Issue link: http://winesandvines.uberflip.com/i/80303
GRAPE GRO WING plowing was literally horse powered, and the technique then adapted to be tractor mounted. The variety of tools available is endless and consists mainly of two styles, both of which rely on a retractable arm that can dodge in-between and around each vine or post. The traditional dodge plow, disc and knife system is the most common system I have seen. The plow is used to 'pull out' soil from the under-vine strip in winter. It is then thrown back with a disc in early spring to form a small mound that is knifed with a blade attach- ment during the summer. The alternative is one of the many rotating head systems that operate in between vines and posts in the same manner but have a hydrauli- cally driven, rotating head that cultivates the soil. Positives • Under-vine plowing/knifing can be quite gentle in the hands of a good operator • Weed or pasture regrowth can be left to provide some organic matter and plant root restructuring of soil between passes • Good weed control is possible • Double-sided and automatic systems are now more reliable and easier to operate • Can operate regardless of wind conditions • Becomes easier and faster as soil condi- tion is improved Negatives • Rotating head systems, in particular, can damage soil structure through violent scarification • Slow • Uses more fuel than herbicide systems • Over use can result in a reduction of soil health indicators • Single-sided systems are still consider- ably more expensive than herbicide • The window of opportunity may be small on some soil types, depending on soil moisture • Damage to vines and infrastructure (particularly irrigation) is possible • It is slow and difficult at first until soil condition is improved Mowing Under-vine mowing is increasing in popularity, particularly among those with an aversion to cultivation. Mowing offers the possibility to encourage plant diver- sity under the vine rather than chemical treatments or cultivation, which generate a vacuum for weeds to fill. Mowers tend to be slow to operate, but double-sided options cover the ground at a speed faster 62 WINES & VINES SEPTEMBER 2012 than cultivation, although slower than applying herbicide. Mowers may be a good option in warm areas with limited summer weed growth. However, they may be a less-feasible option where summer rainfall or irrigation encourages regrowth, necessitating multiple passes. Positives • Creates no ecological vacuum in the sys- tem and encourages a diverse under-vine population of plants • Limits soil-structure damage associated with cultivation (particularly with rotat- ing head cultivation systems) • Faster than cultivation Negatives • Under-vine competition for moisture • Multiple passes may be required • Damage to vines and irrigation • Generally faster than cultivating under vine but still slower than herbicide • Fuel use Mulching Thick under-vine mulching has proven to be effective as a weed-control agent. Straw, grape pomace or coarse composted mulches are the most common. Where ap- plied thickly enough, control can be very good and additional benefits of moisture retention, topsoil-cooling, microbial and nutrient inputs all may assist in offset- ting the cost of application. Issues such as material provenance, excessive nutrient loads and contamination all require care- ful consideration. Typically, growers look to achieve three years of control depending on the vineyard and product used. The two major factors in determining whether this method works well are density (thickness) of application and product texture. Control is poor where mulches are applied too thinly or when weeds are able to grow in the mulch itself because the texture is too fine. Fixing weed problems organically is difficult in poorly applied mulch because mechanical weeders and mowers are unable to operate effectively with large volumes of straw or mulch choking their progress along the row. Positives • Can offer excellent control and comple- mentary benefits (e.g., moisture retention) Negatives • Expense • Possible contamination Grazing sheep can be an excellent solution for Grazing Grazing sheep or cattle in vineyards is not a new concept; it has always been a management option for some. My observa- tion is that economic pressures have made this technique even more popular in recent times. When employed well, running stock in a vineyard can produce excellent results in terms of weed control. In particular, sheep are a great tool for managing weed problems. Additionally, grazing often has the effect of changing the weed/pasture population. For example, grazing heavily on capeweed-infested vineyards often re- sults in a medic/clover- and grass-dominant pasture in the subsequent season. There are some potential pitfalls for organically certified growers who need to carefully manage the provenance of stock brought onto the property. Similarly, conventional growers should give consideration to the possibility of stock bringing in weed seeds. The downside of intensive grazing is compaction and overgrazing, both of which need to be managed carefully. Strip or cell grazing techniques may have vineyard applications in the future. Positives • Minimal or no cost where stock are eas- ily available • Can be very effective • Often results in a positive manipulation of plant populations Negatives • Seasonal: can only be done outside of the vine-growing season (stock like green vine leaves and fruit) • Compaction/overgrazing • Another thing to manage • Contamination • Cost of stock if buying rather than share farming • May damage irrigation infrastructure