Qingwu Xue

Improving predictions of developmental stages in winter wheat: a modified Wang and Engel model ☆

Accurate simulations of plant development is an important component in crop simulation models and for use in managerial decisions, such as fertilizer applications or pest control. The three major environmental factors that control development in winter wheat (Triticum aestivum L.) are temperature, photoperiod, and vernalization. Results from a previous study showed that the prediction of several developmental stages from booting to physiological maturity were better with the Wang and Engel (WE) model compared to CERES-Wheat, but not for the prediction of terminal spikelet initiation (TS). In the WE model, the vernalization function [f(V)] is a three-stage linear function and the life cycle of the wheat crop is divided into two phases, vegetative (emergence–anthesis) and reproductive (anthesis–physiological maturity). The objective of this study was to modify the WE model by introducing a nonlinear f(V), and dividing the vegetative phase into two sub-phases (emergence–terminal spikelet initiation and terminal spikelet initiation-anthesis). A series of field experiments were carried out at Lincoln, NE, USA, to provide independent data on the date of developmental stages of two winter wheat cultivars (Arapahoe and Karl 92) for evaluating the original and the modified WE model. The root mean square error (RMSE) with the modified WE model was 5 days for Arapahoe and 6 days for Karl 92 for all developmental stages, which corresponds to a 45% decrease in the RMSE compared with the original WE model.

Root growth and water uptake in winter wheat under deficit irrigation

Root growth is critical for crops to use soil water under water-limited conditions. A field study was conducted to investigate the effect of available soil water on root and shoot growth, and root water uptake in winter wheat (Triticum aestivum L.) under deficit irrigation in a semi-arid environment. Treatments consisted of rainfed, deficit irrigation at different developmental stages, and adequate irrigation. The rainfed plots had the lowest shoot dry weight because available soil water decreased rapidly from booting to late grain filling. For the deficit-irrigation treatments, crops that received irrigation at jointing and booting had higher shoot dry weight than those that received irrigation at anthesis and middle grain filling. Rapid root growth occurred in both rainfed and irrigated crops from floral initiation to anthesis, and maximum rooting depth occurred by booting. Root length density and dry weight decreased after anthesis. From floral initiation to booting, root length density and growth rate were higher in rainfed than in irrigated crops. However, root length density and growth rate were lower in rainfed than in irrigated crops from booting to anthesis. As a result, the difference in root length density between rainfed and irrigated treatments was small during grain filling. The root growth and water use below 1.4 m were limited by a caliche (45% CaCO3) layer at about 1.4 m profile. The mean water uptake rate decreased as available soil water decreased. During grain filling, root water uptake was higher from the irrigated crops than from the rainfed. Irrigation from jointing to anthesis increased seasonal evapotranspiration, grain yield, harvest index and water-use efficiency based on yield (WUE), but did not affect water-use efficiency based on aboveground biomass. There was no significant difference in WUE among irrigation treatments except one-irrigation at middle grain filling. Due to a relatively deep root system in rainfed crops, the higher grain yield and WUE in irrigated crops compared to rainfed crops was not a result of rooting depth or root length density, but increased harvest index, and higher water uptake rate during grain filling.

Spring wheat seed size and seeding rate effects on yield loss due to wild oat (Avena fatua) interference

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 appear to have greater vigor and are able to acquire a larger share of plant growth factors relative to plants derived from small seed. Nomenclature: Wild oat, Avena fatua L. AVEFA; wheat, Triticum aestivum L. ‘McNeal’.

Spring wheat seed size and seeding rate affect wild oat demographics

Abstract Wild oat continues to reduce spring wheat yields and profits despite the wide spread use of herbicides. Further reductions in the occurrence of wild oat could be achieved with the development of competitive cropping systems. Field studies were conducted to investigate the effects of wheat seed size and seeding rate on wild oat demographic processes under a range of wild oat densities. Spring wheat competitiveness increased as seed size and seeding rate increased, significantly reducing wild oat biomass and seed production. Averaged across all other factors, spring wheat plants derived from large seed reduced wild oat panicle numbers 15% and biomass and seed production 25% compared with small seed. Increasing spring wheat seeding rate from 175 to 280 plants m−2 reduced the number of panicles 10% and wild oat biomass and seed production 20%. The combined effect of large seed plus increased seeding rate reduced wild oat biomass and seed production 45%. Results demonstrate that the use of large seed size and increased seeding rates can improve wheat competitiveness and provide an effective means to reduce wild oat biomass and seed production. Nomenclature: Wild oat, Avena fatua L. AVEFA; spring wheat, Triticum aestivum L. ‘McNeal’.

Effect of nitrogen on root and shoot relations and gas exchange in winter wheat

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.

