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

November 9, 2010

Water analysis and applying a leaching fraction for saline conditions

Written by: David Doll (UCCE Merced) and Daniel Sonke (Sureharvest, Inc). As discussed previously, sodium and chloride build-up in soils can cause crop loss by stunting plant growth. While much of the Central Valley has access to high quality surface irrigation water through irrigation districts, many almond orchards around the state have irrigation sources of variable quality. The first step in managing salinity is to know the source of salts. Water sources should be analyzed to determine the suitability for irrigation. Measurements of electrical conductivity (EC), sodium, calcium, and magnesium concentrations (cations), chloride, carbonate, bicarbonate, and sulfate concentrations (anions), pH, boron, and nitrate-nitrogen should be made. Most of these are standard.  Testing should occur on a regular basis since aquifer quality can change over time. Once the data is received from the test, the data should be checked for accuracy. First, the combined totals of all of the cations and the combined totals of all of the anions should be equal. Exclude boron and nitrate-nitrogen from these calculations. Next, if the EC is 5 dS/m or less, check to see if the sum of the cations is equal to 10 times the value of the EC. If these numbers are close, but not exact, the test is of good quality with all measurements made. If the EC and sum of cations are equal, most likely one of the cations/anions were estimated by subtraction rather than direct measurement. In the case of questionable quality, re-run the sample. Waters with ECs between 5 and 20 dS/m should use a multiplication factor of 12 instead of 10. Guidelines for water quality have been established to help identify excess salinity in water supplies. Estimating a 15% leaching fraction and the use of peach rootstocks (Nemaguard), the following table should be used as a guide to evaluate waters for suitable for irrigation

September 20, 2010

2010 Almond Harvest Around the Corner…

Harvest has started in the Southern San Joaquin Valley, and will be starting in the Northern San Joaquin Valley in the coming week. Here are some points to consider for the upcoming harvest: A few articles posted last year can provide a few tips to help with the decision of harvest timing:1. Preparing for Harvest. 2. Taking a Harvest Sample for an IPM checkup. Keep in mind that earlier harvested nuts may have to dry on the ground for 1-2 weeks, while nuts partially dried on the tree will require less time. Nuts that remain in the tree will have a longer period of susceptibility to NOW, while almonds on the ground are susceptible to ants, mold (due to increased humidity), and rain events. A quick orchard walk through looking for fire ants and pavement ants should provide the information needed for this decision. As soon as the almonds are picked-up, irrigate the trees. Adding a little nitrogen at this point is also advised. It may be possible to water the trees earlier dependent upon the irrigation system. Drip users may be able to irrigate as soon as the trees are shaken, while some micro-sprinklers may have small enough pattern that does not wet wind-rowed nuts. If stockpiling in the field, cover the almonds with a white tarp – or better yet, a two tarp system that includes a black under layer and a white tarp on top. The white tarp or b/w combo has been shown to reduce stockpile temperature and condensation, helping to reduce the environmental conditions favorable for aflatoxin production. Uncover the piles when possible to prevent the accumulation of moisture underneath the plastic. Fumigation of the stockpiles may be necessary. If rain is imminent, keeping the almonds in the tree will increase the dry time of

August 16, 2010

Hull Samples for Boron Analysis

What is the most common nutrient deficiency in Northern San Joaquin Valley almonds? If you said nitrogen or zinc you are wrong. While zinc and nitrogen are commonly applied to area orchards, boron is often neglected and therefore boron deficiency is far more common. If you haven’t applied boron TO THE GROUND recently and your orchard is east of the San Joaquin River, you are almost certainly deficient. Boron is essential for pollen tube growth. There are no obvious foliar symptoms of moderate boron deficiency, but less than optimum boron can reduce nut set. Analysis of mature almond hulls is a much better indicator of boron status than a leaf analysis. Wait until harvest to collect hulls because they will continue to accumulate boron while splitting. Trees with hull boron levels of less than 120 ppm may benefit from a postharvest boron spray (1-2 lb of a 21% B product in 100 gallons of water per acre). This will help with pollen germ tube growth in the flowers next spring but will not improve overall boron status of the tree. Hull boron of less than 80 ppm indicates the need for a ground application. Fertilize with the equivalent of 10 – 20 pounds of a 21% boron product per acre. Boron can be injected through micro-irrigation systems, broadcast or sprayed on the ground, or included in a herbicide spray. Herbicide sprays containing glyphosate may need to be buffered to prevent reduction of herbicidal activity. Hull levels over 200 ppm indicate excessive boron.

