Effect of Intercropping on Fruit Yield and Financial Benefits of Rosa roxburghii Tratt Orchard in Southwest China

: The practice of intercropping in Rosa roxburghii Tratt orchards holds potential for enhancing fruit yield and financial benefits, yet remains insufficiently explored. To address this, we delved into the effects of intercropping on fruit yield and financial viability of R. roxburghii orchards in Longli County, southern China. Orchards of varying ages (4 years old and 5 years old; 7 years old and 8 years old) were subjected to different treatments: (i) Zea mays and Capsicum annuum intercropping, and clean tillage for younger orchards, and (ii) Lolium perenne , natural grass, and clean tillage for older orchards. Each treatment was assessed for its impact on fruit yield and financial benefits. In younger orchards, intercropping with Z. mays and C. annuum did not significantly elevate fruit yield compared to clean tillage in the 4-year-old orchard; however, C. annuum intercropping significantly improved fruit yield in the 5-year-old orchard. Concurrently, intercropping significantly augmented the total financial benefit by 9234.35–10,486.25 CNY ha − 1 ( Z. mays ) and 14,304.90–16,629.18 CNY ha − 1 ( C. annuum ) compared to clean tillage. In older orchards, L. perenne intercropping significantly elevated fruit yield by 598.84–803.64 kg · ha − 1 , while natural grass reduced it by 394.61–986.24 kg · ha − 1 , compared to clean tillage. Additionally, L. perenne intercropping significantly boosted the total financial benefit by 8873.92–9956.56 CNY ha − 1 , whereas natural grass negatively impacted financial benefits by 78.42–2444.94 CNY ha − 1 compared to clean tillage. Collectively, our results illustrate that judicious selection of intercrops, based on orchard age and conditions, can significantly enhance both fruit yield and financial advantages in R. roxburghii orchards. This study furnishes vital insights for orchard management and accentuates the prospective merits of intercropping in fruit production systems.


Introduction
Fruits are universally recognized for their vital contributions to human health, offering a rich supply of vitamins, organic acids, antioxidants, minerals, fibers, polyphenols, and other bioactive constituents [1][2][3].With the continuous improvement in living standards, there has been a consistent rise in global fruit consumption [4,5].Fruit orchards, occupying about 10% of the agricultural production land worldwide, are crucial in catering to this escalating demand [6].Notably, China has established itself as the foremost producer and consumer of fruits on a global scale [7,8].As reported by the FAO [9], between 2012 explored to enhance R. roxburghii yield [49][50][51][52], the potential of orchard intercropping in the context of R. roxburghii cultivation remains largely unexplored.
To quantify the substantial benefits of orchard intercropping for enhancing sustainable and financially viable practices in R. roxburghii orchards, this study investigated the effects of intercropping on fruit yield and financial benefits in both 4-and 7-year R. roxburghii orchards.By scrutinizing the outcomes of diverse intercrops, this inquiry aims to unveil the potential of intercropping to elevate R. roxburghii yield and financial viability.The exploration of this is crucial for tailoring agronomic practices that could significantly benefit R. roxburghii cultivators in Guizhou province and potentially offer insights for other fruit orchards with similar agroecological characteristics.This study represents the endeavors to investigate the impacts of orchard intercropping on both fruit yield and financial benefits in R. roxburghii orchards, specifically in the context of southwest China.Through a comparative analysis of diverse intercrops in 4-year-old and 7-year-old R. roxburghii orchards, our findings would shed light on effective intercropping strategies that align with local agricultural practices, thereby providing a novel and practical approach to enhancing the sustainability and financial viability of R. roxburghii cultivation in this region.

Experimental Site
The study was conducted in two different towns in Longli County, Guizhou Province, China.The first study area was located in Gujiao town, at 106 • 58 ′ E and 26 • 29 ′ N. The area had an altitude of 1135 m and annual average temperature of 14.8 • C. The coldest monthly average temperature was 4.6 • C, and the hottest monthly average temperature was 23.6 • C. The annual precipitation was about 1100 mm, mostly concentrated in summer.The annual sunshine hours were 1160 h and the frost-free period was 283 days.The soil type is yellow soil with a thickness of 50-80 cm.
The second study area was located in Xima town, at 107 • 29 ′ E, 26 • 18 ′ N. The area had an altitude of 1150 m and annual average temperature of 14.6 • C. The coldest monthly average temperature was 4.9 • C and the hottest monthly average temperature was 24.2 • C. The annual precipitation was 1100 mm, mostly concentrated in summer.The annual sunshine hours were 1160 h and the frost-free period was more than 280 d.The soil type is yellow soil with a thickness of 50-80 cm.

