Exploring the Impact of Different Fertilization Practices and Regional Climate Variables on Cabbage (Brassica oleracea L. Var. Capitata) Yield

Abstract

Maintaining stable crop yields is crucial for sustainable agriculture. This study investigated the impact of various fertilization regimes, combined with regional climate variables, on the yield stability of cabbage (Brassica oleracea L. var. capitata) in southern Taiwan. Conducted from 2011 to 2023 on well-maintained soils that were established in 1988, the study examined two crop rotation systems (R1 and R2) and three fertilization treatments: chemical fertilizer, integrated fertilizer, and organic fertilizer. Despite the consistent annual application of fertilizers, the regression analysis revealed a significant decline in cabbage yields across all six treatment combinations, mainly due to reduced weights of single cabbages. To identify contributing factors, the yield data were analyzed alongside weather and soil data, collected over more than a decade. A Pearson correlation analysis showed that increased sunshine duration, solar radiation, and higher relative humidity were significantly negatively correlated with cabbage yields in both the R1 and R2 rotation systems. Additionally, the regression tree analysis indicated that solar radiation exceeding 16.917 MJ m⁻² per day was associated with lower yields. A further analysis of the total nitrogen accumulation revealed increasing nitrogen concentrations in the outer leaves of cabbages during this period, potentially contributing to the reduced head yields. These findings highlight that fertilization had a minimal influence on yield, even in well-established soils. Mitigating the effects of weather variables is, therefore, critical to reducing their adverse impact on crop yields.

1. Introduction

Yield stability plays a critical role in agricultural sustainability, ensuring consistent and reliable food production year after year. It reflects the capacity of an agricultural system to maintain stable yields despite variations in weather, soil quality, and other environmental factors [1]. This stability is vital for farmers and breeders, who seek to develop resilient crops that are capable of withstanding environmental stresses while maintaining productivity. Long-term field experiments are often employed to evaluate yield stability, enabling the identification of the most robust genotypes and effective agronomic practices [2]. By prioritizing yield stability, agricultural systems can better adapt to the challenges posed by climate change and ensure the sustainability of crop production [3].

Cabbage (Brassica oleracea L. var. capitata), a cool-season crop belonging to the Brassicaceae family, is widely cultivated for its dense, edible head. Originating in Europe, cabbage has adapted well to temperate and subtropical climates and was introduced in Taiwan during the Dutch colonial period. It became a prominent crop in Taiwan following its early introduction to China in the 14th century [4]. In organic farming, cabbage is particularly valued for its adaptability and low pest pressure under proper management. Sustainable agricultural practices, including crop rotation, composting, and natural pest control, further enhance its cultivation and contribute to soil health, making cabbage a promising cornerstone of eco-friendly farming systems.

Taiwan’s rapidly changing climate underscores the importance of addressing crop yield stability. Between 1980 and 2009, Taiwan experienced a notable warming trend of 0.29 °C per decade, accompanied by a reduction in annual rain days by 6.26 days per decade [5]. These climatic shifts pose challenges for cabbage production, as the crop thrives in cooler temperatures and is predominantly planted in autumn in southern Taiwan. Higher temperatures adversely affect head formation and increase the plant’s susceptibility to pests and diseases [6]. Additionally, warmer climates foster pest proliferation, shorten growing seasons, and reduce yields [7]. While adequate sunlight is essential for optimal growth, excessive sunlight in hot climates can lead to heat stress and damage [6]. Extreme weather events and unpredictable climate patterns further disrupt cabbage cultivation, complicating planting schedules and economic returns for farmers [8].

Research highlights the advantages of organic farming in improving the properties of soil, including through the accumulation of organic matter, enhanced aggregate stability [9], increased fertility [10], and greater microbial diversity [11]. Soil organic matter (SOM) is particularly crucial for plant growth in organic systems [12], while its enrichment also contributes to climate change mitigation by sequestering atmospheric carbon dioxide [13]. On the other hand, prolonged dependence on chemical fertilizers, while efficient, has resulted in adverse effects such as soil acidification [14] and an increased prevalence of soil-borne diseases [15]. A comparative assessment of various fertilization methods is therefore necessary to achieve a balance between sustainable crop production and environmental conservation.