August 2, 2010

Orchard Cover Cropping pt 1

Written by: Jessica Corcorran, Pomology Intern, UCCE Merced County Jessica was selected by a committee to serve in the Summer Pomology Internship Program funded by the Almond Board of California. Being assigned within Merced County, she is working on several research projects, attending farm calls, and getting a feel for what it takes to be an extension agent. It is our hope that her career path will lead to extension work, hopefully serving the almond industry within California. She is entering her Senior Year at Cal Poly. The use of orchard cover crops is not a new practice. The benefits of cover crops have long been recognized and have been widely used in agriculture. In recent years, cover crop use has increased due to a multitude of reasons which include soils health improvement, increased soil fertility, and increased water retention and penetration. In today’s post, I will cover the impacts of cover cropping on soil health. In subsequent posts, I will discuss other benefits of cover cropping, general pros and cons, as well as the practicalities of implementing a cover crop in an orchard.   Cover crops have the ability to greatly improve soil quality and structure. Water penetration is often compromised by soil compaction in orchard soils.  The roots of the cover crop and their ability to move through the soil can help to reduce soil compaction by tillage and harvesting equipment.  Plow pans have even shown to be corrected by the use of cover crops. The fibrous roots of the cover crop also help to stabilize soil aggregates, which improve soil structure and aids in effective water infiltration. The addition of organic matter in the soil invites beneficial microorganisms. During the breakdown of organic matter, indigestible compounds are formed that are resistant to decomposition. These compounds bind soil particles

July 16, 2010

2010 Hull Split time…

I feel that the majority of topics regarding hull split have been discussed in prior entries, so I thought I would briefly make a few points of considerations for 2010: 1). Navel Orange Worm (NOW)/ Peach Twig Borer (PTB): Both insects cause damage to almonds, often NOW damage hiding PTB damage. Both insects are susceptible to the same insecticides. The 2010 treatment window for the 2nd flight of PTB will be overlapping with hullsplit. This is good because we can make one spray for NOW and PTB. This is bad because in years were the 2nd PTB flight occurred during hullsplit, worm damage was higher.  If no PTB treatments have been made and no NOW/PTB treatments are scheduled, I would plan to make one within the coming week. Reduced risk products or pyrethroids will provide control for both worms. Related topics previously covered: Peach Twig Borer, Navel orange worm, and hull split insect management. 2). Apply pesticides slowly – do not exceed 2 MPH with spray rigs. 3). Hull rot: Hopefully nitrogen applications have ended. Plan to reduce water to 80% ET for the coming two weeks. By the last week of July, first week of august, resume full ET. This will help reduce hull rot. Please see the previous article on hull rot. 4). Mites: Haven’t been much of a problem this year, but keep in mind that the use of a pyrethroid at hullsplit will most likely cause a mite flare up by harvest. A miticide should also be applied at hullsplit if a pyrethroid is used. There are a few products available that can knock down high populations of spider mites should a flair up occur. It is critical that these products are applied before webbing appears. 5). Harvest: Hullsplit appears to be a week later this year, suggesting that harvest will be

July 12, 2010

April/May/June Almond Nut Development – Rationale for Proper Irrigation and Fertilization

The cool spring has brought up a few questions about almond development that I will do my best to answer today. Does the cool weather slow nut development? Yes, it does. By reducing the heating units, almond development is delayed. Similar to peaches, the cooler the weather, the longer it takes to complete the fruit sizing and kernel formation. This usually means that later season events will be delayed – such as hullsplit and harvest.   How can we determine if nut development is complete?  By pulling almonds off of tree and taking cross-sections, it is easy to observe the development of the embryo. As seen in figure 1, the embryo will grow from the tip and eventually fill the entire shell. Preceding embryo development is the endosperm and nucellus which makes up the “jelly” of the almond. The endosperm tends to be a bit more cloudier than the nucellus and proceeds embryo development. Once the embryo is completely developed (i.e. the kernel has filled the shell), weight accumulation will begin in the kernel  This generally tends to happen around early June and continue to hullsplit. Why is knowing when the completion of nut development important? Most of our UC recommended practices regarding irrigation and fertilization are based around nut development. If you are running short on water due to a curtailment, you might have heard that water can be cut back in Mid-June to help stretch your budget. This point in mid-June refers to when the embryo is completely developed and the dry weight accumulation is nearly done. Cutting water sooner than this will lead to reduction of crop weight, shrivels, and in some cases, nut abortion. In a cooler year, this point may be delayed – so if you are planning on deficit irrigating this summer, make sure your kernel development is complete.   This same principle is also the basis of most fertilizer timing recommendations. Fertilizer should

