetch, clover, and rye) to straw mulch, bloom glyphosate, and cultivation for water use patterns. Neutron probe tubes within each plot were read weekly at 15-cm intervals down to 120 cm. A second method to examine water use patterns used double florist pots with native soil sunken within the plots to provide a removable sample of the cover. These pots were lifted and weighed at intervals to examine in situ water use. The pot weight loss data generally correlated well with the neutron probe data. Precautions are needed related to differences in natural rooting depth, more rapid drying of pot vs. normal soil volume and representativeness of plant cover and health. The neutron probe method gives more complete data, but the pot method may be a useful simple, inexpensive method of examining relative water use patterns of cover crops with natural boundary layers that exist in discontinuous fruit plantings.

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Terence R. Bates, Richard M. Dunst, Theodore Taft, and Michael Vercant

One- and 2-year-old 'Concord' (Vitis labruscana L.) grapevines were used to study the effect of soil pH on vegetative growth and nutrition. Ninety-eight, own-rooted, 'Concord' grapevines were planted in 94.6-L pots containing vineyard soil adjusted to seven soil pH levels ranging from 3.5 to 7.5. After the first growing season, seven vines from each soil pH treatment were randomly selected, destructively harvested, and measured for root and shoot growth. The remaining 49 vines over-wintered in the pots, were defruited in year two, and were destructively harvested at the end of the second growing season. There was a reduction in root biomass below soil pH of 4.5 and a greater reduction in shoot biomass leading to a higher root: shoot ratio. There were no significant differences in vegetative growth of young 'Concord' vines from a soil pH of 5.0-7.5. However, there was a trend toward lower shoot biomass and higher root: shoot ratio at the highest soil pH level. Phylloxera nodosities on roots were present in equal densities at all soil pH values. However, the negative impact of phylloxera on vine dry mass was greater on vines under nutrient stress at the highest and lowest pH treatments than on those with adequate nutrition at the mid-range soil pH values.

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Terence R. Bates, Richard M. Dunst, and Paula Joy

Three-year-old field-grown 'Concord' (Vitis labruscana Bailey) grapevines were destructively harvested at eight growth stages during 1998 to quantify growth, carbohydrate distribution, and nutrient concentrations of different organs. The roots were the major storage organ for carbohydrates and nutrients, accounting for 84% of the starch and 75% of nitrogen stored in the vines at the beginning of the season. About 78% of the reserve starch in the vine was used for prebloom root and shoot growth. Early-season fine-root growth was a sink for stored vine nitrogen; however, the fine roots quickly became a nitrogen uptake source, providing at least 84% of the spring growth nitrogen. Total root biomass increased from bloom to leaf fall, but reserve carbohydrates and nutrients lost in the prebloom period did not begin to recover in roots until the end of rapid shoot development in late July. Crop removal at harvest, and a late-season root flush, further increased vegetative carbohydrate and nutrient reserves in the short postharvest period.