Terry L Prichard

Using EM and VERIS technology to assess land suitability for orchard and vineyard development

Orchard and vineyard producers conduct preplant site evaluations to help prevent planting permanent tree and vine crops on lands where the crop will not perform to its highest potential or attain its full life expectancy. Physical soil characteristics within specific soil profiles and spatially throughout an orchard influence decisions on land preparation, irrigation system selection, horticultural choices, and nutrient management. Producers depend on soil surveys to help them understand the soil characteristics of the land and may be interested in technology that provides additional information. Electromagnetic induction (EM38) and four-probe soil resistance sensors (VERIS) are being used in combination with global positioning systems to map spatial variability of soils using apparent soil electrical conductivity (ECa). The hypothesis evaluated in this study is whether rapid, in situ, and relatively low-cost methods of measuring ECa (EM38 and VERIS) can effectively identify and map physical soil variability in non-saline soils. The supposition is that in non-saline soils, ECa levels will relate well to soil texture and water-holding capacity and can be used to map physical soil variability. In turn, the information can be used to guide decisions on preplant tillage, irrigation system design, water and nutritional management, and other horticultural considerations. Two sites in the Sacramento Valley were mapped each with EM38 and VERIS methods. Site-specific management zones were identified by each provider on ECa maps for each site, and then soil samples were collected by University of California researchers to verify these zones. Results showed that on non-saline soils, ECa measured with both EM38 and VERIS correlate with physical soil properties such as gravel, sand, silt, and clay content but the relationship between conductivity and these physical soil properties varied from moderately strong to weak. The strength of the correlation may be affected by several factors including how dominant soil texture is on conductivity relative to other soil properties and on methods of equipment operation, data analysis and interpretation. Overall, the commercial providers of ECa surveys in this study delivered reasonable levels of accuracy that were consistent with results reported in previous studies. At one site, an ECa map developed with VERIS provided more detail on physical soil variability to supplement published soil surveys and aided in the planning and development of a walnut orchard. At a second site, almond yield appeared to correlate well with distinctly different soil zones identified with EM38 mapping.

Estimating furrow infiltration

Abstract Furrow irrigation, the most common irrigation method in California, can be difficult to manage efficiently because of lack of quantitative information on infiltration rates. Conventional methods of measuring infiltration rates are not likely to be used on routine evaluations of furrow irrigation system. However, volume-balance simulation models of furrow irrigation, which estimate infiltration from water advance data, offer a potential for estimating infiltration in furrows. Six models were evaluated using detail data from 200 furrow evaluations. Results showed an inverse relationship between the exponent of the power advance equation and the exponent of the infiltration equation. This relationship tended to cause the models to greatly underestimate cumulative infiltration as the advance exponent approach unity. The models ability to predict system performance under different flow rates given an initial flow rate was also investigated.

Measuring Applied Water in Surface-Irrigated Orchards

Author(s): Schwankl, Lawrence J; Prichard, Terry L; Hanson, Blaine R | Abstract: A helpful guide on reducing agricultural runoff from irrigated properties caused by irrigation practices or winter rainfall.