| In order to research high efficient water use mechanism and soil environmental effects of inthe northwest Arid Regions, China, a combination of mulch means and irrigation experimentswere conducted during two consecutive years of2011and2012, at Minqin Experimental Station,Gansu Hydraulic Research Institute, in Minqin city, Gansu, China. The experiments followed acompletely randomized double factors design with four coverage levels: no coverage (N), strawmulching (S), plastic film mulching (F), crushed wheat straw padding plastic film mulching (SF);and three irrigation quota levels: H,900m3/hm2; M,750m3/hm2; L,600m3/hm2. There are12treatments, repeating3times. The main results are as follows.(1) Mulch means significantly affected crop emergence rate (P<0.01). The experiment aboutsunflower emergence rate in2011showed that, SF was increased by14.33%with S, and49.32%with N. In2012, corn test results show that, SF was higher49.50%than S,21.36%than N. Inshort, the emergence rate with SF was close to with F, far higher than S and N. So, SF can be usedto solve the question "low emergence rate" with S in the northwest Arid Regions, China.(2) Mulching means significantly affected the sunflowers’ height, stem diameter, productionincluding its component factors, characters, harvest index in2011(P0.01) sunflowers plantedwith SF means have the widest stem diameter and the heaviest100kernel weight, and those withF means follows. However, sunflowers in plastic film mulching were the best in plant height, dryweight of root, stem and leaf, single plant biomass and grain weight, biological yield, grain yieldwhile sunflowers with F means take the second place. Irrigation quota doesn’t have a remarkablemain effect on plant height and stem diameter before the irrigation whereas it does after theirrigation. The interaction between different mulching means and different irrigation quota leveldoesn’t show a significant effect on the production and its components, characters (P0.05)while it exerts a significant effect on the harvest index. All factors including plant height, stemdiameter, production and component factors, characters, harvest index of production considered,FM, SFM are the optimal portfolios, that is plastic film mulching and M irrigation quota,crushed wheat straw padding plastic film and M irrigation quota.(3) Mulching means significantly affected the corns’ height, stem diameter, productionincluding its component factors, characters, harvest index(P0.01).The difference in mean value of stem diameter with different mulching means was very significant(P0.01), the sequence being SF S F N. The stem diameter with SF increased by2.20mm0.26mm0.93mm respectively, compared with those with N S F. There is a significantdifference between SF and N,S (P0.01) with the production of kernel being3444.72kg/hm24415.79kg/hm2higher than that with N, S respectively. The main effect of mulching means onear length, baldhead length was significant (P0.05) while the main effect on ear diameter, rowand weight was not significant (P0.05). Therefore, it can be concluded that crushed wheat strawpadding plastic film and plastic film mulching don’t have an impact corn production and itscomponent factors. The main effect of irrigation quota level on corn plant height, stem diameterand production including its component factors, characters, harvest index was not great. Theinteraction between different mulching means and different irrigation quota level did show somesignificant effect on the production and its components, characters and harvest index. Consideringthe above factors, SFM is the optimal portfolio and FM takes the second place. (4) The main effect of mulching means and irrigation quota level on water content of0~120cm soil was not significant before irrigation while significant after irrigation. The overallsoil water content of crushed wheat straw padding plastic film was greater that of plastic filmmulching. The initial value of SF was a bit lower than that of F. The soil water content with SFwas the highest after planting25days. The reason for good water conservation effectiveness wasdue to the double effect of plastic film and straws. The higher irrigation level (H) has the higherwater content and the medium irrigation level (M) follows, the lower (L), the last, which was dueto different irrigation level. Hence, concerning the water conservation effect, SFH is the best andSFM takes the second place.(5) In terms of the horizontal time axis, daily variation of the soil temperature and airtemperature of0~25cm soil with different mulching means showed a trend of a gradual increasewith depth first and then a gradual retardation. Regardless of the mulching means, the peak valuealways occurred at the surface. The peak value of plastic film mulching (F)with a warming effectemerged one hour earlier than that of peak no mulching treatment while the peak value of crushedwheat straw padding (SF) and straw mulching (S) with a cooling effect was one hour late. Thefilm of crushed wheat straw padding plastic film mulching (SF) had a warming effect, so its peakwas t7higher than that of straw mulching (S). Like the peak value, the widest breadth value ofthe temperature range for every mulching means appears on the surface. The temperature range ofplastic film mulching (F) with a warming effect was wider than that of no coverage (N); Thetemperature range of crushed wheat straw padding plastic film mulching (SF) and straw mulching(S) was narrower because of their cooling effect. The temperature range of crushed wheat strawpadding plastic film mulching (SF) was7wider than that of straw mulching (S). The change intemperature has three types: in the morning (6:00~7:00), soil temperature increased with anincrease of depth, lower on the surface, and higher in underground; At noon (8:00~16:00), thehighest soil temperature emerge at the surface, the surface radiant; Evening (17:00~20:00), soiltemperature peak appeared in5cm and10cm, the middle radiant. On the same day, the soiltemperature