Field Trial Design
The field trial was conducted at two different sites, Xima town and Gujiao town, to investigate the effects of intercropping on R. roxburghii orchards.Both sites featured 'Guinong No.5' variety of R. roxburghii with a row spacing of 2 m × 3 m, planted in the north-south direction.Fertilization was applied twice during the experiment using a compound fertilizer (N:P:K = 15:15:15) in early April and mid-July.All plots relied on rainfall, and herbicides were not used.
At Xima town, three planting patterns were designed: (1) intercropping with Zea mays ('Guiyu 1' variety) at a plant spacing of 0.30 m and a row spacing of 0.40 m, planted in early April; (2) intercropping with Capsicum annuum ('Guila 21' variety) at a plant spacing of 0.30 m and a row spacing of 0.40 m, planted in early April; (3) clean tillage (the control) with weeding conducted in March, July, and October.Randomized block design was followed for the research.Each planting pattern had three plots, each with an area of 225 m 2 .Pruning was carried out in June and September.In the second year, the same experiment was continued, and the management mode of 5-year-old R. roxburghii and intercrops was the same as that in the first year.
At Gujiao town, a 7-year-old R. roxburghii orchard was selected for the study.The experiment involved three treatments: (1) planting of Lolium perenne L. ('Diamond T' variety) in the entire R. roxburghii orchard with a seeding rate of 22.5 kg ha −1 ; (2) natural grass (comprising mainly Setaria viridis, Digitaria sanguinalis, Imperata cylindrica, Eleusine indica, Oxalis corniculata, etc.); (3) clean tillage (the control) with weeding conducted in March, July, and October.Randomized block design was followed for the research.Each treatment had three plots, each with an area of 600 m 2 .Pruning was carried out in June and September.In the second year, the same experiment was continued, and the management mode of 8-year-old R. roxburghii and intercrops was the same as that in the first year.
The difference between the two sites lies in the intercropping patterns (Figure 1): at Xima town, Zea mays and Capsicum annuum were intercropped with R. roxburghii, while at Gujiao town, intercropping involved natural grass and L. perenne.
Pruning was carried out in June and September.In the second year, the same experiment was continued, and the management mode of 5-year-old R. roxburghii and intercrops was the same as that in the first year.
At Gujiao town, a 7-year-old R. roxburghii orchard was selected for the study.The experiment involved three treatments: (1) planting of Lolium perenne L. ('Diamond T' variety) in the entire R. roxburghii orchard with a seeding rate of 22.5 kg ha −1 ; (2) natural grass (comprising mainly Setaria viridis, Digitaria sanguinalis, Imperata cylindrica, Eleusine indica, Oxalis corniculata, etc.); (3) clean tillage (the control) with weeding conducted in March, July, and October.Randomized block design was followed for the research.Each treatment had three plots, each with an area of 600 m 2 .Pruning was carried out in June and September.In the second year, the same experiment was continued, and the management mode of 8-year-old R. roxburghii and intercrops was the same as that in the first year.
The difference between the two sites lies in the intercropping patterns (Figure 1): at Xima town, Zea mays and Capsicum annuum were intercropped with R. roxburghii, while at Gujiao town, intercropping involved natural grass and L. perenne.

Sampling and Yield Measurement
In order to obtain accurate and reliable data concerning the yield of R. roxburghii and intercropped species, meticulous sampling and measurement procedures were undertaken as outlined below: R. roxburghii Yield Determination: In September, at the mature stage of R. roxburghii, ten trees were randomly selected from each experimental plot for yield determination.The fruits from each selected tree were harvested, and their total weight was recorded.

