根系分区交替灌溉条件下水肥供应对番茄果实硝酸盐含量的影响

为了研究根系分区交替灌溉条件下灌水量和氮、磷、钾肥及有机肥用量对番茄果实硝酸盐含量的影响,采用五元二次正交旋转组合设计,通过盆栽试验,建立了番茄果实中硝酸盐含量与水肥因子的数学模型,并对各单一因素的效应及两两因素的耦合效应进行了分析。结果表明,在其他因子为中间水平时,番茄果实中的硝酸盐含量,随灌水量呈先降低后增加的变化规律;随施氮量和施磷量呈先增加后降低的变化趋势;随有机肥用量呈逐渐增加的趋势;但不受钾肥用量的影响。交互效应表现为,施磷量与有机肥用量、施氮量与施磷量间的相互作用会促使番茄果实硝酸盐含量提高;灌水量与施钾量和有机肥量、施氮量与施钾量间的相互作用有利于降低番茄果实硝酸盐累积。耦合效应表现为,除不施有机肥时随灌水量增加番茄果实硝酸盐含量显著增加外,对于其它任何有机肥及钾肥施用水平,果实硝酸盐含量皆随灌水量增加呈先减小后增加趋势;灌水量高于中水平时,番茄果实硝酸盐含量随着钾肥与有机肥用量的增加而减少。不论施磷量与施钾量如何变化,番茄果实硝酸盐含量皆随施氮量呈现先增加后减小的变化趋势,降低氮肥用量同时提高磷肥用量有利于降低番茄果实硝酸盐累积,而提高施钾量仅在施氮量高于中水平时能显著降低番茄果实硝酸盐含量。适当增加磷肥用量、减小有机肥用量能显著降低番茄果实硝酸盐的累积。

Effects of water and fertilizers on nitrate content in tomato fruits under alternate partial root-zone irrigation

In recent years, the quality and security of vegetables have being increasingly concerned by people and investigated by researchers. However, vegetable quality decline is very common due to excessive irrigation and irrational fertilization. The nitrate content is an important index which is used to evaluate vegetable quality. Although tomatoes have been grown successfully for many years in many parts of the world, there is no accurate formula or recipe on both the amount of irrigation and fertilizer levels to get high quality tomato fruit. Alternate partial root-zone irrigation (APRI) is a new water-saving technique and may improve crop water use efficiency and fertilizer use efficiency. To determine the effects of irrigation amount and fertilizer rates of nitrogen, phosphorus, potassium and manure on the nitrate content in tomato fruits under APRI, the quadratic orthogonal regressive rotation design with five factors was used in pot experiment, in which five rates were set for every experimental factor. A regression model on the amount of irrigation water and fertilizers and the nitrate content in tomato fruits was established. Based on the regression equation, the single, interactive and coupling effects of these five experimental factors on the nitrate content in tomato fruit were analyzed. The results showed that if other factors were zero codes, the nitrate content in tomato decreased firstly and then rose with irrigation water increase, while it showed a reverse trend with N and P fertilizer levels. The nitrate content in tomato increased gradually with manure amount, but it was not affected by K fertilizer level. The interactions on the nitrate content in tomato fruits between P fertilizer and manure levels, N and P fertilizer levels showed positive effects, while the interactions between irrigation amount and K fertilizer or manure level, as well as N and K fertilizer levels were negative effects. The coupling effects between two of these five experimental factors showed that the nitrate content in tomato fruits increased markedly with higher irrigation amount when no manure was applied, while it decreased firstly and then increased with irrigation amount for the other manure and all K fertilizer rates. The nitrate content in tomato decreased with K fertilizer or manure increase when irrigation amount was above the mid level. The nitrate content in tomato increased firstly and then decreased with N fertilizer increase for any P or K fertilizer rate. The nitrate content was less when P fertilizer rate was at the highest than any other level,and it was the lowest when P and N fertilizer rate were at the highest and the lowest, respectively, suggesting that lower N fertilizer and higher P fertilizer rates could decrease the accumulation of nitrate content in tomatoes. Interestingly, the situation was different for K fertilizer. Higher K fertilizer rate could reduce the nitrate content significantly only when the N fertilizer rate was above the mid level. The coupling effects of P fertilizer with manure rates on the nitrate content in tomato fruits indicated that increasing P fertilizer properly and decreasing manure application at the same time could greatly contribute to less nitrate content in tomato fruits.