Seasonal Variations in Water Uptake Patterns of Winter Wheat under Different Irrigation and Fertilization Treatments

Abstract

Irrigation and fertilization both affect the water cycle in agricultural ecosystems. It is difficult to quantify root water uptake (RWU) which varies with crop development and seasons. In this study, a Bayesian mixing model (MixSIAR) coupling with dual stable isotopes (D and 18 O) was used to quantify RWU patterns for winter wheat under different irrigation and fertilization treatments between 2014 and 2015 in Beijing, China. The main RWU depth during the greening-jointing, jointing-heading, heading-filling, and filling-harvest stages was 0-20 cm, 20-70 cm, 0-20 cm, and 20-70 cm, respectively, which showed water uptake proportions of 67.0%, 42.0%, 38.7%, and 34.9%, respectively. Significant differences in RWU patterns appeared between the 2014 and 2015 seasons. The main RWU depth increased gradually from 0-20 cm at the greening-jointing stage to 20-70 cm at the jointing-heading stage and 70-150 cm during the heading to harvest period in 2014. However, winter wheat primarily took up soil water from the 0-70 cm layer in 2015. The average water uptake proportion in the top layer (0-20 cm) in 2015 (42.6%) was remarkably higher than that in 2014 (28.7%). There was a significantly negative relationship (p < 0.01) between the water uptake proportion and the proportion of root length at the filling-harvest stage in 2014, while no significant correlation (p > 0.05) was found in 2015. Variable distributions of root characteristics and soil moisture induced by different irrigation and fertilization comprehensively affected the RWU profile, particularly under severe drought environments in 2015. Treatments with fertilization of 105 kg hm −2 N or irrigation of 20 mm during the greening-jointing stage significantly promoted water uptake contribution in the 70-150 cm (32.2%) and 150-200 cm (23.5%) layers at the jointing-heading stage in 2015, while other treatments had a shallow dominant RWU depth (0-20 cm). The planned wetting layer should be kept within the main RWU depth of 0-70 cm for improving irrigation water use efficiency.Since RWU generally does not lead to isotopic fractionation or the magnitude of fractionation is too low to be observable for the majority of plant species, stable isotopic analysis is a powerful and valuable tool to identify and quantify RWU via the measurements of δD and δ 18 O abundance in waters [7,8]. Widely used methods to determine RWU patterns include the IsoSource [9] and Bayesian mixing models (e.g., SIAR [10], MixSIR [11], and MixSIAR [12]). In comparison, the Bayesian mixing models are particularly efficient in the case of multiple layers for illustrating the interest of reaching the best vertical resolution and maximizing the number of identified potential sources [7]. The MixSIAR model incorporates advances in MixSIR and SIAR that considers multiple sources of uncertainty and provides potential proportions of source contributions [12]. The MixSIAR model has been employed successfully to determine the contributions of soil water at different layers to the water uptake of field crops and na...

Water sources for root water uptake: Using stable isotopes of hydrogen and oxygen as a research tool in agricultural and agroforestry systems

“…In the study by Ma and Song (2016) maize was fertilized with different nitrogen application rates from zero to 368 kg N ha −1 , resulting in clear differences in the proportional contribution of soil water at different depths. Similarly, fertilization with 105 kg N ha -1 or irrigation of 20 mm during the greening-jointing stage significantly promoted soil water uptake of winter wheat at 70-150 cm and 150-200 cm whereas other treatments led to the much shallower RWU depths of 0-20 cm (Ma and Song, 2018).…”

“…Variability in RWU patterns as a function of the growing stage has also been reported for other crops, both herbaceous and trees. For instance, the primary soil depths of RWU for winter wheat (Triticum aestivum) were found to be between 0 and 50 cm for the majority of the growing period (Zhang et al, 2011a;Wang et al, 2016;Yang et al, 2018), and especially in the 0-20 cm soil layers during the wintering and seedling phases (Zhao et al, 2018a), and increasing depths were observed during the end of the growing period (Cheng and Liu, 2017;Ma and Song, 2018) and up to 220 cm in the filling stage (Guo et al, 2016). Similar trends were found for cotton (Li et al, 2017).…”

“…These could include the improvement of local to regional farming practices such as irrigation or fertilization treatment schemes (e.g. Du et al, 2018;Ma and Song, 2018). Strategic planning at longer timescales would also benefit from insights into the ability of plants to access different sources, especially under changing hydro-climatological conditions such as extreme weather events, droughts or altered flow regimes (e.g.…”

Water uptake patterns of pea and barley responded to drought but not to cropping systems

“…Root water uptake patterns are often discussed for their important role in plant water relations, but responses of crop root water uptake patterns to drought took place in pots or under controlled conditions (e.g., Zegada-Lizarazu & Iijima, 2004;Araki & Iijima, 2005), so that information on field conditions is particularly scarce, except maize (Ma & Song, 2016), wheat (Ma & Song, 2018), oilseed rape, and barley in monoculture (Wu et al, 2016). Furthermore, studies comparing the role of different cropping systems for crop water uptake are completely lacking.…”

Water Uptake Patterns of Alfalfa under Winter Irrigation in Cold and Arid Grassland

“…The reason for this may be due to the increment of water content and heat capacity of the root layer soil caused by freezing irrigation. This prevented drastic changes in temperature in the alfalfa root zone before winter and provided good environmental conditions to acclimatize alfalfa to cold conditions, thus improving the alfalfa overwintering rate [70][71][72][73][74]. Also, repeated thawing and freezing of soil and the days and nights after freezing irrigation played a role in loosening the soil and improving alfalfa habitat conditions.…”