Sampling and Yield Measurement
In order to obtain accurate and reliable data concerning the yield of R. roxburghii and intercropped species, meticulous sampling and measurement procedures were undertaken as outlined below: R. roxburghii Yield Determination: In September, at the mature stage of R. roxburghii, ten trees were randomly selected from each experimental plot for yield determination.The fruits from each selected tree were harvested, and their total weight was recorded.The yield per hectare was then calculated by extrapolating the average yield obtained from the ten sampled trees to the entire plot area, considering the planting density.
L. perenne and Natural Grass Management: The mowing of L. perenne and natural grass was carried out four times a year, specifically in April, June, July, and September to maintain optimum growth conditions.During each mowing event, a 2 m 2 area was designated within each plot, and the fresh weight of the harvested grass was recorded between 3 and 5 pm during sunny weather to ensure consistent moisture content.
Z. mays Harvesting and Yield Calculation: In October, a 2 m 2 area was selected within each plot for Z. mays grain sampling.The harvested grains were weighed to obtain the fresh weight, following which a 500 g subsample of grains was collected and placed in nylon mesh bags.The subsample was then taken to the laboratory, where it was dried to a constant weight at 105 • C. The water content was subsequently measured to calculate the yield per hectare of Z. mays grain on a dry weight basis.
C. annuum Harvesting: In July, a 2 m 2 area was selected from each plot for sampling C. annuum.The harvested C. annuum was weighed to obtain the fresh weight.Unlike Z. mays, C. annuum was not subjected to drying as it is sold fresh, and thus, its fresh weight was used for yield and financial benefit calculations.

Financial Benefit Analysis
The basic parameters of the financial benefit analysis were obtained using an actual cost expenditure and market [53] (Tables 1-3).The investment unit price of R. roxburghii and intercrop cultivation is calculated by the actual expenditure.The fruit financial benefit of R. roxburghii is the sales income of R. roxburghii fruit minus the cultivation cost.The financial benefit of intercrops is the sales revenue of the edible part of the intercrops minus the cultivation cost.Total financial benefits of the intercropping system are equal to the financial benefit of R. roxburghii plus the financial benefit of intercrops.Because green management was performed in our R. roxburghii orchard and no pesticides were used during the experiment, there was no pesticide cost input.Table 2 shows the investment unit price parameters of the three intercropping methods.Because the investment cost of the two years of intercropping is the same, the investment discounting is not described in the text.

Statistical Analyses
Microsoft Excel 2016 software was adopted to organize the experimental data.SPSS software (version 26) was used to test the normality of the data, and normally distributed data were subjected to variance analysis and multiple comparisons.Two-way ANOVA was followed for the research.The significance test for the mean of fruit yield and financial benefit was conducted using the least significant difference (LSD) test method.Data were visualized using OriginPro 2023 software.

Effect of Intercropping on R. roxburghii Yield
The effect of intercropping on the fruit yield of R. roxburghii was related to the intercropping pattern and years (Figure 2).In the 4-year-old R. roxburghii orchard in Gujiao, compared with clean tillage, Z. mays and C. annuum did not significantly increase the fruit yield of R. roxburghii in the first year, but C. annuum increased the fruit yield of R. roxburghii in the second year (p < 0.01) (Figure 2a).In the 7-year-old R. roxburghii orchard in Xima, compared with clean tillage, natural grass and intercropping L. perenne in the first year did not significantly affect the fruit yield of R. roxburghii, but natural grass in the second year reduced the fruit yield of R. roxburghii (p < 0.01).L. perenne increased the fruit yield of R. roxburghii in the second year (p < 0.05) (Figure 2b).In addition, compared with natural grass, intercropping L. perenne increased the fruit yield of R. roxburghii (p < 0.001) in the second year of intercropping at the orchard in Xima.In the Gujiao orchard, continuous intercropping of Z. mays increased the yield of R. roxburghii (p < 0.05), while continuous intercropping of C. annuum increased the yield of R. roxburghii (p < 0.01) (Figure 2c).In the Xima orchard, continuous intercropping of L. perenne had a positive effect on the yield of R. roxburghii (p < 0.01) (Figure 2d).

Intercropping Effects on the Fruit Financial Benefits
The effect of intercropping on the fruit financial benefits of R. roxburghii was also related to the intercropping category and intercropping years (Figure 3).Specifically, in the 4-year-old orchard at the foot of the valley, compared with clean tillage, intercropping Z. mays and C. annuum in the first year did not significantly improve the fruit financial benefits of R. roxburghii; however, intercropping C. annuum in the second year had a very significant promotion effect on the fruit financial benefits of R. roxburghii, although natural grass in the second year reduced the fruit financial benefits of R. roxburghii (p < 0.01).L.

