In soils managed to have adequate to high Mehlich‐3 phosphorus (P) concentrations throughout the US Maize Belt, the majority of crop P is soil‐derived. Struvite, a low water solubility ammonium phosphate fertilizer, may be therefore substituted for relatively high water‐soluble monoammonium phosphate (MAP) without adversely impacting maize (Zea mays L.) P uptake and growth, while minimizing fertilizer P loss risk. We determined the relative contribution of struvite and MAP to maize P uptake and soil solution P in soils representative of the US Maize Belt by radiolabelling fertilizers with 33P. We found 8% (struvite) to 22% (MAP) of early‐to‐mid vegetative growth stage (V7) maize P was fertilizer‐derived, and thus, 78%–92% was soil‐derived. Despite similar aboveground P uptake and maize growth, maize P use efficiency (PUE) determined directly by 33P was <5% for MAP (4.9%) and struvite (1.9%) indicating that in soils with adequate to high crop‐available P, early season fertilizer PUE is relatively low. If prorated to harvest stage, in‐season PUE was estimated to be 8% for struvite and 20% for MAP. MAP and struvite did not differ in relative contributions to water‐extractable P, a proxy for P loss risk, potentially reflecting lag effects in struvite P dissolution and/or the relatively fine particle size of synthesized fertilizers (<0.1 mm diameter). Since maize aboveground biomass and P uptake were similar for both struvite and MAP, struvite could be an effective P fertilizer for soils with adequate to high Mehlich‐3 P concentrations common across the US Maize Belt.

中文翻译：

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33P-同位素标记磷酸铵肥料显示早期生长玉米的大部分磷来自土壤


在整个美国玉米种植带的土壤中，Mehlich-3 磷 (P) 浓度达到足够高的水平，大部分作物的磷来自土壤。因此，鸟粪石是一种低水溶性磷酸铵肥料，可以替代水溶性相对较高的磷酸一铵 (MAP)，而不会对玉米 (Zea mays L.) 磷的吸收和生长产生不利影响，同时最大限度地降低肥料磷损失风险。我们通过用 33P 对肥料进行放射性标记，确定了鸟粪石和 MAP 对美国玉米带代表性土壤中玉米磷吸收和土壤溶液磷的相对贡献。我们发现，早期至中期营养生长阶段（V7）玉米的磷有 8%（鸟粪石）至 22%（MAP）来自肥料，因此 78%–92% 来自土壤。尽管地上磷吸收和玉米生长相似，但由 33P 直接测定的玉米磷利用效率 (PUE) 对于 MAP (4.9%) 和鸟粪石 (1.9%) 为 <5%，这表明在作物有效磷充足至高的土壤中，早期季节肥料PUE相对较低。如果按照收获阶段按比例计算，鸟粪石的季节 PUE 估计为 8%，MAP 为 20%。 MAP 和鸟粪石对水可提取磷的相对贡献没有差异，可水提取磷是磷损失风险的代表，可能反映鸟粪石磷溶解的滞后效应和/或合成肥料相对细的粒径（<0.1 毫米直径）。由于鸟粪石和 MAP 的玉米地上生物量和磷吸收量相似，因此鸟粪石对于美国玉米种植带常见的 Mehlich-3 P 浓度充足至高的土壤来说可能是一种有效的磷肥。