几种蔬菜对硝态氮、铵态氮的相对吸收能力

采用溶液培养方法探讨了莴笋、菠菜、小白菜和大青菜 4种蔬菜作物对硝、铵态氮的相对吸收能力以及这两种氮源对它们生长发育的影响。结果表明 ,单独供给NO3-N ,4种作物均生长发育良好 ;供给NO3--N +NH4+-N(NO3-∶NH4+=1∶1) ,生长量均有所下降 ,而单独供给NH4+-N时 ,生长量则大幅度下降。莴笋单独供给NO3--N时 ,其吸氮量显著高于供给NO3--N +NH4+-N的处理 ,大青菜、菠菜供给NO3--N +NH4+-N与单独供给NO3--N相比吸氮量大体相当 ;小白菜同时供应NO3--N +NH4+N时吸氮量最高 ,供给NO3--N时次之 ,供给NH4+-N时显著降低。供给NH4+-N时 4种作物吸氮量均比其它氮源显著降低。 4种作物对NO3--N与NH4+-N的吸收具有明显的偏向性。供给等氮量铵、硝态氮 (NO3--N +NH4+-N处理 )时 ,菠菜、小白菜吸收的NO3-N显著多于NH4+-N ,表现出喜硝性 ,莴笋则与此相反 ,表现出喜铵性 ;而大青菜对两种形态氮素的吸收量相差不多 ,表现出兼性吸收的特点。但上述偏向性具有阶段特点 ,即喜硝作物可能在某一阶段表现出喜铵性状

Uptake capacity of several vegetable crops to nitrate and ammonium

Solution culture experiment was conducted in order to investigate the relative uptake capacity or preference to nitrate and ammonium of lettuce, spinach, cabbage and garden sass, as well as the influence of 3 different nitrogen sources on growth and development of these 4 crops. The obtained results showed:(1) When the distilled water was supplied as the growth medium in the nutrient solution, different nitrogen sources affected greatly on the growth and development of lettuce, spinach, cabbage and garden sass. When nitrate was the sole N source, all these vegetable crops growed very well; when the same amount of nitrate and ammonium was supplied in the nutrient solution, the growth amount of 4 crops decreased to some extent; While ammonium was the sole N source, the growth amounts of 4 vegetable crops decreased greatly, when NO₃^--,NO₃^--+NH₄⁺(1∶1), NH₄⁺ were the N source for 4 crops, respectively. The ratios among dry matter weight of 4 crops were: lettuce was 1∶0 57∶0 12,spinach was 1∶0 91∶0 37,cabbage was 1∶1 07∶0 36, and garden sass was 1∶1 05∶0 21,respectively.But the mechanism why ammonium inhibited crop growth is worth studying further.(2) During the solution culture, the total nitrogen uptake amount of the tested crops had close relation to the nitrogen source. To lettuce, the nitrogen uptake amount as nitrate supplied was significantly higher than that when the same amount of nitrate and ammonium was supplied, if comparing the same amount of nitrate and ammonium treatment with solely supplying nitrate nitrogen treatment, and the nitrogen uptake amounts of garden sass and spinach were almost same; While supplying the same amount of NO₃^- and NH₄⁺,the nitrogen uptake amount of cabbage was the largest, when solely supplying nitrate it greatly decreased, and ammonium was supplied,the nitrogen uptake amount was the lowerest. To all of 4 crops, when ammonium was the sole N source, the N uptake amount was the lowerest. (3) The tested crops had apparent preference to uptake of nitrate or ammonium. When the same amount of ammonium and nitrate was supplied, the uptaked nitrate by spinach and cabbage was larger than ammonium, but the lettuce was vice verse(N, 8.91±1.56, 12.31±1.24 mg /plant, respectively),and the absorped nitrogen of two forms by garden sass were almost the same. The preference had characteristics of stage, generally speaking, the crop which prefer nitrate to ammonium maybe show property of favours ammonium at certain stage.