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Peter R. Hicklenton and Kenneth G. Cairns

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Peter R. Hicklenton and Kenneth G. Cairns

Nutrient release from Nutricote Type 100 (100-day N release; 16N-4.4P-8.1K), and from a 1:3 mixture of Nutricote Type 40 (40-day N release; 16N-4.4P-8.1K) and Type 100 was affected by time and temperature. The Type 40/100 mixture released nutrients more rapidly over a 5 to 35C range in laboratory studies. Seasonal growth of containerized cotoneaster (Cotoneaster dammeri C.K. Schneid `Coral Beauty') and juniper (Juniperus horizontalis Moench. `Plumosa Compacta') increased with increasing application rates of either Nutricote Type 100 or a 1:3 mixture of Type 40/100 over the range 2-10 kg·m-3. Between 25 June and 27 July, cotoneaster grew more rapidly in media with Type 40/100 Nutricote, but by the end of the season (27 Sept.), fertilizer type showed no effect on plant dry weight. Shoot N was higher in cotoneaster plants grown with Type 40/100 Nutricote than with the Type 100 formulation during the first 2 months of growth, reflecting the more rapid release and uptake of N from the mixture. During the last month the situation was reversed, as nutrients from the Type 40/100 mixture were depleted. Potassium and P shoot concentrations were not affected by fertilizer type. Juniper growth and shoot concentrations of N, K, and P were not affected by fertilizer type at any time during the season. The results provided no evidence that seasonal growth could be enhanced in either cotoneaster (grows rapidly) or juniper (slower growing) by mixing rapid and more slowly releasing types of Nutricote.

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Peter R. Hicklenton and Kenneth G. Cairns

Containerized Cotoneaster dammeri `Coral Beauty' and Forsythia `Northern Gold' were grown in a 2 bark: 1 peat: 1 sand (by volume) medium containing 5 kg·m–3 Nutricote 16N–4.4P–8.1K, Type 140, under four irrigation regimes: drip (DR; 20 min/day; two periods), overhead (OV; 90 min/day; two periods), overhead pulse (OP; 28 min/day; four periods), and subirrigation (SU). Volumes of 0.33, 0.35, and 0.14 liters·day–1 were delivered to each container in the DR, OV, and OP systems, respectively. SU was supplied from a geotextile-covered sand bed. End-of-season dry weights of Cotoneaster and Forsythia were 41% and 55% greater, respectively, in SU-grown plants compared to their OV-irrigated counterparts. Differences in growth between the other three regimes were minor for both species. Pre-dawn and dusk water potentials did not differ between plants in the four regimes, but midday potentials were slightly lower in SU- and DI-irrigated plants. End-of-season foliar N and P content differed only slightly between irrigation treatments, but K levels were significantly higher in SU plants. The reasons for better growth under SU remain obscure but may be related to improved medium nutrient retention and improved fertilizer use efficiency under an irrigation regime in which water moves upwards from the pot base to top.