This study evaluates the effects of different rotation and fertilization regimes on cabbage yield stability in southern Taiwan, focusing on their relationship with local climate variables. Cabbage was selected due to its high nutritional value and significance in crop rotation systems [16]. The crop’s susceptibility to heavy rainfall and pests makes it an ideal model for examining the interaction between climate variability and agricultural practices. This long-term experiment spanned 13 years and assessed four key parameters—weather, soil, yield, and leaf element composition—under three fertilization treatment conditions: chemical fertilizer, integrated fertilizer (half organic combined with half chemical), and organic fertilizer. The insights from this study are intended to inform specific adaptation strategies by identifying mechanisms affecting yield stability in response to climate and soil changes.

2. Materials and Methods

2.1. Local Weather Data Collection

Daily weather data for six climate parameters—average temperature (Tave), maximum temperature (Tmax), minimum temperature (Tmin), relative humidity (RH), precipitation (Prep), sunshine duration (SD), and solar radiation (SR)—were automatically collected from 1990 to the present at the agricultural meteorological station 72V14 (22°51′24.8″ N, 120°30′21.8″ E, 24 m above sea level). The station is less than 1 km from the experimental field. The daily weather data were averaged to represent the autumn cropping season for cabbage growth (1 October–31 January) and used in the Pearson correlation and regression analyses. The temperature range (Tran) was defined as the difference between the daily Tmax and Tmin. Thermal time (DD) was defined as the temperature accumulation throughout the autumn cropping season.

2.2. Experimental Field

This study employed a commercial cabbage variety, Brassica oleracea L. var. capitata “K-Y cross”, a non-GMO cultivar. The seedlings of this variety were purchased from local providers and cultivated for approximately 30 days before germination. These seedlings were planted in this experimental field on the same day. The experimental field soil, classified as hyperthermic, udic, haplaquept, mixed, and calcareous, with a silty loam texture, was initially measured in 1988.

The field was designed with two crop rotation systems, paddy–upland rotation (R1) and upland rotation (R2). The whole-year (three cropping seasons) planting schedule involved rice–rice–cabbage in R1 and sweet corn–sesbania–cabbage in R2. Each rotation included three fertilization treatments: organic fertilizer only (OF), chemical fertilizer only (CF), and integrated fertilizer (IF), which consisted of half organic and half chemical fertilizers based on equivalent nitrogen (N) inputs. While different crops were rotated annually, the same cabbage variety was planted in both the upland and paddy–upland systems every autumn cropping season from 2011 to 2023.

The cabbage beds measured 1.3 m in width and 36 m in length, with double rows spaced 0.5 m apart and plants spaced 0.6 m apart. Each fertilization treatment plot covered 0.1 hectare. No chemical pesticides or herbicides were applied in any plot. Cabbage was typically transplanted in late October and harvested around 70 days later. After harvest, crop residues were plowed back into the soil across all fertilization treatments.

2.3. Fertilization

The fertilization methods were in accordance with methods described in previous studies [16,17]. Chemical fertilizer was applied at a rate of 180-60-60 (N-P₂O₅-K₂O) kg per hectare, with urea for N, superphosphate for P, and potassium chloride for K. Half of the N and K and all of the P were applied as basal fertilizers incorporated into the soil one week before transplantation, while the remaining N and K were split equally and applied as top dressing on around the 15th and 40th day post-transplantation.

The application rate of organic fertilizer was based on the assumption that 50% of the N in the organic fertilizer would become available to the plants during the cropping season. Therefore, vegetable, farmyard, and bone dust mixture compost have been applied as organic fertilizers from 2005 to the present (360 kg ha⁻¹). Each corresponding treatment was kept constant for every cropping season. Before this experiment established a record, each fertilizer treatment had been applied for over 20 years in the same area as uniformly as possible to obtain homogeneous soil properties. Three continuous cropping schedules, implemented annually, also provided reliable support for farmland management. As a result, we believe it reasonable to assume that any significantly different yield trends that were observed between plots were caused by the different fertilizer treatments. This point of view was also put forward by Yang et al., who conducted a series of analyses of such long-term data with sampling replicates [18].

2.4. Sampling and Statistical Analyses

The soil’s chemical properties were analyzed using established protocols [19,20] evaluating key parameters such as pH, organic matter content, and nutrient levels including phosphorus, potassium, calcium, magnesium, iron, manganese, copper, and zinc. Additionally, the concentrations of sodium and the electrical conductivity were measured to further understand the soil’s fertility and overall health. Soil samples from the top 0–15 cm layer were sieved through 10-mesh screens to remove stones and debris. To account for the lack of replication, the plots were subdivided into four subplots, and ten plants were randomly harvested per subplot to form four composite samples. The plants were separated into heads, leaves (wrapper leaves), and roots; dried at 65 °C to a constant weight; and ground to pass through a 40-mesh screen. The total N in the plant materials was determined via combustion analysis (PerkinElmer 2400 II Elemental Analyzer, PerkinElmer, Shelton, CT, USA).

