Studies On Population Productivity And Ecophysiological Characteristics Of Rice Under Different Planting Methods

In order to compare population productivity and ecophysiological characteristics of rice under precision artificial transplanting with dry nursery middle and strong seedlings (AT), mechanical transplanting with small seedlings (MT) and direct seeding (DS) in the rice-wheat cropping system in the lower Yangtze River, a comparative experiment was carried out during year2008-2009in Sunan Taihu Lake rice district in Changshu (N31.40), Suzhong Lixiahe rice district in Jiangyan (N32.3°) and Xinghua (N32.6°) and Subei Huaibei rice district in Donghai (N34.5°), Jiangsu province. The experiment was designed for each planting method moderate sowing and transplanting date, respectively, which was representative with local large scale production, according to wheat annual harvest time of different latitude point and requirement of rice sowing and transplanting timely. Furthermore, the experiment was also selected suitable variety growth stage types for local and its main popularizing representative varieties according to the heat conditions in different latitude regions and possible safety growth days of rice under different planting methods in the rice-wheat cropping system. Systematic comparative studies on yield, growth stage and utilization of temperature and illumination, characteristics of photosynthetic and matter production, tillering properties, root system morphological and physiological characteristics, grain-filling properties, nitrogen uptake and utilization, rice quality and population lodging resistance were conducted to clarify the difference in population productivity and ecophysiological characteristics of rice under different planting methods. Then it could provide theoretical and practical basis for scientific selection and rational layout of different planting methods and its supporting varieties. The main results were as follows:(1) Rice yields under different planting methods were significantly different, AT was the highest, then was MT, DS was the lowest. Compared with AT, yield of MT and DS reduced by300-750kg and1200-2700kg per ha, respectively. Moreover, it demonstrated the law that the reducing extent was greater with the latitude increasing, Sunan<Suzhong<Subei. Yield of MT and DS reduced by300-450kg and1200-1500kg,450-600kg and1350-1650kg,600-750kg and2400-2700kg per ha in Sunan, Suzhong, Subei, respectively. In the same region, the reducing extent of late-maturing varieties was greater than that of early-maturing varieties, and conventional rice greater than hybrid rice. The growth process of MT and DS delayed and whole growth stage shortened than that of AT. The shortening number of days of MT than that of AT was11-14, and DS was25-30. and it showed a trend of the higher the latitude the more the shortening number of days. Various growth stages would be shortened, and from sowing to jointing was the most which accounted to over60%of the total shortening days. The accumulative temperatures and light hours of MT and DS significantly reduced, and in particular, the utilization efficiency of accumulative temperatures and light hours of DS was only81.8%and77.4%in Subei. The utilization efficiency of accumulative temperatures and light hours was different because of variety types in different regions. The utilization efficiency of early-maturing late japonica rice (EMLJ) was higher in Sunan, while late-maturing medium japonica rice (LMMJ) and medium-maturing medium japonica rice (MMMJ) in Suzhong and Subei, respectively. The preliminary division for the suitable range and its supporting suitable variety types of different planting methods is that AT and MT are all suitable in Sunan, Suzhong and Subei while DS is suitable in Sunan, sub-suitable in Suzhong and unsuitable in Subei. The supporting variety types for AT is EMLJ and MMLJ, EMLJ, MMMJ and that of MT is EMLJ, LMMJ, MMMJ in Sunan, Suzhong, Subei, respectively. That of DS is EMLJ, LMMJ and MMMJ in Sunan, Suzhong, respectively and unsuitable in Subei.(2) There was no significant difference in population dry matter weight of rice under different planting methods before jointing, after jointing AT was the highest, then was MT, DS was the lowest, and the difference was increasing with the growing process. However, per stem dry matter weight of AT was the highest, while that of DS was the lowest in the whole growth period; For dry matter accumulation at different stages, there was no significant difference from sowing to jointing, while AT was significantly higher than MT and MT was significantly higher than DS at the stages from jointing to heading and from heading to maturity. The ratio to total dry matter weight increased in turn of AT, MT, DS from sowing to jointing, was in generally quite from jointing to heading, and reduced in turn from heading to maturity; For dry matter distribution, the ratio of panicle and stem to total dry matter weight at maturity reduced in turn of AT, MT, DS, while that of leaf and sheath increased in turn. However, the ratio of leaf at booting, heading and waxy stage reduced in turn; For dry matter export and transformation, the export rate and transformation rate of leaf and stem reduced in turn of AT, MT, DS, moreover, stem had the phenomenon of matter transported back after waxy stage, volume of matter transported back of AT was the most, while that of DS was the least. The export rate of sheath was in generally quite, but transformation rate of AT and MT was lower than that of DS; For photosynthetic production, before jointing, leaf area index was in generally quite, photosynthetic potential reduced in turn of AT, MT, DS, crop growth rate and net assimilation rate increased in turn. From jointing to heading, photosynthetic potential also reduced in turn of AT, MT, DS, but there was no significant difference for crop growth rate and net assimilation rate. The leaf area of productive tillers rate at heading had no significant difference among different planting methods, but the leaf area rate from flag leaf to3rd leaf of AT was significantly higher than that of MT. and MT was significantly higher than that of DS. After heading, leaf area index, photosynthetic potential, crop growth rate and net assimilation rate of AT was the highest, while that of DS was the lowest. It suggested that compared with MT and DS, dry matter accumulation of AT is appropriate at the early stage, significantly higher at the middle and late stage, so total dry matter accumulation is significantly higher and its distribution is reasonable, export and transformation rate is high, and photosynthetic production capacity is great after heading.