Effects of mechanochemically activated phosphate rock on maize growth and phosphorus use

It is well known that mechanochemically activated phosphate rock (MAPR) could improve extractable phosphorus (P) (extracted in 2% citric acid) greatly in an ecological way. To evaluate the agronomic effectiveness of MAPR, we conducted a field experiment using spring maize in Luvisol (pH 6.47) soil in Northeast China for three consecutive years. Treatments consist of variation of P levels for substitution of triple superphosphate (TSP) (100% TSP, 10% MAPR, 20% MAPR, 50% MAPR, 100% MAPR). Compared with 100% TSP, all the combined applications of MAPR and TSP were as effective on straw yield. Treatments of 10% MAPR and 20% MAPR had similar effect on grain yield and P uptake, while 50% MAPR and 100% MAPR were significantly lower. For P partial nutrient productivity and apparent P recovery with the treatment of 20% MAPR had equal effectivity, likewise. For soil POlsen, treatment of 10% MAPR was equally operative, while 20% MAPR had the similar performance only in the last year (i.e. 2016). It is concluded that 10-20% of TSP can be effectively replaced by MAPR without affecting spring maize yield in soil with neutral pH.