Evaluating Effects of Regulated Deficit Irrigation under Mulched on Yield and Quality of Pumpkin in a Cold and Arid Climate

Comprehensive evaluation of the water-fertilizer coupling effects on pumpkin under different irrigation volumes

Compared to conventional irrigation and fertilization, the Water-fertilizer coupling can significantly enhance the efficiency of water and fertilizer utilization, thereby promoting crop growth and increasing yield. Targeting the challenges of poor crop growth, low yield, and inefficient water and fertilizer utilization in the arid region of northwest China under conventional irrigation and fertilization practices. Therefore, a two-year on-farm experiment in 2022 and 2023 was conducted to study the effects of water-fertilizer coupling regulation on pumpkin growth, yield, water consumption (ET), and water and fertilizer use efficiency. Simultaneously the comprehensive evaluation of multiple objectives was carried out using principal component analysis (PCA) methods, so as to propose an suitable water-fertilizer coupling regulation scheme for the region. The experiment was set up as a two-factor trial using water-fertilizer integration technology under three irrigation volume (W1 = 37.5 mm, W2 = 45.5 mm, W3 = 52.5mm) and three organic fertilizer application amounts (F1 = 3900-300 kg ha-1, F2 = 4800-450 kg·ha-1, F3 = 5700-600 kg·ha-1), with the traditional irrigation and fertilization scheme from local farmers as control treatments (CK). The results indicated that irrigation volume and organic fertilizer application significantly affected pumpkin growth, yield, and water and fertilizer use efficiency (P<0.05). Pumpkin yield increased with increasing irrigation volume. Increasing organic fertilizer levels within a certain range benefited pumpkin plant growth, dry matter accumulation, and yield, however, excessive application beyond a certain level had inhibited effects on those. The increased fertilizer application under the same irrigation volume enhanced the efficiency of water and fertilizer utilization. However excessive irrigation only resulted in inefficient water consumption, reducing the water and fertilizer use efficiency. The Comprehensive evaluation by PCA revealed that the F2W3 treatment outperformed all the others, effectively addressing the triple objectives of increasing production, improving efficiency, and promoting green production. Therefore, F2W3 (Irrigation volume: 52.5 mm; Fertilizer application amounts: 4800-450 kg/ha-1) as a water and fertilizer management scheme for efficient pumpkin production in the arid region of northwest China.

Crop coefficient determination and evapotranspiration estimation of watermelon under water deficit in a cold and arid environment

To investigate the evapotranspiration and crop coefficient of oasis watermelon under water deficit (WD), mild (60%-70% field capacity, FC)and moderate (50%-60% FC) WD levels were set up at the various growth stages of watermelon, including seedling stage (SS), vine stage (VS), flowering and fruiting stage (FS), expansion stage (ES), and maturity stage (MS), with adequate water supply (70%-80% FC) during the growing season as a control. A two-year (2020-2021) field trial was carried out in the Hexi oasis area of China to explore the effect of WD on watermelon evapotranspiration characteristics and crop coefficient under sub-membrane drip irrigation. The results indicated that the daily reference crop evapotranspiration showed a sawtooth fluctuation which was extremely significantly and positively correlated with temperature, sunshine hours, and wind speed. The water consumption during the entire growing season of watermelon varied from 281-323 mm (2020) and 290-334 mm (2021), among which the phasic evapotranspiration valued the maximum during ES, accounting for 37.85% (2020) and 38.94% (2021) in total, followed in the order of VS, SS, MS, and FS. The evapotranspiration intensity of watermelon increased rapidly from SS to VS, reaching the maximum with 5.82 mm·d^-1 at ES, after which it gradually decreased. The crop coefficient at SS, VS, FS, ES, and MS varied from 0.400 to 0.477, from 0.550 to 0.771, from 0.824 to 1.168, from 0.910 to 1.247, and from 0.541 to 0.803, respectively. Any period of WD reduced the crop coefficient and evapotranspiration intensity of watermelon at that stage. And then the relationship between LAI and crop coefficient can be characterized better by an exponential regression, thereby establishing a model for estimating the evapotranspiration of watermelon with a Nash efficiency coefficient of 0.9 or more. Hence, the water demand characteristics of oasis watermelon differ significantly during different growth stages, and reasonable irrigation and water control management measures need to be conducted in conjunction with the water requirements features of each growth stage. Also, this work aims to provide a theoretical basis for the irrigation management of watermelon under sub-membrane drip irrigation in desert oases of cold and arid environments.

Modelling and Evaluation of Potato Water Production Functions in a Cold and Arid Environment

This study was conducted at the Yimin Irrigation Experiment Station, Minle County, Zhangye City, Gansu Province, from April to October in 2019 and 2020. The relationship between water consumption and yield of potato at different stages of fertility under deficit-regulated irrigation was analyzed in a field trial study over two growing seasons. The results showed that the average annual water consumption in the tuber bulking stage was the largest, reaching 185.35~239.52 mm, followed by the average annual water consumption in the tuber initiation stage and starch accumulation stage, which were 100.02~132.30 mm and 82.48~112.36 mm, respectively, and the average annual water consumption in the seedling stage was the least, at 49.32~69.81 mm. Simultaneously, the average annual yield of potatoes in the treatment of WD1 was the highest, reaching 47,766.96 kg·hm−2, followed by CK, which was 43,707.6 kg·hm−2, and the yield of WD6 was the smallest in the treatment of moderate water deficit during tuber initiation, which was only 35,721.25 kg·hm−2. Combining the four moisture production function models of Jensen, Minhas, Blank and Stewart, the Jensen and Stewart models were identified as suitable for the potato moisture production function in a cold and arid environment. The water production function model was used to investigate the relationship between water consumption and yield in each growth period of potato, and to provide a theoretical basis for the optimization of the irrigation system under deficit-regulating irrigation conditions for potato in this irrigation area.