Aims

Struvite (MgNH₄PO₄·6H₂O), a low water solubility (<3%) mineral that is increasingly recovered from wastewater treatment plants, has potential to be used as a slow release ammonium phosphate fertilizer, especially when blended with highly water soluble phosphorus (P) fertilizers such as monoammonium phosphate (MAP).

Methods

Maize and soybean were fertilized using a gradient of struvite substitution for MAP, entailing five struvite: MAP blends in a factorial combination with struvite granule size (1.5, 3.0 mm diameter) and fertilizer placement (incorporation, banding). Crop biomass, and P and N uptake (total, concentration) were used to evaluate crop response, and post-harvest soil Mehlich-3 P was measured to assess soluble P loss risk.

Results

Maize biomass response was similar using up to 50% struvite and similar in soybean using up to 25% struvite. Total P uptake by maize was similar across 0–75% struvite blends, but significantly lower for 100% struvite. Maize apparent fertilizer P uptake and apparent fertilizer P uptake efficiency was greatest for 100% MAP. Despite differences in biomass, soybean apparent fertilizer P uptake and apparent P use efficiency were similar across struvite blends. Soybean P uptake was significantly greater when fertilized with 100% struvite than with 25 and 50% struvite. Inverse correlation of plant P and N concentrations with biomass indicated a biomass dilution effect. Residual soil Mehlich-3 P decreased with increasing struvite substitution of MAP.

Conclusions

Struvite:MAP blends (25–50% struvite) appear to lower soluble P loss risk compared to MAP without restricting early season (vegetative) growth of maize and soybean, and this can differ by crop species.

中文翻译：

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鸟粪石和磷酸一铵共混物对玉米和大豆的磷肥响应

目的

鸟粪石（MgNH ₄ PO ₄ ·6H ₂ O）是一种低水溶性（<3％）的矿物，越来越多地从废水处理厂回收，有潜力用作缓释磷酸铵肥料，尤其是与高水混合时可溶性磷（P）肥料，例如磷酸一铵（MAP）。

方法

玉米和大豆使用鸟粪石替代MAP进行梯度施肥，需要五种鸟粪石：MAP混合，并具有鸟粪石颗粒尺寸（1.5、3.0毫米直径）和肥料定位（掺入，捆扎）。使用作物生物量以及磷和氮的吸收（总量，浓度）评估作物的反应，并测量收获后土壤Mehlich-3 P的含量以评估可溶性磷的损失风险。

结果

使用高达50％鸟粪石的玉米生物量响应相似，而使用25％鸟粪石的大豆生物量响应相似。在0-75％的鸟粪石混合物中，玉米的总P吸收量相似，但对于100％的鸟粪石则显着降低。对于100％的MAP，玉米的表观肥料P吸收量和表观肥料P吸收效率最高。尽管生物量存在差异，但在鸟粪石混合物中，大豆表观肥料对磷的吸收和表观磷的利用效率相似。施以100％鸟粪石比施以25％和50％鸟粪石施肥时，大豆P吸收显着更大。植物P和N浓度与生物量成反比，表明生物量稀释作用。残存土壤Mehlich-3 P随着MAP的鸟粪石替代增加而降低。

结论

鸟粪石：MAP混合物（25-50％鸟粪石）与MAP相比似乎具有较低的可溶性磷流失风险，而没有限制玉米和大豆的早期（营养性）生长，并且这可能因作物种类而异。