叶面喷施镁肥对缺镁番茄养分吸收和分配的影响

摘要

针对近年来北方日光温室中栽培番茄缺镁普遍发生和日益严重的问题,研究了叶面喷施MgSO、Mg(NO3)2及不同施用量对秋冬茬缺镁番茄K、Ca、Mg吸收和分配的影响,以期为番茄缺镁的矫正提供科学依据.结果表明:(1)随番茄生育进程各处理番茄叶片Mg和K含量呈下降趋势,Ca含量先下降后基本稳定,其中,Mg和Ca以第1穗果膨大期到第2穗果膨大期下降幅度最大,降幅分别为17.8％和39.1％.(2)喷施Mg肥显著提高叶片中Mg的浓度及携出量,喷施含镁0.4％的MgSO4 ·7H2O溶液叶片镁含量及携出量较对照分别提高了1.55和1.78倍,而对根、茎和果实中Mg的浓度及携出量无明显影响;从产量上看,喷施含镁0.2％和0.4％ MgSO4·7H2O及0.2％Mg(NO3)2·6H2O溶液与不喷施相比产量分别提高了8.0％、8.9％和5.3％,但差异不显著.(3)土壤交换性K/Mg均大于适宜值,K、Mg养分比例严重失调,而石灰性土壤养分失调后叶面补施Mg肥,Mg从叶片向其他部位的转运有限,必须降低钾肥施用量,使养分平衡供应.%Magnesium is an essential nutrient and a constituent of chlorophyll.The deficiency of Mg is common in tomato grown in calcareous soil under solar greenhouse in North China in recent years.It largely affects the fruit yield and quality.Five treatments comprising of different concentration and magnesium fertilizer sources were applied to autumnwinter season tomato by foliage spray.The results showed that:(1) the contents of magnesium and potassium in tomato leaves decreased with time while the calcium content decreased in first and then became stable.The decreasing trend of magnesium and calcium were highest during the period from the first cluster fruit expanding stage to the second cluster fruit expanding stage,the decrease was 17.8％ and 39.1％,respectively.(2) Spraying magnesium fertilizer increased the magnesium concentration and nutrient uptake in tomato leaves,but there was no significant difference among the treatments in magnesium concentration and nutrient uptake in roots,stem and fruits (P ＞ 0.05).Mg applied at 0.4％(MgSO4 ·7H2O) improved magnesium concentration (1.55 times) and nutrient uptake (1.78 times) in tomato leaves compared with the CK.The improvement in tomato yield at both Mg concentrations (0.2 and 0.4％) of MgSO4 ·7H2O and 0.2％ of Mg(NO3)2·6H2O was 8.0,8.9 and 5.3％ respectively compared with that of CK.However,the differ ence was not significant among treatments (P ＞ O.05).(3) The soil exchangeable K/Mg ratio exceeded 0.5,which indicated a serious nutrient imbalance in soil.Even under magnesium spray,the transportation of magnesium from leaves to other organs of tomato was limited.Therefore,some measures should be taken to reduce potassium fertilizer rate and maintain the nutrients balanced in soil.