Category Archive: Soils and Growing
Soil and foliar application of Zinc to maize and wheat grown on a Zambian Alfisol
The deficiency of zinc (Zn) in human nutrition, commonly found in cereal-based diets accounts for impaired growth (stunting) in children. Since cereals are generally low in this element, bio-fortification may represent an opportunity to increase Zn intake by humans. A study was carried out to evaluate Zn uptake by maize and wheat when they are supplied with increasing rates of foliar or soil applied Zn. Maize and wheat were grown in the field and supplied with 0, 10, 20, 30, or 40 kg Zn ha-1 as ZnSO4 applied to the soil, or, 0,1,2,4, or 8 kg Zn ha-1 as foliar spray. Zinc application to soil increased maize and wheat yields beyond increments obtained with foliar application, but Zn mass concentration in maize grain was better with foliar applications. Mean maize yield was 1.78 ton ha-1 with soil application and 1.14 ton ha-1 with foliar application. This was in relation to an average of 52 mg Zn uptake by maize under each of the application methods. Wheat yield was 3.69 ton ha-1 under soil application and 2.74 ton ha-1 under foliar application. In this case, Zn uptake was higher under soil application (11.31 mg) than under foliar application (7.25 mg). Sesquioxide bound Zn was shown to be best correlated with plant Zn uptake. It was shown that Zn application is beneficial on Zambian soils, and while soil application increases crop yields, foliar application can be more useful to increase Zn mass concentration in maize.
Lal Bahadura, C. S. Malhia & Zora Singhb1
Publishing models and article dates explained
Published online: 21 Nov 2008
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To compare the effect of methods (foliar and soil) and rate of application of zinc sulphate on zinc and phosphorus uptake, tree size, yield and fruit quality of mango (Mangifera indica L.) cv. Dusheri, zinc sulphate was applied as a foliar spray application (0.25, 0.50, 1.0%) and soil (0.5, 1.0, 2.0 kg tree?1) treatments during the second week of October (during flower bud differentiation period). All the zinc sulphate treatments of soil and foliar spray were effective in increasing the leaf zinc concentrations above recommended adequate level of (>20 mg kg?1) whereas control trees maintained low leaf zinc concentrations (13.8 to 13.3 mg kg?1). The uptake of foliar?applied zinc was more rapid than that of soil applied zinc. All the treatments of zinc sulphate except the foliar spray treatment of zinc sulphate (0.25%) significantly increased zinc concentrations in the fruit pulp as compared with those in the control trees. The percent increase in the stem girth of trees was highest with the soil application of zinc sulphate (0.5 kg tree1) followed by foliar application of zinc sulphate (1.0%) as compared with all other treatments. The percent increase in the tree canopy volume was highest with the foliar application of zinc sulphate (1.0%) followed by soil application of zinc sulphate (1.0 kg tree1) as compared with control and all other treatments. There was no significant (P<0.05) increase in yield, fruit size and weight, pulp or stone weight with any treatment of zinc sulphate. Total soluble solid (TSS) in the fruit was significantly higher (18.6%) with the treatment of soil application of zinc sulphate (0.5 kg tree1) as compared with all other treatments of zinc sulphate and the control. Acid and sugar content of the fruit was not significantly affected by the foliar or soil application of zinc sulphate.
A Masters Thesis by Gregg A. Young
Discussion and test results on the effect of various organic phosphorus fertilizers on high pH soils in Colorado. From the Colorado State University Extension. PDF
Humus and Worm Castings
Humus and Humility – Recently we sent out an article that I (GK) wrote entitled “Understanding Humus”. It was fairly long, so probably not many read it. However, a few who did gave it what has to be described as high praise. Try as I might, being self-effacing, at some point, becomes suspect. Fortunately, I continue to make enough mistakes to remain authentically imperfect and unavoidably modest. An example is in the Humus article.
Castings Correction – In the section about composition of worm castings, I stated that worms accumulate high levels of minerals; and what I should have said, or explained, is that they transform unavailable minerals into available nutrient minerals as soil particles pass through their intestines. More than two thousand years ago Aristotle proclaimed that earthworms were the intestines of the earth. Smart guy.
