3种水分管理条件下施用木炭和磷酸二铵对水稻Cd、As累积的影响

Accumulation of Cd and As in Rice(Oryza sativa)Under Different Water Management Coupled With Charcoal and Diammonium Phosphate Amendment.

通过测定土壤和水稻体内Cd、As含量及水稻产量,探究常规灌溉(W1)、全生育期淹水(W2)和湿润灌溉(W3)耕作条件下,施用木炭和磷酸二铵对水稻Cd、As累积的影响。结果表明,3种水分管理条件下施用木炭和磷酸二铵均显著提高土壤pH值,pH值随水稻生长呈先增加后下降趋势,最后趋于中性;土壤氧化还原电位随水分增加呈下降趋势,其值由高到低依次为W1>W3>W2水分管理条件,W2水分管理条件始终处于弱还原状态。同一水分管理条件下施用木炭和磷酸二铵,土壤有效态Cd以及水稻根、茎叶和籽粒Cd含量均随施用量的增加而减少。W1、W2和W3水分管理条件下,对照组水稻籽粒Cd含量分别为(0.23±0.02)、(0.19±0.03)和(0.22±0.04)mg·kg^-1,施用木炭和磷酸二铵后水稻籽粒Cd含量均小于0.2 mg·kg^-1;其中,W2水分管理条件下配施0.44 kg·m^-2木炭或15.00 g·m^-2磷酸二铵的降低效果较好。3种水分管理条件下施用木炭和磷酸二铵均使土壤有效态As含量增加;相比较而言,W2水分管理条件下各处理土壤有效态As含量最少,介于0.88~1.22 mg·kg^-1之间。W2水分管理条件下各处理水稻根、茎叶和籽粒As含量较低,且籽粒无机As含量均小于0.2 mg·kg^-1。3种水分管理条件下施用木炭和磷酸二铵均能促进水稻生长,提高水稻产量。水稻产量与土壤有效态Cd含量呈极显著负相关,与土壤有效态As含量无显著相关性。因此,在确保水稻籽粒无机As含量不超过0.2 mg·kg^-1条件下,实际生产中可采用W2水分管理配施0.44 kg·m^-2木炭或15.00 g·m^-2磷酸二铵的方法促进水稻增产,并有效降低水稻籽粒Cd累积。

According to the field experiment next to a lead-zinc mining area in Anhui Province,the available cadmium(Cd)and arsenic(As)in farmland as well as rice yields were evaluated as affected by charcoal and diammonium phosphate(DAP)treatments under conventional irrigation(W1),whole growth period flooding(W2),and wet irrigation(W3).Moreover,the pH values,oxidation-reduction potential(Eh),and Cd and As accumulation in rice tissues were also investigated in this study.The results demonstrate that the application of charcoal and DAP enhanced the pH values in soils under all the three conditions of water management.With the rice growth,the pH value in farmland increased firstly and then decreased to neutral.The Eh values of soils showed a declining tendency with the increase of moisture.The Eh values under the different water management conditions followed the sequence of W1>W3>W2.Furthermore,the Eh values at W2 condition showed a weak reductive state.At the same water management condition,the available Cd content in soil and Cd content in root,stem leaves and grains decreased as the application amount of charcoal and DAP increased,respectively.In control group,the Cd contents in rice grains under W1,W2,and W3 treatments were(0.23±0.02),(0.19±0.03),and(0.22±0.04)mg·kg^-1,respectively.After the charcoal and DAP application,Cd accumulation in rice grains was lower than 0.2 mg·kg^-1 for all treatments.It was found that the reduction in Cd accumulation had an optimum efficiency in application of 0.44 kg·m^-2 charcoal or 15.00 g·m^-2 DAP under W2 treatment.On the other hand,the available As content increased after the charcoal and DAP application.The available As content in soil showed the lowest concentration range(0.88-1.22 mg·kg^-1)in W2 treatments.In the W2 treatment group,it was observed that the available As content in soil and As accumulation were lower in rice roots,stem leaves and grains.Meanwhile,the inorganic As contents in rice grains were lower than 0.2 mg·kg^-1.Overall,application of charcoal and DAP improved rice growth and increased rice yield.The rice yields were negatively correlated with the available Cd content in soil,but no significant correlation with the available As content was observed.Therefore,the application of 0.44 kg·m^-2 charcoal or 15.00 g·m^-2 DAP coupled with W2 water treatment could be adopted to promote rice yields in the condition of ensuring that As content in rice grains below 0.2 mg·kg^-1,which simultaneously decreased the accumulation of Cd in rice grains.