Effect And Mechanism Of Subsoil Fertilization On The Albic Luvisol Improvement

The field tests, the pot experiments and the indoor stimulation experiments were carried out. Through the investagation of the contribution rate of the subsoil and its affter-effect of the combination tests, the effect and its mechanism of subsoil fertilization on the albic luvisol were clarified. The results obtained from the experiments are as follows:1. The contribution rate of subsoil of black soil to the yield that 20～40cm layers is more than 10%, and the layers of 40～50cm is only close to 5%, and the 20～60 layers of albic luvisol subsoil is only 4.5%.2. The steady effect for increasing yield can be achieved by subsoil fertilization. The results from the two field tests showed that the yield increasing rate was in the order of the colligating fertilizer with P+Ca >the subsoil fertilization with P> the subsoil fertilization with Ca>the subsoil mixing tillage. As the materiel for subsoil fertilization, P is better than Ca.3. The aviliable P of the treatment of Aw by the subsoil fertilization with P has great progress than before in the albic luvisol.The EC and pH have not very obvious effect with it. The average value of EC, pH and exchangeable-Ca have increased by applying Ca in the subsoil. The high hardness of Aw is eliminated by the subsoil fertilization, which down the hardness and improve the three phase of soil. 4 years after treating, the bulk density of 20～50cm has lower than CK, and the porosity is increased by 5～6.68%。4. The P adsorption rate is in the order of the B horizon>the Aw + B mixing layer >the Aw horizon > the A horizon. Ca application can increase the P adsorption rate and decrease its P desorption rate, however, manure application can decrease the P adsorption rate and increase its P desorption rate.Results of the extraction of inorganic P form from the indoor stimulation experiments showed that the Fe-P occupied the main contribution for the soil availiable P, and then Ca2-P and their coaction of Fe-P +Ca2-P, and hence Fe-P is the major form of the soil availiable P. The correlativity analysis shows that the available phosphorus has a very significant positive relation with Ca2-P, Ca8-P, Al-P after treatment.