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Sustainable improvement of vegetable quality, water and nutrient use efficiency using dynamic fertigation - HL0165LFV

Aim of Initiative
To increase efficiency of inputs in the production of perishable field vegetable crops, reduce wastage in the retail sector, and in line with impending regulatory pressures, to provide an integrated framework for the precise scheduling and delivery of water and nutrients to the root zone to manage crop quality, marketable yield and shelf-life. This will be driven by developing an understanding of the influence of nutrient supply during development on crop quality, and the physical principles governing the precise application of water and nutrients in a sustainable way.

Commercial and Technical Background

· Increasingly, the retailer has to provide quality guarantees for perishable produce to the consumer, who needs assurance that the fresh vegetables he buys is produced in a safe and environmentally-sustainable system. The retailer needs to compete on price and this can only be achieved through efficient management of the retail supply chain to optimise quality at each stage, whilst reducing material wastage and associated transport and packaging costs.

· Increased consumer demand for high quality fresh convenience produce is driving rapid market growth in the added value prepared salads and prepacked vegetable sectors. Fresh produce is highly perishable and significant wastage is seen throughout the chain, from producer to retailer and consumer. Techniques are needed that improve resource use efficiency in a way that enables effective management of raw material quality from the field to the consumer, whilst increasing supply chain efficiency to deliver good value to the consumer with minimal environmental impact.

· Conventional fertiliser applications do not necessarily ensure nutrient supply is optimised at all growth stages. Growers may fertilise as insurance against nutrient stress, tending to over-apply fertilisers, which when coupled with high water inputs (poor irrigation management or heavy rain) results in strong leaching to the environment. Under supra-optimal nutrient conditions, crops can accumulate 'luxury' amounts of the nutrient in their foliage resulting in elevated foliar nitrate levels. There is therefore an urgent need for more targeted fertiliser use, with greater efforts being devoted to developing efficient methods of nutrient management, particularly through using drip fertigation technology, which is far more efficient than conventionally-use overhead irrigation systems. Fertigation, the combination of irrigation and fertiliser application, offers opportunities for precision manipulation of nutrient supply during growth, whilst increasing the efficiency of water and nutrient application.

· Model systems need to be studied in order to provide the basis for extrapolation to a wide range of field vegetable crops. Salads and beans have been selected as the model crop species as they are both high value crops with expanding market potential. Both require intensive labour and resource inputs and both are grown in the country's nitrogen vulnerable zones (NVZs) and therefore need careful management to meet legislation relating to nutrient runoff. Salad crops represent a model short-season, vegetative leafy vegetable, whilst beans represent a long-season reproductive legume with marked phenological developmental stages.
· The UK field salad and bean growers have identified a need for sustainable systems for improving efficient application of water and nutrients in order to minimise leaching and pollution of water resources, whilst effectively managing marketable yield and quality at harvest and post-harvest.

· The industry wishes to exploit fertigation approaches to achieve this, but the scientific information for implementing the technology reliably under UK conditions needs developing. Novel drip irrigation software, developed for semi-arid regions, needs to be adapted for UK use. The use of drip irrigation offers the possibility of efficient, targeted application and manipulation of water and nutrients during crop development to a far greater extent than is possible using conventional solid fertilisers. This technology needs to integrate knowledge of nutrient manipulation with automated systems for monitoring and controlling soil moisture and conductivity, currently being developed by project consortium members, in order to increase efficiency and consistency of application.

The Problem/Opportunity

· "The UK is a water scarce country and quality demands are increasing" (quote Jacob Tompkins, Policy Development Adviser, Water UK). The UK Draft Water Bill and EU Water Framework Directive puts increased legislative pressure on growers to improve water use efficiency, including the licencing of abstraction for trickle irrigation, with new EU legislation defining maximum nitrate levels in edible produce (3). The establishment of NVZs restricts the timing and seasonal levels of organic nitrogen application to a maximum of 210 kg/ha reducing to 170 kg/ha total N which must be limited to crop use (after 19/12/2002), with financial penalties of up to £20,000 for those prosecuted by the Environment Agency for consistent failure to comply. Efficient, accurate application of N to meet crop requirement is an essential part of conforming to the legislation. Most salad and bean producers will be located in flat, low-lying floodplains designated as NVZ areas. Investment in technologies that improve water and nutrient use efficiency will be essential to meet these legislative requirements.

