| At present, there are many serious questions including unscientific management of waterand fertilizer, unutilized technical implementation, and high yield without high efficiency inwheat planting management and super-high yield cultivation. In this study, field planting,planting density, fertilizers and irrigation, were combined to four planting patterns, i.e.farmers’ traditional cultivation pattern (T1), optimized cultivation pattern1in comparisonwith T1(T2), super high yield cultivation pattern (T3) and optimized cultivation pattern2incomparison with T3(T4). Experiments were performed in the located fields at2008~2010and15N isotope was further applied. In these experiments, effects of different plantingpatterns on wheat root system, water consumption, production of dry matters, grain yields,and relationships between root systems and grain yields as well as water and nitrogenutilization were also explored. The experimental results are summarized as follows:1. Characteristics of wheat root systems under different cultivation managementpatternsGrowth of wheat roots were greatly affected by cultivation management patterns. In1msoil layer, Temporal variations of total root dry weight (TRDW), total root length (TRL),average root diameter (ARD), total root surface area (TRSA), and total root volume (TRV)in four patterns exhibited a single peak curve with “slow increase-rapid increase-slowdecrease”, and characteristics of root parameters can be calculated with the growth curve ofBeta equation. The maximum of TRDW and TRL in T1appeared at the heading stage,whereas those in T2, T3and T4were postponed to anthesis. The peak appearance time (te)and the maximum growth rate (tm) of TRDW and TRL in T2, T3and T4were retarded. The maximum values (wmax), average growth rate （c）and maximum growth rage (cm) ofTRDW, TRL and ARD in T2, T3and T4were significantly higher than those in T1. Thesesuggested that, in comparesion with T1, T2and T3can effectively quicken the root growthrate and elongation time, increase the root width, area and volume, alleviate the rootsenescence, enoughly provide water and nutrients for shoots and grains, eventually increasethe dry matter and grain yields. Compared with high-yield wheat plants, high yield-andhigh efficiency-plants were characterized with suitable root systems in upper soil layer,more root systems in middle and lower soil layers, increased intensity of root length, rootdiameter, root volumes, and root furface areas.2. Water utilization characteristics and water utilization efficiency in differentcultivation management patternsThere were significant differences in water utilization efficiency among four cultivationmanagement patterns. Among four cultivation management patterns, T1and T3absorbedthe most amount of water, mainly from irrigated water, whereas low water utilizationefficiency in stored water in soil. T2mainly utilized rainfall and stored water in soil, and T4could utilize both the irrigated water and rainfall. Four cultivation management patternsutilized the most water distributed at40~60cm soil layer. T1and T3utilized more storedwater in soil at cultivated layer, but little from deep soil layer. However, T2and T4couldeffectively utilized the stored water at middle and low soil layers, with high water utilizationefficiency, precipitation utilization efficiency, soil water utilization efficiency, and irrigationutilization efficiency. Thus, it is also speculated that effective absorption and utilization onprecipitation and stored water in soil could be the main route of high grain yields and waterutilization efficiency in wheat field.3. Nitrogen absorption and transformation characteristics of wheat plants underdifferent cultivation management patternsT2and T4treatments can markedly improved the absorption ability of nitrogen at thebeginning stages of wheat growth and development, and increase assimilation ability ofnitrogen in the later stages. Accumulated nitrogen in T1and T3mainly were mainly fromthe transformation of nitrogen absorbed in vegetative organs before anthesis. T2and T4hadhigher N harvest index dependent on effective improvement in both N transformation beforeanthesis and assimilation after anthesis. Using15N isotope method, we found that amountsof N transformation from soil in vegetative organs (leaf, stem, sheath, and glume) and its attribution rates to accumulated N in grains were more than amounts of absorbed N fromfertilizers. In addition, the rate of N transformation from soil was higher than that offertilizers, and transformed amounts and efficiency of top-dressed nitrogen, and itsattribution rate to accumulated nitrogen in grains were higher than basal nitrogen. Becauseof changes in amounts and methods of applied nitrogen, T2and T4treatments help toenhance the absorption of nitrogen fertilizer and improve the nitrogen utilization efficiency,whereas N transformation efficiency, and attribution rates to accumulated nitrogen in grainswere lower than those in T2and T4, and the residual and loss ratios in T1and T3becamehigher, which could lead to lower utilization efficiency of fertilizers in these two treatments.4. Characterization on production and transformation of dry matter under differentcultivation management patternsT2and T4cultivation management patterns can optimize wheat group structure, increasethe number and rates of tillers per plant, improve ear characteristics, decrease the number ofsterile spikelets and increase the number of born small spikes. Grains of per spike andweights of1000grains in T2, T3and T4cultivation management patterns were significantlymore than those of T1in the two experiment’s years, and differences in yields in thesecultivation management patterns were no significant between two years. However,difference in the yield of T1cultivation pattern (570.3kg. hm-2) was significant betweentwo experiment’s years. This indicated