| The production of wheat could be improved by adjusting the seeding time and plantdensities. The varieties (XinDong22, XinDong27, XinChun6and XinChun22) was tested inour researches. The experiment set up different dates of seeding and plant densities treatment,for winter wheat was set up two sowing dates(S1: on September27and S2: on October7)and three planting densities(D1:rate of150kg·hm-2;D2: rate of225kg·hm-2and D3: rateof300kg·hm-2),for spring wheat was set up two sowing dates(S1: on March20; S2: onMarch27and S3: on April4)and three planting densities(D1:;D2: and D3),and in which wediscussed the effect of the date of seeding and plant densities on Stem growth dynamic, leafarea index, dry matter, photosynthesis characters, yield and components of yield for wheat.The results were shown as follow:1. The highest production was found at S2D2treatment for winter wheat. The grain yieldwas affected significantly by sowing date and plant densities for the winter wheat under dripirrigation condition. The plant densities had a significant effect on grain number per spike,harvested spikes and thousand grain weights. The harvested spikes increased with plantdensities, while a decline was found for grain number per spike and thousand grain weights.The grain yield of spring wheat and spring wheat was the highest at D2treatment on March20, but the spring wheat at D3treatment had the highest on March27and on April4.Thespring wheat didn’t show a significant difference for grain number per spike, but a significantdecline was found for harvested spikes, thousand grain weights and grain yield as sowing datedelaying. the harvested spikes increased, but grain number per spike and thousand gainweight decreased with plant densities.2.Density has no impact on the process of drip irrigationed wheat, with the delaying ofsowing date, winter wheat emergence time became longer, but the whole days of wheatbecame shorter; for spring wheat emergence time shortened, the total growth period shorten.3.There was a significant increasing for the basic seedling numbers, total stem numbers,harvested panicles as the plant densities increasing for wheat, but a significant decreasing wasalso found for the ratio of spikes to tillers. For winter wheat, the harvested numbers increaseddue to decreasing stem numbers, but increasing ratio of spikes to tillers as the seeding timewas delayed. For spring wheat, but the ratio spikes to tillers was decreased. The yield wasaffected due to decreasing the harvested numbers and the ratio of spikes to tillers as delayingthe seeding time.4.The wheat had the highest LAI at booting stage. For winter wheat, the S2had a higherLAI compared to S1. In addition, The LAI had an increasing with plant densities atS1sowingdate, and had an increasing firstly then decreasing as plant density increasing at S2sowing date。At S2sowing date the LAI is D2>D3>D1,and there was a significant decreasingfor D3at about fourteen day after flowering stage. The same result had been found for spring wheat at S2and S3treatments. At the booting stage, the LAI obtained the highest value anddecreased at flowering stage. The LAI had a quick decline at the fourteenth day afterflowering as the plant densities increasing and seeding time delaying.5.The dry matter at harvested stage had a significant decreasing for the wheat undersubsurface drip irrigation condition as the seeding time delaying. There was a increasing fordry matter and the contribution of photosynthate to grain with the plant densities at S1treatment for winter wheat. However, the winter wheat at D2treatment had a significanthigher dry matter and the contribution of photosynthate to grain compared to that at D1andD3at S2treatment. It is helpful for dry matter and contribution of photosynthate to grain toimprove when the sowing date was appropriate. There was an increasing tendency for amountof mobilization of pre-anthesis stored assimilate and contribution of post-anthesis assimilateto grain weight, which was the highest at S2D2treatment, as seeding date delaying. The drymatter showed a decreasing trend as the sowing time delaying, but an increasing tendencywith plant densities for the spring wheat under drip irrigation condition. There was asignificant decreasing for amount of mobilization of pre-anthesis stored assimilate andcontribution of post-anthesis assimilate to grain weight as the sowing time delaying.6.The SPAD of the wheat flag leaf at different treatments firstly had a increasing trendand then a decline at the whole growth period. There was a highest value at flowering stage.The SPAD was significantly affected by sowing date and plant densities. As the sowing datedelaying, the SPAD increased after elongation stage. The SPAD decreased with plant densitiesand a fast decline was found as the plant densities increasing on the fourteenth day afterflowering stage. The SPAD of spring wheat had a increasing and then decreasing tendency onthe whole growth period, and wheat flag leaf decreased quickly as the sowing date delaying orthe plant densities increasing. In addition, a significant difference was found between D1andD3treatment.7.The canopy apparent photosynthetic rate (CAP) of winter wheat under drip irrigationcondition insreased significantly as sowing date delaying, but increased significantly withplant densities after flowering stage. The CAP at D1treatment had a significant differencecompared to that at D2and D3, but there was not difference between D2and D3. In addition,The CAP at D3decreased at the fourteenth day after flowering because of a very significantintraspecies competition.The canopy apparent photosynthetic rate (CAP) of spring wheatunder drip irrigation condition decreased significantly as sowing date delaying, but increasedsignificantly with plant densities after flowering stage. The CAP at D1treatment had asignificant difference compared to that at D2and D3, but there was not difference between D2and D3. In addition, The CAP at D3decreased at the fourteenth day after flowering becauseof a very significant intraspecies competition. |
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