The Utilization Potential Of The Main Organic Nutrient Resources In China

More recently the over use of chemical fertilizer in China has become an issue of public concern*meanwhile,organic nutrient sources such as animal manure and crop residues have not been fully returned to cropland,which lead to a low fertilizer nutrient recovery as well as environmental problems such as eutrophication of surface water,greenhouse gas emission and soil acidification.It is of great significance to investigate the quantity and the utilization potential of organic nutrient resources in China for making full use of animal manure and crop residues resources,improving fertilizer use efficiency,achieving zero growth of chemical fertilizers and ensuring national food security.In this research,the quantity of animal manure and crop residues,and their nutrient resources in China in 2015 were estimated based on Chinese statistics Yearbook and other published references,and the distribution characteristics of organic nutrient resources and the potential for replacement of fertilizer nutrients are identified.DNA-based stable isotope probing(DNA-SIP)and MiSeq sequencing were employed to characterize root-feeding denitrifier communities containing nitrite reductase genes(nirS and nirK)in the rhizosphere of wheat grown in soils with three distinct long-term(32-year)fertilization regimes.The main findings obtained are as follows:1.The main crop straw resources in China were 718.7853 million tons in 2015,which contain6.256 million tons of nitrogen(N),1.979 million tons of phosphorus(P2O5)and 11.595 million tons of potassium(K2O)respectively,accounting for 40.2%,19.5%and 88.6%of total chemical fertilizer consumption in China,separately.The top four crop straw resources are from rice,wheat,maize and oilseed,respectively,which shared 29.0%,19.9%,37.5%and 7.6%of total straw nutrients,respectively.Under 100%of crop straw returning to the field,total nutrients equivalent of 54.4kgN/hm2,15.5kgP2O5/hm2 and 88.1kgK2O/hm2 can be brought back to the soils.2.The main animal manure resources in China was 3158.4 million tons in 2015,which contain 14.78 million tons of N,9.01 million tons of P2O5 and 14.53 million tons of K2O respectively,accounting for 69.4%,112.3%and 132.6%of total chemical fertilizer consumption in China,respectively.The full amount of animal manure returning to the field in China is equivalent to total of 122.7 kgN/hm2,74.8 kgP2O5/hm2 and 120.7 kgK2O/hm2.Under this condition,27,480 and 20,641 million tons of N and P2O5 nutrients can be provided from the animal manures in North Central China,while 32,450 million tons of K2O from Southeast China,a great potential for substitution of chemical fertilizers in these regions.3、In soils amended with chemical fertilizers only,wheat root-derived 13C was dominantly assimilated by nirS-type denitrifiers such as Alcaligenaceae and nirK-type denitrifiers such as Phyllobacteriaceae,whereas organic fertilization resulted in larger diversity of 13C-labeled denitrifier communities.The host plant has a limited effect on denitrifier distribution,and the fertilization leads to soil conditions change,which defines the core nir-type denitrifiers in the plant rhizosphere.