Cultivation Strategy For Constructing Winter Wheat Population With High Yield And High Efficiency

The exponential increase in population and gradual decrease in arable land has imposed tremendous pressure to increase wheat productivity. High consumptions of fertilizer and water are commonly used to increase wheat yield. Consequently, fertilizer or water use efficiency is extremely low. Therefore, the primary goal of wheat cultivation studies is to harmonize the contradiction between high yield and high efficiency. The rational wheat population with both high yield and high efficiency could be constructed based on the proper cultivar, seeding rate, sowing date, and nutrient management. With a large-spike wheat cultivar ‘Tainong 18’, we performed a field experiment involving four integrated management strategies to evaluate the integrated effects on yield formation, photosynthetically active radiation(PAR) interception and utilization, water absorption and utilization, and nitrogen(N) accumulation and utilization. The integrated management treatments were designed as follows: current practice(T1), improved practice(T2), high-yield management(T3), and further improved practice(T4). We also performed an additional experiment to evaluate the effects of N application rates on grain yield and N use of wheat. N levels were designed as follows: 0(N0), 168(N168), 240(N240), and 300 kg ha-1(N300). The objective of this study was to elucidate the functional mechanism on the synchronous enhancements of grain yield, radiation use efficiency(RUE), N use efficiency(NUE), and water use efficiency(WUE) under integrated treatments. It can supply theoretical basis and technical support for constructing wheat population with high yield and high efficiency. The main results were as follows: 1 Grain yields under different integrated management treatmentsGrain yields among the treatments showed specific trends, as follows: T3 > T4 > T2 > T1. Average grain yield obtained with the T4 treatment was 95.85% of that with T3 and was significantly higher than with T1 and T2 by 21.72% and 6.10%, respectively.The spike number per unit area among the treatments showed the following rank order: T4 > T3 > T2 ≥ T1. The highest tiller number at jointing and highest ear-bearing tiller percentage obtained with T4 ultimately resulted in the highest spike number per unit area. For the grain number per spike, the order was T1 > T2 ≈ T3 > T4. Both single-spike dry weight and single-stem biological yield at anthesis were positively correlated with grain number per spike. The grain number per spike with T4 was the lowest with the lowest single-spike dry weight and single-stem biological yield at anthesis, while the grain number per spike with T1 was the highest with the highest single-spike dry weight and single-stem biological yield at anthesis. Thousand-kernel weights among the treatments followed the ranking T2 > T3 ≈ T4 > T1. Grain weight was positively related to the average grain filling rate. The heaviest grain weight was obtained with T2 and lightest grain weight was obtained with T1 due mainly to their having the highest and lowest grain filling rates, respectively. Results indicated that the higher spike number obtained with T4 compensated for reductions in both grain number per spike and thousand-kernel weight compared to T2, thus producing a higher grain yield than T2. The grain yield with T1 was lowest, with the lowest spike number and thousand-kernel weight, despite showing the highest grain number per spike. The increased spike number with T4 compared to T3 did not compensate for the marked decrease in grain number per spike, which led to decreased grain yield. 2 Radiation use efficiency under different integrated management treatmentsT3 and T4 always maintained higher levels of leaf area index(LAI) compared to T1 and T2. Moreover, T4 obtained the equal(2013~2014) or higher LAI(2014~2015) compared to T3 during late grain filling period, which suggested that T4 could relatively slow down the senility of leaves. As LAI increased PAR interception ratio increased, however, for each additional increase in LAI the increase in PAR interception ratio was smaller. The higher levels of LAI obtained with T3 and T4 resulted in the higher PAR interception.The pre-anthesis PAR interception among the treatments showed the following rank order: T3 ≈ T1 > T4 ≈ T2, for the pre-anthesis RUEint, the order was T3 > T4 ≈ T2 > T1, thus pre-anthesis dry matter accumulation showed the following rank order: T3 > T4 > T2 ≈ T1. For the post-anthesis PAR interception, the order was T4 ≥ T3 ≥ T2 ≥ T1, while for post-anthesis RUEint, the order was T4 ≥ T3 > T2 > T1, thus post-anthesis dry matter accumulation showed the following rank order: T4 ≥ T3 > T2 > T1. The total PAR interception among the treatments showed the following rank order: T3 > T4 > T1 > T2. Average RUEint showed the following rank order: T4 ≈ T3 > T2 > T1. Average RUEint obtained with T4 was significantly higher than with T1 and T2 by 14.15% and 4.59%, respectively. For total dry matter