Measuring plant available phosphorus to increase crop yields and minimise nutrient leaching

磷是植物的关键营养素，需要作为肥料添加，以促进农作物的高效和经济生产。目前还没有通用的土壤测试可以可靠地预测应该添加多少肥料以获得最佳作物生长。如果添加太多，成本会很高，磷酸盐会泄漏到湖泊和河流中，造成严重的污染问题，称为富营养化。如果添加太少，作物产量就会很差，而且不经济。由于世界上可用的磷储量有限，因此情况十分危急。石灰土通常通过改善植物的养分供应而使酸性土壤受益，但由于锁定了部分磷酸盐，使其无法被植物利用，因此可能使磷酸盐问题进一步复杂化。一种名为DGT的新分析技术模拟了土壤中磷与植物相互作用的方式，可以很好地预测应该添加多少磷肥以实现最佳植物生长。在将DGT设备放置在土壤中期间，DGT积累的磷直到现在都是在实验室中使用常规程序测量的，但是可以提供即时读数的新的手持式XRF设备已经可用。该项目将首先确定DGT与便携式XRF分析可用于测量土壤中可用于植物的磷。它将把新的测量方法与现有的化学测试方法进行比较，并研究它在多大程度上可以用来预测在一系列土壤中生长的两种作物类型（一种芸苔作物和一种豆类作物）的肥料需求。在一组土壤被石灰化的实验中，新方法将被用来促进对石灰化如何影响植物磷的可用性以及石灰化如何可能影响磷向水体的释放（由于作物根区的沥滤）的理解。这项工作将为磷肥和石灰的施用策略提供信息，并为农民提供一个相当快速，更重要的是，可靠的评估肥料需求的工具提供基础。这项工作的成果将为农民带来明显的经济利益。减少农业土壤中的磷流失到水道中所产生的环境收益将使公众和与环境有关的政府机构受益，在某些情况下，通过限制从饮用水中去除磷的成本，水公司也将受益。

Phosphorus is a key nutrient for plants and needs to be added as fertiliser to facilitate efficient and economic production of agricultural crops. There is no general soil test which can reliably predict how much fertiliser should be added for optimal crop growth. If too much is added it is costly and phosphate can leak into lakes and rivers, causing severe pollution problems known as eutrophication. If too little is added crop yields are poor and uneconomic. The situation is critical because world reserves of usable phosphorus are limited. Liming soils, which generally benefits acidic soils by improving nutrient availability to plants may further complicate the phosphate problem by locking up part of the phosphate so that it cannot be used by plants. A new analytical technique called DGT, which mimics the way that phosphorus in the soil interacts with the plant, provides a good prediction of how much phosphate fertiliser should be added for optimal plant growth. The phosphorus accumulated by DGT during the placement of the DGT device in the soil has until now been measured in the laboratory using conventional procedures, but a new handheld XRF device that can provide an instant readout has become available. This project will first establish that DGT with analysis by portable XRF can used to measure the phosphorus in soils that is available to plants. It will compare the new measurement with established chemical tests and investigate how well it can be used to predict fertiliser requirements for two crop types (a brassica crop and a legume) grown in a range of soils. In a set of experiments where soils are limed, the new method will be used to advance understanding of how liming affects phosphorus availability to plants and of how liming is likely to affect the release of phosphorus to water bodies (due to leaching from the crop rootzone). This work will inform strategies for applying phosphate fertiliser and lime and provide a basis for providing farmers with a fairly rapid and, more importantly, reliable tool for assessing fertiliser requirements. The outcome of the work will provide clear economic benefits to farmers. Environmental gains stemming from reduced loss of phosphorus from agricultural soils into watercourses will benefit the general public and government agencies concerned with the environment, and in some cases water companies by limiting the costs of removing P from drinking water.