Critical Leaf Concentrations for Deficiencies of Nitrogen, Potassium, Phosphorus, Sulphur, and Magnesium in Perennial Ryegrass

Abstract

SUMMARYCritical leaf concentrations for deficiency of nitrogen, potassium, phosphorus, sulphur, and magnesium were estimated for perennial ryegrass {Lolium perenne L.) grown in sand culture. The values associated with a 10% reduction in dry matter yield were as follows (all results expressed as g kg~^ DM except for the nitrate-nitrogen value which appears as /ig g~^ DM): Kjeldahl-nitrogen 32; nitrate-nitrogen 500; potassium 28; phosphorus 21; sulphur 18; and magnesium 0-7. A major difference between the critical leaf concentrations estimated in this study and the tentative values published elsewhere was for potassium. Concentrations required in the shoot for near maximum growth were higher than previously reported. Differences in the nitrogen status of the plants probably account for this result. The depressing effect of potassium on the absorption of magnesium and calcium is discussed in relation to plant and animal nutrition. Sulphur was found to be inefficiently absorbed by phosphorus deficient plants despite non-limiting amounts of sulphur applied in the nutrient solution. A possible explanation for this effect may be linked to the observation that the transport of sulphate into the chloroplast was coupled with that of phosphate. The concentration of macroelements required in the nutrient solution to produce maximum shoot growth of perennial ryegrass was very much greater than that generally applied to plants grown in sand culture.

Effects of Biosolids-Derived Organomineral Fertilizers, Urea, and Biosolids Granules on Crop and Soil Established with Ryegrass (Lolium perenne L.)

“…Nitrogen in harvested plant material recorded with OMF and urea applied at 300 kg ha −1 of N were relatively lower (range: 2.2-2.8%) than a critical leaf concentration for deficiency of N of 3.2% by weight (Smith, Cornforth, and Henderson 1985). This threshold value is defined as N concentration in the leaves below which reductions in maximum yield of 10% or greater may occur due to insufficient supply of that nutrient (Smith, Cornforth, and Henderson 1985). However, nitrogen in harvested plant material with OMF and urea were within the range required by high-producing dairy cattle (Aavola and Kärner 2008).…”

“…Low N supply to grass crops compromises growth rate, tiller density, and biomass production, and reduces N concentration in plant (Wilman and Mohamed 1980;Delagarde, Peyraud, and Delaby 1997). Nitrogen in harvested plant material recorded with OMF and urea applied at 300 kg ha −1 of N were relatively lower (range: 2.2-2.8%) than a critical leaf concentration for deficiency of N of 3.2% by weight (Smith, Cornforth, and Henderson 1985). This threshold value is defined as N concentration in the leaves below which reductions in maximum yield of 10% or greater may occur due to insufficient supply of that nutrient (Smith, Cornforth, and Henderson 1985).…”

Potassium requirement for leaf biomass yield and K nutrition of stevia

“…Yin and Vyn (2004) estimated the critical leaf K concentration for maximum yield of soybeans to be 25.9 g kg -1 . Smith et al (1985) showed that perennial ryegrass produced 98% of the maximum dry matter where K concentrations in the shoots were greater than 36 g kg -1 .…”

Animal Health Problems Caused by Silicon and Other Mineral Imbalances

“…However, increases in solution K concentration reduce uptake of both Ca and Mg by plants, even at higher solution K levels resulting in less than maximum forage yield. Smith et al (1985) reported that Mg concentrations level out at 1.9 g kg" when herbage contains 25 g K kg"; whereas Ca concentration continues to decrease to a low of 6 g kg" as forage K increases to 65 g K kg". High herbage K levels also depresses Mg and Ca absorption by ruminants.…”