生物炭负载氮还田对水稻生长、根系形态及氮素利用的影响

建立连接富营养化水体养分与农田养分的枢纽是减少农田养分投入、缓解水体富营养化的难点.为探明生物炭材料负载氮还田的可行性,开展了基于溶液氮及生物炭负载氮两种氮源添加方式的水稻根箱试验.结果表明,生物炭负载氮添加方式分别较溶液氮添加方式降低了水稻地上部分生物量及氮累积16%及14%,提高了生物量根冠比25%～27%,降低了氮利用效率.不定根的根长及体积是两种氮源添加方式在水稻地下部分差异的体现,地下部分生物量及氮累积与土壤铵态氮含量呈正相关关系,而地上部分氮累积与根尖数呈负相关关系.生物炭负载氮完全替代化学肥料施用农田会影响水稻生物量及氮素利用.但生物炭负载氮与普通化学肥料共同施用,水稻并不会显现利用偏好.生物炭负载氮对水稻氮素利用无不良影响,且能有效提高土壤矿质态氮固持量.因此,生物炭可以作为载体实现水体到农田土壤的氮素迁移,鉴于化肥氮替代比例对作物生长的影响,适宜替代比例还需进一步研究确定.

Effects of Returning Nitrogen by Biochar Loading on Paddy Growth, Root Morphology, and Nitrogen Use Efficiency

Building a nutrient channel between eutrophic water and agricultural fields could reduce nutrient input into fields and alleviate eutrophication by returning nitrogen. In order to determine the feasibility of returning nitrogen by biochar loading, a rhizobox experiment was conducted with two nitrogen applied methods, namely SN (applied nitrogen by nitrogen fertilizer solution) and BN (applied nitrogen by nitrogen-loaded biochar). The results showed that BN, in comparison with SN, decreased the biomass and nitrogen uptake of the aboveground paddy by 16% and 14%, respectively, increased biomass root-shoot ratios by 25%-27%, and reduced nitrogen recovery use efficiency. Two nitrogen application methods affected the length and volume of paddy adventitious roots. Paddy underground biomass and nitrogen uptake were positively correlated with soil ammonium content, whereas paddy aboveground nitrogen uptake was negatively correlated with root tips. It was suggested that the paddy biomass and nitrogen uptake would be influenced when nitrogen was applied solely by nitrogen-loaded biochar. However, no affinity and no significance in nitrogen use efficiency were found for plant uptake between chemical nitrogen and biochar-loaded nitrogen. Additionally, biochar promoted soil mineral nitrogen content for further plant uptake. Therefore, biochar could be used as the carrier for returning nitrogen from waterbodies to fields. The replacement rate of chemical nitrogen fertilizer is the key to influencing plant growth and needs future study.