· New developments in the areas of soil moisture and pore water conductivity measurement technology provide new opportunities for adapting and developing systems to deliver precise control of root zone moisture and nutrient supply with maximum efficiency. The proposed research offers improved timing, rate and spatial delivery of moisture and nutrients for optimising quality in the UK, but will need to be adapted and evaluated before it can be applied reliably to UK crops and situations.

· The ‘Bag Salad’ industry has enjoyed considerable growth in the last decade. It has achieved this largely through increased market penetration – more consumers / households purchasing the product. Market penetration is now estimated at around 70%. As the market for prepared salads matures (and penetration reaches it’s ceiling), further growth will be driven by increased ‘frequency of purchase’ and ‘weight of purchase’.

· One significant barrier to increasing these factors is the apparent shelf life of the product. It is known that 78% of purchases are consumed within 2 days – consumers (who shop weekly) are unable to buy salads reliably for consumption over the whole week. Consequently, extending the shelf life has the potential to significantly increase the number of units purchased at a time.

· Cut salad crops are prone to high wastage pre- and post-processing (30%) so that while recent annual market growth has been 15-20%, sustaining future expansion will depend upon improvements in production efficiency, crop quality and reduction of wastage in the field, factory and retail chain to encourage repeat purchase by the consumer.

· Runner beans suffer from high levels of flower and pod abortion, combined with up to 50% wastage at early harvests due to pod quality defects and although drip irrigation is already used for bean production, little known about scheduling nutrient supply during development and how this influences quality and wastage.

· Increased pressure for quality assurance in the retail chain requires improved systems for batch quality control and produce management. The industry needs to evaluate techniques for objective quality measurement and prediction that can be developed as diagnostic instruments.

Previous DEFRA and EU-funded research at HRI in hydroponic systems has shown that manipulation of N, P, K and Ca in beans and salads influences growth, development, yield (1) and post-processing quality (2), yet there is little understanding of the influence of nutrient supply on quality (and particularly post-harvest quality) in soil-based systems. HortLINK and EU funded research at HRI (projects HortLink 232, EU FA-S2-CT98-9089) have demonstrated that the quality of field-grown processed salads can be influenced by nutrient supply, which is one of the few factors that growers can control.

Proposed Research will

(i) optimise the efficiency of delivery and utilisation of water and nutrients in the root zone for Green Batavia - a model salad and Runner Bean - a model legume crop;
(ii) identify and quantify the interactions between nutrient supply and quality, at harvest and post-harvest;
(iii) result in development of a new soil sensor combined with soil infiltration models, to give closed-loop feedback irrigation control;
(iv) evaluate the potential for quality assessment and prediction of quality using colorimetry and chlorophyll fluorescence.

The project will deliver improved protocols for efficient application of irrigation and nutrients for quality management in field vegetable crops. It will improve the efficiency of the whole supply chain, reduce material wastage and form the basis for development of an integrated framework for precise delivery of water and nutrients to the root zone appropriate to environmental conditions and the stage of crop development.

Project Documents
• Abstract : HL0165 Abstract   (21k)
Time-Scale and Cost
From: 2003

To: 2007

Cost: £683,616
Contractor / Funded Organisations
Geest PLC, Horticulture Research International, Field (GB) Ltd, Biohybrids International Limited, Tesco Stores Plc, RJM Consultancy, Delta-T Devices, Earthcare Environmental Ltd, Fairfield Control Systems Ltd, Kemira Agro Oy, Bomfords, J E Piccaver & Co (Gedney Marsh), ADC Bioscientific, Anglian Water Services Ltd, Intercrop Ltd
Natural Resource Use              
Natural Resources and Labour              
Sustainable Farming and Food              
Waste Management              
Fields of Study