- Author: Mark Bolda
Here is another interesting aspect of plant nutrition drawn from the October 23 Soil Fertility Short Course at UC Davis.
Phosphorous (P), an essential element for plants, does not occur alone in nature and rather it combines with oxygen and hydrogen. Bonded with four oxygen atoms P makes phosphate, and when bonded with three atoms of oxygen and one atom of hydrogen, P forms phosphite.
The fully oxidized phosphate (the one with four oxygen atoms) is the most stable form of P in the environment, and is preferentially taken up by microbes and plant roots. Then again, phosphate is adsorbed to soil particles more than phosphite, meaning it is less available. However, it does not necessarily follow that this enhanced availability of P via phosphite results in more uptake by plants, but even so, fertilizer formulations of phosphite plus calcium, magnesium or potassium have been formulated with the intent of taking advantage of this greater solubility in the soil.
Several studies examining a greater availability of P through phosphite have found that when phosphite is applied at an equivalent rate of P to phosphate fertilizer, it consistently underperformed when measured in terms of crop productivity, especially in the first year of cropping. In the way of explanation, the slower oxidation process of phosphite to the plant-root preferred phosphate, may be part of the equation of why the phosphite is not as effective as phosphate, in spite of having greater mobility.
In lay terms we can say, yes, phosphite might more available to plants in the soil, but they don’t want it as much as they want phosphate.
On the other hand, foliar applications of phosphite have shown that, while it can be converted to phosphate on the leaves by microbes living there, it is more readily absorbed into the foliage of some crop plants like citrus and avocados. Phosphite application (usually once at pre-bloom and perhaps a second time later in the season) to the foliage of avocados or oranges has resulted in more flowers, greater fruit yield and size, total soluble solids and anthocyanin concentrations.
For further reading, see the paper below, which among other things implies that the positive results experienced in oranges and avocados could be replicated in berries…
http://www.spectrumanalytic.com/support/library/pdf/Phosphite_Fertilizers_What%20are%20they.pdf
- Author: Mark Bolda
The California Strawberry Commission is sponsoring a "Farming without Fumigants Symposium" this coming December 5.
Meeting will be held at the Elk's Lodge in Watsonville, and will start at 830 am. For further information, please see the agendas posted below.
- Author: Mark Bolda
NOW ACCEPTING APPLICATIONS FOR SCHOLARSHIPS FOR SMALL-SCALE FARMERS
TO ATTEND THE CALIFORNIA SMALL FARM CONFERENCE
APPLICATION DEADLINE: DECEMBER 6, 2013
The California Small Farm Conference awards scholarships to small farmers and ranchers, student farmer/ranchers, farmer/rancher employees and farmer market managers to attend the conference. This year’s California Small Farm Conference will be held at the DoubleTree Hotel in Rohnert Park, CA, on March 9 – 11, 2014.Scholarships are awarded based on a number of criteria including farm and household income. Scholarship awards include registration to the three-day conference, all workshops and networking sessions, conference meals, and a Sunday Field Course at a discounted rate of $25. Lodging and travel costs are offered depending upon the distance traveled to Rohnert Park, California.
Applications may be obtained as follows:
- Download the online application from our website at: http://www.californiafarmconference.com/index.php/attend/scholarship or
- Call 1-888-712-4188 to request an application by mail or fax, or
- Email conference@californiafarmconference.com to request an application
All applications must be received by December 6, 2013. Applications received after close of business on December 6, 2013 through December 31, 2013 shall be placed on a waiting list.
About California Small Farm Conference Founded in 1982 by the Small Farm Center at the University of California, Davis, the California Small Farm Conference (http://www.californiafarmconference.com/) is the state’s premier gathering for not only small farmers, but farmers’ market managers, agricultural students, researchers, writers and food advocates to come together to network, learn, discuss and grow. The Conference is a unique opportunity for smaller‐acreage producersto gain insight from technical experts, network with other farmers and ranchers, and learn sustainable farming practices, business aspects, and more.
The upcoming California Small Farm Conference will be held at the DoubleTree Hotel in Rohnert Park, CA, on March 9 – 11, 2014.