(3) The great contribution to yields of MT and DS were mainly from main stem and primary tillers group, in particular for DS, the proportion of stem yield was up to27.5%, while that of secondary tillers group only about5%. However, for AT the stem yield proportion was small (16.7%), yield of secondary tillers group accounted for nearly20%. The proportion of primary tillers group yield was relatively stable among different planting methods and it ranged from65.84%to67.09%. The number of tiller leaf position of AT was more, earbearing tiller percentage was higher and panicle number per plant was more. The primary tillers group emerged from leaf1to leaf10on main stem, among them leaves5to8were the superior positions for tiller emerging and panicle formation, secondary tillers group emerged and earbeared mainly in1/5,1/6,1/7. The primary tillers group of MT emerged from leaf3to leaf7on main stem, among them leaves4to7were the superior positions, secondary tillers group emerged mainly in1/4,2/4,1/5, but earbeared mainly in1/4. The primary tillers group of DS emerged from leaf1to leaf5on main stem, among them leaves1to4were the superior positions, secondary tillers emerged more, but earbeared only in1/1,2/1,1/2, with a very low earbearing percentage. These three planting methods did not give tillering three times and more than three times. The tillers group of main stem and superior leaf positions in each planting method had higher population productivity and better panicle traits, made great contributions to the yield, and more than85%of the yield came from these stems and tillers. It suggested that tillering properties of rice under different planting methods are different and increasing percentage of earbearing tiller and panicle number per plant and playing regulation fully of tillers group will improve the yield.(4) Population roots number of rice under different planting methods was DS>MT>AT, however, the difference became less and less with growth process. Total population roots length was DS>MT>AT at jointing and MT>AT>DS at heading and maturity. Single root number was no significant difference among different planting methods and total single root length was AT>MT>DS. Diameter per root became thinner in turn of AT, MT, DS. Length per root was no significant difference between AT and MT, but both were significantly higher than that of DS. Population roots dry weight was no significant difference between MT and DS at jointing, but both were significantly higher than that of AT. There was no significant difference among different planting methods at heading, but AT was the highest while that of DS was the lowest at maturity and the difference was very significant. Single root dry weight was all AT>MT>DS at jointing, heading and maturity and the difference among different planting methods most reached very significant level. Decreasing rate of root dry weight after heading was DS>MT>AT. Shoot dry weight reduced in turn of AT, MT, DS, but root-shoot ratio increased in turn. Compared with AT, roots of MT and DS were mainly distributed within the soil layer of0-10cm, especially for DS the root proportion of0-5cm soil layer could up to65%. Population roots absorption area was no significant difference among different planting methods at jointing, and was AT>MT>DS at heading and the difference among different planting methods was very significant, and there was no significant difference between MT and AT while both were very significant higher than that of DS at maturity. Single root absorption area was no significant difference between AT and MT at jointing and maturity while both were very significant higher than that of DS, and was AT>MT>DS at heading and the difference among different planting methods was very significant. Population roots bleeding intensity after heading increased in turn of AT, MT, DS, but single root bleeding intensity reduced in turn. It suggested that compared with AT and MT, root of DS distribution shallower, length per root shorter and diameter thinner, number of population roots more, however, total single root length shorter, root dry weight lower, absorption area and bleeding intensity after heading less. Compared with AT, root of MT diameter thinner, distribution shallower, after heading population and single root dry weight lower and decline faster, and total single root length and bleeding intensity less.(5) The grain-filling processes of superior and inferior grains of rice under different planting methods were obviously asynchronous type. The time reaching the maximum grain-filling rate (Tmax) of superior grains was early, maximum grain-filling rate (GRmax), mean grain-filling rate (GRmean),the final weight of a kernel (A) and initial grain-filling potential (R0) were significantly greater than those of inferior grains. GRmax and GRmean of superior grains of DS were significantly lower than those of AT and MT, Tmax was obviously delayed, active grain-filling period (D) and effective grain-filling time (T99) significantly increased. GRmax and GRmean of inferior grains of MT were the highest, and AT was slightly lower than those of DS. Tmax of DS was the earliest, MT was the second, and the latest was AT. D and T99reduced in order of AT, MT and DS; For grain-filling characteristics of different