Genotypic variation of gas exchange parameters and carbon isotope discrimination in winter wheat

Summary Carbon isotope discrimination (Δ) has been suggested as an indirect selection tool for plant water use efficiency and yield potential in wheat ( Triticum aestivum L.). Plant available soil water content (PASW) and vapor pressure deficit (VPD) are among some important factors affecting gas exchange and Δ. A two-year field experiment was conducted to (1) investigate the differences in gas exchange parameters: net CO 2 assimilation rate (An), stomatal conductance (Gs), intercellular CO 2 concentration (Ci), An/Ci, transpiration rate (E), water use efficiency (WUE), and Δ between older and newer cultivars in winter wheat; and (2) determine the relationships between Δ and gas exchange parameters, WUE and grain yield as influenced by PASW and VPD. Differences in An and An/Ci between the two years was influenced more by PASW conditions than by cultivar. In general, WUE decreased in all cultivars when PASW

Physiology and transcriptomics of water-deficit stress responses in wheat cultivars TAM 111 and TAM 112

Hard red winter wheat crops on the U.S. Southern Great Plains often experience moderate to severe drought stress, especially during the grain filling stage, resulting in significant yield losses. Cultivars TAM 111 and TAM 112 are widely cultivated in the region, share parentage and showed superior but distinct adaption mechanisms under water-deficit (WD) conditions. Nevertheless, the physiological and molecular basis of their adaptation remains unknown. A greenhouse study was conducted to understand the differences in the physiological and transcriptomic responses of TAM 111 and TAM 112 to WD stress. Whole-plant data indicated that TAM 112 used more water, produced more biomass and grain yield under WD compared to TAM 111. Leaf-level data at the grain filling stage indicated that TAM 112 had elevated abscisic acid (ABA) content and reduced stomatal conductance and photosynthesis as compared to TAM 111. Sustained WD during the grain filling stage also resulted in greater flag leaf transcriptome changes in TAM 112 than TAM 111. Transcripts associated with photosynthesis, carbohydrate metabolism, phytohormone metabolism, and other dehydration responses were uniquely regulated between cultivars. These results suggested a differential role for ABA in regulating physiological and transcriptomic changes associated with WD stress and potential involvement in the superior adaptation and yield of TAM 112.

Evaluation of the AquaCrop model for simulating yield response of winter wheat to water on the southern Loess Plateau of China.

The objective of this study was to evaluate the performance of the FAO-AquaCrop model in winter wheat in the southern Loess Plateau of China. Multi-year field experimental data from 2004 and 2011 were used to calibrate and validate the model for simulating biomass, canopy cover (CC), soil water content, and grain yield under rainfed conditions. The model performance was evaluated using root mean square error (RMSE) and Willmott index of agreement (d) as criteria. The RMSE ranged from 0.16 to 0.38 t/ha for simulating aboveground biomass, 1.87 to 4.15% for CC, 0.50 to 1.44 t/ha for grain yield, and 5.70 to 22.56 mm for soil water content. The d ranged from 0.22 to 0.89, 0.25 to 0.43, 0.36 to 0.62 and 0.95 to 0.98 for aboveground biomass, CC, soil water content and grain yield, respectively. Generally, the model performed better for simulating CC and yield than biomass and soil water content. The results further indicated that AquaCrop is capable of simulating winter wheat yield under rainfed conditions. Further improvement may be needed to capture the variation of different management practices such as fertility and irrigation levels in this region.

Biomass composition of perennial grasses for biofuel production in North Dakota, USA

Background: Successful development of biofuels from biomass feedstocks depends on high yields and acceptable quality. We investigated the chemical composition of ten perennial grasses and mixtures across environments in North Dakota, USA. The contents of neutral detergent fiber (NDF), acid detergent fiber, acid detergent lignin (ADL), hemicellulose (HCE), cellulose (CE) and ash were determined. Results: Biomass chemical composition was affected by environment and species/mixtures, and their interaction. Biomass under drier conditions had higher NDF, ADL and HCE contents but lower CE contents. Tall and intermediate wheatgrass had higher NDF, acid detergent fiber and CE but lower ash contents than the other species and mixtures. Switchgrass and mixtures had higher HCE. Tall wheatgrass and Sunburst switchgrass had the lowest ADL content as compared with other species. Biomass with higher yield had higher cellulose content but lower ash content. Conclusion: Combined with higher yields, tall and intermediate wheatgrass and switchgrass had the optimal chemical compositions for biomass feedstocks production.

Grain Yield and Water Use Efficiency in Extremely-Late Sown Winter Wheat Cultivars under Two Irrigation Regimes in the North China Plain

Wheat production is threatened by water shortages and groundwater over-draft in the North China Plain (NCP). In recent years, winter wheat has been increasingly sown extremely late in early to mid-November after harvesting cotton or pepper. To improve water use efficiency (WUE) and guide the extremely late sowing practices, a 3-year field experiment was conducted under two irrigation regimes (W1, one-irrigation, 75 mm at jointing; W2, two-irrigation, 75 mm at jointing and 75 mm at anthesis) in 3 cultivars differing in spike size (HS4399, small spike; JM22, medium spike; WM8, large spike). Wheat was sown in early to mid-November at a high seeding rate of 800–850 seeds m−2. Average yields of 7.42 t ha−1 and WUE of 1.84 kg m−3 were achieved with an average seasonal evapotranspiration (ET) of 404 mm. Compared with W2, wheat under W1 did not have yield penalty in 2 of 3 years, and had 7.9% lower seasonal ET and 7.5% higher WUE. The higher WUE and stable yield under W1 was associated with higher 1000-grain weight (TGW) and harvest index (HI). Among the 3 cultivars, JM22 had 5.9%–8.9% higher yield and 4.2%–9.3% higher WUE than WM8 and HS4399. The higher yield in JM22 was attributed mainly to higher HI and TGW due to increased post-anthesis biomass and deeper seasonal soil water extraction. In conclusion, one-irrigation with a medium-sized spike cultivar JM22 could be a useful strategy to maintain yield and high WUE in extremely late-sown winter wheat at a high seeding rate in the NCP.