Optimizing crop quality and yield: Assessing the impact of integrated potassium management on Chinese cabbage (Brassica rapa L. subsp. chinensis)

Potassium, a pivotal macronutrient essential for growth, development, and crop yield, serves as a critical determinant of soil productivity. Its depletion disrupts the equilibrium of soil nutrients, prompting an investigation into integrated potassium management strategies to address this challenge. A field experiment was conducted during the winter season of 2020 using a randomized complete block design, with eight treatments, each replicated three times in Chinese cabbage (Brassica rapa L. subsp. chinensis). These treatments comprised standard (100 %) and reduced (75 % and 50 %) rates of the recommended dose of potassium (RDK) via muriate of potash (MOP). Variations in the inclusion and exclusion of plant growth-promoting rhizobacteria (PGPR), farmyard manure (FYM) as 25 % of the potassium recommendation, and foliar spray of nano potash were systematically implemented. Findings unequivocally demonstrated that the treatmentT8, involving 100 % RDK +25 % K through FYM + PGPR + nano K fertilizer spray at 25 and 40 DAS, yielded significant improvements in both green fodder (64.0 t ha−1) and dry fodder (7.87 t ha−1).Moreover, T8 exhibited the highest values for total ash (8.75 %), total ash yield (68.9 ± 2.88 kg ha−1), ether extract (2.85 %), ether extract yield (22.4 ± 0.88 kg ha−1), crude protein (9.71 %), and total crude protein yield (76.4 ± 3.21 kg ha−1). Conversely, a marked reduction was observed in various fiber components and carbohydrate fractions upon application of the T8 treatment. The lowest values of yield, crude protein content, total ash ether extract were recorded in treatment T1 (control) applied with no potassium. This investigation underscores the inadequacy of the recommended potassium dose in achieving optimal productivity, necessitating a re-evaluation of potassium fertilization levels. The integrated approach involving FYM, PGPR, and nano potash, coupled with the recommended potassium dose through MOP, emerges as a promising avenue for augmenting both yield and quality parameters in Chinese cabbage.

Potassium, a pivotal macronutrient essential for growth, development, and crop yield, serves as a critical determinant of soil productivity.Its depletion disrupts the equilibrium of soil nutrients, prompting an investigation into integrated potassium management strategies to address this challenge.A field experiment was conducted during the winter season of 2020 using a randomized complete block design, with eight treatments, each replicated three times in Chinese cabbage (Brassica rapa L. subsp.chinensis).These treatments comprised standard (100 %) and reduced (75 % and 50 %) rates of the recommended dose of potassium (RDK) via muriate of potash (MOP).Variations in the inclusion and exclusion of plant growth-promoting rhizobacteria (PGPR), farmyard manure (FYM) as 25 % of the potassium recommendation, and foliar spray of nano potash were systematically implemented.Findings unequivocally demonstrated that the treatmentT 8 , involving 100 % RDK +25 % K through FYM + PGPR + nano K fertilizer spray at 25 and 40 DAS, yielded significant improvements in both green fodder (64.0 t ha − 1 ) and dry fodder (7.87 t ha − 1 ).Moreover, T 8 exhibited the highest values for total ash (8.75 %), total ash yield (68.9 ± 2.88 kg ha − 1 ), ether extract (2.85 %), ether extract yield (22.4 ± 0.88 kg ha − 1 ), crude protein (9.71 %), and total crude protein yield (76.4 ± 3.21 kg ha − 1 ).Conversely, a marked

