The overall aim of the project is to develop recommendations for demand-driven fertilisation and in this way create a more environmentally friendly and economic way of fertilisation. The project was carried out in two steps, one in a climate chamber (Ultuna) and one in the field (Landvik) with creeping bentgrass, velvet bentgrass, colonial bentgrass, chewings fescue and slender creeping red fescue. Annual bluegrass was also initially included in the study, but had to be excluded due to heavy nematode infestation.
The main results from the growth chamber study confirmed that turf grasses do not deviate in any major respect from other plant species with regard to the influence of shoot N concentration on growth-related processes. Root development, leaf stiffness and fructan storage are all favoured when the shoot N concentration is low, i.e. when the rate of N supply limits growth. Factors negatively affecting growth such as shade, drought, low cutting height and high or low temperatures will reduce nutrient requirements. As a consequence, N supply must be reduced to meet the decreased nutrient needs and thereby prevent the shoot N concentration from increasing, which will otherwise negatively affect root growth, carbohydrate storage and leaf morphology, and hence playing quality. Thus, irrespective of whether the aim is high playing quality or fast growth in order to repair damage, choice of the appropriate shoot N concentration and the ability to maintain this N concentration at a constant level throughout the growing season are crucial for turf development.
A nitrogen concentration of approximately 3.3% in dry leaves is enough for achieving a healthy turf and high playing quality of both fescues and bentgrasses. Values of 5% in fescues and 6% in bentgrasses represent the upper limits when fast growth is required.
Creeping bentgrass was ranked highest with regard to nutrient demand and required 30% more N compared with colonial and velvet bentgrass and twice as much N as fescues.
Based on our results from the field and climate chamber studies, we drew the conclusion that day length and temperature, together with the growth potential of the species, can successfully be used as driving variables when quantifying the running fertiliser needs from early spring to late autumn. In this way, stability in shoot N status can be achieved. The risk of exceeding the N uptake ability of the turf, and hence causing nutrient leaching, is low as long as the growth capacity of the turf is not fully used.
Department of Urban and Rural Development
Swedish University of Agricultural Science