Effects of Nitrogen and Potassium Fertilization on Perennial Ryegrass Cold Tolerance During Deacclimation in Late Winter and Early Spring

Abstract

<jats:p>Turf loss from freezing injury results in costly re-establishment, especially with turfgrasses such as perennial ryegrass (<jats:italic>Lolium perenne</jats:italic> L.) having poor low-temperature hardiness. Studies are limited as to the influence of N and K on cold tolerance during dehardening periods in late winter when grasses are most susceptible to freezing injury. The objective of this study was to evaluate perennial ryegrass low temperature hardiness during deacclimation in response to N and K and associated effects on crown hydration, median killing temperature (LT<jats:sub>50</jats:sub>), shoot growth rate, tissue K concentration, soil exchangeable K, and low temperature disease. Treatments included five rate levels of N (49, 147, 245, 343, and 441 kg·ha<jats:sup>-1</jats:sup>·yr<jats:sup>-1</jats:sup>) in all factorial combinations with 3 rate levels of K (49, 245, and 441 kg·ha<jats:sup>-1</jats:sup>·yr<jats:sup>-1</jats:sup>). Low temperature tolerance was assessed using whole plant survival and electrolyte leakage (EL). Interactions between N and K were detected for all field measurements. The effects of N and K on survival LT<jats:sub>50</jats:sub> were detected only during late winter periods in February 2004, N and K differences were lost by March. Late winter cold survival was negatively correlated with crown moisture, growth rate, and tissue K. Tissue K concentrations ranged from 28.6 to 35.9 g·kg<jats:sup>–1</jats:sup> DM while soil K ranged from 121 to 261 mg·kg<jats:sup>–1</jats:sup>. Soil extractable K was not correlated with tissue K. Survival and EL LT<jats:sub>50</jats:sub> were uncorrelated due to N and K interaction. Survival LT<jats:sub>50</jats:sub> ranged from –9.0 to –13.6 °C. Maximum cold hardiness occurred when low to moderate N (49 to 147 kg·ha<jats:sup>-1</jats:sup>·yr<jats:sup>-1</jats:sup>) was applied with medium-high to high levels of K (245 to 441 kg·ha<jats:sup>-1</jats:sup>·yr<jats:sup>-1</jats:sup>), which corresponded to soil exchangeable K levels ranging from 200 to 260 mg·kg<jats:sup>–1</jats:sup>. Alternatively, similar K fertilization and soil K levels combined with high rates of N (343 and 441 kg·ha<jats:sup>-1</jats:sup>·yr<jats:sup>-1</jats:sup>) increased freeze stress and low temperature fungi (<jats:italic>Typhula incarnata</jats:italic>). At N rates routinely applied to perennial ryegrass, higher soil extractable K beyond those levels currently recommended for optimum shoot growth could provide some benefit in enhancing cold hardiness. Late fall applied N did not appear to increase the potential for winter injury.</jats:p>

Effects of Nitrogen and Potassium on Wear Mechanisms in Perennial Ryegrass: I. Wear Tolerance and Recovery

“…Soil-available K in response to N-K treatments was similar to past studies (Webster and Ebdon, 2005), namely, soil-available K decreased linearly with increasing fertilizer N and increased linearly with increasing levels of applied K. By the termination of the study, all N-K combinations treated with 245 kg K ha -1 yr -1 and higher were medium high to very high in soil-available K, while N-K combinations treated with 49 kg K ha -1 yr -1 were medium to high in soil-available K depending on the N rate. Available soil K, averaged over 2006 and 2007 sampling periods, ranged from a low of 62 mg K kg -1 (medium) for the 441 kg N with 49 kg K ha -1 yr -1 treatment combination to a high of 274 mg K kg -1 (very high) for the 49 kg N with 441 kg K ha -1 yr -1 treatment combination.…”

“…No diff erence was observed with K except at 2WAT in 2007. This greater recovery promoted by potassium is most likely due to greater vigor and growth exhibited by perennial ryegrass that has been reported with this particular N-K treatment combination and species (Webster and Ebdon, 2005). Additionally, 441 kg K ha -1 in combination with 441 kg N ha -1 exhibited signifi cantly higher ratings during recovery at 2WAT than 49 and 245 kg K ha -1 yr -1 rates.…”

The Critical Role of Potassium in Plant Stress Response

“…Bogdevitch [96] found that oats that were supplied with sufficient K could survive late frost without obvious damage, whereas much of the crop that was grown on K-deficient soil did not survive. This finding could be attributed to a regulation of osmotic and water potential and a reduction of electrolyte leakage caused by cold stress [8,97]. High concentrations of K + protected against freezing by lowering the freezing point of the plant’s cell solution.…”

Context Matters for Warming: Interannual Variation in Grass Biomass Responses to 7 Years of Warming and N Addition

“…Similarly, warming can increase plant frost damage by melting the snowpack in mid-winter, prompting plants to deacclimate prematurely others 2009, 2011). N addition can increase vulnerability to winter frost damage in some species (Welterlen and Watschke 1985;Webster and Edbon 2005). Freezing damage to roots can also affect the ability of plants to take up N that becomes available or is added to the system over spring and summer (Tierney and others 2001;Vankoughnett and Henry 2013).…”