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

Abstract

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.

Nutrients Uptake and Accumulation in Plant Parts of Fragrant Rosa Species Irrigated with Treated and Untreated Wastewater

“…Batarseh [64] found higher contents of Na and K accompanied by higher ECs in TWW and UTWW. These results were contrary with the findings of McDonnell et al [62], who stated that an excess of K in plant parts leads to a reduction in Na concentration. Alghobar and Suresha [65] stated that UTWW and TWW significantly increased the concentration of Na in plant tissues of rice crops.…”

“…This decreasing value to Ca under TWW and UTWW irrigation might be due to higher Mg and other nutrients (especially K) contents, which could have acted antagonistically to the Ca uptake by the roots [60]. According to documentation of McDonnell et al [62], an elevation in K level in plants is accompanied by a reduction in the contents Ca and Na.…”

Potential Nutrient Recovery in a Green Biorefinery for Production of Feed, Fuel and Fertilizer for Organic Farming

“…Indeed, the N:P:K ratio in the digestate is also similar to the N:P:K ratio in the mineral fertilizer (i.e. 4:1:6) utilized in that study, except for a lower proportion of K. The relatively high K content in the digestate might be beneficial upon fertilization of sandy soils, which generally present limited amounts of K and other nutrients because of the nutrient washing out resulting from the lack of binding sites [7,24]. However, the concentration of plant macronutrients in the digestate might be low for practical reasons.…”

Combining controlled-release urea with potassium chloride to reduce soil N/K leaching and promote growth of Italian ryegrass

“…KCl is commonly used in agricultural production. It has a low price and high nutrient content, and the application of appropriate amounts can promote the growth of Italian ryegrass 19 . In addition, K can improve the photosynthetic capacity and disease resistance of plants and then extend the green period 20 .…”