stages, maximum of mean grain-filling rate and contribution rate both was the middle stage, and its contribution rate of superior and inferior grains were up to60.53%and50.78%, respectively. Grain-filling days, mean grain-filling rate and contribution rate of early, middle and late stage among different planting methods were different due to grain position;1000-grain weight was positively correlated with maximum grain-filling rate, mean grain-filling rate and active grain-filling period of superior and inferior grains, and the correlation coefficients with GRmax and GRmean of inferior grains were up to significant level. Seed-setting rate was a degree positive or negative correlation with the grain-filling parameters of superior and inferior grains, but except active grain-filling period of superior grains, all of the correlation coefficients were not up to significant level. It suggested that although grain-filling processes of rice under different planting methods are all asynchronous types, the grain-filling parameters such as GRmax and Tmax of superior and inferior grains have great difference. It would play an important role in improving1000-grain weight to improve grain-filling rate and especially the grain-filling rate of inferior grains under the conditions of maintaining the final weight of a kernel and seed-setting rate stable.(6) N content and uptake in plant of rice under different planting methods was DS>MT>AT at jointing and AT>MT>DS at heading and maturity. Total N uptake at maturity of AT was higher than that of MT and DS by11.68%and39.03%and MT was higher than DS by24.49%. N uptake rate was DS>MT>AT before jointing and AT>MT>DS from jointing to heading and from heading to maturity. Maximum N uptake rate of AT and MT was the period from jointing to heading, and that of DS of MMMJ was the period from jointing to heading while EMLJ and LMMJ was before jointing. N period accumulation from jointing to heading and from heading to maturity were AT>MT>DS and the difference among different planting methods all reached significant or very significant level. N recovery efficiency of AT, MT and DS were44.49%,39.00%and31.41%, respectively. N recovery efficiency among different growth type varieties of AT and MT was EMLJ>LMMJ>MMMJ while that of DS was MMMJ>LMMJ>EMLJ and for the same growth type japonica conventional rice was higher than that of japonica hybrid rice. N requirement for100kg grain of AT, MT and DS were1.959(1.900-2.009) kg,1.842(1.681-1.914) kg,1.638(1.540-1.721) kg, respectively. It was no significant difference between AT and MT while both were significant higher than that of DS for japonica conventional rice. For japonica hybrid rice, the difference among different planting methods all reached significant level. It suggested that nitrogen uptake and utilization properties of rice under different planting methods are different and aslo affected by variety growth types. Therefore, it is important to select scientific planting method and supporting suitable variety type to achieve nitrogen efficient uptake and utilization.(7) Brown rice rate was no significant difference among different planting methods. The order of milled rice and head milled rice rate among different planting methods was AT>MT>DS in EMLJ, while MT>AT>DS in LMMJ and MMMJ; Chalkiness rate was AT>MT>DS, chalkiness size was MT>AT>DS. Chalkiness degree was AT>MT>DS in EMLJ and conventional LMMJ, while MT>AT>DS in MMMJ and hybrid LMMJ; Amylose content was DS>MT>AT and gel consistency was AT>MT>DS; Protein content between AT and MT was in generally quite, and DS was slightly lower than that of AT and MT, but there was no significant difference in addition to MMMJ; Peak viscosity, trough viscosity and breakdown was AT>MT>DS, setback was DS>MT>AT, peak time among different planting methods was no significant difference, final viscosity was AT>MT>DS in EMLJ and conventional LMMJ while DS>MT>AT in MMMJ and hybrid LMMJ, pasting temperature was DS>MT>AT in EMLJ and conventional LMMJ while AT>MT>DS in MMMJ and hybrid LMMJ. It suggested that rice quality under different planting methods is different and aslo affected by variety growth types. It is beneficial to obtain good quality characters to choose reasonable planting methods and supporting appropriate rice varieties types.(8) The population lodging resistance of rice under different planting methods was significantly different. The lodging index of AT was the lowest and population lodging resistance was the best, while DS was the highest and population lodging resistance was the worst. The main reason for difference of the lodging index among different planting methods was the size of the breaking resistance. The breaking resistance of the basal1st,2nd,3rd,4th internode and plant height, gravity center height, culm diameter, culm wall thickness, dry weight of culm, dry weight of leaf sheath, dry weight of unit internode, length and fresh weight from basal internode to top, bending moment had significantly or very significant positive correlation, while with ratio of gravity center height to plant height and internodes length was significant or very significant negative correlation. Compared with MT and DS, the increase in plant height of AT was due to internodes numbers increased, length of panicle and1st and2nd top internode increased. However, the length of the2-3internodes in the basal stem which was apt to lodge was shorter than that of MT and DS. Culm diameter and wall thickness of every basal internodes of AT were obviously increased, and dry weight of culm and sheath were larger, the dry weight of unit internode was significantly increased, so the stem plumpness status of AT was better. It suggested that the optimal combination of some main culm physical characteristics of rice was different under different planting methods. The direct reasons for breaking resistance increased and lodging index reduced of AT were short and thick basal internodes, large wall thickness and good culm plumpness status.