Get all the latest updates on the 27th annual California Small Farm Conference by “liking” us on Facebook http://www.facebook.com/CaliforniaSmallFarmConference where we regularly post news, photos, tips and more.
2014ScholarshipPressReleaseShort-FINAL
- Author: Mark Bolda
There are two ways to interpret soil testing of the cations calcium (Ca) and magnesium (Mg), from the field: one by basic cation exchange ratios and the other by sufficiency. Base cation saturation ratios appear in most soil reports (see area circled in red below) and consist of percentages of calcium, magnesium and also potassium, sodium and hydrogen. Tim Hartz from UC Davis addressed this topic head on at the recent UC Soil Fertility Short Course held on October 23.
Proponents for examining cation ratios, for example Albrecht and Stiener, have held that there is an ideal cation ratio, meaning that the optimum soil environment for crop plants occurs when the cation exchange complex is 65% Ca : 10% Mg : 5% K : 20% H. To some extent this makes sense, since it has been shown that the base saturation of an individual cation can affect its availability to plants and that the uptake of one cation may affect the uptake of others.
However, research testing a variety of ratios of cations in the soil, especially Ca and Mg, has not found much in the way of identifying a true ideal ratio. As an example given at the short course in Davis, a study in Wisconsin that doubled and even quadrupled the exchangeable Ca: Mg ratio resulted in no difference in yield of alfalfa hay per acre.
It was rather suggested that growers and managers should concentrate on making sure each nutrient is in sufficiency for plant uptake rather than on reaching some favorable cation saturation ratio.
Most California soils have an abundance of calcium and magnesium in them already. In the soil test shown below, which is from a representative raspberry soil of the Pajaro Valley, we have 4100 ppm (mg/Kg) of calcium and 670 ppm magnesium, which when we multiply times two equals 8200 lbs of calcium and 1340 lbs of magnesium in the top 6” of soil, compared to the approximately 100 lbs of calcium and 25 lbs or so of magnesium that we need for a decent berry crop. We have A LOT of calcium and magnesium in our soils.
Moreover, it’s pretty expensive to try and alter the calcium and magnesium ratios of a soil. For example, more than 1700 lbs of gypsum will be needed to be added per acre to raise the calcium by 20 ppm. So, outside of extreme misbalances of calcium and magnesium which result in structural problems like crusting, it’s probably not worth the effort and money to obtain a ratio which doesn’t seem to offer anything extra in the way of nutrient sufficiency.
In conclusion, the truth of the matter is really that even though cations do compete with another for plant uptake and have different effects on soil structure, it is nevertheless completely possible to have high plant productivity with a wide range of ratios of calcium to magnesium.
The link below is an article with a full discussion of the concept of soil cation ratios.
http://www.soils.wisc.edu/extension/wcmc/2004proceedings/Kelling1.pdf
- Author: Mark Bolda
I have had occasion in my travels over the past two weeks to find a good quantity of what is depicted in the two photos below: J-rooting of strawberry plants.
J-rooting of strawberry plants occurs when the root is too long for the planting hole (Photo 1 below shows how big a healthy transplant can be - lots of those this year by the way) which has been made for it and subsequently the root tips end up pointing upwards rather than down. All too frequently, these upward pointing root tips end up being outside of the hole in the open air, as depicted in Photo 2 below.
It is not difficult to understand why J rooting is not beneficial to the plant. Root extension in plants takes place from the root tips, and having them exposed to the open air, drying out and dying does nothing to help this process along and represents a setback to the establishing plant. To be blunt, it’s a bad practice to be planting this way and shows a costly lack of attention to detail.
Transplanting is hard, back breaking work and it’s not too difficult to empathize and understand how J rooting can happen all too easily. Growers can help their planting crews along and get the roots straight down by several ways. Already having a deep hole or slot to be placing the transplant into helps a lot. Additionally, growers can ask that nurseries trim the roots to reduce the length of root of the transplant to better the odds of everything going straight down. In field quality control on the day of planting by the person in charge also goes a long way in making sure J rooting doesn’t become a pattern in for one individual or the crew.