Introduction
Livestock plays a vital role in economy by employment generation as well as providing supplementary family income in the countries with small and marginal farmers.Livestock performance is mainly dependent on its feeding.Forages are the mainstay of animal wealth.The profitability of livestock production is directly dependent on the sources of feed and fodder; hence, the quality of fodder can play an important role in increasing the animal productivity [1,2].However, the unavailability of quality fodder to meet the nutritional requirement remains a significant barrier, contributing to lower productivity and profitability in livestock sector.
Introducing crops that offer both high-quality and abundant fodder during lean periods can significantly enhance livestock health and productivity [3,4].Chinese cabbage (Brassica rapa L. subsp.chinensis) emerges as a promising solution within the Brassicaceae family, not only providing nutritious fodder but also edible oil, making it versatile for North India agriculture.Its rapid growth cycle (75-80 days) positions Chinese cabbage as an ideal option for ensuring consistent green fodder supply during periods of scarcity.However, achieving ideal fodder quality and quantity hinges on factors such as optimal sowing time, effective weed control [5], and standard week (12th November − 18th November) witnessed the maximum average relative humidity (98.3 %), while the 40th standard week during the crop period experienced the highest evaporation rate (4.8 mm day − 1 ), maximum temperature (34.5 • C), and sunshine hours (8.6 h day − 1 ).The soil composition of the experimental field is characterized as clay loam, exhibiting elevated levels of organic carbon (0.66 %), a neutral pH (7.46), low nitrogen content (198 kg ha − 1 ), high phosphorous content (29.1 kg ha − 1 ), and medium potassium availability (235 kg ha − 1 ).
The experimental design employed in this study was a randomized complete block design (RCBD), consisting of eight treatment combinations (Table 1).The treatments encompassed the following categorizations: T 1 -control (No K); T 2 -recommended dose of fertilizer (RDK) via muriate of potash (MOP); T 3 -75 % RDK (MOP) + nano K fertilizer spray at 25 and 40 days after sowing (DAS); T 4 -50 % RDK + PGPR + nano K fertilizer spray at 25 and 40 DAS; T 5 -75 % RDK + PGPR + nano K fertilizer spray at 25 and 40 DAS; T 6 -50 % RDK+25 % K infusion through FYM + PGPR + nano K fertilizer spray at 25 and 40 DAS; T 7 -75 % RDK + 25 % K enrichment through FYM + PGPR + nano K fertilizer spray at 25 and 40 DAS; T 8 -100 % RDK + 25 % K augmentation through FYM + PGPR and nano K fertilizer spray at 25 and 40 DAS.The seedbed preparation adhered to the specific requirements of the crop, executed using a cultivator and leveller with a subtle gradient to facilitate optimal irrigation.The chosen fodder mustard variety, "Chinese cabbage," was sown at a seed rate of 5 kg ha − 1 with a spacing of 30 cm × 10 cm.Fertilizer application was meticulously carried out at a rate of 120 kg N ha − 1 and 60 kg P 2 O 5 ha − 1 .Of this, half of the nitrogen and the full amount of phosphorus were applied as the basal dose, with the remaining nitrogen administered at 30 DAS.Potassium supplementation was accomplished through muriate of potash, farmyard manure as the basal dose, and a foliar application of nano potash at 0.3 % at 25 and 40 DAS, in accordance with the stipulations outlined in Table 1.To incorporate 25 % of the recommended fertilizer dose through farmyard manure, FYM analysis was conducted on a dry weight basis.The requisite amount of FYM for 25 % potassium application was then calculated.To maintain a balanced dose of nitrogen and phosphorus, the quantity provided through FYM was also determined and subtracted from the overall fertilizer dose.Furthermore, the seeds underwent inoculation with plant growth-promoting rhizobacteria, following the specified treatment details.The cultivation of Chinese cabbage (Brassica rapa L. subsp.chinensis) involved three replications for each treatment.

Estimation of yield and proximate composition of Chinese cabbage
Chinese cabbage underwent manual harvesting, with the recording of fresh weight and subsequent conversion of yield (kg plot − 1 ) into tons per hectare (t ha − 1 ).Representative samples were systematically extracted from each experimental plot and subjected to a 48h desiccation period in a hot air oven maintained at 60 • C. The resulting dry fodder yield was then computed in tons per hectare.Subsequent to desiccation, the samples underwent crushing in a Wiley mill and were sieved at a 1 mm aperture, followed by preservation in sealed polythene bags for subsequent analytical procedures.The analysis of the fodder's proximate composition, encompassing crude protein (CP), ether extract (EE), and total ash (TA), was conducted utilizing the association of official analytical chemists (AOAC) method [18].The calculation of crude protein involved the multiplication of the nitrogen content, determined through the Kjeldhal method, by a factor of 6.25.Subsequently, the values for crude protein, ether extract, and total ash content were further multiplied by the dry fodder yield, resulting in the derivation of crude protein yield, ether extract yield, and total ash yield on a per-hectare basis.

