Showing papers by "Qingwu Xue published in 2004"
TL;DR: In this article, a 2-year field experiment was conducted in winter wheat (Triticum aestivum L.) to evaluate a nonlinear model and two versions of the phyllochron approach to predict LAR, and to compare the differences in predictions of leaf appearance using daily, hourly, and maximum and minimum air temperatures.
112 citations
TL;DR: Investigation of the effects of spring wheat seed size and seeding rate on wheat spike production, biomass, and grain yield under a range of wild oat densities found plants derived from large seed appear to have greater vigor and are able to acquire a larger share of plant growth factors relative to plantsderived from small seed.
Abstract: The development of competitive cropping systems could minimize the negative effects of wild oat competition on cereal grain yield, and in the process, help augment herbicide use. A 3-yr field experiment was conducted at Kalispell, MT, to investigate the effects of spring wheat seed size and seeding rate on wheat spike production, biomass, and grain yield under a range of wild oat densities. Wheat plant density, spikes, biomass, and yield all increased as seed size and seeding rates increased. Averaged across all other factors, the use of higher seeding rates and larger seed sizes improved yields by 12 and 18%, respectively. Accordingly, grain yield was more highly correlated with seed size than with seeding rate effects. However, the combined use of both tactics resulted in a more competitive cropping system, improving grain yields by 30%. Seeding rate effects were related to spike production, whereas seed size effects were related to biomass production. As such, plants derived from large seed ap...
71 citations
TL;DR: In this article, the effect of soil water potential (Ψs) on the responses of gas exchange to VPD in four field-grown winter wheat (Triticum aestivum L.) cultivars was investigated.
50 citations
TL;DR: The seedling growth of two drought-resistant wheat varieties was studied under solution culture in a plant growth chamber and the results showed that the shoot dry weight and leaf gas exchange parameters increased with the increase of nitrogen supply, but decreased when nitrogen supply reached a certain level.
Abstract: The seedling growth of two drought-resistant wheat varieties was studied under solution culture in a plant growth chamber. The results showed that the shoot dry weight and leaf gas exchange parameters increased with the increase of nitrogen supply, but decreased when nitrogen supply reached a certain level. The optimum nitrogen concentrations for shoot dry weight and gas exchange were different among the varieties. The root growth was negatively correlated with the increase of nitrogen supply. The distribution of root length in different layers was similar for the two varieties. The root length was the longest at the layer of 5-15 cm, the shortest below 15 cm, and in between at the layer of 0-5 cm. The water use efficiency (WUE) decreased with increasing ratio of root to shoot (R/S), while leaf photosynthetic rate tended to increase initially and then decrease. The increase in R/S was unfavorable to increase WUE, and the appropriate R/S for leaf photosynthetic rate was about 0.5.
43 citations
TL;DR: In this paper, a nonlinear multiplicative model by Wang & Engel (WE) for pre- dicting phenological development in differing winter wheat cultivars was evaluated using data from a 3 yr field experiment.
Abstract: Accurate prediction of phenological development is important in the winter wheat Triticum aestivum agroecosystem. From a practical perspective, applications of pesticides and fertil- izers are carried out at specific phenological stages. In crop-simulation modeling, the prediction of yield components (kernel number and kernel weight) and wheat-grain yield relies on accurate pre- diction of phenology. In this study, a nonlinear multiplicative model by Wang & Engel (WE) for pre- dicting phenological development in differing winter wheat cultivars was evaluated using data from a 3 yr field experiment. In the vegetative phase (emergence to anthesis) the daily development rate (r) was simulated based on the product of a maximum development rate (Rmax) in the vegetative phase, a temperature response function (ƒ(T)), a photoperiod response function (ƒ(P)), and a vernal- ization response function (ƒ(V)). ƒ(T) was a nonlinear function of the 3 cardinal temperatures for phe- nological development (minimum, Tmin, optimum, Topt, and maximum, Tmax). ƒ(P) was an exponential function of the actual and critical photoperiods and a sensitivity parameter unique to each cultivar. ƒ(V) was calculated using ƒ(T) based on the cardinal temperatures for vernalization (Tmin,vn, Topt,vn, and Tmax,vn). In the reproductive phase, r was simulated based on the product of Rmax for the repro- ductive phase and ƒ(T). Predictions from this nonlinear model were compared to predictions from the phenology submodel of CERES-Wheat V3.0 (CW3). The nonlinear model performed very well for predicting phenological development in the 3 winter wheat cultivars, the mean root mean square error (RMSE) ranged from 2.9 to 4.1 d from booting to maturity. For the CW3 model, the mean RMSE ranged from 4.8 to 5.9 d for the same phenological stages. The WE model predicted double ridge with a mean RMSE of 7.3 d. Both models predicted terminal spikelet with a mean RMSE ranging from 6.2 to 7.1 d. The WE model was generally a better predictor of phenology between booting and maturity than the CW3 model.
31 citations