David Doll6 CommentsFebruary 17, 2015Horticulture, Irrigation

More Leaves than Flowers: Why?

I have received a few reports about poor bloom conditions on ‘Nonpareil.’ In these cases, flower density appears to be low and leaves are starting to push (See Figure 1) indicating that the fruit buds did not develop over the past year. From the reports, trees tend to be between the ages of 6 and 12 years old and have been observed across Merced County. A number of issues may be responsible, including the following: Water stress. Reductions in water resources over the past year have led to reduce vegetative growth in many orchards. This lack of growth prevents the formation of vegetative buds (in-season) which develop into fruit bud (post-harvest through dormant period). Research has shown that spurs that remain in good light positions tend to “take a year off” after bearing fruit, while others receiving too much shade die. Therefore, canopy growth must be maintained to some extent to keep crop loads high. Salinity Induced Water Stress. Increasing soil salinity decreases the osmotic potential of the soil, making the plant “work harder” for water. This leads to water stress and reduces the energy diverted into vegetative growth and floral bud development. High yields over the past few years. Trees producing large yields in successive years have been observed to have an “off year.” This is due to most of the plants energy being diverted into the crop load, reducing the amount available for developing new fruiting spur positions. As discussed earlier, if this happens in successive years, the number of viable fruit spurs may be reduced leading to a reduced crop. Re-leafing in the Fall after leaf drop from foliar disease, salt, or mites. Bloom density would be lower if the tree defoliated last summer or fall from lack of water, too high of salt levels, foliar disease,

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Franz Niederholzer3 CommentsAugust 30, 2014Irrigation

After a tough year, make key irrigation maintenance a priority.

Written By: Franz Niederholzer, UCCE Farm Advisor, Colusa/Sutter/Yuba Counties Despite strong nut pricing, the drought is making 2014 a very tough year for growers, their trees, and in many cases, their irrigation systems.  Low quality irrigation water, potentially stressing trees and irrigation systems, was/is applied to many orchards this year that normally received higher quality water.  Irrigation system maintenance, especially cleaning drip lines to ensure uniform and adequate water flow, should be high on the do-to list this fall.  The following is a quick review of key practices to keep drip emitters from clogging.  For more complete information, see the sources listed at the end of the post.

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David Doll4 CommentsAugust 22, 2014Irrigation

Water Stress and Varietal Differences

A few visits and emails have highlighted differences in leaf drop patterns observed across varieties within an orchard. Full rows of trees will have yellow leaves that drop in time, characteristic of water stress while other varieties appear unaffected. These “in-field” observations suggest that almond varieties respond differently to the amount of water applied. For example, the variety ‘Monterey’ and ‘Aldrich’ have been observed to show signs of stress before ‘Nonpareil’ trees even though crop load is similar. In these cases, these trees may undergo severe leaf drop while ‘Nonpareil’ appears unaffected.

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David Doll5 CommentsJune 7, 2014Horticulture, Irrigation

Water Stress, Early Hullsplit, and Kernel Size

I have been getting a few reports of hull-split in almonds from varying points across the state. We were expecting an earlier than normal hull-split, but many would agree that this is earlier than expected. Much of the splitting trees are in the more stressed areas of the fields, or in orchards with reduced water allocations. Although I haven’t observed this until this season, early hullsplit induced by spring-time water stress has been described in the literature.

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David Doll3 CommentsMarch 24, 2014Irrigation, Salinity

Well Water Analysis to ID Salinity Issues

There will be an increase reliance on groundwater for 2014. Wells that have been typically relied on to subsidize water allocations are now providing the primary source of water for the drought stricken almond orchards. If using a well, it is important to sample the water. Sampling will determine the characteristics of the water such as dissolved salts, pH, and major cations and anions. Sampling should be performed regularly, and more frequently if well performance or pumping depth has changed. 

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David Doll5 CommentsFebruary 14, 2014Irrigation

Determining Orchard Water Needs With Yields

In delivering workshops on irrigation (and drought) management, there are always a few questions on how to estimate canopy coverage without the use of special equipment. Not being content with the typical answer of “Use your best guess,” I began to review the research, and found that an estimate of photosynthetically active radiation (PAR) (also known as mid-day light interception) can be calculated from orchard yields. This question was asked because in a water short year, the available water needs to be spread out evenly as the respective % of evapotranspiration. This following will help determine how much water your trees are using.

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David Doll8 CommentsJanuary 16, 2014Irrigation

Severe Drought Management Recommendations for Almond

UC researchers have urged growers not to take aggressive actions in reducing tree size or crop load in response to the West side water shortages this year. Severe pruning will increase new growth which would increase the leaf surface and evapo-transpiration rates (ETc) of the tree. Crop thinning has a similar effect and is also not recommended. By reducing crop load, the source/sink ratio of the tree is disturbed, causing the tree to put nutrients into vegetative growth instead of the nuts.

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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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