To minimize spatial and temporal heterogeneity in the soil and climate data, our analyses were based on more than a decade of observation. Trends and correlations between yield, soil properties, and climate parameters were assessed using SAS-EG software (v7.1, SAS Institute Inc., USA). Least-squares linear regression was employed to test the hypothesis of no significant changes in these variables over time [21]. A Pearson correlation analysis was used to evaluate relationships among yield, climate parameters, and soil properties. Multiple linear regression with stepwise regression was used to identify key climate and soil variables affecting the yield. A regression tree (decision tree) analysis, conducted using JMP Statistical Software (JMP 18, release 18.2.1, JMP Statistical Discovery LLC., USA), split best method was employed to determine the most critical climate variables influencing the cabbage yield and their interactions.

3. Results and Discussion

3.1. Weather Trends

The daily climate parameters were categorized into three cropping seasons: spring (1 February–31 May), summer (1 June–30 September), and autumn (1 October–31 January), aligning with the growth period of cabbage in the autumn cropping season. The trends in the temperatures, Tave, Tmin and Tmax did not show significant changes. However, the SD (p < 0.001), SR (p < 0.001) and RH (p < 0.05) exhibited slight but statistically significant increasing trends from 2011 to 2023 (Figure 1A,B). The precipitation patterns were unevenly distributed across these periods. The linear trend for the SD indicated a significant increase of 0.3527 h per year, while the RH showed a moderate rise of 0.6506% per year. Although the relationship between the SD and RH remains inconclusive, decreased wind speeds in Taiwan [5] may account for the observed rise in RH. However, based on analysis of the dataset from 1990 to 2023, we found a significant correlation between Tmax and RH throughout the entire year, with a correlation coefficient of r = 0.398 (p < 0.001). This relationship is particularly pronounced during the cabbage growth stage, cold season months, as evidenced by the following correlation coefficients: October (r = 0.731), November (r = 0.727), December (r = 0.603), and January (r = 0.574). These findings suggest that temperature fluctuations in the cooler months may have a strong influence on relative humidity levels.

3.2. Soil Properties

Two rotation systems had been implemented since 2004: R1 (paddy–upland rotation) and R2 (upland rotation). Each system included the three fertilization treatments. Between 2011 and 2023, organic matter showed a declining trend, particularly in soils that were treated with organic fertilizers in both the R1 and R2 systems (p < 0.05) (Figure 1C). The average organic matter content was recorded during 2011~2023 as follows: R1_OF: 4.42%; R1_IF: 3.42%; R1_CF: 2.05%; R2_OF: 3.31%; R2_IF: 2.52%; and R2_CF: 1.73%.

Overall, the soil’s pH values remained relatively stable, with the organic fertilizer treatments maintaining higher pH values (R1_OF: 6.89; R2_OF: 7.14) compared with the chemical fertilizer treatments (R1_CF: 6.28; R2_CF: 6.13). When compared with the original soil, the R1_OF soil displayed significant enrichment in organic matter (+53.4%), P (+267.7%), K (+63.1%), Ca (+199.9%), and Mg (+226.6%), while the R2_CF soil exhibited notable depletions in organic matter (−33.3%), pH (−10.2%), and Ca (−3.86%) in 2023. Trends of declining pH levels were observed in all six treatments, except for the R2_OF soil (Figure 1D). The frequent occurrence of acid rain (pH < 5.0) in Kaohsiung—accounting for 21% of observation days in 2018 according to Taiwan’s Environmental Protection Administration—likely contributed to this increasing soil acidity.

3.3. Cabbage Yield

The cabbage subplot yields exhibited a significant decreasing trend across all six treatments, with similar distribution patterns being observed from 2011 to 2023. In the R1 rotation system, the yields declined significantly for OF (p < 0.05), IF (p < 0.001), and CF (p < 0.01) (Figure 2A). Similarly, in the R2 rotation system, the yields showed significant declining trends for OF (p < 0.001), IF (p < 0.001), and CF (p < 0.01) (Figure 2B). The overall yield in R2 was found to be higher than in R1, primarily due to the cultivation of sesbania as a green manure crop during the summer. The use of sesbania in R2 likely improved soil fertility and structure, contributing to better growth conditions for subsequent cabbage.