May 25, 2010

Almond Leaf Rust – Treat now to prevent late season defoliation

Almond leaf rust (Tranzschelia discolor f. sp. dulcis)can cause defoliation of almond trees during the late season. Rust is favored by high humidity and is worse in years in which late rains occur. Appearing as small yellow lesions on the upper surface of leaves with brownish/red pustules on the bottom (Pictures below), rust will first appear in late spring or early summer. The disease does not appear to affect the fruit. Spread through the orchard is through air movement, which blows spores from an infected leaf to an uninfected leaf. Infected leaves will eventually fall off of the tree affecting crop and tree health. The disease overwinters on leaf material. Prevention: Orchards favoring high humidity often have rust problems. Encouraging air movement by planting on wider spacings (22′ between rows), hedging, or selective pruning may help reduce canopy humidity. Microsprinklers and solid set sprinklers may increase canopy humidity since evaporation of sprayed water may occur. Sanitation (leaf mowing, breakdown) should be employed to reduce overwintering inoculum. Treatment: In orchards that have a history of rust, a two spray fungicide program should be used to reduce disease and clean up the orchard. The first application should be applied 5 weeks after petal fall and followed up with a 2nd application at 10 weeks post petal fall. DMI (FRAC Group 3) or strobilurins (FRAC Group 11) provide good to excellent control. Broad spectrum fungicides such as sulfur and topsin provide a good, cheap control and also allow an option for fungicide rotation. More information on fungicide efficacy can be found here. Applications of zinc sulfate (20-40 lbs/acre) applied in late October/early November should be made to help reduce overwintering populations of rust. The zinc will hasten leaf fall, and prevent the rust inoculum from increasing. In orchards of severe infestation, applying a

April 5, 2010

Fertilizing one-year old trees – be careful!

Nitrogen is the most important element we can apply to our tree fruit crops. Almond growth and productivity depend on the availability and uptake of nitrogen. Most fertilizer recommendations are based on making nitrogen available to our trees so that a nitrogen shortage does not limit tree growth or productivity. Young almond trees don’t require as much nitrogen as older trees. I like Wilbur Reil’s rule of “one ounce of actual nitrogen per year of age of tree”. That rate can be applied several times per season, but never more than that at any one application. Thus, a first leaf (first year in your orchard) almond tree should not receive more than one ounce of actual nitrogen per any application. A five year old almond tree should not receive more than 5 ounces of actual nitrogen per one single application. The University of California only recommends one ounce of actual nitrogen per one year old tree over the course of the season, but I have been told by many growers and PCAs that this rate is not enough for the growth they desire. So, if you want to put out five ounces of actual nitrogen per one year old tree, do so in five applications and not all at once! I have seen many trees burned by nitrogen, especially if liquid fertilizers like UN-32 (urea ammonium nitrate 32 %) or CAN 17 (a clear solution of calcium nitrate and ammonium nitrate) are used in single applications. These liquid fertilizers are very effective and easy to use but it doesn’t take much to burn young trees. I do not suggest using these liquid fertilizers on first leaf trees–I prefer to see triple 15-15-15 (15% Nitrogen – 15% Phosphorous – 15 % Potassium) fertilizers used on first leaf trees. I like to

March 15, 2010

Inquiries about Bacterial Canker on Almond

This week I have had a few questions regarding post harvest treatments for Bacterial Canker of almond. I thought it would be a good idea to use these questions as the theme for this weeks post. What is bacterial canker?Bacterial canker is commonly found on Prunus species (Peach, cherry, apricot, plum, almond, etc.). Caused by Pseudomonas syringe, a common surface inhabiting bacteria, the disease is often observed in the spring. Symptoms include limb dieback with rough, irregular cankers (Figure 1). Cankers do not extend into the soil and a very unique smell is present. In some cases, cankers do not form, but a “sour sap” stage occurs. This stage is characterized by brown inner bark with a distinctive fermentive, sour smell – hence the name. Generally, almond trees in the 2nd through 5th leaf are affected. Figure 1: Almond tree killed by bacterial canker. Note that the canker has an irregular shape and does not extend into the soil. How does bacterial canker spread?Pseudomonas syringe survives on plant surfaces and is spread by splashing rain. The bacteria is found throughout the entire orchard and is impossible to eradicate. The disease commonly occurs in the spring during periods of mild temperatures and high humidity. It does not spread like other diseases, but is common on trees that are stressed. Therefore, soils that have poor water/nutrient holding capacity (i.e. sand), have been replanted with several generations of Prunus sp. orchards, and have the presence of ring nematode are prone to this disease. Figure 2: Photo of an almond with a scaffold infected with bacterial canker. Note the irregular margin of the canker.What can I do to prevent the problem?In soils that have exhibited the disease, pre-plant fumigation with Telone or Methyl Bromide (if it is still available) provides the ability for the

December 15, 2009