Spring Root-flush

 

Spring Root-flush

Winter dormancy is an important development stage in the tree growth cycle. During this time period crops rest and recharge for the upcoming growing season. Both cold air and soil temperatures are required to supply much needed “chill hours” for resting trees. “Chill hours” are a lot like REM sleep to you and me. REM sleep is the nightly deep-sleep that is vital for keeping us healthy and well rested upon awakening. Simply put, trees need cold temperatures to slow (or stop) their growth activities. When temperatures are too mild, trees do not receive adequate “chill hours” and break dormancy in an energy-deficit condition. In other words, trees don’t sleep well and awaken stressed.

 

 

Spring root-flush:

In California, normally happens with prunus species like almond, early peach, plum, nectarine, apricot and cherry varieties, in the 3rd to 4th week of January. This activity begins when soil temperature (in top 2-4”) reaches 45°F and precedes bloom by approximately three weeks. Buds visibly swell with water and nutrients. The new hair-root growth is needed to support the upcoming crop with water and nutrients. Once root-flush is underway, growers should take advantage by beginning fertigation or soil fertility applications. Nutrient focus should be on root health and crop support.

 

Temperature:

Soil temperature is a major driving factor in the onset of spring rootflush. Currently, soil temperatures, in California are 50-52°F (well above 45°F) due to the high volume of rain (4-5”) that has fallen in the past four to five weeks and continues to saturate much of the state. California has another 4-6” of rain forecast in the next week. Due to this increase in soil temperature, rootflush is now underway.

 

Chill hours:

http://fruitsandnuts.ucdavis.edu/Weather_Services/chilling_accumulation_models/Chill_Calculators/?type=chill  [Check your current chill hours]

Another concern is that “chill hours” are below normal for early January and trees are not getting the rest they need. Rootflush is underway and therefore so is root respiration. Respiration is the plant process of “burning up” or releasing stored nutrient energy for plant use. This is a problem because new roots are using up nutrient energy that is meant for the upcoming bloom.  Due to these circumstances, an energy deficit is beginning that cannot be restored from dormant rest. If you enter the bloom stage in an energy deficit (stressed) condition, it will affect the plant’s ability to pollinate, set and “stick” crop. One symptom of bloom stress is “June drop”. Plants self-regulate by aborting excess crop to ensure they do not run short on nutrients. They are programmed to know how much crop load they can support based on their health and availability of nutrition.

 

Feed the Soil:

When short on “chill hours”, the next-best alternative is to supply energy to the plant via “plant-ready” nutrition. Treatment emphasis should be on the soil, since the roots are already at work. Using an orthophosphate source provides much needed “plant-ready” phosphorus for root growth and health. A unique root benefit is a fungicide-like response within the rootzone. This is especially important in waterlogged conditions. Unlike polyphosphate fertilizers, orthophosphate is not temperature dependent. This means it is readily absorbed by new roots in cold soil temperatures (<63-68°F). In addition to feeding the soil, this is also an ideal time to re-inoculate the rhizosphere with soil microbiology. The more diverse your soil microbiology, the better your soil-nutrient and water efficiency you will experience. Dr. William Albrecht said, “We must not forget that microbes are what make a living soil ‘alive’…microbes, eat at the first sitting…Plants eat second. Plants and microbes must be in symbiotic activity and not in competition for fertility if our productive soils are to be maintained.” So, how productive are your soils? As the farmer, it is good stewardship to know and make necessary adjustments to nurture the soil and ensure it is still productive for the next generation.

Here’s to your success!