Intercropping Effects on the Fruit Financial Benefits
The effect of intercropping on the fruit financial benefits of R. roxburghii was also related to the intercropping category and intercropping years (Figure 3).Specifically, in the 4-year-old orchard at the foot of the valley, compared with clean tillage, intercropping Z. mays and C. annuum in the first year did not significantly improve the fruit financial benefits of R. roxburghii; however, intercropping C. annuum in the second year had a very significant promotion effect on the fruit financial benefits of R. roxburghii, although natural grass in the second year reduced the fruit financial benefits of R. roxburghii (p < 0.01).L. perenne intercropping significantly increased the fruit financial benefits of R. roxburghii in the second year (Figure 3b).In the Gujiao town orchard, compared with the first year of intercropping, continuous intercropping Z. mays had a significant effect on the fruit financial benefits of R. roxburghii, and continuous intercropping C. annuum significantly increased the fruit financial effects of R. roxburghii (Figure 3c).In the orchard at Xima town, compared with the first year of intercropping, continuous natural grass did not increase the fruit financial benefits of R. roxburghii (p > 0.05), but continuous intercropping with L. perenne significantly increased the fruit financial benefits of R. roxburghii (Figure 3d).financial benefits of R. roxburghii, and continuous intercropping C. annuum significantly increased the fruit financial effects of R. roxburghii (Figure 3c).In the orchard at Xima town, compared with the first year of intercropping, continuous natural grass did not increase the fruit financial benefits of R. roxburghii (p > 0.05), but continuous intercropping with L. perenne significantly increased the fruit financial benefits of R. roxburghii (Figure 3d).

Intercropping Effects on the Intercrops' Financial Benefits
The financial benefits of intercropping crops are mainly related to intercropping patterns (Figure 4).In the 4-year-old orchard at Gujiao town, the financial benefits of intercropping Z. mays were 4159.37-4414.49CNY ha −1 , and the financial benefits of C. annuum were 8552.76-8592.78CNY ha −1 (Figure 4a).Because the yield of intercropping C. annuum (3882.00-3891.90kg•ha −1 ) is higher than that of Z. mays (2911.50-2995.50kg•ha −1 ), and the price of C. annuum is higher than that of Z. mays, the financial benefit of intercropping C.

Intercropping Effects on the Intercrops' Financial Benefits
The financial benefits of intercropping crops are mainly related to intercropping patterns (Figure 4).In the 4-year-old orchard at Gujiao town, the financial benefits of intercropping Z. mays were 4159.37-4414.49CNY ha −1 , and the financial benefits of C. annuum were 8552.76-8592.78CNY ha −1 (Figure 4a).Because the yield of intercropping C. annuum (3882.00-3891.90kg•ha −1 ) is higher than that of Z. mays (2911.50-2995.50kg•ha −1 ), and the price of C. annuum is higher than that of Z. mays, the financial benefit of intercropping C. annuum is significantly higher than that of Z. mays (p < 0.01) (Figure 4a).In the 7-yearold orchard at Xima town, both clean tillage and natural grass have only inputs and no output, resulting in negative values of these two models, while the output of intercropping L. perenne is greater than the input, so the financial benefit of intercropping L. perenne is positive (Figure 4b).The financial benefits of intercrops were not significant (p < 0.05) due to the small changes in inter-annual crop yield and price (Figure 4c,d).
Agronomy 2023, 13, x FOR PEER REVIEW 9 of 16 (3882.00-3891.90kg•ha −1 ) is higher than that of Z. mays (2911.50-2995.50kg•ha −1 ), and the price of C. annuum is higher than that of Z. mays, the financial benefit of intercropping C. annuum is significantly higher than that of Z. mays (p < 0.01) (Figure 4a).In the 7-year-old orchard at Xima town, both clean tillage and natural grass have only inputs and no output, resulting in negative values of these two models, while the output of intercropping L. perenne is greater than the input, so the financial benefit of intercropping L. perenne is positive (Figure 4b).The financial benefits of intercrops were not significant (p < 0.05) due to the small changes in inter-annual crop yield and price (Figure 4c,d).

