Effect Of Post-sowing Soil Compaction And Pre-winter Irrigation On Cold Resistence And Yield Of Winter Wheat

In order to clarify the effect of post-sowing soil compaction and pre-winter irrigation on soilconditions, growth and development and grain formation of winter wheat, field experiments werecarried out during2012-2014growing years at Gaobeidian, Hebei Province, using two winter wheatcultivars, Shimai12and Shixin828as materials. The experiments for two cultivars were all designed assplit plot arrangement, with irrigation as main plots (with and without pre-winter irrigation,respectively), and soil compaction as split plots (with and without soil compaction after sowing,respectively). The main results were summarized as follows.The soil water contents during winter and spring were higher, and the soil temperature was morestable under the treatment with pre-winter irrigation than those without pre-winter irrigation. Comparedwith no compaction, the soil water contents during pre-winter period and at double ridge stage increased,and the pre-winter soil temperature was higher at night. Surface soil hardness was increased under theconditions of soil compaction and pre-winter irrigation, but the soil hardness of the deeper layers wasdecreased under pre-winter irragation.Under the conditions without pre-winter irrigation, when winter dormancy of2012-2013started,the activity of superoxide dismutase (SOD) in tillering nodes of the two wheat cultivars were all higherunder the treatment without post-sowing soil compaction than those with soil compaction. The SODactivity in leaf blads, however, was defferent between the two cultivars. When winter dormancy of2013-2014started, under the conditions without pre-winter irrigation, the SOD activity in tilleringnodes of the cultivar Shimai12was higher in the treatment with soil compaction than those without soilcompaction. During deep winter dormancy of2013-2014(December20and January12), the SODactivity in tillering nodes of the cultivar Shixin828of the treatments without pre-winter irrigation butwith soil compaction, and with pre-winter irrigation but without soil compaction were higher than thatneither pre-winter irrigation nor soil compaction. The SOD activity in tillering nodes of Shimai12ofthe treatments with pre-winter irrigation and soil compaction, and with irrigation but without soilcompaction, were higher than that neither pre-winter irrigation nor soil compaction.Under the conditions without pre-winter irrigation of2012-2013growing year, the activity ofperoxidase (POD) in tillering nodes and leaf blades of the cultivar Shixin828was higher under thetreatment without post-sowing soil compaction than that with soil compaction. The POD activity ofShimai12, however, was different between in tillering nodes and in leaf blades, and was differentbetween the winter dormancy started or not. Under the conditions without pre-winter irrigation of2013-2014, the POD activity of Shimai12was higher in the treatment with post-sowing soilcompaction than that without soil compaction. Under the same conditions with or without soil compaction, the POD activity of the two cultivars was usually higher in the treatment with pre-winterirrigation than that without irrigation during deep winter dormancy (December20and January12).The effect of post-sowing soil compaction and pre-winter irrigation on the contents ofmalonaldehyde (MDA) in tillering nodes and leaf blades of wheat was different between the twocultivars. Under the same condition with or without pre-winter irrigation, the MDA contents of thecultivar Shimai12with soil compaction was higher than that without soil compaction; but it was reversefor the cultivar Shixin828. Under the same condition with or without soil compaction, the MDAcontents of the cultivar Shimai12with pre-winter irrigation was higher than that without irrigation; butit was different for the cultivar Shixin828deponding on the organs and whether with soil compaction ornot. Before winter dormancy period, the soluble sugar content and starch content in tillering nodes andleaf blades of winter wheat increased, and it reached the maximum on December7. The content ofsoluble sugar in the two organs was all lower under irrigation treatments than that without irrigation.The effect of post-sowing soil compaction on soluble sugar content was different between the twocultivars. The starch content in tillering nodes of the cultivar Shixin828was higher in the treatmentwithout soil compaction than that with soil compaction. But for Shimai12, however, the starch contentin tillering nodes and leaf blades was higher in the treatment with soil compaction than that without soilcompaction. The starch content in tillering nodes and leaf blades of the irrigation treatments declinedwhen