Effects of Phosphorus Application Levels on Its Uptake and Utilization in Foxtail Millet

Foxtail millet is a traditional minor crop in China, known for its strong resistance to stress, tolerance to barren lands, and wide adaptation. Phosphorus is an essential element for crop growth and development, and the appropriate application of phosphorus can enhance crop yield and quality. However, the optimal phosphorus fertilization levels for the growth of foxtail millet have yet to be determined. This study aims to explore the effects of different phosphorus application levels (T₁, T₂, T₃, and T₄), on phosphorus accumulation and use efficiency and crop yield and quality in the foxtail millet cultivars ‘B376’ and ‘B27’, which have different phosphorus efficiencies. Additionally, we investigated the effects of phosphorus accumulation and use efficiency on the heading and filling stages of these cultivars. The results show that the total phosphorus content and accumulation levels in the ‘B376’ and ‘B27’ cultivars vary at different developmental stages and in different plant parts. Furthermore, crop yield and quality in both cultivars vary in response to the different phosphorus application levels. In terms of yield, the phosphorus-tolerant variety ‘B376’ reaches its highest at T₂, while the phosphorus-sensitive variety ‘B27’ achieves its maximum yield at T₃. For quality, ‘B376’ exhibits the highest moisture and crude fat content under T₄, and the highest protein and the lowest amylose content under T₃. On the other hand, ‘B27’ achieves its highest moisture content under T₄, its highest crude fat and protein levels under T₃, and its lowest amylose content under T₂. Therefore, the response to different phosphorus application levels differs between the two cultivars with different phosphorus use efficiencies. Moreover, under different phosphorus fertilization levels, the average crop yield, moisture, fat, and amylose content averages of the phosphorus-tolerant ‘B376’ cultivar are 16.1%, 1.2%, 7.0%, and 4.1% higher than those of the phosphorus-sensitive ‘B27’ cultivar. Additionally, phosphorus use efficiency is positively correlated with the moisture and crude fat contents of foxtail millet. In conclusion, the phosphorus-tolerant cultivar demonstrates superior phosphorus accumulation, absorption, and utilization capacities compared to the phosphorus-sensitive cultivar. These results suggest that in the phosphorus-tolerant ‘B376’, optimal phosphorus fertilization levels enhance the development of roots, stems, and leaves at the T₂ (P₄₅) level, and promote the accumulation of moisture and crude fat in foxtail millet grains, thereby improving their taste and quality. Our findings provide a theoretical basis for phosphorus fertilizer utilization in foxtail millet cultivation and will help determine the optimal fertilization levels for foxtail millet growth.