Nitrogen-fertilised grass in a subtropical dairy system. 1. Effect of level of nitrogen fertiliser on pasture yield and soil chemical characteristics

Abstract

The effects of five levels of nitrogen (N) fertiliser on pasture yield and composition and soil chemical characteristics of Rhodes grass (Cholris gayana) cv. Pasture under grazing and cutting in a subtropical environment of 800 mm annual rainfall were studied over 6 years. Pasture received annual basal dressings of superphosphate (250 kg/ha) and potassium chloride (125 kg/ha for plots, 125 kg/ha . alternate year for grazed paddocks). Urea was applied in 3 equal dressings in September, December, and February, at rates equal to 0, 150, 300, 450, and 600 kg N/ha. year. Stocking rate was 2 Holstein-Friesian milking cows/ha throughout the year, and separate areas of grazing oats (0.4 ha/cow), cracked grain (0.8 t/cow.year), and hay or silage were used to supplement pasture. Under both cutting and grazing, pasture dry matter (DM) yield increased linearly with applied N to about 300 kg N/ha. year, with little further increase at higher levels. Under grazing there was evidence of a decrease in yield at 600 kg N/ha.year, due to total death of the pasture following frosting in winter and the need for regeneration from seedlings in spring; this regeneration was slowed by the large amount of surface litter. Grass N contents decreased and phosphorus and potassium contents decreased with increasing levels of applied N. All 3 nutrients increased from year 1 to 6. Leaf content of grazed pasture was highest during spring (>30% DM) and declined through to autumn (<20% DM), with no consistent effect of N level. Leaf content was consistently higher under cutting (>50%) but was not altered by level of applied N. Soil nitrate-N levels increased (P<0.05) with level of applied N, from 4 to 42 mg/L at 0 and 600 kg N/ha. year, respectively. After 6 years of fertilisation at 300 and 450 N/ha.year, nitrate-N levels were similar to those for 600 kg N/ha.year. Soil pH decreased (P<0.05) with applied N, by 0.15 and 0.28 units annually for 150 and 600 kg N/ha.year, respectively. We conclude that in this environment large responses in pasture growth occur under both cutting and grazing to levels of applied N to about 300 kg N/ha.year, with little response beyond this level.

Comparative productivity of irrigated short-term ryegrass (Lolium multiflorum) pasture receiving nitrogen, grown alone or in a mixture with white (Trifolium repens) and Persian (T. resupinatum) clovers

“…The values in this study for efficiency of N use are similar to those for perennial ryegrass (Sollenberger et al 1984), irrigated oats and raingrown Callide Rhodes grass (Cowan et al 1995), but less than those for raingrown tropical grasses (Henzell 1963) and orchardgrass (Sollenberger et al 1984). First year results in this study are similar to those on Italian ryegrass in South Africa by Eckard (1989), but the second and third year results were lower.…”

“…A study by Steele (1976) showed little movement down the profile of a podsolic soil from an application of 100 kg N/ha as urea in solution. Cowan et al (1995) also showed little movement down the profile of a heavy clay soil at equivalent rates to those used in our study. Our data has, however, been derived from sowings in different paddocks each year.…”

Herbage production and persistence of two tropical perennial grasses and forage sorghum under different nitrogen fertilization and defoliation regimes in a summer‐dominant rainfall environment, Australia

“…Slow recovery from winter has also been reported for Rhodes grass cv. Callide in Queensland dairy pastures in south‐east Queensland (Cowan et al ., ; Lowe et al ., ). Lowe et al .…”

Scope to improve phosphorus (P) management and balance efficiency of crop and pasture soils with contrasting P status and buffering indices

“…Farm-gate data for 339 enterprises and an additional 437 records data for specific products were drawn from a number of sources (Ayers et al 1977a, b;Southwood et al 1976;McCaskill and Cayley 2000;Chapman et al 2003;Li et al 2006;Simpson et al 2010;Burkitt et al 2007;Russell 1960;Cannon 1969;Morley et al 1969;Curll and Smith 1977;Lloyd Davies et al 1998;Waller et al 2001a,b;Holst et al 2006;McGregor 2010a,b;Stockdale and King 1980;King and Stockdale 1980;Cowan et al 1995;Curll 1977;Carter and Day 1970;Ovens et al 2008;Weaver et al 2008;Bell 2009). For the 339 enterprises, there were 159 farm-gate budgets for beef, 78 for dairy, 28 for mixed cropping and grazing, 7 for cropping and 67 for sheep.…”