Michael A. McElhiney, district conservationist, Natural Resources Conservation Service, helped prepare this section.

In the following paragraphs are discussed the major management practices applicable to the soils in this area that are suited to irrigated and nonirrigated crops. The major management concerns when farming the soils are maintaining or improving production and minimizing erosion.

Needed management practices include, but are not limited to chiseling and subsoiling, conservation crop rotation, residue management, no-till and mulch till, conservation tillage, cover crop, excess water removal, hayland management, irrigation land leveling, irrigation water management, prescribed grazing, subsurface water removal, surface water control and toxic salt reduction. Technical terms used in this section are defined in the glossary.

Chiseling and Subsoiling are used to increase the effective rooting depth in soils that have a plowpan. Chiseling the plowpan will enhance permeability and internal drainage, help prevent a perched water table, and allow deeper root penetration. Chiseling will temporarily benefit clay soils, such as Clear Lake, Capay and El Solyo. However, these clay soils may rapidly return to their original condition.

Conservation Cropping Rotation consists of growing crops in combination with cultural and management practices. A successful cropping system is achieved if the crops and practices used provide benefits that more than offset the effects of soil depleting crops and deteriorating practices. Crop rotations are recommended on all tilled soils in the area.

On irrigated cropland, practices include the rotation of various row and field crops, and the return of crop residue to the soil. It may include using cover crops of grasses and legumes, adequate fertilization, and weed and pest control. Examples are corn and small grain in rotation or beans, tomatoes, and alfalfa in rotation.

On non-irrigated cropland, a summer fallow system is used for small grain production. This system consists of leaving land weed free during alternate summers to store moisture in the soil. This permits normal planting operations in tilled soil, and reduces the disease problems of continuous cropping. With advances in no-till grain drills, herbicides, and disease resistant wheat varieties it may be possible to produce a crop every year. A typical cropping sequence on Vernalis and Zacharias soils consist of small grain planted in the fall and harvested in early summer. The stubble remains standing until spring of the second year when it can be incorporated into the soil. During the second summer the field is fallowed and weeds are controlled by cultivation. Keeping as much residue as possible on the surface of the land during the rainy season will reduce the hazard of erosion on sloping soils. The use of subsurface tillage implements such as chisels, blade type sweeps, or rodweeders is recommended on soils that do not have high gravel content near the surface.

Residue Management, No-till, and Mulch Till involves keeping to a minimum the number of operation necessary to prepare a seedbed, plant the crop, control the weeds, and still maintain at least 30 percent of the soil surface covered by residue after planting. Excessive tillage operations tend to break down soil structure, cause compaction, reduce soil organic matter, and could create a plowpan below the tilled layer. These conditions increase the hazards of soil erosion, decrease the soil’s water intake capability, and restrict root penetration. Varying the depths of tillage operations will help to prevent the development of a plowpan. Combining tillage operations to reduce the number of trips over a field and delaying tillage operations while soils are wet are other important factors in maintaining soil tilth, preventing compaction and conserving energy. This type of tillage is particularly beneficial on the Salado, Vernalis and Zacharias soils.

Cover Crops are needed in orchards and vineyards and on soils left fallow during the rainy season. Cover crops help maintain or increase water infiltration and allow for winter access for cultural operations. Cover crops help control erosion on sloping land and keep dust to a minimum that improves working conditions and discourages spider mites. During the spring, prior to the frost season, the cover crop can be mowed at a height of 2 to 4 inches to reduce possible frost damage to the crop. The cover crop should then be allowed to produce seed.

Residue Management consists of returning crop residues to the soil. Residues returned to the soil help maintain soil tilth, organic matter, and fertility and help to reduce erosion. On soils with slopes greater than 2 percent and on soils subject to wind erosion, residue should be left on or near the soil surface during critical erosion periods. Organic matter influences the development and stabilization of soil structure and the general soil physical environment including increased infiltration and available water capacity.

It is particularly important that a supply or organic matter be continually returned to the soil. The easiest and most common way of doing this is to return the residues produced by the crops grown. High residue producing crops such as corn, oats, and wheat should make up for the low residue producing crops such as tomatoes and sugar beets in a cropping system. Other excellent sources of organic matter are prunings from orchards and vineyards, animal manure, and grasses and legumes.

