Soil Management for Orchards and Vineyards
Soil Preparation for Orchards and Vineyards
Establishing an orchard or vineyard requires significant research and planning, in order to grow healthy trees or vines. Orchard and vineyard site selection and preparation are the first management decisions that affect the productivity of a tree or vine. Whether considering a new site, replanting a former site, or updating to current varieties or production systems, there are many important decisions to make. Site preparation involves a number of pre-planting activities. This is the time when changes can be made to the site to improve soil conditions, water handling, and the overall efficiency of managing the orchard or vineyard. Important considerations in site preparation include soil properties, soil testing, land clearing, subsoiling to alleviate soil compaction, tillage, planting cover crops, and site drainage. Attention to the details of site preparation can help increase the likelihood of producing a sustainable crop for the foreseeable future.
Soil Properties
Soil properties are the most important consideration rather than any one specific soil type. Even in a region well suited to orchard and vineyard production, there may be unsuitable soils throughout that region and within a given orchard or vineyard. When determining suitability of farmland for orchards and vineyards, the grower will need to consider the following: soil depth, water holding capacity, and depth to restrictive features. Also, it is important to avoid areas with flooding, seasonal high-water table, and shallow depth.
Soil Testing
Detailed soil testing is required before an orchard or vineyard is established so that pH and fertility can be adjusted if necessary. Possibly the most meaningful value of a soil test to fruit producers is the pH and lime test index. In addition, soil test results are helpful in determining fertilizer needs. It is much easier and more desirable to adjust the soil pH and nutrient status before planting. Ideally, the initial soil samples and corrective actions should be done for a planting site a year or two before planting. This allows time for the needed soil amendments to produce their most desirable effects.
Land Clearing
Land clearing is any operation which includes the removal of excess undesirable vegetation or debris from a site, such as trees, shrubs, stumps, logs, or rocks. Debris piles can be burned at the edges of the orchard or vineyard, preferably away from where plants are to be planted. The site should be mapped to identify intermittent streams, surface water runoff channels and steep slopes such as ravines.
Subsoiling
AThe next step is subsoiling (often called ripping) to break up hardpans or compaction layers to allow both easy and rapid root penetration and water infiltration (Figure 19.1). The winged shank blade is the main piece of equipment used for ripping which helps lift the soil behind the tractor and distribute it evenly. Winged subsoilers require higher draught force but can disturb a volume of soil two to three times greater than a conventional subsoiler, resulting in more effective disturbance. In contrast, the conventional shank that comes standard with most ripping caterpillars simply cuts a single line through the soil without elevating it and often requires more passes on the site.
Time for Subsoiling
The soil-water content at the time of subsoiling partly determines the effectiveness of the operation. Although a moist soil requires less draft when ripping, more surface compaction occurs from the heavy equipment, so the soil does not break up and mix as readily. Dry soil conditions break up and mix more readily. Desirable soil water content for clay is 10 percent, loam 5 percent and sandy soil 2.5 percent by weight. Soils with a shallow water table (less than 6 feet from soil surface) may never dry sufficiently to effectively modify them without installing drainage first.
Subsoiling Depth and Spacing
Two factors that specifically influence the effectiveness of subsoiling are the depth of the shanks and the distance between them. There are three reliable rules to apply:
Tillage
After subsoiling the next step is tillage to manipulate the soil into a desired condition for planting the trees and vines and in some cases cover crops. Generally, the main purpose of tillage is to loosen the soil and increase soil aggregation, so as to provide adequate soil pore volume in the main rooting area of the trees and vines. This is done to promote water infiltration, water storage and drainage, and to allow easy penetration of plant roots, as well as to provide adequate aeration. Tillage is usually can be divided in two types primary and secondary.
Planting Cover Crops
Cover crops are ideally established one to two years before trees or vines are planted. This allows the cover crop to be well established before equipment and frequent foot traffic occurs in the early phases of the orchard or vineyard. Alternatively, a cover crop may be established in the 3rd or 4th year after planting, as the trees or vines reach cropping age. A cover crop should be sown immediately after tillage, particularly on steep land. If the cover crop is established before planting a systemic herbicide can be used to kill the permanent cover crop by applying it to the intra-row—the area of the row where trees or vines are going to be planted (Figure 19.2).
Site Drainage
External drainage refers to the water flow over a piece of land (Section 22.3). Practically all fruit species are intolerant of standing water (cranberries are the obvious exception), so avoid boggy spots or areas where the water drains out too slowly. Soil factors that cause a soil to experience drainage problems include the texture (higher clay content causes slower permeability), soil structure (a massive structure without macropores causes poor percolation), compaction of surface or subsurface soil by equipment, and sealing of the soil surface and depositional crusts in lower-lying areas. For almost all fruit plants, a soil’s texture can be more important than its native fertility. “Heavy” clay loams, for instance, are often highly fertile and good, therefore, for row crops like corn, cotton, and soybeans, but most fruit plants would struggle in such a soil.
Drainage Options
Diversion Ditches. Diversion ditches are soil structures constructed at intervals across the slope. They collect water from slopes and divert it into natural drainage ways.
Water and Sediment Control Basins. Raising a berm across a gully with a subsurface outlet pipe that discharges at the base of the slope will collect runoff, and this will stop erosion by slowing down water and collecting the sediment.
Buffer Strips. All orchards or vineyards require headlands and grassed areas around their perimeters to allow machinery to turn around.
Drainage Tile. Subsurface drainage tile, commonly used in orchards or vineyards with moderate to heavy-textured soils, also helps protect water quality in two ways.
Orchard and Vineyard Layout. Planting orchards or vineyards so that the rows run across the slope rather than up and down the slope can reduce erosion by up to 50 percent.
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