that T1cultivation pattern had lower capacity toresist the adverse environments. Compared with T1, T2, T3and T4enhanced the ability ofdry matter transformation from vegetative organs to reproductive organ (grain), and theaccumulated amounts distributed proportions of dry matters in grains. T2and T4treatmentsachieved high grain yields throughout increasing the assimilated amounts of dry matters ingrains, whereas T3by optimizing more accumulated dry matters before anthesis andassimilated dry matters after anthesis. Grain yields were positively related to theaccumulated amounts of dry matters at each growth stages and the rates of growth, whereasnegatively and positively related to the contribution rate of dry matters before and afteranthesis, respectively. It is speculated that, on the premise of richly accumulated dry mattersbefore anthesis, higher wheat grain yields can be achieved by promoting the transformationof dry matters stored in vegetative organs to grains before anthesis, and enhancing theability of dry matter assimilation after anthesis, and increasing the amounts and distributedproportions of dry matters in grain. 5. Relationship among root system, grain yield, and water and nitrogen absorption andutilizationThe gray correlation coefficients indicated that more root systems in deep soil layer in T2and T4treatments, and root growth parameters (RDWD, RLD, ARD, TRSA and TRV) hadhigh coefficients (r0i) to grain yields and had relative relations to grain yields. This indicatedthat formation and distribution of root systems in middle and deep soil layers play importantroles in higher grain yields. Accordingly, to promote the growth of root systems andincrease their number in middle and deep soil layers can be key practical routes andtechnologies to increase wheat grain yield.The results of correlation coefficients between grain yields, and water and nitrogenutilization efficiency indicated that there were significant and positive relation betweengrain yields and nitrogen utilization efficiency (NUTE), nitrogen agronomic efficiency(NAE), physiological efficiency (NPE), but negative relation to nitrogen productionefficiency (NPFP). There were positive relation between yield water utilization efficiency(WUEY) and nitrogen absorption (NUPE), NUTE, NPFP, NPE and NHI, and there werealso positive relations between precipitation water utilization (WUEP), irrigation waterutilization efficiency (WUEI) and irrigation efficiency (IE) and NUPE, NUTE, and NAE.Accordingly, suitable planting patterns helps to increase the grain yield and to improvewater and nitrogen absorption and utilization efficiency.The results of correlation coefficients between growth charactristics of root system andutilization efficiency of water indicated that there were positive relation between TRDWand TRL, and WUEY, WUEP, WUEIand IE in jointing and heading periods, especially fromfilling to maturation. There were also positive relation between ARD and WUEY, WUEP,WUEIand IE in all growth stages. And there were also positive relation between TRSA andTRV, and WUEY, WUEP, WUEI, and IE in all growth stages, except for over-winteringstage. This indicates that to alleviate root sensesence, increase root production and length inlater growth stages, and increase the average diameter, surface area and volume of rootshelps to improve the utilization of precipitation and irrigation and water utilizationefficiency.The results of correlation coefficients between growth charactristics of root system andnitrogen utilization efficiency indicated there was negative relation between TRDW andNUPE, NPFP and NHI, whereas significant and positive relation between TRDW and NUTE from anthesis to maturation. From heading to maturation stages, TRL had diverseand positive relation to NUPE, NUTE, NAE NPFP and NHI, and TRSA and TRV hadnegative relation to NUPE, NAE and NPFP, while positive relation to NUTE. From fillingto maturation stages, TRSA and TRV had significant and positive relation to NPE and NHI.These suggest that overmuch root biomass inhibits the absorption of root system to nitrogen,resulting in the decreased nitrogen production efficiency, agronomic efficiency and harvestindex. However, to increase the space of root growth in middle and late growth stages, andincrease the connetion between roots and soil wateer and nituients help to enhance theabsorption and utilization of nitrogen in wheat plants and improve nitrogen utilization.Combined with the data in the present study and ecological conditions in north of Henanprovince, T2and T4patterns were characterized with120～150kg.hm-2sowed seeds,180～240kg.hm-2nitrogen,75～90kg.hm-2P2O5,60～90kg.hm-2K2O and3000kg.hm-2organic fertilizers, reasonable water and fertilizers application, deep plowing with machines,width-narrow sowing and postponed top-dressed nitrogen application, and they had morereasonable root systems and dry matters, and more efficient water and nitrogen applicationthan T1and T3patterns. Thus, T2and T4treatments can effectively decrease negativeeffects caused by drought, low temperature and other abiotic factors on wheat growth,development and grain yield, resulting in high and stable grain yields, low cost, and moreefficiency. Excess fertilizer application, complicated field management, and higher risk inlodging, disease, and insects in T3treatment leaded to its scare application at large fieldareas. However, T4treatment can decrease the amounts of sowed seeds and irrigated water,optimize the basal and dressing proportions, and applied stages of nitrogen, and be similarwith the amounts of nitrogen fertilizers in farmers’ traditional cultivation pattern, withgrain yields13.4%～24.4%higher than those in farmers’ traditional cultivation pattern.Thus, T4pattern had better ability to abnormal climates and is easily used by farmers infield production. |
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