Estimation of fiber and carbohydrate fractions of Chinese cabbage
The methodology employed for assessing neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) adhered to the protocols outlined by Van Soest, Robertson and Lewis [19].Acid insoluble ash (AIA) was determined from the acid detergent fiber using the methodology described by Oke [20].Neutral detergent insoluble nitrogen (NDIN) and acid detergent insoluble nitrogen (ADIN) were quantified by analyzing residues from NDF and ADF, respectively, employing the Kjeldahl Nitrogen estimation process as outlined by Ref. [21].The values for neutral detergent insoluble crude protein (NDICP) and acid detergent insoluble crude protein (ADICP), expressed as a percentage of dry matter (DM), were computed by multiplying the NDIN and ADIN values by a factor of 6.25.To represent NDICP and ADICP on a percentage of crude protein (CP) basis, the values initially calculated on a percentage of dry matter basis were subsequently divided by the CP content of the sample.Total carbohydrate (%), structural carbohydrate (%), non-structural carbohydrate (%), cellulose (%), and hemicellulose (%) were estimated in accordance with the procedures delineated by Van Soest, Robertson and Lewis [19].

Table 1
Treatment description of integrated potassium management in the experimental conditions.

Feed quality estimation of Chinese cabbage
The nutritive characteristics of the feed, specifically dry matter intake (DMI), dry matter digestibility (DMD), total digestible nutrients (TDN), relative feed value (RFV), and relative forage quality (RFQ), were assessed employing the methodologies outlined by Horrocks and Valentine [22] and Undersander, Moore and Schneider [23].The computation of these parameters followed established formulae as prescribed by these authors.

Statistical analysis
The data obtained from the field experiment underwent statistical analysis utilizing R-software version 4.1.2at a significance level of 5 % (p ≤ 0.05).The analysis of variance (ANOVA) test was employed to assess and compare the means, following the methodology outlined by Gomez and Gomez [24].GraphPad PRISM 8.0 facilitated the creation of graphical representations, while correlation analysis was conducted using JASP version 0.18.3.0.

Green and dry fodder yield
The green and dry fodder yield of Chinese cabbage (Brassica rapa L. subsp.chinensis) exhibited significant variations as a consequence of integrated K application (Fig. 1).Among the treatments, T 8 recorded the highest green yield (64.0 ± 2.2 t ha − 1 ) and dry fodder yield (7.87 ± 0.33 t ha − 1 ).In contrast, the control treatment (T 1 ) exhibited the lowest green (47.3 ± 3.7 t ha − 1 ) and dry fodder yield (4.88 ± 0.44 t ha − 1 ).Treatment T 8 demonstrated comparable results with T 7 , T 2 , and T 5 .Additionally, T 1 was statistically similar to T 3 , T 4 , and T 6 for green fodder yield, while being equivalent to T 4 and T 6 for dry fodder yield.Notably, the integrated K application, particularly 100 % RDK through MOP alone, significantly enhanced the yield of Chinese cabbage in this experiment.This showed that integrated K application significantly enhanced Chinese cabbage green and dry fodder yields compared to control.

