Franz Niederholzer8 CommentsNovember 20, 2012Nutrient, Salinity, Soil

Broadcasting compost within Orchards

Compost spreaders are working in almond orchards in this area.  The addition of composted organic matter – often composted yard waste — to soil should generally benefit soil physical and chemical properties.  However, it isn’t a source of short-term plant available nitrogen.  Research by UC Davis specialists Tim Hartz and Jeff Mitchell has shown that composted yard waste, when mixed with sand and held under constant, optimum moisture and temperature (the optimum conditions for mineralization of organic nitrogen) produces a very little plant available nitrogen (2% of total nitrogen in the compost) in the short run (12-24 weeks).  When compost is broadcast on the soil surface and not incorporated, plant available nitrogen should be even less.  Dr. Hartz did conclude that manures and composts had value in long-term soil building in vegetable crop production, where those materials are incorporated into the soil.  [Untreated/uncomposted manure use in almonds is a food quality risk and not supported by the almond industry.] Why bring up compost use? Growers are willing to pay for it and seem happy with the results.  Here’s why.  If California agriculture ends up in a regulatory situation where nutrient budgets are required of growers, it should be recognized that the short term nitrogen benefits from composted yard waste are almost non-existent and the long term benefits are unknown. Previous entries on compost applications can be found here and here.

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Allan Fulton0 commentsDecember 7, 2010Soil

Understanding and Applying Information from a Soil Test: Part 2 – NPK

Part 1 of this series emphasized that soil testing is complementary to plant tissue testing and not a substitute in orchard management.  Considerations to ensure soil testing provides representative and useful information and interpretation of two common soil test parameters: 1) Saturation Percentage (SP); and 2) pH were also discussed.   This article will focus on the nutrients nitrogen (N), phosphorus (P), and potassium (K). Nitrogen Nitrogen occurs in soils as organic and inorganic forms and soil testing may be performed to measure levels of either. Nitrate nitrogen (NO3-N) is most commonly measured in standard soil tests because it is the primary form of nitrogen available to trees and, therefore, an indicator of nitrogen soil fertility.  However, soil concentrations of NO3-N depend upon the biological activity and may fluctuate with changes in soil temperature, soil moisture, and other conditions.  Nitrate is also easily leached with rainfall or irrigation so current soil tests may not reflect future levels of nitrogen soil fertility.  Table 1 provides guidelines for evaluating NO3-N soil fertility levels.  Table 1.  Guidelines for interpreting nitrate nitrogen (NO3-N) levels in soil test results. Fertility Level ppm lbs/acre1 Low <10 <36 Medium 10-20 36-72 High 20-30 72-108 Excessive >30 >108 1 Some laboratories report NO3-N as lbs/ac rather than as a concentration (ppm).  A soil bulk density is assumed in this calculation so the NO3-N fertility levels should be considered an estimate rather than an absolute level.   Ammonium  nitrogen (NH4-N) is also a plant available form of nitrogen in orchard soils and it can be determined with soil testing upon request.  In general, NH4-N is not determined and reported with a standard soil test.  Ammonium nitrogen does not usually accumulate in soil because soil temperature and moisture conditions that are suitable for tree growth are also ideal for conversion of

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Allan Fulton3 CommentsNovember 23, 2010Soil

Understanding and Applying Information from a Soil Test: pH and Saturation Percentage

This article will focus on the role of soil testing in orchard management, describe steps to acquire informative soil testing information, and discuss two of the more familiar parameters in a soil test report: pH and saturation percentage (SP). Soil testing helps understand the orchard soil environment and how to prevent or correct nutrient deficiencies, toxicities, or conditions that affect the availability of water to the trees in a cost effective manner.  Soil testing may forewarn a problem before it actually affects growth and production. Therefore, it helps anticipate possible problems and offers the earliest opportunity to manage them.  Soil testing is not a substitute for plant tissue testing, rather it is complementary.  If soil and leaf tissue analyses both indicate a deficiency or toxicity, the diagnosis is obvious. If a soil analysis indicates a deficiency or toxicity but a leaf tissue test does not, it may only be a matter of time before the deficiency or toxicity develops in the trees.  Conversely, if leaf tissue analysis indicates a deficiency or toxicity but soil testing does not, it may point out that either the soil testing does not represent how the trees’ root system integrates the soil environment or that the soil environment has changed more rapidly than the nutritional status of the tree. There are two basic philosophies for sampling soils. When marginal soil is known or suspected to exist, consider routine soil testing (at least every two or three years) to understand trends and guide long-term management. When confident that the soil is fertile, non-saline, and suitable for orchard crops such as walnut, almond, and prune, sampling is only necessary to troubleshoot problems.  Some situations do arise where a switch in sampling approach may be necessary. For example, when a change from a higher quality to lower quality

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Allan Fulton2 CommentsNovember 9, 2010Soil

Soil Testing and Analysis: What to Expect in the Report

Agricultural laboratories usually analyze and report soil salinity and fertility levels in the same report.   Saturation percentage, electrical conductivity, sodium, calcium, magnesium, chloride, bicarbonate and carbonate, sulfate, and boron are all part of salinity.  Indices such as the Sodium Adsorption Ratio (SAR) and Exchangeable Sodium Percentage (ESP) are calculated from these basic measurements of soil salinity and included in the report.  Soil testing for salinity is designed to diagnose osmotic effects, specific ion toxicities, and infiltration problems.  When the salinity (electrical conductivity) of the soil-water surrounding the root exceeds the tolerance of a salt sensitive crop like walnut, the gradient between the solute concentration in the root cells and the soil-water around the root lessens, reducing water availability to trees.  Trees influenced by osmotic effects will not grow as vigorously.   Specific ion toxicity involves the accumulation of sodium, chloride, or boron in soils to high enough levels that the risk of these elements accumulating to toxic levels in leaf tissue of trees increases.  Symptoms of ion toxicity may include death of leaf tissue along the margins or in the interveinal areas of leaves.  Soils that develop slow water infiltration and permeability rates are sometimes related to low levels of electrical conductivity and calcium, and high levels of sodium or magnesium. Fertility focuses on essential plant nutrients, which is evaluated based upon soil pH and proper quantities of nitrogen, phosphorus, potassium, zinc, iron, manganese, copper, and molybdenum in the soil to promote walnut tree growth and fruit development.  While calcium, magnesium, boron, and chloride are important to diagnose salinity, they are also of interest from the standpoint of fertility in terms of deficiency, sufficiency, and balances. Salts and nutrients exist in soils as three forms (see schematic) and this is reflected in soil test reports.  Bulk minerals and organic reserves release

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