Many organically managed farms in Europe have low levels of soil phosphorus (P). Arable farms that rely strongly on biological nitrogen fixation (BNF) have been shown to have rather low outputs and a tendency to deplete soil P and potassium (K) compared with arable farms that have a lower reliance on BNF and higher external inputs. Therefore, research focusing on providing a balanced input of nitrogen (N), P, K and sulphur (S) from alternative sources is of interest to organically managed farms in Europe.

The aim of this study was to quantify P availability from different organic wastes applied alone or in combination to improve the mixtures’ N:P:K:S ratio. P availability was measured by P uptake and recovery in ryegrass grown in pots. The isotope dilution approach was used in which a non-labelled fertiliser is added to a soil that has been pre-incubated and equilibrated with labelled ³³P.

The P recovery of the different organic wastes varied significantly (10–20 %). Manure and anaerobically digested manure mixed with ash from straw had the lowest P recovery. All the organic waste treatments had higher plant growth and P uptake compared with the negative control, but none of them reached the values observed after application of mineral P. Mixing digested manure with ash increased soil pH at the end of the experiment, which may explain the lower P availability. The highest P recovery was found in digested products, either manure alone or mixed with municipal waste or the industrial waste product Fertigro®. However, the mixture of digested manure and Fertigro® led to lower dry matter production, whereas Fertigro® used alone resulted in high leaf P concentrations but depressed shoot and root growth, presumably due to salinity effects and a decrease in soil pH. Anaerobic digestion increased the availability of P, which may be explained by the lower immobilisation potential of the remaining organic matter in the digestate.

This study highlights the potential challenges when attempting to improve the N:P:K:S ratios of waste-based fertilisers through mixing due to material interactions. However, such effects are likely to be overexpressed in pot trials that have a limited soil volume. Field trials are therefore needed to quantify such effects in practice.

欧洲许多有机管理的农场土壤磷（P）水平较低。与对 BNF 依赖程度较低且外部投入较高的耕地相比，强烈依赖生物固氮 (BNF) 的耕地产量相当低，并且倾向于消耗土壤 P 和钾 (K)。因此，专注于从替代来源提供氮 (N)、P、K 和硫 (S) 的平衡输入的研究对欧洲的有机管理农场很感兴趣。

本研究的目的是量化单独或组合使用的不同有机废物的 P 可用性，以提高混合物的 N:P:K:S 比率。磷的有效性通过盆栽黑麦草的磷吸收和恢复来衡量。^{使用同位素稀释方法，其中将未标记的肥料添加到已用标记的33} P预孵育和平衡的土壤中。

不同有机废物的 P 回收率差异很大 (10-20%)。粪肥和厌氧消化粪肥与秸秆灰混合的磷回收率最低。与阴性对照相比，所有有机废物处理均具有更高的植物生长和磷吸收，但均未达到施用矿物磷后观察到的值。在实验结束时，将消化的粪便与灰分混合增加了土壤的 pH 值，这可以解释较低的 P 可用性。在消化产品中发现最高的 P 回收率，无论是单独的粪肥还是与城市废物或工业废物 Fertigro® 混合。然而，消化粪肥和 Fertigro® 的混合物导致干物质产量降低，而单独使用 Fertigro® 导致叶片 P 浓度高，但抑制了枝条和根部的生长，大概是由于盐分的影响和土壤pH值的降低。厌氧消化增加了磷的利用率，这可能是由于消化物中剩余有机物的较低固定化潜力。

本研究强调了在尝试通过混合材料相互作用来提高废物基肥料的 N:P:K:S 比率时的潜在挑战。然而，在土壤体积有限的盆栽试验中，这种影响可能会过度表达。因此，需要实地试验来量化实践中的这种影响。