Proximate composition
Crude protein percentage and crude protein yield exhibited a statistically significant (p ≤ 0.05) response to integrated K fertilization (Fig. 2A).Treatments applied with K showed significant superiority over the control (T 1 ).Specifically, treatment T 8 , resulted in the highest crude protein content of 9.71 ± 0.01 % and a crude protein yield of 76.4 ± 3.21 kg ha − 1 .This treatment showed statistical similarity with T 7 , which had a crude protein content of 9.69 ± 0.06 % and a crude protein yield of 75.5 ± 8.26 kg ha − 1 .Additionally, T 2 exhibited a crude protein content of 9.66 ± 0.01 % and a crude protein yield of 72.0 ± 8.25 kg ha − 1 .Similarly, T 5 had a crude protein content of 9.66 ± 0.05 % and a crude protein yield of 69.0 ± 4.07 kg ha − 1 .Both T 2 and T 5 were significantly superior to the control (T 1 ), which recorded crude protein content of 9.43 ± 0.10 % and crude protein yield of 46.0 ± 4.46 kg ha − 1 .The study highlights the substantial role of integrated potassium management in enhancing crude protein and crude protein yield in Chinese cabbage.
The total ash content and yield of Chinese cabbage were significantly influenced by integrated potassium application across different treatments (Fig. 2B).Treatment T 8 had the highest ash content (8.75 ± 0.01 %) and ash yield (68.9 ± 2.88 kg ha − 1 ), comparable to T 7 (8.74 ± 0.02 % and 68.1 ± 7.39 kg ha − 1 ).Treatments T 2 (8.70 ± 0.18 % and 64.9 ± 8.61 kg ha − 1 ) and T 5 (8.64 ± 0.27 % and 61.7 ± 2.80 kg ha − 1 ) also showed high ash content and yield.The lowest values were in T 1 (7.35 ± 0.02 % and 35.9 ± 3.15 kg ha − 1 ).Statistical analysis confirmed the significant impact of integrated potassium management on both ash content and yield in Chinese cabbage.Integrated K application significantly enhances both ether extract content and ether extract yield (Fig. 2C).Specifically, treatment T 8 demonstrated the highest ether extract content (2.85 ± 0.01 %) and yield (22.4 ± 0.88 kg ha − 1 ).Treatment T 7 followed closely with an ether extract content of 2.84 ± 0.01 % and a yield of 22.1 ± 2.45 kg ha − 1 .Treatment T 2 exhibited an ether extract content of 2.85 ± 0.05 % and a yield of 21.2 ± 2.19 kg ha − 1 .Treatment T 5 recorded an ether extract content of 2.84 ± 0.01 % and a yield of 20.3 ± 1.34 kg ha − 1 , significantly outperforming the control treatment, which had an ether extract content of 2.50 ± 0.02 % and a yield of 12.2 ± 1.02 kg ha − 1 .These results highlight the substantial role of integrated K management in augmenting both ether extract content and yield in Chinese cabbage.

Fiber and carbohydrate fractions
Fiber fractions, including NDF, ADF, ADL, and AIA, exhibited significant alterations with integrated K management in Chinese cabbage (Table 2).Notably, all treatments involving integrated K management demonstrated reduced levels of NDF, ADF, ADL, and AIA in comparison to the control (T 1 ).Treatment T 8 yielded significantly lower values (p ≤ 0.05) for NDF (53.3 ± 1.71 %), ADF (31.5 ± 0.82 %), ADL (5.96 ± 0.02 %), and AIA (4.29 ± 0.05 %).Notably, these values were statistically comparable to those obtained with treatment T 7 , T 2 , and T 5 , all of which were found to be significantly superior to the control treatment (T 1 ).The observed alterations in fiber fractions in Chinese cabbage fodder were attributed to the significant influence of integrated K management strategies employed in the experiment.
The lowest NDIN value (0.370 ± 0.010) was observed in treatment T 8 , which was statistically similar to T 7 and T 2 .The highest NDIN value (0.580 ± 0.011) was found in the control treatment (T 1 ).For NDICP, T 8 had the lowest values (2.31 ± 0.06 on a dry matter basis and 23.8 ± 0.7 on a crude protein basis), similar to T 7 , T 2 , and T 5 , while T 1 had the highest values (3.62 ± 0.07 and 38.4 ± 1.0, respectively).Integrated K management significantly influenced NDIN and NDICP values.Further, treatment T 8 recorded the lowest ADIN value (0.210 ± 0.009), statistically similar to T 7 , and lower than T 1 (Table 2).Likewise, the lowest ADICP values (Table 2) were in T 8 (1.31 ± 0.054 and 13.5 ± 0.56), comparable to T 7 , T 2 , and T 5 , while the highest values were in T 1 (1.81 ± 0.012 and 19.2 ± 0.15).These results indicate that integrated K fertilization significantly reduces ADIN and ADICP values in Chinese cabbage.
Integrated K management significantly influences the cellulose content in Chinese cabbage.The lowest cellulose content (25.4 ± 0.84 %) was achieved in the T 2 treatment, which was comparable to the T 8 (25.54 %) and T 7 treatments.Similarly, the T 5 treatment exhibited cellulose content similar to T 8 and T 7 .Conversely, hemicellulose content remained unaffected by integrated potassium management (Fig. 3A).The minimum hemicellulose content was observed in the T 7 treatment (21.6 ± 1.07 %), followed closely by the T 8 treatment (21.8 ± 1.85 %).These findings highlight the nuanced impact of integrated K management on cellulose and hemicellulose content in Chinese cabbage.Significant variations in total carbohydrate content of Chinese cabbage were observed due to integrated K management (Fig. 3B).The highest total carbohydrate (T-CHO) content was found in the T 1 treatment (80.7 ± 0.07 %), which received no potassium.In contrast, the lowest T-CHO content was recorded in the T 8 treatment (78.7 ± 0.02 %).This level was comparable to the T 7 (78.7 ± 0.08 %), T2 (78.8 ± 0.12 %), and T 5 treatments (78.84 %).The highest structural carbohydrate content (55.4 ± 0.38 %) was also observed in the T 1 treatment, while the lowest (51.0 ± 1.75 %) was in the T 8 treatment, with T 2 and T 5 showing similar results.Non-structural carbohydrate content showed no significant differences (Fig. 3B).

