Determining the critical plant test potassium concentration for annual and Italian ryegrass on dairy pastures in south‐western Australia

Determining the critical plant test potassium concentration for annual and Italian ryegrass on dairy pastures in south‐western Australia

Potassium fertilization in intensive grassland systems is particularly important on sandy soils with limited K storage capacity. A 3‐year plot experiment was conducted in south‐western Australia to determine the critical K concentration in herbage dry matter (DM) of annual and Italian ryegrass requi...

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Bibliographic Details
Published in:Grass and forage science Vol. 73; no. 1; pp. 112 - 122
Main Authors: McDonnell, R. P., Staines, M. vH, Bolland, M. D. A.
Format: Journal Article
Language:English
Published: Oxford Wiley Subscription Services, Inc 01-03-2018
Subjects:
Calcium
Colwell K
Defoliation
Dry matter
Factorial design
Fertilization
Fertilizer application
Fertilizers
Grassland management
Grasslands
Hydroxyapatite
Lolium multiflorum
Lolium perenne
Lolium rigidum
Magnesium
maximum yield
Pasture
Potassium
Regrowth
sandy soil
Sandy soils
Sodium
Soil management
Storage capacity
Yield
Australia
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Summary:Potassium fertilization in intensive grassland systems is particularly important on sandy soils with limited K storage capacity. A 3‐year plot experiment was conducted in south‐western Australia to determine the critical K concentration in herbage dry matter (DM) of annual and Italian ryegrass required to achieve 0.95 of the maximum yield, under best‐practice grassland management. A factorial design was employed with eight fertilizer K rates (range 0–360 kg ha−1 year−1) and two ryegrass species replicated four times, on a sandy soil site managed over 7 years to deplete mean soil Colwell K concentration to 42 mg/kg. Herbage was defoliated six times per year at the 3‐leaf stage of regrowth. Herbage DM yield, macronutrient and micronutrient concentrations were measured at each defoliation. Dry‐matter yield increased significantly (p < .001) with increasing levels of K fertilizer in all 3 years and the effect was curvilinear, while 0.95 of the maximum herbage DM yield was achieved at an annual K fertilizer application rate of 96, 96 and 79 kg/ha respectively. At these K fertilizer application levels, the mean K concentration of herbage DM over the 3 years was derived to be 11.4, 12.7 and 11.2 g/kg respectively. Sodium, magnesium and calcium concentrations of herbage DM all declined significantly (p < .001) as the K concentration increased. Grassland producers on sandy soils should target a K concentration in herbage DM of 16 g/kg for annual ryegrass and Italian ryegrass‐dominant swards to ensure K availability is not limiting herbage production.
ISSN:0142-5242
1365-2494
DOI:10.1111/gfs.12286