presents the low-high-low unimodal cycle. Soil temperature of0to25cm depthfrom the middle of June after planting showed a rising trend, and after that the temperature isstable. Chopped straw mat film covering (SF) and no cover processing (N),(F) of plastic filmmulching, straw blocking the sun’s radiation directly, with straw mulching (S) cooling effect;Compared with straw plastic film mulching (F)and no coverage(N), the crushed wheat strawpadding plastic film mulching (SF) stopped solar direct radiation and has a cooling effect(6) In the crop growth period, mulch means improved soil bulk density in0-40cm soil layer.N, S and SF could reduce soil bulk density and increase soil total porosity increased soil totalporosity in0-10cm soil layer, while F increased the soil bulk density and decreased soil totalporosity. Compared with N, SF had the characteristics of low soil bulk density and high totalporosity in the topsoil (0~40cm), while F and S had those of high soil bulk density, low soil totalporosity. It showed that SF could improve the soil structure and porosity, which was beneficial tocrop root growth.(7) With the soil depth in0~120cm profile, soil pH value of mulch means decreased at thesunflower field in2011. SF could reduce the soil pH value in0~30cm. Compared with N, S and F,the soil pH value were decreased respectively by3.51%,2.15%and3.69%. In2012, at the cornfield, with the advance of the corn growth, the average soil pH value of mulch means in0~120cmshowed an obvious decreasing trend. Among mulch means, pH in SF was the minimum, and that of F was the maximum. This is results that crushed straw degradation process and root exudatesdecreased the soil pH value. This showed that SF could significantly reduce soil pH value in thesoil surface, prevented soil secondary salinization, which made the desertification of irrigationdistrict contained and the soil environment further improved. In seedling sunflower and maize, forthe many exposed field and strong evaporation, mulch means aggregated soil salinity in soilsurface with different degree, especially in0~5cm with F. In the whole growth period, saltaccumulation in surface weakened with the progress of growth period gradually; SF significantlyinhibited salt accumulation in0~5cm of soil, but F apparently made salt accumulation increase insurface soil. From the profile view, salt structure changed significantly in0~120cm of soil, and Fincreased soil salt content, while SF had the role of desalination. This is because after sowingirrigation SF had good water retention effects, made soil water content fuller, get soil salt movedown with water, and the less moisture the lower salinity irrigation in the lower layer. In this way,salinity leaving crops root zone is conducive to the growth of crop roots. So, Planting sunlowerand corn with SF could obviously inhibit soil soluble salt accumulation into the surface, made thefarmland soil environment improved further, and more effectively prevented and controlled thedesertification of irrigation district.(8) The HCO-3content at0~120cm soil in sunflower field showed the trend of "big in themiddle, small in both ends". SF can reduce the HCO-3content in topsoil (0~30cm), and increasedit in deep soil (60~100cm). In sunflower seedling stage, N, S, F accumulated Cl-and SO2-4into0~5cm soil, especially F most obviously; while SF could inhibit the accumulation of Cl-and SO2-4into soil surface. SF could reduce Cl-and SO2-4content in topsoil, and increased it in the lowerlayer. It was mainly because that double water retention role of SF made Cl-and SO2-4leached intothe lower soil.(9) With the development stages of sunflower, the Ca2+and Mg2+content with mulch meansin0~120cm decreased. F has accelerated the loss of Ca2+and Mg2+in topsoil (0~40cm), while Sand SF could inhibit their loss. It was because that SF decreased the pH value, and inhibitedsolubility of fixed state calcium and magnesium reducing of the stationary state of calcium andmagnesium. It was the result of plant root respiration, root exudates, and decomposition of crushedwheat straw and the crop root after harvesting. SF slowly declined Ca2+content in30~60cm fromseedling to blossom, and quickly increased it from blossom to harvest. However, F decreasedquickly, and increased slowly. The K+content in0~120cm soil profile of sunflower field was lessin particular. K+accumulated in0~10cm soil, especially in0~5cm soil with S and SF. Insunflower seedling, the Na+content obviously accumulated in0~5cm with N, S and F, especiallywith F. While, SF could inhibit the Na+accumulate into the soil surface. At the same time, Na+content with SF in40~60cm soil increased significantly, because Na+with SF in the surface andcultivated soil was leached down. During blossom and harvest period, the Na+content at60~120cm soil increased significantly, because of more obviously leaching effect with SF. Fromthe point of soil depth, the SAR in0~30cm soil was smaller, that in30~60cm soil was maximum,and that in60~120cm soil was between0~30cm and30~60cm. On the one hand, this is becausethat Na+was leached into the lower layer, at the same time, the Na+content increased in the lowerlayer. On the other hand, it is the result that Ca2+and Mg2+content decreased in the lower layer.The SAR in the soil surface and cultivated soil with SF was significantly lower than othertreatments.This is because that the ratio of soluble Na+in0~5cm soil with SF decreased, while theratio of soluble Ca2+and Mg2+increased. However, soil SAR with SF in30~120cm increased, which explained that ratio of soluble Na+in the lower soil increased, while ratio of Ca2+and Mg2+decreased accordingly. Thus, it can be seen that SF would make the cationic composition changedin the profile. Salt ions beneficial to crops accumulated, those harmful to crops were leached. Thiswould play a certain positive role of improving the soil environment, preventing soil salinization,and curing irrigation area desertification in the northwest arid area, China. |
PDF Full Text Request