winter dormancy started (December7), but increased thereafter (December20).The analysis and estimate by means of principal components analysis showed that, the effects ofpost-sowing soil compaction and pre-winter irrigation on cold resistence of winter wheat were differentdeponding on previous crops and rainfall distribution during growing period. Soil compaction andpre-winter irrigation treatments had little effects on cold resistance of wheat during2012-2013growingyear when pre-winter precipitation was sufficient and without previous crop straw returning to the field.But the cold resistence of wheat increased during2013-2014, during which there was little pre-winterprecipitation, and the soil was loose because of large amount of previous maize straws incorporation.The secondary roots at erecting, jointing and anthesis stages of wheat of the pre-winter irrigationtreatment were less than those without pre-winter irrigation. And the culms per hectare, LAI, and drymatter accumulation amounts at all the growth stages in spring of wheat of the pre-winter irrigationtreatment were less than those without pre-winter irrigation. The pre-anthesis dry matter accumulationof the treatment with compaction decreased comparing with that without compaction. But the dry matteraccumulation amounts were not significantly different between those with and without compaction atmaturity, because the photosynthetic rate and chlorophyll SPAD of leaves of the treatment withcompaction decreased slowly after anthesis, so that more dry matters accumulated after anthesis. Grainfilling simulation by Logistic equation and the parameters of grain filling characters showed that, theeffect of post-sowing soil compaction and pre-winter irrigation on grain filling was different. The wholegrain filling duration was expanded under soil compaction treatment, through longer durations of linergrain filling period T2and chronic grain weight increasing period T3. The whole grain filling rate wasincreased, however, under pre-winter irrigation treatment, through higher grain filling rates during liner grain filling period P2and chronic grain weight increasing period P3, so that the grain weight increased.The amounts of spikes per hectare of the treatment with compaction was less than that withoutcompaction, but the grain yield difference between compaction and no compaction was not significant,because of the more grains per spike and the higher1000grain weight for the treatment withcompaction. The grain yield of the treatment with pre-winter irrigation tended to decrease, even thoughthe higher1000grain weight compared with that without pre-winter irrigation, because mainly of lessspikes per hectare and grains per spike, especially the significant decrease of grains per spike.The pre-anthesis dry matter accumulation amount, translocation amount and transloction rate tograin, and the contribution of pre-anthesis dry matter translocation to grains of the two cultivars were alllower under soil compaction and irrigation treatments compared with those without soil compaction orirrigation, respectively. The amount of post-anthesis dry matter accumulation in grains, however,increased. Compared with no pre-winter irrigation, the nitrogen accumulation of total plant and in leafblades, sheathes and stems and spikes was all lower at anthesis, and N translocation amount fromabsorbed N before anthesis to grain and its contribution to grain also reduced, but grain N accumulationafter anthesis and N post-anthesis contribution to grain increased.The translocation amount and translocation rate of nitrogen absorbed before anthesis to grain, andits contribution to grain N was decreased under the condition of soil compaction, but N accumulationafter anthesis and its contribution to grain increased. Thus there was not different beteewn thetreatments with and without soil compaction, because of the compensation effect of more post-anthesisaccumulation of nitrogen. The water use efficiency of the two caltivers reduced in the treatments withpre-winter irrigation. There was little effect of soil compaction on nitrogen use efficiency, but the effectof irrigation on nitrogen use efficiency was different beteewn the two caltivars.According to the results of the study, pre-winter irrigation is an effective measure to protect wheatseedlings from cold injury based on the unpredictability of long term weather. But in terms ofimproving yield and water use efficiency, it is not necessary under the conditions of sufficient soilmoisture after sowing. Under such conditions, post-sowing soil compaction should be applied toalleviate the adverse effect of low temperature and temperature fluctuation on winter wheat, especiallyunder the conditions with large amount of previous crop staws returning.