Publication 360, Fruit Production Recommendations: Magnesium


Pub 360: Fruit Production Recommendations > Chapter 3, Soil Management, Fertilizer Use, Crop Nutrition and Cover Crops > Magnesium

Excerpt from Publication 360, Fruit Production Recommendations 2010-11,
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Cover of Publication 360, Fruit Production RecommendationsTable of Contents

  1. Introduction
  2. Other topics in Soil Management, Fertilizer Use, Crop Nutrition and Cover Crops
  3. Ch. 3, Soil Management, Fertilizer Use, Crop Nutrition & Cover Crops - PDF 189 kb
  4. Related Links

 

Introduction

Magnesium is an essential part of chlorophyll and aids in the formation of sugars, oils and fats.

In apples, magnesium deficiency can cause premature fruit drop, especially with McIntosh.

A foliar spray will correct magnesium deficiency in the current year only, and should be combined with soil application for a longer term solution.

Magnesium is mobile within the plant and therefore deficiency usually appears first on the older leaves as it translocates to the growing tissue. The leaf tissue between the veins turns yellow, while the veins remain green. Severe deficiencies will cause the leaf margins to curl.

In conjunction with an OMAFRA-accredited magnesium soil test, consult Table 3-16. Magnesium Soil Test Ratings and Interpretations for all Fruit Crops, below.

Excessive potassium applications can induce a magnesium deficiency, therefore avoid using high rates of potash on soils with a low magnesium rating.

Table 3-15a. Application Rates for Magnesium (PDF 77 kb)

A number of micronutrients are available as chelates, with various formulations and nutrient contents. Check the product labels for crop specific recommendations. The effective use rate for chelated products is the same as for other formulations.

Nutrient = Magnesium (Mg)

Source% Nutrient

Other nutrients

Soil Application

Foliar Application

dolomitic limestone 6-13% 16-22% calcium yesno
epsom salts 9% 13% sulphuryesyes
sulphate of potash magnesia11%22% potash K2O
20% sulphur
yesno

 

Table 3-16. Magnesium Soil Test Ratings and Interpretation for all Fruit Crops (PDF 70 kb)

Soil Magnesium* (ppm Mg) Rating Recommendation
Below 20
HR
 Magnesium should be applied for all crops. If pH is below 6.5 apply dolomitic lime. At higher pH values apply 30 kg soluble magnesium (Mg)/ha. Potash applications in excess of those recommended by soil test will increase the probability of Mg deficiency.
20-39
MR
 Magnesium is not required unless potassium soil test is above 250. If soil test K is above 250 and pH is below 6.5 apply dolomitic lime. At higher pH values with K above 250, apply 30 kg soluble magnesium (Mg)/ha.
40-100
LR
 If lime is required use dolomitic.
100+
NR
 If lime is required either dolomitic or calcitic may be used.

* 1 M ammonium acetate extract
HR = high response; MR = medium response; LR = low response; NR = no response to applied nutrient.

Related Links

 


For more information:
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E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 8 June 2007
Last Reviewed: 22 July 2010