Feed quality
The DMI content of Chinese cabbage was significantly improved due to the application of integrated K sources in different treatments (Table 3).The highest DMI content (2.25 ± 0.07 %) was observed in treatment T 8 .This result was statistically comparable to T 7 treatment (2.25 ± 0.02 %).Additionally, treatment T 2 (2.23 ± 0.00 %) and T 5 demonstrated substantial DMI content.Conversely, the lowest DMI content was recorded in T 1 (2.03 ± 0.01 %).Analysis of variance revealed a significant impact of integrated K management on both the green and dry fodder yield of Chinese cabbage.The DMD content of Chinese cabbage substantial improved due to application of integrated K management (Table 3).Specifically, treatment T 8 demonstrated the highest DMD content at 64.4 ± 0.6 %, and found comparable to treatment T 7 , T 2 , and T 5 .The lowest DMD values were observed in treatment T 1 (control), which recorded values 61.5 ± 0.2 %.Further, the treatment T 2 , exhibited the * DMI-dry matter intake, DMD-Dry matter digestibility, TDN-total digestible nutrient, RFV-relative feed value and RFQ-relative feed quality.highest TDN content at 60.7 ± 1.05 % (Table 3).This observation was statistically comparable to the TDN content in treatment T 8 , T 7 , and T 5 .Notably, these treatments significantly outperformed treatment T 1 (56.0 ± 0.37 %).
The data analysis unveiled that the treatment T 8 exhibited the highest RFV and RFQ values, recording 112.4 ± 3.78 %, (Table 3).This outcome was statistically comparable to the relative feed values observed in treatment T 7 , T 2 , and T 5 .Notably, treatment T 8 demonstrated a significant superiority over treatment T 1 (97.0 ± 0.89 %).Furthermore, treatment T 8 recorded a notably higher relative feed quality of 111.2 ± 4.1 %, as detailed in Table 3.This result was statistically comparable to the relative feed quality observed in treatment T 7 , T 2 , and T 5 .Importantly, treatment T 8 demonstrated a significant superiority over treatment T 1 (92.6 ± 1.1 %).

Overall impact of integrated K management on yield, proximate composition, fiber fractions and feed quality of Chinese cabbage
The impact of integrated K management applied with MOP, PGPR, FYM, and foliar spray of nano potash on yield, proximate composition, fiber fractions and feed quality of Chinese cabbage were analyzed by principal component analysis and correlation matrix among the treatments and various parameters.The data analysis yielded significant principal components, PC1 and PC2, in the experimentation, explaining 99.63 % and 0.36 % variance, respectively (Fig. 4A).Treatments grouped into two clusters: cluster I includes treatments T 1 , T 3 , T 4 , T 6 , and cluster II includes treatments T 2 , T 5 , T 7 , T 8 .Cluster I correlated positively with PC1 but negatively with PC2, while cluster II correlated positively with PC1 and PC2.Parameters grouped into four clusters: cluster I (NDF, T-CHO, Stru-Carb and DMD), cluster II (GFY, TDN, RFV, and RFQ), cluster III (DFY, TA, EE, CP, ADL, AIA NSC, and DMI), and cluster IV (ADF, cellulose, and hemicellulose).Additionally, treatment T 8 also contributed significantly in improving green fodder yield, total digestible nutrients, structural carbohydrates, total carbohydrates, dry matter digestibility, relative feed value and relative feed Fig. 4B.
M. Choudhary et al. quality, and neutral detergent fiber content.
The statistical analyzed data shown in the correlation (r) plot matrices (Fig. 4B) underscored significant positive associations (r) > 0.648 among yield, crude protein, ether extract and total ash content in Chinese cabbage whereas a strong negative correlation (r) > − 0.693 was observed among yield, crude protein, ether extract, total ash content and fiber fractions such as NDF, ADF, ADL, and AIA in Chinese cabbage.

