David Doll4 CommentsJune 30, 2019Horticulture, Soil

Cover crop research review: How can it help almonds?

Cynthia Crézé (1), Jeffrey Mitchell (1), Andreas Westphal (2), Danielle Lightle (3), David Doll (3), Mohammad Yaghmour (3), Neal Williams (4), Amanda Hodson(4), Houston Wilson (5), Kent Daane (6), Brad Hanson (1), Steven Haring (1), Cameron Zuber (3) & Amélie Gaudin (1) Department of Plant Sciences, University of California – Davis Department of Nematology, University of California – Riverside University of California Agriculture and Natural Resources – Cooperative Extension Department of Entomology and Nematology, University of California – Davis Department of Entomology, University of California – Riverside Department of Environmental Science, Policy and Management, University of California – Berkeley Although cover cropping is compatible with almond production and is often implemented in other orchard systems, this practice has never been widely implemented in California. The potential benefits are recognized by growers, especially their value for pollinator forage and soil health but operational concerns, lack of cost-benefit analyses and unclear best management practices have hampered wide adoption. As cover cropping can provide significant sustainability benefits, there is an urgent need to assess and develop feasible and beneficial cover crop systems for California almond production. Here is some insight gathered by a research team assessing the impacts of multiple cover crop management strategies on: 1) soil health, 2) water use and dynamics, 3) bee visitation and pollination, 4) weed and pest pressure (NOW) and 5) almond yields in four orchards across the Central Valley precipitation gradient. Cover crop research trial in almond: Project website: https://almondcovercrop.faculty.ucdavis.edu Design: Three commercial orchards in Corning (Tehama county, 2nd leaf), Merced (Merced county, 16th leaf) and Arvin (Kern county, 16th leaf). One experimental station: Kearney (Fresno county). Two cover crops: Soil Mix (2 legumes, 2 brassicas & 1 grass), Pollinator Mix (5 brassicas, Project Apis M – https://www.projectapism.org/pam-mustard-mix.html) Compared to resident vegetation & to bare soil. Cover

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David Doll0 commentsJune 16, 2016Irrigation, Soil

Managing Water Infiltration Problems

Over the past few weeks, there have been several farm visits discussing water infiltration issues. In many of these cases, chemical sealing of the surface soil has occurred. This creates a crust that reduces the movement of the water into the soil. In subsequent irrigation, when water is applied faster than the rate of infiltration, puddling occurs, leading to an increase in evaporation as well as saturated soil conditions. This impacts water use efficiency and tree health. A season of irrigation can require between 36 and 52 inches of applied water per acre. This is often applied to a limited area of an orchard, which is defined as the wetting pattern. Each irrigation system has a different wetting pattern, with micro-sprinklers somewhere around 30-60% of the orchard area, and drip around 20%. This means that, dependent on the system, the wetted area may receive 2-5 times more water than the targeted season’s application per acre. In other words, if  four acre feet/acre were applied using a drip system that wets around 20% of the orchard floor, the soil in that wetting profile has nearly 20 acre feet of water that must pass through in order to infiltrate the soil. This is a tremendous volume of water to pass through the soil, and it can leach away beneficial elements which leads to chemical sealing and infiltration problems. When infiltration rates slow, it is important to know the causes as not all infiltration issues are the same. Taking an analysis of the water and soil is a good place to start. Unlike soil sampling conducted in the fall, soil sampling of the top 2-3″ of soil should occur to identify the chemical imbalance.  Analyzing the soil and water will give an idea of salt load, SAR, pH, as well as other elements. This will help identify

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Franz Niederholzer5 CommentsJune 22, 2013Irrigation, Soil

Gyp in June

Written by: Franz Niederholzer, UC Farm Advisor, Colusa/Sutter/Yuba Counties,  Allan Fulton, UC Farm Advisor, Tehama/Shasta/Glenn/Colusa Counties It’s June – the best time to apply gypsum to the soil surface in orchards with flood or wide coverage sprinklers.  Why now? But first, what does gypsum do and not do?  Adding gypsum to the soil can significantly increase the rate of irrigation water infiltration when using 1) very clean (usually canal/surface) irrigation water (EC < 0.5 dS/m); 2) when the soil surface sodium adsorption ration (SAR) is 5 to 10x that of the irrigation water EC; or 3) when calcium to magnesium ratios in the water are not at least 1:1.  Adding gypsum also provides additional calcium and sulfate for nutrition, if needed.  Gypsum, calcium sulfate, is a neutral salt so it affects soil pH very slowly causing it to seek neutral soil pH (7.0).  It won’t break up hard pans or soil layers with distinctly different soil textures or compaction that impede water infiltration.  Gypsum stabilizes the soil.  It reduces dispersion of larger soil aggregates when a dry soil is irrigated.  In turn this reduces the formation of soil crusts and helps maintain more soil porosity and higher water intake rates. How much gypsum is recommended to improve irrigation water infiltration for the conditions described above? Injecting 500 to 1000 lbs finely ground gypsum per acre foot of water should increase irrigation water EC by 0.15-0.3 dS/m, enough to improve infiltration of very clean water or reduce the effects of sodium and magnesium. If not using micro-irrigation, broadcast up to one ton/acre of finely ground gypsum onto the soil surface and do not till it into the soil.  It will dissolve in the water as irrigations are applied and improve the water quality.  The best time to apply gypsum on the

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