Effects Of Nitrogen Regulation And Cultivation Model On Sink-source Construction, Photosynthetic Production And Grain Yield In Rice At Two Kinds Of Ecological Conditions

Ecological condition, nitrogen regulation and cultivation model are important factors affect rice production, the study on optimization nitrogen regulation principle and high-yielding mechanism for kinds of cultivation models at different ecological condition would have a great significance in fertilizer efficient utilization and high and stable yields for rice. The effects of nitrogen regulation and cultivation models on sink-source construction, photosynthetic production and yield formation were studied under field at Wenjiang and Hanyuan by hybrid rice Eryou 498 during 2009 to 2010. the nitrogen regulation measure included nitrogen application rate and nitrogen application stagey, and cultivation models included wide-narrow row spacing cultivation, triangle cultivation, planting with the wide row and narrow plant space, scattered planting cultivation. The main results are follows:1. Effects of nitrogen regulation and cultivation modes on population and yield formation in rice at two ecological conditionsBecause of improving population quality, increasing dry matter accumulation and comprehensively improving yield components at Hanyuan with a superior temperature and light condition, the yield potential improved significantly; The high yield population had suitable productive panicles number, more spikelet number per panicle and higher seed setting rate at Wenjiang, while had sufficient productive panicles number and large panicle at Hanyuan. It is no avail to improving population quality basing on high LAI (leaf area index) under too high or too low nitrogen application rate. With increasing ratio of nitrogen application at panicle initiation stage, the LAI decreased, but population quality after heading improved.From the above, the 180 kg ha-1 of nitrogen application is the optimum amount for all cultivation models. when the total nitrogen application amount was 180 kg ha-1, the rational ratio of nitrogen application for transplanting stage, tillering stage and booting stage was 6:3:1 under wide-narrow row spacing cultivation and triangle cultivation, 5:2:3 under planting with the wide row and narrow plant space,4:1:5 and 5:2:3 under scattered planting cultivation at Wenjiang and Hanyuan respectively. It was suggested that achieving high yield by improving crop population quality basing on reasonable population size and increasing dry matter production after heading should adopt suitable nitrogen application strategy according to ecological condition and cultivation model. The study also proposed population quality indexes of super-high yielding-rice at two kinds of ecological conditions, and found there were different ways to construct population under different cultivation models, so the difficulty of each cultivation models in meeting requirement of high yield population was various. All kinds of cultivation models could improving population quality basing higher levels under suitable nitrogen regulation, but it is difficult to construct high yield population for wide-narrow row spacing cultivation and planting with the wide row and narrow plant space as well as scattered planting cultivation at Hanyuan with a superior temperature and light condition, their yield potential was lower than triangle cultivation.2. Effects of nitrogen regulation and cultivation modes on sink-source construction in rice at two ecological conditionsThe sink-source characteristics at Hanyuan showed that sink potential enlarged and source enhanced. Though the characters of the vascular bundles of the neck-panicle improved, the flow loading not decreased for more assimilates exported from source, and assimilates supplying rate for sink was insufficient, so it was difficult to increase filling intensity. However, because filling substance received by grain was more abundant by prolonging active filling time, grain filling rate and grain plumpness index increased, and accordingly effective sink-filling rate and actual sink-filling amount improved significantly.Besides, improve grain filling level basing enough size of sink was critical to increasing grain yield at Wenjiang, and overburden flow loading resulted in poor grain filling; Obtaining a high yield at Hanyuan depended on simultaneous enlarging sink size and improving grain filling to some extent, because the effects of flow limitation caused by enlarging sink size on grain filling decreased, the supply capacity of source was the key to achieve high level of grain filling. Under suitable nitrogen application rate, the capacity of source improved by coordinative development in leaf and stem as well as root, sink potential enlarged, transfer efficiency of the vascular bundles increased, so grain filling showed good, sink and source as well as flow got a coordinate development at a high level, actual sink-filling amount improved finally. With increasing ratio of nitrogen application at panicle initiation stage, the capacity of source improved although sink potential decreased, it is beneficial to promote grain filling. As a result, actual sink-filling amount improved by increasing effective sink-filling rate at Wenjiang. but at Hanyuan, it was difficult to improve grain filling by excessive increasing ratio of nitrogen application at panicle initiation stage, which would led to decreasing actual sink-filling amount for cutting