The objectives of this study were to determine the influence of waterlogging alone, drought alone, and alternating drought and waterlogging on cotton (Gossypium hirsutum L.) yield and yield components. Water deficit and waterlogging experiments were conducted at the flowering and boll‐setting stages of cotton. The lint and cottonseed yields were reduced after waterlogging alone, drought alone, and alternating drought and waterlogging. The lint and cottonseed yields under alternating drought and waterlogging were greater than those under drought alone. When alternating drought and waterlogging, the drought stage decreased the lint and cottonseed yields, whereas the waterlogging stage had a compensatory effect. The decrease in the number of opening bolls might be the major reason for the observed decrease in lint and cottonseed yields. Waterlogging alone, drought alone, and alternating drought and waterlogging all led to an increase in the proportion of the boll wall biomass and a decrease in the proportion of the fiber biomass of cotton bolls. The proportion of the seed biomass of cotton bolls always decreased, except under alternating drought and heavy waterlogging in 2015. The fiber/seed biomass ratio decreased, except under drought alone in 2015. These findings might provide data to support the prevention of cotton yield loss under drought and waterlogging.
Accurate estimation of crop yield under aeration stress is crucial for field water table management. In this study, the CROPR crop model was improved in two aspects: (i) a new aeration factor, which was related to a drainage index, was proposed and used to represent the condition of soil aeration; and (ii) a multiplicative structure, instead of the original additive structure, was used in the calculation of dry matter accumulation to include the after-effect of aeration stress. Four-year lysimeter experiments on cotton (Gossypium hirsutum L.) growth under aeration stress were conducted from 2008 to 2011 to calibrate and validate both the original and improved CROPR. The results indicated that the improved CROPR performed better than the original CROPR and was suitable for simulating cotton yield under aeration stress. In the calibration, with the improved CROPR, the root-mean-squared error (RMSE) of seed cotton yield was 832.84 kg ha–1 with a normalised value (NRMSE) of 15.87%, whereas with the original CROPR, the RMSE was 973.03 kg ha–1 with an NRMSE of 18.55%. In the validation, with the improved CROPR, the RMSE of seed cotton yield was 686.22 kg ha–1 with an NRMSE of 14.87%; with the original CROPR, the RMSE was 1019.02 kg ha–1 with an NRMSE of 22.08%.
Cotton suffers from alternations of flood and drought in China. A lysimeter trial was conducted to investigate the responses of various cotton yield indices under water-stress treatments including, flood (five-day, eight-day), drought (10-day, 15-day), and five-day flood followed by 10-day drought, during the flowering and boll-forming stage. The results showed that the seed cotton yield was significantly (p < 0.05) reduced under all water-stress treatments, while the harvest index was not affected under any treatment. Significant decreases in dry matter yield, boll number, and boll hull mass were detected under flood treatments but not under drought treatments. The percentage cotton yield losses per day induced by flood and drought were 6.22% and 2.48%, respectively. Under water stress, the associations between seed cotton yield and relevant yield indices were weakened, but yield losses were still strongly related to the decreases in dry matter yield and boll number. Flood followed by drought caused significant reductions in all yield indices except harvest index; however, the reduction was much lower than the additive reductions induced by flood and drought. These results provide bases for scheduling irrigation and drainage under climate change.
The Qingtongxia Irrigation District (QID) is one of the key agricultural bases in the Yellow River Basin. It is located in the upstream part of the Yellow River in the north of China and covers about 350 000 ha of farmland. The climate in the district is arid and semi-arid. The annual average precipitation is about 200 mm. Water shortage is one of the main restrictions on agricultural development. In recent years, large amounts of water have been drawn from the Yellow River, which not only contributes to the severity of water shortages in the middle and downstream part of the Yellow River Basin, but also leads to the rise of the groundwater table and related waterlogging and salinization of the farmland.This article focuses on the analysis of the effects of field groundwater table control under different irrigation water amounts on the soil water and salinity content and on relative crop yield. Two experimental areas, Pingluo and Huinong, were selected to collect the required field data. The agro-hydrological model SWAP was used to analyse the water flow and salt transport for different groundwater table and irrigation scenarios. Six scenarios, which resulted from two groundwater table regimes combined with three irrigation amounts, were simulated. The groundwater table regimes represent the present and future target groundwater table situation and the three irrigation amounts represent different water-saving options. Waterlogged land is also simulated. The results show that:High regional groundwater tables are the main reason for the large amount of drainage water and low crop yield. Due to the regional high groundwater table, reducing irrigation amounts in the field without lowering the field groundwater table will not lead to a large reduction of drainage water, and will cause a further reduction in crop yield. The salinity storage in the soil profile at the end of the growing season will increase when the irrigation amount is reduced, and when the groundwater région est aride à semi-aride, les précipitations annuelles y sont d'environ 200 mm, le manque d'eau constitue donc un des éléments qui entravent le développement de l'agriculture. Ces dernières années, d'important volumes ont été prélévés du Fleuve Jaune, ce qui cause non seulement une pénurie à l'aval, mais aussi la remontée des nappes souterraines de la région, des stagnations et la salinisation des terres. Le présent article met l'accent sur l'analyse des effets du contrôle de la nappe sous différents régimes d'apport d'eau, sur l'état dynamique de l'eau et du sel et le rendement agricole. Deux zones expérimentales ont été choisies à Pingluo et à Huinong pour collecter des données. Avec le modèle agro-hydraulique SWAP, l'état dynamique de l'eau et du sel et le rendement agricole correspondant à six scénarios différents de gestion agro-hydraulique ont été analysés. Ces six scénarios résultent de la combinaison de deux régimes de contrôle de la nappe et de trois régimes d'irrigation. Les deux régimes de contrôle de la nappe représentent le nive...
Canal lining is commonly used to reduce seepage loss and increase water use efficiency. However, few studies have quantitatively estimated the seepage control effects of different lining materials under different service times. Ponding tests were conducted on the same canal section with four different lining statuses to investigate the canal lining effect on seepage control and its impact factors in arid areas. The cracks and holes in different lining materials were surveyed, and the canal seepage rates under the four test treatments were calculated by monitoring the water level change in the canal. The results show that the cracks in the joints of the two precast concrete slabs and holes in the geomembrane, which are located 0.25 m above the canal bottom on two sides of the canal, are responsible for the increased seepage loss. The new concrete and geomembrane lining combination reduces seepage by 86% compared with no lining, while seepage can be reduced by 68% using the concrete and geomembrane lining combination after three service years, and the amount decreases to 11% by using geomembrane lining with a three year service time. Based on the experiment and literature, a statistical relationship between the seepage reduction and lining service time was established, which provided a possible and easy way to estimate seepage losses from lined canals and improve the estimation accuracy using an empirical formula. Without considering the service time lining effect, the seepage loss is underestimated by 58%, and the canal water use efficiency is overestimated.
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