The long-term utilization of inorganic fertilizers in pakchoi cultivation can result in increased nitrate levels, potentially posing health risks to human consumers. For this study, we investigated the efficacy of organic fertilizers as a promising alternative for enhancing soil structure, improving fertility, and increasing the yield of pakchoi. A two-year field trial was conducted from 2022 to 2023 to examine the effects of the combined application of organic fertilizer on the growth and yield of pakchoi. Three types of irrigation water, namely fresh water (F), brackish water (B), and magnetized–ionized brackish water (MIB), were used in combination with five different organic fertilizer rates (0, 20, 40, 60, and 80 kg/ha, denoted as 0, 1, 2, 3, and 4). The results revealed that treatments F2, F3, B2, B3, and MIB3 significantly improved the growth indexes of pakchoi. Notably, treatments F3, B3, and MIB3 resulted in an earlier onset of the fast growth period for leaf area index and fresh weight. During this period, we observed the highest cumulative growing degree days (ΔCGDD) values, which were 628.36 °C for plant height (MIB4), 475.01 °C for leaf area index (B3), 259.73 °C for fresh weight (B3), and 416.82 °C for dry matter accumulation (B3). The logistic model indicated an increase in eigenvalue at an organic fertilizer application rate of 60 kg/ha, while excessive fertilization had inhibitory effects. Under brackish water irrigation, both plant height and leaf area index demonstrated significant positive effects on yield, with plant height having a particularly noteworthy direct effect at a coefficient of 0.935. MIB water irrigation demonstrated superior advantages for promoting pakchoi growth, leading to significantly higher rates of fresh weight and dry matter accumulation compared to traditional brackish water irrigation. The maximum value of each growth index exerted a significant direct influence on its respective growth parameter, whereas ΔCGDD demonstrated a relatively smaller or potentially negative effect. Applying organic fertilizer appropriately can assist in the production of pakchoi and provide a scientific basis for increasing yield.

Water scarcity and the overuse of chemical fertilizers present significant challenges to modern agriculture, critically affecting crop photosynthesis, yield, quality, and productivity sustainability. This research assesses the impact of organic fertilizer on the photosynthetic attributes, yield, and quality of pakchoi under varying irrigation water conditions, including fresh water and brackish water. Findings reveal that the modified rectangular hyperbolic model most accurately captures the photosynthetic reaction to organic fertilization, outperforming other evaluated models. The maximum net photosynthesis rate (P_nmax), yield, soluble sugar (SS), and soluble protein content (SP) all exhibited a downward-opening quadratic parabolic trend with increasing amounts of organic fertilizer application. Specifically, under fresh-water irrigation, the optimal P_nmax, yield, SS, and SP were obtained at organic fertilizer rates of 65.77, 74.63, 45.33, and 40.79 kg/ha, respectively, achieving peak values of 20.71 µmol/(m²·s), 50,832 kg/ha, 35.63 g/kg, and 6.25 g/kg. This investigation provides a foundational basis for further research into the intricate relationship between water salinity stress and nutrient management, with the goal of crafting more sophisticated and sustainable farming methodologies. The insights gained could significantly influence organic fertilizer practices, promoting not only higher yields but also superior quality in agricultural outputs.

The issues of limited water availability and excessive fertilizer utilization, both of which negatively impact soil health and crop productivity, are key focal points in the pursuit of sustainable agricultural progress. Given these crucial obstacles, it is crucial to utilize accurate methods of irrigation and fertilization in order to improve the condition of the soil and promote the progress of sustainable farming. The objective of this research is to determine the optimal indicators for creating a minimal data set (MDS) that can assess the influence of organic fertilizers on the quality of pakchoi soil in varying irrigation water sources. Principal component analysis and norm values were utilized to create the MDS, and its accuracy was confirmed by examining coefficients of Nash efficiency and relative deviation. The results of our study showed that there was not much difference in soil bulk density (BD), but there was moderate variation in soil water content (SWC), soil salt content (SSC), alkali-hydrolyzed nitrogen (AN), available phosphorus (AP), available potassium (AK), and organic matter (OM). The selected MDS indicators included BD, AN, and OM. The soil quality index (SQI) achieved a high R² value of 0.952, indicating a strong correlation. Furthermore, the nonlinear evaluation model showed a high level of effectiveness and efficiency, with E_f and E_r values of 0.899 and 0.046, respectively. The effectiveness of this model in evaluating soil quality under different irrigation water conditions is evident. Notably, treatments involving magnetized–ionized brackish water (average SQI = 0.524) and the application of 20 kg/ha organic fertilizer (average SQI = 0.719) demonstrate the capacity to enhance soil quality. The present study presents a pragmatic, productive, and economical quantitative evaluation approach that can be used for worldwide vegetable farming with the utilization of clean water, saline water, magnetized–ionized saline water, and organic manure. Thus, we encourage vegetable growers to consider adopting both magnetized–ionized brackish water and organic fertilizers, and the utilization of the nonlinear soil quality index evaluation model is recommended as it offers a sensitive and effective approach to assessing soil quality across various irrigation and organic fertilizer schemes.