关中地区大蒜临界氮浓度稀释曲线及验证

Establishment and verification of critical nitrogen concentration dilution curve of garlic in Guanzhong plain

过量施氮是关中地区大蒜生产的突出问题。构建针对关中地区主栽大蒜品种的临界氮浓度稀释曲线模型,进行氮素营养诊断和调控,对大蒜减氮稳产十分必要。基于2 a的大田试验,选用关中地区2个代表性主栽大蒜品种(苍山和改良蒜),设置施氮水平0(N0)、60(N60)、120(N120)、180(N180)、240(N240)、300(N300)kg/hm^2(基追比4:4:2),分析不同施氮水平对地上部干物质和植株氮浓度的影响,分别构建了2个品种大蒜的临界氮浓度稀释曲线模型。结果表明:关中大蒜地上部临界氮浓度与最大干物质符合幂函数关系。使用基于临界氮浓度稀释曲线模型构建的氮营养指数模型对各处理氮素营养状况进行诊断,N240处理的氮营养指数接近于1,且可以获得最大的地上部干物质和相对产量。同时,氮营养指数与相对地上部干物质、相对产量的相关性均达到极显著水平。因此,240 kg/hm2可以作为关中地区大蒜施氮量的重要参考,该研究构建的大蒜临界氮浓度稀释曲线模型和氮营养指数模型对于大蒜的氮素营养诊断和精确施氮具有重要的意义。

The garlic(Allium sativum L.)planting in Guanzhong plain of Shaanxi Province has a common problem of excessive application of nitrogen fertilizers.Establishing model of critical nitrogen concentration dilution curve is an effective approach to assess nitrogen status and optimize nitrogen management in garlic production.Based on 2-year field experiments,the model of critical nitrogen concentration dilution curve was constructed for 2 representative garlic varieties‘Cangshan’and‘Gailiangsuan’in local area.In 2015-2016,the experiment was carried out in the Institute of Water Saving Agriculture in Arid Areas of China,Northwest A&F University,Yangling,Shaanxi province,Northwest China(108°5′E、34°19′N);In 2016-2017,the experiment was carried out in Jintiezhai village of Wugong county,Shaanxi province,Northwest China,(108°16′E、34°15′N).The experiment was conducted with 6 nitrogen levels:0(N0),60(N60),120(N120),180(N180),240(N240),300(N300)kg/hm^2.In 2017-2018,the experiment was also conducted in the Institute of Water Saving Agriculture in Arid Areas for model validation.The plant samples of different treatments were collected 5 times during the study periods,i.e.,15,30,40,50,70(or 73)d respectively after garlic returning green in spring.Aboveground dry matter,nitrogen concentration and yield of garlic were determined.With the analysis of critical nitrogen concentration and maximum dry matter in each sample date,the results showed that there existed a negative power function between aboveground maximum dry matter and critical nitrogen concentration of garlic.Using the observed maximum and minimum nitrogen concentration at each sampling date,2 boundary curves were also determined.With the validation of independent test,the normalized root mean square error of‘Cangshan’and‘Gailiangsuan’were 9.37%and 7.75%,respectively.It indicated that the simulation performance of these models were proven to be excellent.The nitrogen nutrition index(NNI)calculated based on critical nitrogen concentration dilution curve could directly reflect the real-time nitrogen nutrition status of garlic.The NNI values of N240 treatment varied around 1 in 2-year experiment for 2 garlic varieties,meanwhile this treatment can also obtain the maximum relative yields of garlic scape and bulb.Moreover,the NNI values of N300 treatment were greater than 1,which suggested that the nitrogen concentration in N300 treatment was excessive,resulting in the waste of nitrogen fertilizer.The NNI of 2 garlic varieties were both increased gradually with the raise of nitrogen application level in this study.With the nitrogen level lower than or equal to N240,the significant correlations between the NNI and aboveground dry matters,relative yields of garlic scape and bulb were found.According to the change of NNI value under different nitrogen levels,we suggested the appropriate nitrogen application rate of 240 kg/hm2 for 2 local garlic varieties in this area.