To gain additional insights, the weights of single cabbages (excluding wrapper leaves) were analyzed. In the R1 rotation system, the weights of single cabbages showed a declining trend for OF (y = −20.504x + 1409), IF (y = −25.202x + 1602.3), and CF (y = −25.515x + 1578.9). A similar trend was observed in the R2 rotation system, except for CF (y = 11.044x + 1814.2), which remained relatively stable. Despite the stability of the CF cabbages’ weights in R2, the lack of significant shifts underscores that the overall decline in cabbage yield primarily stems from reduced weights of single cabbages. This suggests that specific factors within the cultivation system may play critical roles in influencing cabbage yields during 2011–2023.

3.4. Correlation Analysis Among Climate Variables, Soil Properties, and Crop Yield

The cabbage yield distribution patterns were largely consistent across the two rotation systems and three fertilization treatments. To identify factors influencing the yield distribution, their correlations with climate variables and soil properties were assessed. The Pearson correlation analysis revealed that the RH, SD, and SR were significantly correlated with the cabbage yield in both the R1 and R2 systems across all fertilization treatments, except for SD in R1_OF (

Table 1. Pearson correlations between cabbage biological yield and abiotic and biotic factors during the period of 2011–2023 ^#.

Pearson Correlation	Value	R1			R2
		CF +	IF	OF	CF	IF	OF
Single head weight (g)	r	0.7878	0.6896	0.8469	0.3777	0.5076	0.4897
	p	0.0014 **	0.0091 **	0.0003 ***	0.2032	0.0765	0.0894
Average temperature (Tave) (°C)	r	−0.1300	−0.0875	−0.1668	0.0058	−0.0160	−0.1176
	p	0.6719	0.7762	0.5859	0.9848	0.9584	0.7019
Maximum temperature (Tmax) (°C)	r	0.1127	−0.0182	0.1192	0.1731	0.0325	0.0424
	p	0.7138	0.9529	0.6979	0.5715	0.9161	0.8905
Minimum temperature (Tmin) (°C)	r	−0.1404	−0.1009	−0.2877	−0.0005	0.0084	−0.1375
	p	0.6472	0.7428	0.3404	0.9985	0.978	0.6541
Relative humidity (RH) (%)	r	−0.7615	−0.8067	−0.7555	−0.6623	−0.6218	−0.7044
	p	0.0025 **	0.0009 ***	0.0028 **	0.0136 *	0.0233 *	0.0072 **
Precipitation (Prep) (mm)	r	0.0023	−0.0375	−0.2293	0.1080	−0.0089	−0.1120
	p	0.9939	0.9031	0.4511	0.7253	0.9768	0.7154
Sunshine duration (SD) (hr)	r	−0.6725	−0.7449	−0.4834	−0.7400	−0.8314	−0.7519
	p	0.0118 *	0.0035 **	0.0942	0.0038 **	0.0004 ***	0.003 **
Temperature range (Tran) (°C)	r	0.3290	0.1838	0.5440	0.2220	0.0984	0.2822
	p	0.2723	0.5476	0.0546	0.4660	0.7491	0.3501
Solar radiation (SR) (MJ m−2 day−1)	r	−0.7540	−0.8283	−0.6177	−0.8048	−0.8963	−0.8266
	p	0.0029 **	0.0005 ***	0.0245 *	0.0009 ***	<0.0001 ***	0.0005 ***
Thermal time (DD) (°C)	r	0.0102	0.0921	−0.0048	0.1670	0.1668	0.0469
	p	0.9734	0.7646	0.9875	0.5855	0.5860	0.8790
pH (1:1)	r	−0.2286	0.4741	0.2930	0.1043	−0.1344	0.0026
	p	0.4524	0.1016	0.3313	0.7344	0.6615	0.9932
Organic matter (%)	r	0.6226	0.4859	0.1921	0.3599	0.4680	0.3964
	p	0.0230 *	0.0923	0.5295	0.2270	0.1068	0.1799
Phosphorus (ppm)	r	−0.5045	−0.5465	−0.4804	−0.3324	−0.5991	−0.6806
	p	0.0787	0.0533	0.0965	0.2670	0.0305 *	0.0104 *
Potassium (ppm)	r	−0.0603	0.3116	0.1414	−0.2669	−0.5734	−0.1553
	p	0.8447	0.3000	0.645	0.3780	0.0405 *	0.6123
Calcium (ppm)	r	0.0379	0.2299	0.2062	0.3782	0.2775	0.3579
	p	0.9020	0.4498	0.4991	0.2025	0.3586	0.2298
Magnesium (ppm)	r	−0.3347	−0.0884	0.2172	−0.2222	−0.4856	0.1818
	p	0.2636	0.7738	0.4759	0.4654	0.0924	0.5521
Iron (ppm)	r	0.3675	0.4078	0.0763	0.2292	0.3308	0.2149
	p	0.2166	0.1665	0.8042	0.4513	0.2695	0.4806
Manganese (ppm)	r	0.5171	0.5304	0.4392	0.0265	0.3298	0.5142
	p	0.0703	0.0622	0.1332	0.9314	0.271	0.0722
Copper (ppm)	r	0.4228	0.5874	0.4355	0.5265	0.6827	0.6434
	p	0.1500	0.0348 *	0.1369	0.0645	0.0101 *	0.0176 *
Zinc (ppm)	r	0.5094	0.4764	0.3834	0.4686	0.1310	0.2779
	p	0.0754	0.0998	0.1958	0.1063	0.6697	0.3579
Sodium (ppm)	r	0.3338	0.4608	0.0872	0.1800	0.3499	0.6257
	p	0.2649	0.113	0.7768	0.5562	0.2412	0.0221 *
Electrical conductivity (1:5; dS m−1)	r	0.5831	0.2548	0.1128	0.5737	0.3078	0.5706
	p	0.0365 *	0.4007	0.7135	0.0403 *	0.3061	0.0417 *

