Calcium magnesium imbalance in clovers: A cause of negative yield response to liming

Three pot experiments, in which causes of negative yield responses to liming were investigated, are reported. The soil used, Waimumu silt loam (Fragiochrept), differed from others that have been reported to show negative yield response to liming, in that it is only moderately weathered and leached, only moderately acid and has previously shown positive yield responses to liming. Deficiencies of Zn and Mg were identified, but limed (pH 6.8) soils still showed a 40% yield depression even where all nutrients were supplied daily. Phosphorus availability was little affected by liming, and despite Mg and Zn addition, yields were depressed at high lime (pH 6.4) and high P while plants showed leaf symptoms of Mg deficiency. Neither plant nor soil analyses indicated low Mg levels but Ca: Mg ratios in soil were 22:1. When a pH range 5.2–6.1 was produced by liming with CaCO3 and MgCO3 at ratios between 100:0, and 50:50 on an equivalent basis, negative yield response was eliminated at Ca:Mg of 50:50. There was no evidence that Mg was fixed or rendered unavailable at the higher pH levels. A Ca induced Mg deficiency arising when exchangeable Ca:Mg>20 is suggested as the cause. The role of variable surface charge in converting soils that respond positively to lime to a negative response condition is discussed.

[1]  D. Wheeler,et al.  Effects of lime on the chemical composition of ryegrass and white clover grown on a yellow-brown loam , 1983 .

[2]  J. Grove,et al.  Lime Induced Magnesium Stress in Corn: Impact of Magnesium and Phosphorus Availability , 1985 .

[3]  A. Metson.  I. Some factors governing the availability of soil magnesium: A review , 1974 .

[4]  C. During.  Fertilisers and soils in New Zealand farming. , 1984 .

[5]  S. R. Olsen,et al.  Liming as Related to Solubility of P and Plant Growth in an Acid Tropical Soil 1 , 1973 .

[6]  A. C. Borges,et al.  Effect of liming levels and Ca:Mg ratios on yield, nitrogen content and nodulation of soyabeans grown in acid Cerrado soil , 1986 .

[7]  A. Juo,et al.  Liming and nutrient interactions in two Ultisols from Southern Nigeria , 1977, Plant and Soil.

[8]  M. Davis.  Growth and nutrition of legumes on a high country yellow-brown earth subsoil: III. The effect of lime , 1981 .

[9]  T. Wallace,et al.  The Diagnosis of Mineral Deficiencies in Plants by Visual Symptoms A Colour Atlas and Guide , 1943, Nature.

[10]  A. Metson,et al.  Magnesium in New Zealand soils , 1975 .

[11]  W. Lowther,et al.  The interaction of lime and phosphorus on the nodulation and growth of white clover. , 1970 .

[12]  P. Searle.  The measurement of soil cation exchange properties using the single extraction, silver thiourea method - an evaluation using a range of New Zealand soils , 1986 .

[13]  K. F. Nielsen.  Fertilizers and Soils in New Zealand Farming , 1975 .

[14]  D. Christenson,et al.  Yields and Magnesium Uptake by Plants as Affected by Soil pH and Calcium Levels1 , 1973 .

[15]  M. Sumner,et al.  Magnesium fixation—a possible cause of negative yield responses to lime applications , 1978 .

[16]  K. Mcnaught.  Diagnosis of mineral deficiencies in grass-legume pastures by plant analysis. , 1970 .

[17]  F. Adams,et al.  Magnesium Availability as Affected by Deficient and Adequate Levels of Potassium and Lime 1 , 1962 .

[18]  J. Syers,et al.  Effect of Lime on Exchangeable Magnesium in Variable Surface Charge Soils , 1981 .

[19]  A. Juo,et al.  A SINGLE‐EXTRACTION METHOD USING SILVER‐THIOUREA FOR MEASURING EXCHANGEABLE CATIONS AND EFFECTIVE CEC IN SOILS WITH VARIABLE CHARGES , 1980 .