不同氮源与镁配施对甘蓝产量、品质和养分吸收的影响

采用田间试验和室内分析相结合的方法,研究不同氮源与镁配施对甘蓝(Brassica oleracea L.)产量、品质和养分吸收的影响。试验在等氮条件下设4个氮源,分别为不施氮肥、100%铵态氮、50%铵态氮+50%硝态氮、100%硝态氮;设4个硫酸镁施用量,分别为0、75 kg·hm-2、150 kg·hm-2、300 kg·hm-2。结果表明,100%硝态氮与中量(150 kg·hm-2)镁配施处理的甘蓝产量比不施肥处理、100%铵态氮与中量镁配施处理和50%铵态氮+50%硝态氮与中量镁配施处理分别增产56.9%、14.7%和5.2%。施用100%硝态氮处理的甘蓝产量略高于50%硝态氮+50%铵态氮处理,比施用100%铵态氮处理和不施肥处理分别增产13.0%和44.2%。施用低量(75kg·hm-2)镁肥的甘蓝产量比不施镁肥增产9.3%,而增加镁肥用量对甘蓝产量没有显著影响。施用100%硝态氮、50%铵态氮+50%硝态氮和100%铵态氮处理的甘蓝硝酸盐含量比不施氮肥处理分别增加84.4%、63.4%和6.9%。100%硝态氮与高量(300 kg·hm-2)镁肥配合施用的甘蓝硝酸盐含量比不施肥处理、100%铵态氮与高量镁肥配施处理和50%铵态氮+50%硝态氮与高镁肥配施处理分别增加101.4%、82.3%和14.1%。施用高量镁肥处理甘蓝硝酸盐含量比不施肥处理增加11.2%。随着硝态氮比例增加,甘蓝维生素C、还原糖、总氨基酸含量相应增加,镁肥施用量对甘蓝维生素C、还原糖、总氨基酸含量影响明显。随着硝态氮比例增加,甘蓝对磷、钾和钙吸收量显著增加;随着镁施用量增加,磷、钾和镁吸收量相应增加。不同氮源与镁肥相互作用对甘蓝维生素C含量,氮、磷、钾、钙和镁养分吸收均有明显的影响。本研究表明,50%硝态氮和50%铵态氮混合与适量镁肥配合施用,既能增加甘蓝产量,提高维生素C、还原糖和总氨基酸含量,又能减少硝酸盐含量,提高甘蓝品质。

Effects of combined application of different nitrogen sources and magnesium fertilizers on cabbage yield, quality and nutrient uptake

Vegetable crops have preferences for nitrate-nitrogen (N). Nitrate accumulation in vegetable crops is closely related with the form of N and application rate of N fertilizer, especially under over fertilization of N. The purpose of this research was to investigate the effects of combined application of different N sources and magnesium (Mg) fertilizers on yield, quality and nutrient uptake of cabbage (Brassica oleracea L.) under field conditions. The experiment was conducted in a randomized complete block design (RCBD) with three replicates of each treatment. Four N sources (no N, sole nitrate-N, sole ammonium-N, and mixed nitrate/ammonium-N) and four rates of magnesium sulfate fertilizer (0, 75 kg·hm^-2, 150 kg·hm^-2 and 300 kg·hm^-2) were used in the study. Results showed that under the same N conditions, combined application of different N sources and Mg fertilizers had significant effects on yield, quality and nutrient uptake of cabbage. The highest cabbage yield was obtained under combined application of sole nitrate-N and medium rate (150 kg·hm^-2) of Mg fertilizer. Cabbage yield under treatment of sole nitrate-N and medium rate Mg fertilizer increased by 56.9%, 14.7% and 5.2%, respectively, compared with those under no fertilizer, sole ammonium-N, and mixed nitrate/ammonium-N applications with medium rate of Mg fertilizer. N resources had significant influence on cabbage yield. Sole nitrate-N treatment increased cabbage yield by 13.0% over sole ammonium-N treatment. No significant yield difference was noted between sole nitrate-N and mixed nitrate/ammonium-N treatments. Compared with treatments without Mg fertilizer, 75 kg·hm^-2 Mg fertilizer increased cabbage yield by 9.3%. Nevertheless, no significant increase was noted with further increase in Mg fertilizer rate. The highest cabbage nitrate content was about 2 759.0 mg·kg^-1, obtained under combined application of sole nitrate-N with high rate (300 kg·hm^-2) of Mg fertilizer. Compared with no fertilizer treatment, cabbage nitrate content under sole nitrate-N with high Mg fertilizer rate increased by 101.4%, 82.3% and 14.1%, respectively, over those under no fertilizer, sole ammonium-N and mixed nitrate/ammonium-N treatments with high Mg fertilizer rate. While cabbage nitrate content was not influenced by low and medium Mg fertilizer rates, significant increase (11.2%) was noted in nitrate content at high Mg fertilizer rate compared with no fertilizer. Cabbage contents of vitamin C, reducing sugar, total amino acids significantly increased with increasing proportion of nitrate-N. Uptakes of P, K and Ca significantly increased with increasing proportion of nitrate-N. Moreover, uptakes of P, K and Mg also increased with increasing Mg fertilizer rate. Analysis revealed that interactions among different N sources and Mg had significant effects on cabbage vitamin C content and cabbage N, P, K, Ca and Mg uptake. This research indicated that mixed nitrate/ammonium-N application with proper Mg application rates not only enhanced cabbage yield and vitamin C, reducing sugar and total amino acids contents, but also reduced nitrate content and improved nutritional quality of cabbage.