Classical Content – Gardeners have long known that the presence of earthworms in their soil is a sign of good soil health, and their absence a sign of something being wrong. There is an often quoted reference to the mineral content of castings compared to the mineral content of surrounding soil (aka, dirt). Thus, castings are said to contain 5 times the nitrogen, 7 times the phosphorus, 11 times the potassium [and 1.5 (?) times the calcium, and 3 times the magnesium] as ordinary topsoil. How can that happen? The extra minerals can’t come out of thin air, nor, seemingly, out of thin soil. Transmutation of elements would be a stretch.
Enigma Explained – Initially, I figured the worm must somehow extract and concentrate the minerals as ingested soil moves through its body and is then excreted. Here’s what Sir Albert Howard, in Soil and Health (1947), had to say about the process and the make-up of castings:
“The casts are manufactured in the alimentary canal of the earthworm from dead vegetable matter, and particles of soil. In this passage the food of these creatures is neutralized by constant additions of carbonate of lime from the 3 pairs of calciferous glands near the gizzard, where it is finely ground prior to digestion. The casts which are left contain everything the crop needs – – – nitrates, phosphates, and potash [NPK] in abundance, and also in just the condition [soluble?] in which the plants can make use of them.”
Further Explanation – Howard goes on to cite that often-mentioned analysis as follows: “Recent investigations in the United States show that the fresh casts of earthworms are 5 times richer in available nitrogen, 7 times richer in available phosphates and 11 times richer in available potash than in the upper 6 inches of soil.” It’s that word “available”, in contrast with previously non-available, which explains the higher content of nutrient minerals in the castings coming out, versus the “soil” and organic matter going in. As near as I can tell, these numbers came from a single USDA study done in Connecticut in July, 1944.
Restoration Tool – Very large portions of the earth’s soil have been eroded and exhausted over the past 5,000 years all around the world. In recent centuries the rate has been stepped-up many times the rate of natural soil formation. The earthworm potentially is a major tool (if properly fed) for restoring and rebuilding those soils. Here’s further explanation from Dr. Thomas J. Barrett’s 1947 and 1959 book Harnessing the Earthworm:
“In the chemical and mechanical laboratory of the earthworm’s intestines are combined all the processes of topsoil-building. The earthworm swallows great quantities of mineral earth with all that it contains of vegetable and animal remains, bacteria and microscopic life of soil. – – – Finally, it is ejected in and on the surface of the earth as castings – earthworm manure – humus, a crumbly, finely-conditioned topsoil, richly endowed with all the elements of plant nutrition in water-soluble form.”
In Summation – I’m not sure that all (or most) topsoil is from worm castings which are, in turn, humus. Recall that this was the claim of Barrett and Darwin. Darwin calculated that worms deposit 10 tons of castings per acre each year. Sir Albert Howard figured it was 25 tons. In some parts of the world these deposits have been measured to far exceed those amounts. Whether or not topsoil is castings and castings are humus, or that humus requires soil and clay for its formation, the creation of 25 tons per acre or more of new topsoil per year is nothing to sneeze at. This represents a too-often overlooked means of restoring billions (yes, billions) of acres of ground lost to the plow, it’s modern successors, and a century of reckless chemicalized agriculture that are soon going to be necessary to the survival of civilization. In ancient Egypt it was a crime to kill earthworms. Let’s not forget the lowly earthworm. It’s the least we can do. GLK
© 2013 Gary L. Kline
All Rights Reserved
Black Lake Organic
Article by Presley and Leonard
J. T. PRESLEY AND 0. A. LEONARD
Published with the approval of the Director, Mississippi Agricultural Experiment
Station. Paper No. 140, New Series.
Received January 4, 1948
Article by V. A. Tiedjens
Soil samples from many sections of the United States and Canada show a paucity of
available calcium even though the pH reading seems satisfactory. Studies made on these
soils show that the pH test, accurate for most purposes, does not indicate the available
calcium in the presence of other fertilizer ions. A high pH does not necessarily indicate
adequate calcium in the soil.
THE OHIO JOURNAL OF SCIENCE 65(4): 227, July, 1965