The effects of irrigation and fertiliser regimes on N leaching from the production of couch grass (Cynodon dactylon L.) sod, on a free-draining sandy soil, were evaluated in a 22-month field study. The experimental design used a randomised-block, split-plot design with three replicates. Main plots consisted of two irrigation treatments: 70 and 140% daily replacement of pan evaporation; four subplot fertiliser types (watersoluble (predominately NH 4 NO 3 ), control-release, pelletised poultry manure and pelletised biosolids); and three N application rates (100, 200 and 300 kg N ha )1 per crop). Nitrogen leaching was assessed by measuring the leachate volumes and concentrations of N species leached from soil lysimeters (250 mm in diameter by 950 mm in length) installed in 10 m 2 turfgrass plots. Nitrogen leaching ranged from 33 to 167 kg N ha )1 over 22 months, depending upon the irrigation and fertiliser treatment. Irrigation treatment affected N leaching more than fertiliser treatment, and increasing the irrigation from 70 to 140% replacement of daily pan evaporation increased N leaching for all fertiliser types, and by up to four times. Forty six to 76% of losses occurred from the high irrigation treatments during the first 16 weeks after the turfgrass was planted as rhizomes. By contrast, N leaching did not appear to increase following harvest of sod. At the high irrigation treatment, N leaching was greater for the pelletised biosolids than the controlrelease; while at the low irrigation treatment, N leaching did not vary between fertiliser types. A significant proportion of the N leached was in the organic form. Therefore, we recommend total N and mineral N be measured when assessing N leaching from turfgrass. Nitrogen leaching from turfgrass production is low from all fertiliser types when the irrigation matches turfgrass water use and N is applied at a rate and frequency that approximates turfgrass requirements.

Excessive thatch and mat can be detrimental to turfgrass health and management. Mechanical and topdressing techniques to reduce accumulation of thatch and mat were evaluated in a 24-mo fi eld study of kikuyu [Pennisetum clandestinum (Hochst. ex Chiov.)] turfgrass of two contrasting organic matter (OM) contents in the surface 50 mm of soil. Treatments included two kikuyugrass ages (established from 20 wk or 20-yr-old kikuyugrass) and fi ve renovation techniques (none, verticutting, coring, topdressing with sand, coring + topdressing). Th e renovation techniques varied in eff ectiveness depending on the initial OM content of the soil immediately underlying the kikuyugrass. Annual verticutting, or twice annual topdressing with or without annual coring a young kikuyugrass were most successful at restricting the accumulation of soil OM (P < 0.05), with OM content <3.5% by 24 mo. Twice annual topdressing with or without annual coring, most rapidly decreased soil OM in the mature kikuyugrass (P < 0.05), with OM content averaging 6.2% by 24 mo. Combining coring with topdressing did not necessarily further decrease OM contents. Topdressing was up to three times more eff ective at reducing soil OM content than coring alone (P < 0.05). Th e color and N concentration of both kikuyugrass ages was maintained to local standards by all mechanical and topdressing techniques, although verticutting decreased the incidence of mower scalping in the second year. Verticutting was the most eff ective approach for restricting the progressive soft ening of young kikuyugrass with time (P < 0.05), whereas the mature kikuyugrass soft ened by the same amount irrespective of the renovation treatment.

Th e eff ect of N fertilizer rate on Kikuyu turfgrass [Pennisetum clandestinum (Hochst. ex Chiov)] evapotranspiration was evaluated during two summers. Evapotranspiration was measured using weighing lysimeters (205 mm in diameter by 625 mm in length) inserted in turfgrass fi eld plots (10 m 2 ). Th e experiment was a randomized plot design with three replicates. Treatments included two turfgrass ages (established from 20 wk or 20-yr-old turfgrass) and three N application rates (0, 50, or 150 kg N ha -1 yr -1 ). Evapotranspiration ranged from 2.8 to 7.5 mm d -1 (or 56-81% of evaporative demand), and varied with daily evaporative demand, turfgrass age, and N fertilizer rate. Th e older turfgrass used more water than the younger turfgrass during both summers; while increasing the N application rate also increased evapotranspiration for both turfgrass types (younger turfgrass only in the second summer). Evapotranspiration was positively correlated with turfgrass growth (r 2 = 0.74-0.80) and transpiring leaf area (r 2 = 0.78). Older turfgrass at all N treatments, and the younger turfgrass receiving 150 kg N ha -1 yr -1 , had adequate growth, color, and leaf N concentrations. Optimizing fertilizer applications such that the minimum N required to maintain turfgrass quality is applied, is an approach for decreasing water consumption by turfgrass.

The effects of N fertiliser regimes on N leaching and turfgrass quality during the establishment and maintenance of Kikuyu turfgrass (Pennisetum clandestinum (Holst. Ex Chiov)) were evaluated in a 24 month field study. Treatments included two turfgrass ages (established from 20 week or 20 year old turfgrass, the later included a 50 mm 'mat' layer), three N application rates (50, 100 or 150 kg N ha −1 yr −1 ) and three application frequencies (every 4 weeks, 4 applications per year, 2 applications per year); and included turfgrass plots that received no N fertiliser. Nitrogen leaching, measured using soil lysimeters, ranged from 35 to 69 kg N ha −1 by the end of 24 months, and varied with turfgrass age, but not N fertiliser regime. Greatest N losses occurred during turfgrass establishment, with up to 50% of all N leached in the organic form. We recommend measuring both total N and mineral N when assessing N leaching from turfgrass. The quality of the older turfgrass was maintained using less N fertiliser than the younger turfgrass, while increasing N application frequency improved the consistency of turfgrass growth and colour.

The effects on growth, quality and N uptake by turfgrass (Cynodon dactylon L.) during sod production of four fertiliser types applied at three application rates (100, 200 or 300 kg N ha )1 per 'crop') under two irrigation treatments (70% and 140% daily replacement of pan evaporation) were investigated. The fertiliser types were: water-soluble (predominately NH 4 NO 3 ), control-release, pelletised poultry manure, and pelletised biosolids; and the experiment was conducted on a sandy soil in a Mediterranean-type climate. Plots were established from rhizomes, with the turfgrass harvested as sod every 16-28 weeks depending upon the time of the year. Four crops were produced during the study. Applying water-soluble and controlrelease fertilisers doubled shoot growth and improved turfgrass greenness by up to 10% in comparison with plots receiving pelletised poultry manure and pelletised biosolids. Nitrogen uptake into the shoots after four crops (averaged across irrigation treatments and N rates) was 497 kg N ha )1 for the water-soluble fertiliser, 402 kg N ha )1 for the control-release, 188 kg N ha )1 for the pelletised poultry manure and 237 kg N ha )1 for the pelletised biosolids. Consequently, the agronomic nitrogen-use efficiency (NAE, kg DM kg )1 N applied) of the inorganic fertilisers was approximately twice that of the organic fertilisers. Increasing irrigation from 70% to 140% replacement of pan evaporation was detrimental to turfgrass growth and N uptake for the first crop when supplied with the water-soluble fertiliser. Under the low irrigation treatment, inorganic N fertilisers applied at 200-300 kg N ha )1 were adequate for production of turfgrass sod.