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Targeting Phosphorus-Fertiliser Applications to Roots of Wide-Row Crops - HH3509SFV

Plants require phosphorus (P), which they acquire from the soil solution as phosphate [1,2]. Horticulture relies on large inputs of P fertilisers to maintain crop yields and quality. However, horticultural crops generally recover less than 10% of any broadcast P fertiliser in the year it is applied [3,4]. Unfortunately, some of the excess P may be leached from soils as soluble phosphates, or lost by erosion as P bound to soil particles [5-8]. This can lead to diffuse pollution of surface waters, nutrient enrichment of adjacent environments, and a consequent loss of habitats and decline in biodiversity. Therefore, it makes financial and environmental sense to reduce P fertilisation of horticultural crops. It has been observed that both P-inputs, and the P lost to the environment, can be reduced in some wide-row crops by placing a concentrated ‘starter’ P-fertiliser in the vicinity of the developing root system, rather than by broadcasting P-fertilisers [9-12]. The placement of starter fertiliser close to the roots appears to improve the uniformity of a crop, as well as accelerating rooting and early plant growth. Inefficient P fertilisation is a particular problem for the potato crop, which is grown on about 2.5% of arable land and consumes about 8% of the P-fertiliser applied in the UK, and land growing potatoes contributes significantly to P enrichment of surface waters [12]. Evidence in the literature suggests that placing P-fertilisers close to the roots of young potato plants can result in more efficient capture of fertiliser P and often results in a small increase in yield [13-19]. However, the agronomy of P-fertiliser placement has not been investigated systematically, and the physiological traits required of plants to optimise placed P-fertilisers are unknown. The purpose of this project is, therefore, to determine to what extent P inputs to wide-row crops can be reduced by placing starter P-fertiliser within the root zone. The question will be addressed for wide-row crops generally, and then specifically for potato. The later work will focus on elucidating root traits important for P acquisition by young potatoes, and quantifying their genetic diversity and heritability. The project has five objectives: (1) To identify wide-row horticultural crops that may benefit from P-fertiliser placement. This will be achieved through a review of available literature complemented with new data from field trials assaying the effect of P-fertiliser placement on the yield of maize, cabbage, carrot, lettuce, maize, onion and potato. (2) To determine the minimal P-fertiliser placement required to maintain yields of potato. This will be addressed by field experiments in which the P-fertiliser concentration and width of placement are systematically varied. (3) To characterise the genetic diversity and heritability of rooting, P acquisition and early growth traits of 25 potato varieties in the glasshouse. This will provide data on the ability of different potato genotypes to exploit placed P-fertiliser. (4) To identify potato genotypes that respond well to P-fertiliser placement in the field. (5) To develop a mathematical model describing the development of the potato root system and its affect on P acquisition, plant growth and yield. This model will incorporate data from both glasshouse and field experiments. It will be used both to identify root traits that may impact on the interception and uptake of placed P-fertiliser and to predict the effects of P-fertiliser placement strategies on plant growth and crop yield. This project will deliver information to Defra, to the Industry and to the scientific community. It will deliver: (1) a general appraisal of the effectiveness of P-fertiliser placement for reducing P-fertiliser inputs to wide-row crops (2) a study of the responsiveness of potatoes to P-fertiliser placement and recommendations for P-fertilisation of potatoes, (3) basic scientific information on the genetic control of the physiological responses of the potato root system to P-fertiliser placement and (4) a mathematical model to describe the growth and P-foraging characteristics of the potato root system. It will provide information to support future RB209 recommendations [20]. The adoption of such knowledge may ultimately contribute to a reduction in the use of P fertilisers on potatoes and other wide-row crops. This will lower costs, reduce pollution and enhance biodiversity. The project will also provide basic scientific information on the root morphology of potato, and its response to P-fertiliser placement. A comparison of rooting, P acquisition and early growth traits of different potato genotypes with their performance in the field will allow the importance of these traits for the exploitation of P-fertiliser placement to be determined. The development of a mathematical model to describe the development and P acquisition by the potato root system will be used to identify rooting traits that would optimise the exploitation of P-fertiliser placement for improved yields that might be used in varietal screens. The project addresses Defra’s immediate policy objectives to minimise fertiliser inputs and reduce agricultural pollution. It follows the UK Government’s policy of fertiliser and chemical minimisation in line with recent EU directives. Generic research on fertiliser placement to minimise P inputs to horticulture was recommended in a recent Defra-funded review of the potential for reductions of nitrogen and phosphorus inputs in current farm systems [8] and specific research on the effects of P-fertiliser placement on potato yields was recommended in a Defra-funded review of the response of potatoes to phosphate [12]. The project will deliver to Defra's scientific targets in HH35: (1) robust strategies to maximise the efficient use of P fertilisers for crop production while minimising impact on the environment in the context of precision farming, (2) identification of horticultural crops and potato varieties responsive to P fertiliser placement, and (3) information on the physiological and genetic characteristics required for optimal exploitation of P fertiliser placement.
01. To assess the potential of P-fertiliser placement to reduce P inputs to wide-row crops (within 12 months)
02. To perform three field trials to determine the minimal P-fertiliser placement required to maintain potato yields (within 48 months).
03. To characterise the early growth, P acquisition and rooting patterns of potato genotypes in glasshouse experiments (within 54 months).
04. To identify potato genotypes that respond well to P-fertiliser placement in field trials (within 54 months).
05. To develop a mathematical model describing the development of the potato root system and its affect on P acquisition (60 months).
Project Documents
• FRP - Final Report : sid5 HH3509SFV   (2391k)
• Annual Report : Targeting phosphorus-fertiliser applications to roots of wide-row crops   (1336k)
Time-Scale and Cost
From: 2005

To: 2010

Cost: £627,610
Contractor / Funded Organisations
Warwick - HRI
Allocated - WHRI              
Natural Resource Use              
Sustainable Farming and Food              
Fields of Study