| Maize yield significantly increased due to the functions of rainwater collection and heat preservation for the cropping pattern of two ridges and their furrows covered by plastic film (namely plastic film fully mulched ridge-furrow). Some mechanism to increase production was not very clear when this planting pattern has been widely used for planting maize. For instance, how to collect and redistribute rainwater, how to guide them to the maize root zone? Subsequently, how does water that infiltrated into the soil moisture move and distribute in the soil profile. Mastering these physical process is of great significance to further improve the utilization rate of rainwater. Besides, how does the mulching and nitrogen-added affect the corn production? For these purpose, three experiments were designed in this paper to research the rainwater distribution characteristics, soil moisture migration behavior and the relationship between nitrogen levels and maize yield respectively under the cropping patterns of plastic film fully mulched ridge-furrow.1. On April 10 of 2013, dye tracer and simulated rainfall were used to study the effect of film mulching on distribution of rainfall in soil at Gansu Agricultural University Dingxi Experimental Station. Three kinds of planting patterns were designed:flat plot (FP), ridge-furrow (RF), and clear plastic film fully mulched ridge-furrow (FMRF) cropping. Dyed water was showered using a rainfall simulator.24 hours after simulated raining, soil surfaces and vertical soil profiles were photographed and staining features were used to indicate infiltration path and distribution of rainwater in the soil.2. On October 5th of 2013, dye tracer and geostatistical methods were designed to assess the water movement and distribution in soil at the experimental farm of the farm machinery center, MinQin county. Two plots (10.0 m apart) were carefully selected. Plot 1 contained alfalfa without tillage for the past 10 years. Plot 2 contained alfalfa with no tillage for the first 5 years and corn with conventional tillage for the succeeding 5 years. A dye tracer was introduced to these plots and the different types of water flow were visualized using classified dye-stained patterns. In addition, Semivariance analysis was performed to determine spatial variability on a centimeter scale.3. To investigate the effect of four nitrogen level (N0、N207、N311 and N414) on maize yield, two cropping patterns of plastic mulching furrow ridge and bare furrow ridge were conducted in Minqin oasis.The entire soil surface was dyed in the FP and RF plots whereas the dyed regions were confined only within narrow bands at the bottoms of furrows in the FMRF plots. In the vertical soil section perpendicular to crop lines, despite the similar area of dyed regions between three treatments, the maximum depth of the dyed regions across rainfall simulation durations increased by 47-72% and 129-156% in RF and FMRF, respectively, compared to FP treatment. The stained region matched the assumed maize intensely-rooted zone perfectly in the FMRF plots, but this matching was limited in FP or RF plots. In addition, the FMRF profoundly increased soil water content in the stained areas compared to FP or FR cropping system. Our study demonstrated that rainwater in soil has the greatest likelihood to be used by crops in FMRF among the three cropping systems.The role of macropore flow was weaker in the alfalfa plot than in the corn plot because of the difference in flow path and distribution. A belt of high soil moisture content appeared in the vertical soil profile of the alfalfa plot, indicating that the macropore flow showed a deeper stained depth. Several scattered locations in the corn plot contained high amounts of water, suggesting that macropore flow also occurred. Moreover, a lateral flow with a wider stained width was triggered by the compacted tillage pan in the corn plot. Thus, the role of lateral flow was more dominant in the corn plot than in the alfalfa plot. The spatial correlation distance of the soil water content of infiltration patterns was 23.08 cm in the alfalfa plot compared with 10.52 cm in the corn plot. This trend indicated a high spatial variation of moisture in water infiltration patterns of the alfalfa field. In addition, strong spatial autocorrelation was observed in soil water infiltration patterns in both plots. Thus, our results highlighted a significant change of soil water behaviors (macropore flow, lateral flow, and interaction) in crop rotation from alfalfa to corn.Compared with bare furrow ridge, the effects of plastic film on soil temperature was mainly reflected in absorbing and holding warm in daytime while holding warm in nighttime. In addition, plant transpiration was the dominant type of soil water consumption in the plastic mulching furrow ridge, due to the smaller corn plant seedlings and coverage from April 19 to May 20 in each year. Less plant transpiration meantime more soil water evaporation in the bare furrow ridge, hence, the effect of plastic film on water was preserving soil moisture and it was more dominant in May. On May 5, compared with bare furrow ridge, the soil water content in 0-40 cm layer was keep by 38-51% with the film mulch. From July 5 to October 5, the main type of soil water consumption for two cropping patterns was the plant transpiration and it was more dominant in August. The function of keeping water was not obvious in this period of time. Therefore, the good water and heat environment under the plastic mulching furrow ridge promoted the maize germination and the seedling stage was advanced by 6-8 days. This characteristics accelerated the maize growth and development, and the greatest growth extent of the height, stem and aboveground biomass was appeared in plastic mulching furrow ridge advanced by one month. The height, stem and aboveground biomass was more dominant in plastic mulching furrow ridge than in bare furrow ridge during the growth period. The nitrogen demand of maize growth was supplemented in time by nitrogen addition. Thus the height, stem and aboveground biomass was higher, wider and heavier in the high nitrogen level. Three level interaction of the plastic film mulching, nitrogen rate and years significantly affected maize yield. The plastic film mulching significantly promoted the increasing of maize yield. Compared with bare furrow ridge, the range of maize yield increase caused by plastic film was 42-62% in 2012,45-57% in 2013, and 55-70% in 2014 under different nitrogen levels. Nitrogen addition significant affected maize yield. Compared with N0, N207, N311, and N414 increased maize yield by 70%,88% and 98% in 2012,63%,76% and 89% in 2013,58%,138% and 195% in 2014 in the treatment of no mulch; and this increased rang was 54%,66% and 73% in 2012,70%,91% and 102% in 2013,62%,132% and 174% in 2014 in the treatment of film mulched.These research results would provide theoretical basis for applying and expanding the cropping patterns of plastic film fully mulched ridge-furrow in arid zone. |
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