滴灌施肥对设施栽培花椰菜根系和土壤中氮分布的影响

Effects of different fertigation strategies on the distribution of cauliflower's roots and soil nitrogen

针对我国温室蔬菜水肥一体化管理水平低下、灌溉施肥制度不完善等问题,本研究以设施花椰菜为研究对象,展开了不同的滴灌施肥处理对花椰菜根系生长和其生长土壤硝态氮分布规律影响的田间试验。试验设置了由不同水肥顺序组成的4种滴灌施肥处理,即T1(1/5N-4/5W)、T2(1/5W-1/5N-3/5W)、T3(2/5W-1/5N-2/5W)、T4(3/5W-1/5N-1/5W),如T2(1/5W-1/5N-3/5W)表示整个灌水过程的前1/5时间灌水,接下来的1/5时间施肥,后3/5时间灌水冲洗管道,其他类同。在花椰菜生育期内对土壤水分状况进行测定,收获后测定花椰菜产量、品质及根长密度等指标。研究结果表明:1)滴灌施肥对设施花椰菜产量、品质和氮素累积量的影响均未达到显著水平。花椰菜氮素累计总量随着滴灌施肥时间的向后推移先减小后增加,其中T4处理的氮素累计量最高,达50. 23 mg/kg。2)通过对比各处理种植前和收获后的土壤无机氮的变化状况,发现种植前土壤无机氮质量分数呈表层高、深层低的特点,收获后土壤剖面的无机氮分布更为均匀,对比发现T1和T4处理更容易发生硝态氮的淋失。3)灌溉施肥过程中前期施肥处理的根系纵向生长更好,而后期施肥处理的根系横向生长更好,其中T3处理的根长密度最大,为2. 54 cm/cm^3,根系分布范围最广。4)各根系根长参数与土壤硝态氮质量分数均呈一次线性正相关,其中直径<2 mm根系根长的拟合效果最好(R^2=0. 811 8)。综合考虑产量、品质和根系生长分布等指标,灌水过程中前2/5时间灌水,接下来1/5时间施肥,后2/5时间冲洗管道的T3方案较优。

[Background]In older to solve the problems of low level of water and fertilizer management of vegetable facilities and imperfect irrigation and fertilization system in China,field experiments were conducted in a solar-heated greenhouse to study the effects of different fertigation strategies on root growth and distribution of nitrate-nitrogen from a surface point source of urea. [Methods] Four fertigation strategies with different orders in which water and nutrients was applied for an irrigation event were thatT1（ 1/5 N-4/5 W）,T2（ 1/5 W-1/5 N-3/5 W）,T3（ 2/5 W-1/5 N-2/5 W）,and T4（ 3/5 W-1/5 N-1/5 W）,for example,the 1/5 W-1/5 N-3/5 W represented irrigating water at the first 1/5 of the fertigation time,applying nitrogen at the second 1/5 of the fertigation time,and washing pipeline with water at the last 1/5 of the fertigation time,the interpretation of other treatments were similar. Cauliflower was taken as the research object in the experiment,and each treatment was triplicate. Soil moisture was determined once a week during caulifower growth. Yield was recorded for each harvest,and the quality,root length density of cauliflower and soil inorganic nitrogen was determined at the end of the experiment. [Results] 1）Fertigation strategies had no significant effects on yield,quality and nitrogen accumulation of cauliflower.The treatments of applying the nitrogen in the later stage（ T3 and T4） had higher yield by comparing the treatments of applying the nitrogen at the beginning stage（ T1 and T2）. The total nitrogen accumulation of cauliflower showed a trend of decreasing first and then increasing by delaying the nitrogen application to later stage,the nitrogen accumulation in T4 reached the highest of 50. 23 mg/kg. 2） By comparing each treatment in the distribution of inorganic nitrogen during per-planting and post-harvest,we found that the content of inorganic nitrogen in soil before planting was high in surface and low in deep layer and the distribution of inorganic nitrogen in post-harvest soil profile was more uniform. Comparing other treatment,nitrate leaching was more likely to occur in T1 and T4. 3） The measurements of root distribution showed that fertigation at the beginning of the irrigation cycle promoted longitudinal growth of cauliflower’s roots,and fertigation at the end of the irrigation cycle promoted lateral growth of roots.Contrast with other treatments,T3 had the largest root length density（ 2. 54 cm/cm^3） and the widest root distribution. 4） A significant linear relationship between the content of soil nitrate-nitrogen and the root length was found,and the root with diameter 〈 2 mm had better fitting effect than other indexes of root length（ R^2= 0. 811 8）. [Conclusions] Considering yield,quality,nitrogen use efficiency,root length density and the nitrogen content in soil,the strategy of T3,i. e.,applying water at first for 2/5 of the total irrigation time,then applying fertilizer for 1/5 of the total irrigation time,followed by applying water for the last 2/5 of the total irrigation time,was suggested.