Hayland Management is needed on irrigated and nonirrigated hayland for soil protection and to provide for maximum production, maintaining a desirable plant community and extending the life of the planting. Practices needed in a hayland management program include irrigation water management, fertilization, and proper timing of mowing and baling activities when the soils are firm and dry enough to support the load.

When establishing irrigated hay crops, seed in early fall or spring into a firm seedbed. The first mowing should be delayed until the plants are well established. The spacing of borders on flood irrigated hayland should be in multiples of the cutting width of the mower to be used.

Irrigation Land Leveling is necessary to conserve irrigation water. It will help insure that irrigation water is applied uniformly to the entire field without any wet swales or dry ridges. In addition to better water management, land leveling will permit better field arrangements that will conserve labor, time and energy. Following the initial land leveling of a field the first crop to be planted should be an annual crop. This will give the filled areas a chance to settle and the field can be smoothed before planting a longer-lived crop.

Accurate land leveling is important. Laser guided equipment can be used to produce a very uniform grade. Large benefits can be realized by re-leveling periodically and by re-leveling fields that were leveled without the aid of laser equipment.

Irrigation Water Management is achieved by controlling the rate, amount, and timing of irrigation water application to soils to supply crop water needs in a planned and efficient manner. This will efficiently utilize the available water in the soil for desired crop response and minimize soil erosion. It will also control costly water losses and protect water quality. Irrigation methods used in the area are furrow, border, basin, sprinkler, and drip. Furrow and border irrigation is the most common in the area. Their use is limited to nearly level slopes. Sprinkler irrigation is common on orchards and on soils used to germinate tomatoes on leveled land. Basin irrigation is common on apricot orchards. Drip irrigation is used on some orchards in the area.

Prescribed Grazing is needed to prevent soil deterioration, provide for maximum production, maintain a desirable plant community, and extend the life of pastures. Practices used in an irrigated management program include: irrigation water management, rotation grazing, fertilization, harrowing or dragging to scatter animal droppings, mowing as necessary to maintain uniform growth and weed control. Grazing when irrigating or when the soil is wet is not recommended. Grazing can start when plants are 8 to 10 inches high, and livestock should be removed when 3 to 4 inches of stubble remains.

Selection of an adaptable plant mixture when establishing a pasture is important. For most soils in the area, mixtures containing a perennial grass and trefoil or clover will produce an abundance of high quality forage.

When establishing non-irrigated pasture, annual grasses and legumes should be used. During the establishment year grazing should not be permitted and annual weeds should be controlled.

After establishment, grazing should not start until plants are 4 to 6 inches high, and livestock should be removed when 2 to 4 inches of stubble remain. To maintain plant density, annual pastures should be managed so that sufficient plants produce seed to maintain a good stand.

Subsurface Water Removal is required on some soils to keep river seepage and low quality water below the primary rooting zone of plants. Among the soils that may need subsurface drainage are Bolfar, Capay wet phase, Columbia, and Dello.

Subsurface drainage may be improved by constructing open drainage ditches or tile drains.

Proper drainage water disposal methods are needed to dispose of any poor quality water that is collected by the drainage system. High quality ground water should be protected from possible pollution by any drainage water that is of low quality.

Surface Water Control is needed where water from rainfall or irrigation is a problem in low lying areas, adjacent to levees, or at the lower end of irrigated fields. Excess surface water reduces crop production and may be controlled by shaping and grading, construction of open drain ditches, maintaining existing natural drainage ways, irrigation land leveling, irrigation tail water recovery systems, and irrigation water management. Among the soils that need surface water control are Capay, Clear Lake and Dospalos.

Protection from flooding is needed on all soils in the San Joaquin River flood plains in the area. All low lying soils along the San Joaquin River such as Bolfar, Columbia, Dello, and Dospalos require an extensive levee system with pumped outlets to provide flood protection and lower the water table.

Toxic Salt Reduction is needed on soils where salts rise to the surface and accumulate in the root zone over a period of several years. Leaching can reduce the content of soluble salts. Dospalos soils are examples of soils in the San Joaquin River area that can be affected by salinity if water in adjacent rivers and sloughs are of poor quality. If the soil has large amounts of sodium, the soil is considered to be sodic.