Discussion
In the current experiment, K fertilization yielded significantly positive results on Chinese cabbage (Brassica rapa L. subsp.chinensis) fodder yield (Fig. 1).Potassium enhances growth by improving photosynthesis, cell elongation, nutrient translocation, and water absorption in roots [25,26].Furthermore, K+ is instrumental in regulating auxin concentration and its translocation between roots and shoots [27].The synergistic effect of plant growth-promoting rhizobacteria, coupled with farmyard manure (FYM), contributed to enhanced fodder yield through ACC-deaminase activity [3,4].FYM acts as a substrate for soil microbes, promoting increased microbial activity in the rhizosphere, thereby facilitating the enhancement, mobilization, and uptake of nutrients [14].Kumar et al. [28], have indicated that the application of 60 kg K through MOP and 30 kg K through FYM maximizes yield compared to other treatments.Studies conducted by Iqbal and Umar [29] and Farnia and Ghorbani [30] have demonstrated that nano potash, when combined with biofertilizer, enhances biomass yield.In the present study, the higher green and dry fodder yield of Chinese cabbage (Brassica rapa L. subsp.chinensis) was attributed to the integrated application of MOP, PGPR, FYM, and nano K spray at 25 and 40 DAS.Similar positive outcomes were also reported by Baljeet et al. [31].
Crude protein content and yield are pivotal indicators for assessing the quality of fodder crops (Fig. 2A).The quantification of crude protein is intricately linked to the availability of nitrogen and its assimilation rate within plants [32].In the present study, diverse K sources demonstrated a notable influence on nitrogen availability in plants, showcasing a synergistic effect between K and nitrogen.Aulakh and Malhi [33], asserted that K exhibits a synergistic effect on nitrogen uptake and enhances the assimilation rate of various nutrients.Correspondingly, Kumar et al. [28] reported that integrated K application (MOP + FYM) increased crude protein content and yield in maize and wheat crops within a maize-wheat cropping system.The efficacy of foliar application of nano potassium in improving nitrogen content, crude protein content, and crude protein yield in groundnut crops was affirmed by Afify et al. [16].Additionally, Nosheen et al. [34] highlighted the significant role of plant growth-promoting rhizobacteria (PGPR) in facilitating nitrogen availability and acquisition in canola plants, thereby contributing to an augmentation in crude protein content.
The present investigation highlights the substantive role of diverse K sources in augmenting the availability of various mineral nutrients, thereby contributing to heightened enzymatic activities.This elevation in enzymatic activities, correlates with an increase in ether extract content (Fig. 2B).The observed significant variations in ether extract yield can be attributed to the concomitant higher dry fodder yield and enhanced enzymatic activities facilitated by elevated K availability in the Chinese cabbage under the specific treatment.This finding aligns with previous studies conducted by Kushwaha and Masood [35] and Tiwari et al. [36].
Analysis of total ash content in plants provides insights into the inorganic mineral content, excluding nitrogen and sulfur.The marked differences in total ash content observed in Chinese cabbage (Brassica rapa L. subsp.chinensis) are a consequence of the augmented potassium levels supplied through MOP, FYM, PGPR, and foliar spray of nano potash (Fig. 2C).Potassium's pivotal role in the translocation process and its synergistic effect on enhancing macronutrient and micronutrient uptake contribute to elevated nutrient concentrations in various plant parts [37].The application of MOP augments potassium availability for plant uptake, while the use of PGPR and FYM, both independently and in combination, heightens the soluble nutrient concentration in the plant root zone, thereby facilitating increased nutrient uptake [38,39].Additionally, nano potash application amplifies potassium accumulation in different plant parts.The variations in total ash yield stem from the concurrent higher dry fodder yield and increased mineral nutrient concentration in Chinese cabbage under the specific treatment, aligning with findings reported by Ayub et al. [1] and Bhakar et al. [2].Further, the observed improvements in ether extract content and ether extract yield in Chinese cabbage can be attributed to the heightened availability of K, promoting the activation of enzymes responsible for oil content production in plants, as reported by Singh et al. [40].
