| Wheat, the main food crop in North China, is often threatened by drought and water deficit. Itis very important to improve wheat productivity in this area, which is beneficial to increasefarmer profit and ensure national food security. It has been proved through a large number ofpractices that wheat planting models including plastic mulching, straw mulching and no/minimumtillage had significant positive effects on soil water storage, drought alleviation and incomeincrease. In order to investigate the effect of mulching and tillage on soil water conservation, soiltemperature enhancement, grain seed formation and contribution rate of top four leaves andnon-leaf organs to grain weight, a consecutive5-year field experiment was carried out during theperiod from2008to2013by designing different planting models including conventional plantingwith no mulch (T1), one-crop full plastic film mulching with soil covered on plastic (T2),two-crops full plastic film mulching with soil covered on plastic (T3), straw mulching (T4),half-mulched planting with soil covered on plastic (T5), no/minimum tillage (T6), full plasticmulching without soil covered on plastic (T7) and side-mulched planting (T8). The main results inthis research were showed as follows.1. Significant soil water storage effect was observed in T3. T3soil water average content in0-200cm was12.5%higher significantly than that in T1over four years as a whole. During theyears from2011to2012when precipitation was sufficient, soil water contents in0-20cm,20-100cm and100-200cm increased by12.7%,19.9%and41.0%compared to those in T1,respectively. In summer fallow period, T3soil water content amounted to64.3%(29%in T1).During the period from2012to2013when precipitation deficit occurred seriously, T3soil watercontents in0-20cm,20-100cm and100-200cm increased by18.5%,15.9%and21.1%comparedwith those in T1, respectively. In average, Soil water content in T3was20.7%higher than that inT1during the period from anthesising to mature. Moreover, T3average increase of soil watercontent in0-20cm and100-200cm soil layers were14.0%and10.8%in contrast to those of T1,indicating that the increase occurred in the upper soil layers did not result in the decrease in thedeeper layers. Similarly, soil water contents in T6in0-200cm layer increased by7.8%comparedwith T1. But obvious water increase in the upper soil layers was not found in this experiment(0.6%), probably due to strong water loss with high temperature. Only0.9%increase in soil watercontent was found in T2compared with T1(CK) over five years as a whole. T2soil water contentin0-20cm and20-100cm reduced by3.7%and1.4%while increased in100-200cm by1.5%during the period from2011to2012, indicating that T2had some effect on soil water storage inmoisture year. In contrast, T2soil water content in0-20cm increased by4.6%while reduced by4.7%and3.9%in20-100cm and100-200cm during the period from2012-2013, indicating that water had the tendency to move up from the deeper soil layer (100-200cm) in dry year.T5showedstronger water-lifting effect than T2with12.9%soil water increase in0-20cm in contrast to T1(CK). Significant soil water storage effect was also observed in T4with the2.8%increase in0-200cm compared with T1(CK) when averaged over five years. In detail, T4soil water content atseedling stage increased by9.8%while decreased by2.5%at anthesising stage compared to T1(CK) over five years as a whole. In addition, no significant water-lifting effect was observed inthis experiment since soil water content in upper layers (5.9%,0-20cm) showed the similarincrease to the deeper layers (4.0%,100-200cm). T8soil water content in0-200cm increaseaveragely by3.8%compared with T1, showing the significant water storage effect. In contrast toT1(CK), water use efficiency (WUE) in T2, T3, T4, T5, T6, T7and T8increased by21.5%,25.8%,9.1%,20.7%,13.5%,11.7%and0.3%, respectively.2. Significant temperature effects were found in T2and T8.On average over five years, T2soilaverage temperatures at three growth stages of seedling, overwintering and green-recoveringenhanced respectively by1℃,1.1℃and2℃compared with CK(T1), while those at the stages ofjointing, booting, heading and ripening reduced respectively by0.8℃,1.3℃,1.6℃and2.1℃. Asto T8, there existed respectively increased respectively by0.1℃,0.4℃and0.1℃at the stages ofseedlings, overwintering and green-recovering compared with T1(CK), while reducedrespectively by1.4℃,2.5℃,3.3℃and2.1℃at the stages of jointing, pregnant, heading andripening. Consequently, it would be concluded that T2and T8elevated significantly soil averagetemperature during the former period of growth season while in turn reduced it during the laterperiod. Soil average temperatures in T7at six stages including seedlings, overwinter,green-recovering, jointing, booting and heading elevated respectively by1.9℃,2.1℃,1℃,0℃,1.9℃and0.1℃as compared to CK and reduced by0.5℃at harvest, indicating thetemperature-enhancing effect of T7during full growth period. Obvious temperature-decreasingeffect was found in T4during the latter growth period. Through measuring daily dynamic of soilaverage temperature under different kinds of treatments, results showed that soil temperature at5cm and10cm changed faster than those at20cm and25cm. Besides, soil temperature of T2, T4and T8changed slower than those both T1(CK) and T7.3Seeing from wheat population growth dynamic, three kinds of planting models including T2,T4, T5have more individuals and heading per mu than the others. Results through analyzingseeding formation feature showed that seed filling rate in T2was higher and filling duration timewas shorter than that in T1(CK). On the contrary, seeding filling rate in T7was reduced andduration time was lasted compared with T1(CK). Some results were also observed in this researchby investigating contribution rate of top four leaves and non-leaf organs to grain weight of different winter wheat cultivars (line). For example, the contribution rate of whole wheat plantamounted averagely to75.9%, and those of non-leaf organs, top four leaves and flag leaves were39.7%,20.1%and9.3%, respectively. Compared with T1(CK), T3grain weight accumulationfrom different kinds of wheat organs was significantly higher than that of T1(CK) and T4,indicating of more stronger compensation effects of wheat organs (leaf and non-leaf) in T4thanthe others. Results from yield analysis showed that average plot yields of T2, T5, T3, T7, T4, T6andT8increased by18.9%,15.9%,12.0%,9.2%,6.6%,1.4%and1.2%, especially in dry year. Forinstance, grain yield in T2and T3increased67.0%and30.0%during the experiments season from2012to2013as compared to CK, indicating that T2and T5have better yield effects than theothers. By analyzing wheat yield components under different kinds of treatments, Results showedthat spike number, head seed number and plant height were higher than those of T1(CK), whileharvest index and seed volume were lower.In dryland area, significant soil water-lifting ability observed from One-crop full plastics filmmulching with soil covered on plastic (T2) tended to increase and maintain water content in theupper soil layer, which was beneficial to develop strong seedling due to enough tillers andvigorous secondary root. Moreover, T2temperature–adjusting effect (increasing in the formergrowth stage and decreasing in the latter growth stage) improved wheat growth, enhanced WUEand resulted in the significant increase of economic yield. But it was noticeable that excessiveutilization of soil water in the deeper layer was harmful to the sustainable development of drylandsystem as a result of water-lifting effect in T2. Two-crops full plastic film mulching with soilcovered on plastic (T3) which was found to be able to store water during summer fallow periodand enhance WUE proved to be a valuable planting model in dryland system, and it could reduceenvironment pollution because of saving plastics. Straw mulching (T4), no/minimum tillage (T6)and side-mulched planting (T8) have some effect on soil water storage and could be spread insome dryland area. |
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