Introduction (see text pg 187-190)

Seasonal pasture growth curves for New Zealand and Ohio (NB 6-months out of phase)

Climate drives seasonality

	Spring – growth promoted by increasing temperature, increasing light intensity & increasing daylength. Vigorous reproductive phase - growth is 15% greater than would be predicted from climate alone. Physiological studies have not found inherently greater efficiency, but rather i) initial growth is from root reserves, ii) relatively less carbon allocation to roots, iii) slower turnover of flag leaves & iv) taller canopy has better light harvesting Initial spring growth has high quality, Late spring growth (with seed head) typically has low quality
	Summer heat, drought, close grazing decrease growth Lowest forage quality – due to accumulated dead matter (rather than increased death rate)
	Autumn ideal growth conditions, compensatory growth following drought critical period for building carbohydrate reserves in roots and crowns, and building a winter stockpile
	Winter freezing injury, cold prevents growth, only small variation (1-2 weeks) in duration of winter high risk of heaving in alfalfa (esp for a late winter freeze-thaw cycle) high risk of frost kill of ryegrass

  Implications of seasonality

	Inconsistent provision to grazing animals (quality and quantity)
	Need management systems to address surplus and deficit ? additional cost
	Typically in USA this involves housing livestock and confinement feeding, however lower a cost option is to explicitly manage seasonal growth and the seasonal supply of forage

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  Manipulating seasonality

	Many options are available - but relatively small effects
	Grazing: Close fall grazing can deplete carbohydrate status and reduce winter survival Infrequent spring grazing can increase spring yield through allowing seed head development, but will reduce quality Close late-spring grazing can promote tillering and accelerate drought recovery Close summer grazing can intensify drought effects through reduced root growth and heating of soil
	Fertilizer management: Fertilized forage has faster drought recovery During drought – forages are unresponsive to fertilizer Fall K applications can improve alfalfa winter-hardiness Shoulder-season production is increased by fertilizing – but through overall increase in the growth curve
	Irrigation will maximize summer growth – but at a cost
	Forage management. Short-term surplus or deficit of forage will result in an increase or decrease of farm forage cover
	Stockpiled forage during Fall can accumulate sufficient mass (low quality) to get a grazing herd through winter (pg 188)

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  Species effects

	C3 and C4 species Warm-season grasses have poor spring and fall production, but high summer production. Seasonal growth patterns are complementary with cool-season forages, and can result in greater animal production. In Ohio warm-season grasses have less annual yield but high summer production. They are not widely used in Ohio, greater use in western and southern states
	Grasses and legumes Complementary growth patterns – white clover, red clover and alfalfa all have higher summer production
	Grasses have different flowering dates and hence different peaks in spring growth. Annuals are typically earlier than perennials, cultivar differences can be larger than differences between species (see early and late varieties of orchardgrass – OSU)
	Orchardgrass and fescue have better summer production, timothy and kentucky bluegrass have poor summer production ? a case for mixing these i) within fields, ii) within a farm
	Shoulder season production can be achieved with annuals (ryegrass, cereal rye, turnips). There are few options in permanent grasslands.

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