Extension is increasing its on-line training and assets to adapt to COVID-19 restrictions.
Plant evaluation shouldn’t be used as the one device for making fertilizer suggestions. Plant evaluation works finest when utilized in mixture with soil testing.
The ranges for enough focus of Mg for specified plant tissue in Desk 1 have been established for particular levels of progress. When accumulating plant samples, each effort needs to be made to pattern the crop on the stage of progress that’s listed.
A soil check to measure exchangeable Mg is obtainable by most soil testing laboratories. In Minnesota, the potential want for Mg in a fertilizer program is highest the place sandy soils are very acid. If dolomitic lime has been used within the crop rotation, soils normally have a comparatively excessive stage of Mg and it’s not essential to check the soil for this nutrient.
Magnesium suggestions for corn manufacturing are summarized in Desk 2. The Mg options for vegatables and fruits are listed in Desk 3.
The function of magnesium within the soil
Magnesium is the central core of the chlorophyll molecule in plant tissue. Thus, if Mg is poor, the scarcity of chlorophyll ends in poor and stunted plant progress.
Magnesium additionally helps to activate particular enzyme techniques. Enzymes are advanced substances that construct, modify, or break down compounds as a part of a plant’s regular metabolism.
Magnesium within the soil
Magnesium is ample within the earth’s crust. It’s present in all kinds of minerals. Magnesium turns into accessible for plant use as these minerals climate or break down. Nearly all of the soils in western Minnesota have naturally excessive ranges of Mg. For the acid soils of the jap counties, the addition of dolomitic limestone within the crop rotation, when wanted, ought to provide enough Mg for crop progress.
Magnesium is held on the floor of clay and natural matter particles. Though this exchangeable type of Mg is accessible to crops, this nutrient won’t readily leach from soils. The final relationship between types of Mg within the soil is illustrated in Determine 1.
In Minnesota, Mg deficiency has solely been noticed on very acid soils. These soils normally have a sandy loam, loamy sand or sand texture. A Mg deficiency isn’t more likely to happen till the soil pH drops under 5.5. In Minnesota, the acid sandy soils happen within the central and east-central a part of the state.
The low ranges of Mg in soils can happen the place potatoes are grown on acid sandy soils or the place corn follows a potato crop. Generally, grass tetany, a livestock dysfunction attributable to low ranges of Mg within the food plan, is reported the place excessive charges of potash have been utilized to grass pastures. Analysis trials, nonetheless, have proven that using Mg in a fertilizer program for these pastures has not elevated forage yields. For these conditions, it’s inexpensive to complement the animal food plan with a salt that accommodates Mg.
Relationship of magnesium to calcium in soils
There are some who consider that there’s an “ideal” ratio of calcium to magnesium in soils and certainly one of these two vitamins needs to be added in a fertilizer program if this “ideal” ratio doesn’t exist. The necessity for this “ideal” ratio has by no means been verified by numerous analysis efforts all through the Corn Belt which have centered on the significance of ratios. In Wisconsin, for instance, the ratio of calcium to magnesium in soils was adjusted in a spread of two to eight by including completely different quantities of calcium and magnesium in a fertilizer program. This variation had no vital impact on alfalfa and corn yield. As fertilizer suggestions are developed, emphasis needs to be positioned on offering enough quantities of magnesium in soils relatively than the upkeep of a sure ratio of 1 nutrient to a different.
Deficiency signs
Magnesium is a cellular component within the plant and deficiency signs will happen first within the oldest leaves.
Corn
The lack of a wholesome inexperienced shade might be the primary indication of a Mg deficiency. Shade loss displays the scarcity of chlorophyll within the plant. Because the deficiency turns into extra extreme, the world between the veins of the leaves turns into yellow whereas the veins keep inexperienced. In corn, there’s a particular striping the complete size of the leaf, showing first on the decrease leaves (see Determine 2).
Potatoes
In potatoes, the lack of the inexperienced shade begins on the guidelines of the decrease leaves when there’s a delicate Mg deficiency. When the deficiency is extra severe, the yellowing progresses between the veins towards the middle of the leaf. Within the superior levels of Mg deficiency, leaf areas between the veins present small brown lifeless spots (see Determine 3). Illnesses, herbicide injury, and environmental components additionally trigger leaves to die prematurely. So, care needs to be taken in figuring out a Mg deficiency. Use plant evaluation to make certain.
Predicting the necessity for magnesium – “magnesium use in plants”
The important plant tissue concentrations of Mg in chosen crops are listed in Desk 1. Since Mg is a cellular component within the plant, the focus of Mg normally decreases from the highest to the underside of the plant. Additionally, the Mg focus normally decreases because the plant approaches maturity. It’s, subsequently, vital to point the age of the plant and the a part of the plant that was sampled when samples are submitted for a measurement of Mg in plant tissue.
Sources of magnesium
The appliance of dolomitic limestone is essentially the most value efficient methodology for making use of the Mg that’s wanted. The Mg content material of dolomitic limestone varies from 8-10%. To be efficient, this Mg supply needs to be broadcast and included earlier than planting.
There are fertilizers which might be a mix of potassium sulfate and magnesium sulfate. The Mg content material is 11 p.c. The sulfur (S) focus is 22 p.c and the K2O share is 22 p.c. This fertilizer is well utilized in a starter fertilizer for corn or as a Mg supply when there isn’t a need to extend soil pH.
Irrigation water can comprise a considerable quantity of Mg2+ which is available to a crop. Desk 4 summarizes the quantity of Mg utilized per inch of irrigation water at a number of places throughout Minnesota. The annual utility of Mg2+ in irrigation water can exceed the required quantities of this nutrient for crops not delicate to a deficiency. Any Mg utilized with the irrigation water not utilized by the crop will probably be detected by a soil check. Use the interpretations in Desk 2 and Desk 3 to find out if further fertilizer Mg is required.
Abstract
Though the necessity for the addition of Mg to a fertilizer program isn’t widespread in Minnesota, this nutrient can improve crop manufacturing when wanted. The potential for want shouldn’t be ignored. If there’s doubt in regards to the want, analyze the soil to make certain.