Fiber fractions constitute pivotal indicators of fodder quality, with their abundance significantly influencing digestibility.The present investigation observed a noteworthy impact on various fiber fractions, namely NDF, ADF, ADL, and AIA, due to the integrated K fertilization sources (Table 2).Baljeet et al. [31], which underscored the efficacy of balanced nutrient application in reducing fiber fractions in crops.It is well-established that nutrient deficiencies can impede plant metabolic activities, growth, and development.Specifically, a K deficiency induces stress conditions, resulting in elevated NDF, ADF, ADL, and AIA content, as noted by Pholsen and Suksri [41] and Balabanli et al. [42].
The observed differences in NDIN percentage and NDICP percentage on a dry matter basis among treatments may be ascribed to the varying NDF content in treatments subject to integrated K fertilization.Likewise, disparities in ADIN and ADICP on a dry matter basis among treatments could be attributed to variations in ADF content in treatments subjected to integrated K fertilization.These outcomes resonate with the findings of previous researchers, Yolcu et al. [43], Yolcu et al. [44], Matsi et al. [45] and Qiu et al. [46].
Cellulose and hemicellulose constitute essential components of the plant cell wall.The levels of cellulose and hemicellulose within plants exhibit a close association with the content of ADF, NDF, and ADL.In the current investigation, the concentrations of ADF, NDF, and ADL were influenced by the availability of potassium through the integrated K application.Treatment T1, characterized by the highest recorded values of ADF, NDF, and ADL, demonstrated elevated cellulose (%) and hemicellulose content (%) (Fig. 3A).These outcomes align closely with the findings of Pholsen and Suksri [41] and Balabanli et al. [42], who posit that the application of a balanced fertilizer dose mitigates fiber fraction within the plant cell wall.
The treatment incorporating integrated K fertilization exhibited superior values in DMI, DMD, TDN, RFV, and RFQ values compared to the control (T 1 ) The DMI is known to be inversely proportional to NDF content in plants [47] whereas, the observed variation in DMD among treatments is attributed to the positive association of DMD with crude protein and its negative correlation with NDF, ADF, and ADL content in plants [48][49][50].The TDN values displays a negative relationship with ADF and NDF content in plants [51].Further, RFV is gauged based on intake potential and DMD content of the fodder [52].The present study establishes a negative correlation between integrated K application and the NDF and ADF content of the feed.These findings align with the studies of Kaithwas et al. [53] and Tokas et al. [54], confirming the consistency of results across different investigations.
The investigation revealed a robust positive correlation through improving yield, proximate composition, feed quality and reduction in fiber and carbohydrate fractions in Chinese cabbage under integrated K management (Fig. 4A).The correlation matrices (Fig. 4B) elucidate noteworthy positive associations, exceeding 0.648, among the variables of yield, crude protein, ether extract, and total ash content within the context of Chinese cabbage.Conversely, a robust negative correlation, surpassing − 0.693, is evident among yield, crude protein, ether extract, total ash content, and fiber fractions, specifically NDF, ADF, ADL, and AIA, in Chinese cabbage.

Conclusion
Integrated K management approach, specifically incorporating 100 % RDK through MOP, 25 % K through FYM, PGPR, and two applications of nano potassium spray, facilitates the attainment of higher fodder quantity in Chinese cabbage (Brassica rapa L. subsp.chinensis).The integrated application of MOP, PGPR, FYM, and foliar spray of nano potash significantly augments total ash content, ether extract content, and crude protein content.Simultaneously, it markedly diminishes NDF, ADF, ADL, AIA, cellulose (%), hemicellulose (%), and various carbohydrate fractions.Consequently, it is deduced that the integrated application of MOP, FYM, PGPR, and nano potash holds promise for enhancing both the yield and physio-biochemical quality of Chinese cabbage.

Declaration of competing interest
Authors declare that there is no conflict of interest.

Table 2
Effect of integrated potassium management on the fiber fraction of Chinese cabbage.

Table 3
Effect of integrated potassium management on the feed quality of Chinese cabbage.