Effects Of Fertilizer Application On Cadmium Absorption And Accumulation In Rice

Two experiments were conducted to investigate the effects of fertilizer application on cadmium absorption and accumulation in rice:(1)One experiment is to study the effects of different types and amounts of nitrogen fertilizer on cadmium absorption and accumulation in rice,using Zhongzao39 as early rice,Xiangwanxian13hao as late rice,field experiment was carried out in Tongxin village in Changsha County Fulin town in 2016.The experiment set 10 different types and amount of nitrogen fertilizer(N1-N10)and a non nitrogen treatment(N11),and the type and amount of nitrogen fertilizer were compound fertilizer containing 90,180,270 kg nitrogen per hectare(N1-N3),urea nitrogen containing 90,180,270 kg per hectare(N4-N6)and ammonium bicarbonate containing 90,180,270 kg nitrogen per hectare(N7-N9),and ammonium sulfate containing 180 kg nitrogen per hectare(N10).(2)Another experiment is to study the effects of different ratios of base and top-dressing fertilizer on cadmium absorption and accumulation in rice,using Xiangzaoxian32hao and Zhongjiazao17 as early rice,and Xiangwanxian12hao and Wuyou308 as late rice,field experiment was carried out in Jian Feng village Heshan District of Yiyang city in 2016.The experiment included six different ratios of basal and top-dressing fertilizer treatments and non-fertilization treatment with compound fertilizer,the base fertilizer,tiller fertilizer and panicle fertilizer,grain fertilizer ratio was 10:0:0:0(T1),8:2:0:0(T2),6:2:2:0(T3),4:3:3:0(T4),2:4:4:0(T5),0:5:3:2(T6)and a treatment without fertilization completely(T7).The main results are as follows:1.Fertilizer could improve the yield of rice,and the yield of fertilization was more than non fertilization by 4.89%-91.33%.More nitrogen fertilizer could accelerate the growth and development of rice,and increase the dry matter accumulation and yield of rice effectively.These kinds of N fertilizer yield showed ammonium sulfate>ammonium bicarbonate>urea>compound fertilizer,and yield of ammonium sulfate in early and late rice were 9.34 t/hm~2,7.67 t/hm~2.The yield of one-time base fertilizer in early rice was the highest,and with the increase of the ratio of topdressing,effective panicles per unit area was increased first and then decreased,and the number of grains per panicle decreased.The yield of T3 treatment in late rice was the highest,which means with the premise of the base fertilizer,tillering and panicle fertilizer can improve the yield of late rice.2.The influence of dry matter accumulation on fertilizer application in rice was the same as that of yield.Ammonium sulfate had the best effect on increasing dry matter accumulation,and its root,stem and leaf dry weight were highest for 58.06g/m~2,243.83 g/m~2,94 g/m~2.The stem dry matter weights in mature stage first increased then declined with the increase of nitrogen application rate,which showed that there was a critical value of dry matter accumulation in the application of nitrogen fertilizer.More base and tiller fertilizer was conducive to aboveground dry matter accumulation and fertilizer lagging will reduce the dry matter accumulation of root,but increase the stem and panicle dry weight.The ratio of4:3:3:0 on fertilizer application was good for dry matter accumulation both in early and late rice,which was a kind of effective fertilization ratio.3.Different types and amount of nitrogen fertilizer had significant difference effect on the absorption and accumulation of cadmium in rice.The effects of rice organs on cadmium absorption were different,and the relationship in stage was heading stage>booting stage>tillering stage,and the relationship in vegetative organ was root>stem>leaf>brown rice.Non fertilization could improve the content of cadmium in vegetative organs of rice heading stage,and in different types of nitrogen fertilizer,The content of roots,stems and leaves with ammonium bicarbonate in the heading stage was significantly lower than other nitrogen fertilizer,and its'contents were 1.30 mg/kg,0.22 mg/kg,0.12 mg/kg respectively.The contents of cadmium in roots,stems and leaves first increased and then decreased with the increase of nitrogen application amount at both tillering stage and booting stage.In brown rice,the relationship between the metal elements were:chromium>plumbum>arsenic>cadmium.There was a significant positive correlation between chromium and plumbum,and the correlation between the remaining metals was not significant.With the increase of the amount of compound fertilizer,the accumulation of cadmium in brown rice increased.Therefore,the use of ammonium sulfate and the application of lower nitrogen fertilizer could reduce the accumulation of cadmium in rice brown rice.4.The effects of different ratios of base and topdressing on the accumulation of cadmium in rice organs were:root>stem>leaf>brown rice.The contents of different heavy metals in brown rice were:chromium>plumbum,arsenic>cadmium,and there were some correlations between different heavy metals according to different varieties.The content of cadmium in roots,stems and leaves showed"concave"shape,which was decreased first and then increased.When the ratio was 4:3:3:0,the content of cadmium in brown rice was lower,and the content of Xiangzaoxiang32hao,Zhongjiazao17,Xiangwanxiang12hao and Wuyou308 were 0.30mg/kg?0.21mg/kg?0.09mg/kg?0.15mg/kg respectively and 6.30%-63.79%lower than others treatments.Therefore,adequate basal fertilizer with proper application of tillering fertilizer and panicle fertilizer could reduce the accumulation of cadmium in rice effectively.