^# Average daily weather parameters and annual soil properties were collected during the cabbage growth period from 2011 to 2023. The values in one row present simple Pearson correlation coefficients, with symbols indicating statistically significant differences at * p < 0.05, ** p < 0.01, or *** p < 0.0001. ⁺ CF: chemical fertilizer; IF: integrated fertilizer; OF: organic fertilizer.

).

Thus, a multiple regression analysis was conducted to assess the strength of these correlations (

Table 2. Multiple regression analysis of subplot cabbage yield ^#.

Treatments	Multiple Regression Equation +	Model p-Value	R2
R1	Yield = −34.055 − 0.3612(RH) + 15.770(Tran) *** − 3.265(SR) ***	<0.001	0.770
R2	Yield = −2.151 + 12.303(Tran) *** − 3.897(SR) ***	<0.001	0.857
R1 with R2 (N = 78)	Yield = −37.694 + 14.771(Tran) *** − 3.712(SR) ***	<0.001	0.659

^# The factors of multiple regression equation are denoted with statistically different symbols at *** p < 0.0001. ⁺: relative humidity; Tran: temperature range; SR: solar radiation.

). When considering only the R1 treatment, the yield was mainly influenced by two factors, Tran and SR, with an R² of 0.770. The multiple regression equation for yield in the R2 treatment was also significantly impacted by Tran and SR, achieving an R² of 0.828. Finally, the regression equation that incorporated yields from both rotation systems and all three fertilization treatments identified Tran and SR as significant predictors of cabbage yield (p < 0.001), explaining 65.9% of its variability (R² = 0.659). These findings firmly indicate that increasing SR negatively impacts cabbage yields, with extended Tran also playing a significant role in the yield distribution.

Further validation using a decision tree analysis underscored the major influence of SR (Figure 3). When the SR was below 16.917 MJ m⁻² day⁻¹ (almost equal to sunshine duration 7.9138 h per day), the yield averaged 74.17 tons ha⁻¹. In contrast, yields dropped to 44.77 tons ha⁻¹ when the SR exceeded this threshold. A combination of low SR (<16.917 MJ m⁻² day⁻¹) and RH below 70.1992% produced the highest yield of 94.98 tons ha⁻¹. The regression tree model explained 62.3% of the yield variability. Prolonged solar radiation (or sunshine), particularly at high temperatures, was linked to heat stress, increased water loss, and direct damage to plant tissues, reducing the plants’ photosynthetic capacity, impairing their physiological functions, and ultimately lowering yields [22]. These observations align with earlier findings, confirming that increased SR or SD adversely affect cabbage yield. Notably, the cabbage yield was more sensitive to climate variables than to rotation systems or fertilization treatments.

Environmental changes are widely recognized to affect crop yields. For instance, previous studies have identified RH as a critical factor, with 70% RH acting as a threshold for yield reduction. Higher RH decreases yield through disease outbreaks, reduced head quality, and interference with the normal plant physiology [6,23].