down sink potential. In order to establish high yield population at different ecological condition, the suitable nitrogen regulation measures should be adopted according to different cultivation model. Under suitable nitrogen application rate or higher ratio of nitrogen application at basic and tillering, for wide-narrow row spacing cultivation and triangle cultivation, the source-capacity improved, assimilates through neck-panicle increased while flow loading not increased significantly, the grain filling was better, so their actual sink-filling amount improved. Because of getting a coordinate development in sink and source as well as flow under triangle cultivation, its actual sink-filling amount was higher than others. For planting with the wide row and narrow plant space and scattered planting cultivation, it was critical to limiting development of population at early-middle stage, increasing source production ability by improving source quality after heading, coordinating sink-source relationship, promoting grain filling, and improving actual sink-filling finally by decreasing ratio of nitrogen application at basic and tillering.3. Effects of nitrogen regulation and cultivation modes on photosynthetic production in rice at two ecological conditionsThough establishing more reasonable canopy morphological structure, improving single leaf and population photosynthetic characteristics and increasing crop growth rate (CGR), photosynthetic production at Hanyuan was higher than at Wenjiang(especially after heading).With increasing nitrogen application rate, photosynthetic area from flag leaf to third leaf of productive tillers expanded, photosynthetic rate(Pn) in flag leaf was increased, CGR increased with leaf area duration increased during early stage, but photosynthetic characteristics of lower leaf degradation because of rising in photosynthetic disparity in leaf position for Photosynthetic rate in flag leaf, CGR impacted by net assimilation rate(NAR) decreased significantly after heading, so too low or too high nitrogen application rate was not favorable for improving capacity of photosynthetic production. By increasing ratio of nitrogen application at panicle initiation stage, the canopy light transmittance performance improved, leaf photosynthetic characteristics increased, ratio of canopy respiration to total canopy apparent photosynthesis (CR/TCAP) tended to decrease, CGR impacted by NAR showed an increasing tendency, and it was difficult to promote canopy apparent photosynthesis (CAP) under excess nitrogen application rate. The effects of nitrogen regulation on photosynthetic production for cultivation models were not in agreement, it showed that:wide-narrow row spacing cultivation and triangle cultivation change distribution form of plants on field, when the ratio of nitrogen application was 6:3:1, their area from flag leaf to third leaf of productive tillers and Leaf specific weight as well as canopy light transmittance performance all improved, leaf and population photosynthetic characteristics tended increase, CGR was raised for both LAD and NAR increasing, so they had a great advantage in photosynthetic production after heading. However, once temperature and light conditions was improved at Hanyuan, the advantage of triangle cultivation enhanced, while wide-narrow row spacing cultivation reduced. For sprase planting by expanding spacing and reducing plant space and scattered planting cultivation, the difference between them with other cultivation models on canopy characteristics after heading reduced, increase amplitude in leaf assimilation capacity and index related carbon metabolism was higher, capability of photosynthetic production improved, CGR promoted by increasing of both LAD and NAR, so their photosynthetic production Pre-and post heading get a harmonious development under suitable nitrogen application stagey.4. Effects of nitrogen regulation and cultivation modes on radiation use efficiency (RUE) at different ecological conditionCorrelation analysis indicated that there existed very significantly positive correlations between RUE with grain yield at different ecological conditions. There was a close relationship between RUE during early-middle period of filling stage with grain yield at Wenjiang, improving crop population by increasing leaf area from flag leaf to third leaf of productive tillers, leaf area of productive tillers and leaf specific weight was the key to improve RUE during filling stage. But at Hanyuan, improving RUE from jointing to 15 days after heading was the key of yield increase, and the better crop population basing on enough population quantity played a critical role in improvement of RUE. When ratio of basic and tillering nitrogen applied was high, it is beneficial to improve RUE after heading for wide-narrow row spacing cultivation and triangle cultivation, thus their RUE improved during the whole lifetime. Once temperature and light conditions have improved, the advantage in RUE under wide-narrow row spacing cultivation decreased, while the advantage under triangle cultivation increased. The improvement of RUE under planting with the wide row and narrow plant space or scattered planting cultivation during critical stage and even whole lifetime depended on increasing ratio of nitrogen application at panicle initiation stage. In order to reach high yield by improving RUE, each cultivation model should adopted respective suitable nitrogen regulation according to ecological condition.