1961—1964年以武功头道塬的红油土进行了示踪试验,初步结果为:1.施用磷肥不仅可提供值物以大量可给态磷素,而且不影响植物对土壤磷的利用。2.厩肥富含磷素,它既能提供植物所需的磷素,又能以其所含的氮素和腐殖化有机质增进土壤供磷能力,但肥料磷的吸收量略有下降。3.配合施用氮肥后,植物对磷肥和土壤磷的吸收量均有增高。磷肥肥效的提高主要取决于间接的生物作用,而直接的化学作用仅局限于硫酸铵。 Tracer tests were carried out on the red oil soil of Wugongduidou Plateau from 1961 to 1964. The preliminary results were as follows: 1. The application of phosphate fertilizer could not only provide value for a large amount of available phosphorus, but also did not affect plant phosphorus utilization. 2. Manure is rich in phosphorus, which not only provides the phosphorus needed by plants, but also enhances the phosphorus supply capacity of soil with the nitrogen and humified organic matter it contains, but the phosphorus uptake of fertilizer decreases slightly. With the application of nitrogen fertilizer, plant phosphate and soil phosphorus uptake increased. Fertilizer efficiency mainly depends on the indirect biological role, and the direct chemical effect is confined to ammonium sulfate.