The declining yield in R1, linked to reductions in the weights of single cabbages, may result from inadequate nutrient availability under long-term fertilization conditions. Vegetable crops require a continuous supply of N for optimal growth and yield. In this study, the total N accumulation was higher in R2 than R1, both in the growth and harvest stage (4.3 vs. 4.11; 3.55 vs. 3.08) (Figure 4). Within the R2 plot, the plants treated with CF had higher N accumulation than those treated with OF (4.3 vs. 4.12; 3.55 vs. 3.43), whereas the reverse was observed in R1 during the harvest stage. Notably, higher N accumulation in outer leaves correlated with lower cabbage head weights, which is consistent with findings for sweet corn [23]. These results showed that the same annual amount of N supply in organic fertilizer is not sufficient for cabbage growth under changing weather conditions.

Moreover, a comparison of the N accumulation trends within the same rotation system revealed an overall increase over the study period, particularly in the plants treated with CF. The linear regression equations for N accumulation are as follows: R1_OF_HR (y = 0.3225x + 2.3757, R² = 0.5657) and R1_CF_HR (y = 0.5135x + 1.5466, R² = 0.9493) (Figure 5A); R2_OF_HR (y = 0.19x + 2.8612, R² = 0.519) and R2_CF_HR (y = 0.3188x + 2.5996, R² = 0.9031) (Figure 5B). Previous studies have reported similar effects, showing that high RH promotes greater N accumulation in leaves, leading to increased fresh leaf weights but reduced cabbage head weights [24]. These findings confirm a rising trend in N contents in the outer leaves of the cabbages that were grown using both CF and OF, with higher N accumulation being observed for CF. However, the accumulation in the plants treated with CF was insufficient for proper head formation. The slow release of N from organic fertilizers may provide a more sustained nutrient supply, mitigating yield declines under high SR and RH conditions, compared with the rapid nutrient release of CF.

Globally, SOM is declining due to intensive farming, urbanization, and climate change. Approximately 45% of agricultural soils are at risk of degradation, with SOM loss being a primary concern [25]. Over-cultivation, poor residue management, and land use changes are key contributors to the decline in SOM [26], exacerbated by rising temperatures, drought, and microbial activity [27]. Additionally, increased solar radiation accelerates SOM degradation in Mediterranean and tropical regions [28,29]. The higher RH in tropical climates further promotes SOM breakdown, particularly under elevated soil temperature and moisture conditions [30]. SOM plays a critical role in maintaining soil health, improving water retention, and supplying essential nutrients to crops. Consequently, the decline in organic matter observed in this study may be linked to the increased solar radiation and relative humidity. This presents a significant concern not only for cabbage cultivation but also for a wider array of agricultural practices across the region. The implications of reduced organic matter are manifold: it can lead to diminished soil fertility, increased susceptibility to pests and diseases, and lower overall resilience of crops to climate variabilities.

Although the OF treatments maintained favorable soil properties, they could not fully counteract the adverse impacts of the weather on cabbage yields. Across the CF, IF, and OF treatments, the yields showed lower resilience under increasing SR and RH conditions. These findings highlight the importance of stable weather conditions, which may outweigh the benefits of specific fertilization practices.

Moreover, changing cultivation practices—such as incorporating adequate fertilization—along with developing new crop varieties adapted to higher solar radiation and relative humidity, may help mitigate the climate impact on crops. Although the research focused primarily on a regional scope, it highlights an important consideration regarding the potential variability of pheromone effectiveness across different areas of Taiwan. Future research could explore this variability to ensure that the findings are applicable on a broader scale.

4. Conclusions

Organic farming is widely regarded as more sustainable, albeit less productive, compared with conventional farming. In this study, we observed that cabbage yields under organic fertilization conditions were, indeed, lower than those achieved through conventional farming practices, even after 35 years of organic fertilizer application. However, the primary factors contributing to the decline in cabbage yields from 2011 to 2023 were linked to weather conditions—specifically, and extended solar radiation, sunshine duration, and increased relative humidity—rather than the type of fertilization used during this period. Long-term observations and correlation analyses demonstrated that rising solar radiation and relative humidity were the main factors affecting cabbage production, regardless of whether chemical or organic fertilizers were applied. These findings suggest that prolonged sunshine and elevated relative humidity can significantly reduce cabbage yields under conditions of limited nutrient availability. Developing new crop varieties adapted to higher solar radiation or changing appropriate practices may help mitigate the climate impact on crops.