| Cadmium(Cd)is a toxic trace metal element.Natural sources.including volcanic activity,parent rock weathering,and anthropogenic sources including metal mining and smelting,atmospheric deposition,sewage irrigation,livestock and poultry manure,as well as phosphorus fertilizer application,have resulted in cadmium pollution in some farmland in China as well as frequent problems of "cadmium rice" and "cadmium wheat".However,China has more people and less cultivated land.To achieve the rational utilization of contaminated cultivated land resources and ensure food security,it is urgent to make safe use of cadmium-contaminated farmland and ensure the quality of agricultural products.At present,the research on the technology models for the safe utilization of cadmium-contaminated paddy fields in southern China is relatively mature.However,there are relatively few researches on the technology models of safe utilization of cadmium-polluted wheat fields and other drylands in northern China,which urgently need a batch of cost-effective and popularizing technology models of safe utilization.In this study,two-year field trials were conducted to propose a cost-effective technology model for the safe utilization of cadmium-contaminated farmland.Firstly,the effects of five foliar blockers,the zinc sugar alcohol(Zn-SA),silicon sugar alcohol(Si-SA),iron sugar alcohol(Fe-SA),Nongfeng Kangbao(NFKB),Minhe foliar fertilizer(MH-FF),and soil conditioner,Minhe punching fertilizer(MH-PF),applied alone or in combination,on yield and its components,grain cadmium content,as well as risk-benefit analysis during harvest time of Jimai 22 and Jinan 17(two low cadmium accumulation wheat cultivars)were compared.Then,we further studied that under different soil conditions,the effects of soil application of composite spent mushroom substrate(CSMS)alone or foliar application of Zn-SA alone or both in combination on soil pH and available cadmium,yield and its components,grain cadmium content,as well as risk-benefit analysis during harvest time of Jimai 22(low cadmium accumulation wheat cultivar)and Zhoumai 32(high cadmium accumulation wheat cultivar)were compared and the main factors affecting grain cadmium content were explored.The main results are as follows:(1)The results of the first-year field experiment in the Pingdu City of Qingdao showed:For Jimai 22,foliar application of Zn-SA and Si-SA treatment,foliar application of Fe-SA treatment,foliar application of NFKB treatment,foliar application of MH-FF treatment,soil application of MH-PF treatment,and combined treatment of the latter two increased seeds per spike,1000-grain weight,and grain yield by 2%-34%,0.3%-1 0%,5%-27%,respectively;for Jinan 17,all treatments increased 1000-grain weight by 1%-5%,seeds per spike by 1%-22%except for the foliar application of low-concentration NFKB treatment,grain yield by 1%-18%except for the foliar application of high-concentration Zn-SA and Si-SA treatment.Among them,the combined treatment of the foliar application of low-concentration MH-FF,and soil application of low-concentration MH-PF had the best effect on the yield increase of both wheat varieties.For both wheat varieties,all treatments significantly reduced the grain cadmium content by 30%-67%.Among them,the combined treatment of the foliar application of low-concentration MH-FF,and soil application of low-concentration MH-PF had the best effect on cadmium reduction of Jimai 22.However,the cadmium content of grain still exceeded the national standard limit value of food safety by 0.1 mg·kg-1,so it could not be safely used.(2)The results of the second-year field experiment in Pingdu City of Qingdao,Boshan District,and Zichuan District of Zibo City showed:For two wheat cultivars,Jimai 22 and Zhoumai 32,soil application of CSMS treatment or in combination with Zn-SA treatment significantly increased the soil pH by 0.30-0.48,0.61-0.69 and 0.07-0.11,respectively,and significantly reduced the soil available cadmium content by 39%-52%,40%-62%and 31%-35%in the three experimental fields,in Pingdu,Boshan,and Zichuan,respectively.The combined treatments significantly increased seeds per spike,1000-grain weight,and grain yield by 18%-21%,8%-11%,and 22%-37%for the two wheat varieties in the Pingdu experimental field respectively;significantly increased seeds per spike,1000-grain weight,and grain yield by 16%-19%,5%,and 23%-26%for the two wheat varieties in the Boshan experimental field respectively;significantly increased seeds per spike,1000-grain weight,and grain yield by 13%-15%,8%-11%,and 33%-34%for the two wheat varieties in the Zichuan experimental field respectively.The three treatments significantly reduced the grain cadmium content of two wheat varieties by 46%～71%,46%～76%,and 31%～49%in the three experimental fields,in Pingdu,Boshan,and Zichuan,respectively,and the combined effect was better than that of the single treatment,especially the combined treatment made the quality of agricultural products of Jimai 22 in the Boshan experimental field qualified and achieved safe utilization.For both wheat varieties,the soil pH had a significant negative correlation with the soil available cadmium content;the grain cadmium content had a positive correlation with the soil available cadmium content;the grain cadmium content had a significant negative correlation with seeds per spike,1000-grain weight,and grain yield.In summary,the study proposed a technology model that could achieve safe utilization of light to moderate Cd-contaminated farmland:Jimai 22(low cadmium accumulation cultivar)+foliar application of Zn-SA(Zn 0.20 g·L-1)+ soil application of CSMS(3000 kg·hm-2). |