accumulation, the order was T3 > T4 > T2 > T1.There was a strong positive linear relationship between specific leaf nitrogen(SLN) and RUEint. The increase in RUEint was far more important determinant of biomass production for T3 and T4 than the increase in PAR interception, while RUEint for T4 was far more important than that for T3, indicating that further enhancements in biomass production are possible for T4 by imporving SLN(or RUE).3 Water use efficiency under different integrated management treatmentsThe total water consumption amount(WCA) for T1 was the highest with highest irrigation frequency and amount and lowest soil water consumption, while the total WCA for T4 was the lowest with lowest irrigation frequency and amount and highest soil water consumption. T3 and T4 significantly increased the soil water consumption in the top 200 cm soil profile compared to T1 and T2. The soil water consumption in the top 100 cm(especially in the 60~100 cm soil layers) for T4 was significantly higher than that for T3. Results indicated that T4 could achieve the effective absorption of soil storage water in deeper soil layers.The post-anthesis average transpiration rate or amount among the treatments showed the following rank order: T3 > T4 > T2 ≈ T1. For the average evaporation rate or amount, the order was T1 ≈ T2 > T3 > T4. Average transpiration amount for T4 was merely 6.18% lower than for T3, while average evaporation amount for T4 was 44.30% lower than for T3. We observed positive relationships between transpiration rate and LAI and negative relationships between evaporation rate and LAI. The higher levels of LAI obtained with T4 could expand the transpiring surface, enhance the canopy transpiration rate and amount, thus increase the absorption of soil water. The lower soil water in the surface layer for T4 could decrease the evaporation rate and amount, reducing the ineffective water consumption.The post-anthesis canopy transpiration efficiency among the treatments showed the following rank order: T2 > T4 > T1 ≈ T3. For the WUE at the population level, the order was T4 > T3 > T2 > T1, while for the WUE at the yield level, the order was T4 > T3 > T2 > T1. WUE at the yield level for T4 was 43.22%, 12.56%, and 7.12% higher than for T1, T2, and T3, respectively. Correlation analysis demonstrated that WUE at the yield level was negatively and significantly correlated with carbon isotope discrimination(CID). CID could be recommended as the characteristic index to evaluate the WUE. 4 Nitrogen use efficiency under different integrated management treatmentsN-uptake efficiency(UPE) among the treatments showed the following rank order: T2 ≥ T4 > T3 > T1. Average UPE for T4 was 16.62% and 50.75% higher than for T3 and T1, respectively. The aboveground N uptake(AGN) at maturity for all treatments followed a ranking of T3 > T4 > T2 > T1, while available N differed markedly among all treatments, and with a ranking of T3 > T1 > T4 > T2. Although T3 obtained both higher AGN and available N compared to T4, we observed a relatively lower percentage increase in AGN compared to available N, which led to the reduced UPE. We observed positive relationships between AGN and UPE and negative relationships between available N and UPE. T1 produced the lowest AGN and lowest UPE among all treatments, while T2 achieved the highest UPE due to the lowest available N.N-utilization efficiency(UTE) among the treatments showed the following rank order: T2 > T4 ≥ T1 > T3. Average UTE for T4 was 7.74% higher than that for T3. N harvest index(NHI) for all treatments followed a ranking of T2 ≈ T4 > T3 ≥ T1. N accumulation in grains differed markedly among all treatments, and with a ranking of T3 > T4 > T2 > T1. Although T3 produced both higher N accumulation in grains and AGN compared to T4, we observed a relatively lower percentage increase in N accumulation in grains compared to AGN, which led to the reduced NHI. Grain N concentration(GNC) among the treatments showed the following rank order: T3 > T4 > T2 ≈ T1. The higher UTE for T4 than T3 was attributed to its higher NHI and lower GNC.T2 produced the highest NUE of all the integrated treatments. The NUE with T4 was 95.36% of that with T2 and was 51.91 and 25.62% higher than with T1 and T3, respectively. T4 showed a higher NUE than T3 and T1 with both higher UPE and UTE. Meanwhile, T2 achieved a higher NUE than T4 resulting from higher(or equal) UPE and higher UTE, indicating that further improvements are possible in the T4 management strategy. 5 Grain yield and nitrogen use efficiency under different nitrogen application ratesGrain yield exhibited a trend of increase-highest-decrease with an increased N application rate, while the highest grain yield was obtained with N240.A relatively lower percentage increase in AGN compared to available N was observed with an increased N application rate, which led to the reduced UPE. As N application rate increased NHI decreased but GNC increased, which led to the reduced UTE. Results indicated that NUE decreased gradually with an increased N application rate.