Applying proper amounts of soil amendments, returning crop residue to the soil and leaching will reduce some of the sodic properties. Pedcat soils are examples of soils that are affected by both salinity and sodicity. Intensive management is required to reduce salinity and sodicity in these soils to maintain soil productivity. Irrigation water needs to be applied carefully to prevent the buildup of a high water table. Drainage may also be needed.

Soils strongly influence the kind of crop and pasture plants that can be grown in the area. Where climate and topography do not change, crops that can be grown are related closely to the kind of soil.

The climate in the area favors a wide variety of crops, although the hazard of winter frosts makes growth of semitropical fruits such as citrus uncertain. The somewhat cooler temperatures and early fall rains also cause the area to be unsuitable for cotton or raisin grapes.

Irrigated field crops are grown on a variety of soils in the area. Silage corn, oats and wheat are grown on very deep soils with a high water table such as Clear Lake and Dospalos. The conservation practices necessary for sustained productivity includes surface and subsurface water removal systems. In these soils, leaching every 3 to 5 years can control salinity.

Alfalfa does best on very deep, well drained soils such as the Vernalis or Zacharias soils. It also does well on soils such as Dospalos soils in areas where the water table is carefully managed and protection from flooding is provided. Alfalfa can drown out on soils that commonly flood, such as some areas of the Bolfar soils.

Vegetable crops are grown on very deep soils such as Salado, Vernalis and Zacharias. In some areas subsurface water removal is required. Chiseling is a common practice to break up compacted layers. Rotation with field crops helps maintain tilth and reduce disease problems. Portable sprinkler systems that are used to germinate processing tomatoes are replaced by furrow irrigation as the crop develops.

Dry land field crops are grown on Vernalis and Zacharias soils. Slopes range from 2 to 5 percent and are irregular. When cultivated, these soils have a potential water erosion hazard. Runoff and sediment that accumulates in low areas can damage crops. Crop residue and good management practices will control most erosion problems.

Fruit and nut crops are best suited to very deep, medium textured soils in the area such as Vernalis and Zacharias soils. Many types of irrigation systems are used including basin, border, furrow, drip and sprinkler. Orchard cover crops are commonly used in conjunction with sprinkler irrigation to improve water penetration, reduce erosion, reduce dust, improve access between irrigations during the winter season, and reduce excess tail water.

Pastures will do well on a wide variety of soils, but is commonly grown on very deep soils with high water tables such as Columbia and Clear Lake soils. Large portions of former pasturelands have been converted to silage crops for the dairy industry. Most pasture is irrigated with graded borders. Water management, fertilization, and rotational grazing are key management practices.

The average yields per acre that can be expected of the principal irrigated crops in a high level of management are shown in table 7. In any given year, yields may be higher or lower than those indicated in the table because of variations in rainfall and other climatic factors.

The yields are based mainly on the experience and records of farmers, conservationists, and extension agents. Available yield data from nearby counties and results of field trials and demonstrations are also considered.

The management needed to obtain the indicated yields of the various crops depends on the kind of soil and the crop. Management can include drainage, erosion control, and protection from flooding; the proper planting and seeding rates; suitable high-yielding crop varieties; appropriate and timely tillage; control of weeds, plant diseases, and harmful insects; favorable soil reaction and optimum levels of nitrogen, phosphorus, potassium, and trace elements for each crop; effective use of crop residue, barnyard manure, and green manure crops.

For yields of irrigated crops, it is assumed that the irrigation system is adapted to the soils and to the crops grown, that good-quality irrigation water is uniformly applied as needed, and that tillage is kept to a minimum.

The estimated yields reflect the productive capacity of each soil for each of the principal crops. Yields are likely to increase as new production technology is developed. The productivity of a given soil compared with that of other soils, however, is not likely to change.

Crops other than those shown in table 7 are grown in the area, but estimated yields are not listed because the acreage of such crops is small. The local office of the Natural Resources Conservation Service or of the Cooperative Extension Service can provide information about the management and productivity of the soils for those crops.