Intercropping Effects on the Total Financial Benefits
The total financial benefit of the intercropping system was closely related to the intercropping mode and the intercropping duration (Figure 5).In the 4-year-old and 5-year-old orchard at Gujiao town, compared with clean tillage, the total financial benefits of the two intercropping modes of Z. mays and C. annuum were significantly increased by 9234.35-10,486.25 CNY ha −1 and 14,304.90-16,629.18CNY ha −1 , respectively (Figure 5a).In the first year of intercropping, the total financial benefit of the R. roxburghii-C.annuum intercropping mode was significantly higher than that of the R. roxburghii-Z.mays intercropping mode (p < 0.05), while in the second year of intercropping the total financial benefit of the R. roxburghii-C.annuum intercropping pattern was significantly higher than that of the R. roxburghii-Z.mays intercropping pattern (p < 0.01).In the 7-year-old and 8-year-old orchard at Xima town, compared with clean tillage, the natural grass intercropping pattern reduced the total financial benefit, while the R. roxburghii-L.perenne intercropping pattern significantly increased the total financial benefit, which was 8873.92-9956.56CNY ha −1 (Figure 5b).In terms of the total financial benefits of the same model in different years, only continuous intercropping of C. annuum had a significant effect on the total financial benefits in the Gujiao orchard (p < 0.05) (Figure 5c), whereas continuous intercropping of L. perenne significantly increased the total financial benefits in the Xima orchard (Figure 5d).5a).In the first year of intercropping, the total financial benefit of the R. roxburghii-C.annuum intercropping mode was significantly higher than that of the R. roxburghii-Z.mays intercropping mode (p < 0.05), while in the second year of intercropping the total financial benefit of the R. roxburghii-C.annuum intercropping pattern was significantly higher than that of the R. roxburghii-Z.mays intercropping pattern (p < 0.01).In the 7-year-old and 8year-old orchard at Xima town, compared with clean tillage, the natural grass intercropping pattern reduced the total financial benefit, while the R. roxburghii-L.perenne intercropping pattern significantly increased the total financial benefit, which was 8873.92-9956.56CNY ha −1 (Figure 5b).In terms of the total financial benefits of the same model in different years, only continuous intercropping of C. annuum had a significant effect on the total financial benefits in the Gujiao orchard (p < 0.05) (Figure 5c), whereas continuous intercropping of L. perenne significantly increased the total financial benefits in the Xima orchard (Figure 5d).

Discussion
The application of intercropping practices in orchards has garnered recognition for its capacity to optimize soil temperature and humidity, fostering an environment conducive to the robust growth of fruit trees [12,26,54].Intercropping, when appropriately managed, can leverage the natural grass cover to enhance soil moisture retention by mitigating surface temperatures [10,55].However, it is important to acknowledge that the interaction between natural grass growth and fruit yield is not universally positive.In scenarios where natural grass in the orchard exerts weak competition, it can potentially enhance soil moisture retention and benefit R. roxburghii growth.Yet, instances are prevalent where the presence of natural grass leads to reduced R. roxburghii yield due to aggressive weed competition for water and nutrients.In a contrasting approach, intercropping R. roxburghii with strategically chosen crops such as C. annuum, Z. mays, and L. perenne, positioned at intervals from R. roxburghii plants, effectively mitigated competitive pressures.Such intercropping not only curbed weed encroachment but also supplemented nutrients through practices such as soil aeration and weed management.The strategic intercropping involving Z. mays, C. annuum, and L. perenne proved particularly beneficial, fostering an environment conducive to R. roxburghii growth and ultimately yielding a notable increase in fruit yield.This finding is corroborated by Zhu et al. [56], whose research demonstrated that intercropping with Gramineae plants led to heightened Wolfberry productivity through the modification of soil characteristics and enzyme activities.
While our study did not uncover statistically significant differences in yield between intercropping and clean tillage treatments, it is pertinent to recognize that the relatively short intercropping duration in our investigation might not have allowed the intercropping system ample time to fully manifest its yield-enhancing potential.This observation aligns with findings from parallel studies [57] and underscores the dynamic nature of intercropping effects, which can evolve over extended timeframes.To further unravel the nuanced impact of intercropping on augmenting R. roxburghii yield, future research endeavors could contemplate prolonged intercropping periods.Moreover, investigating the broader influence of intercropping on dimensions such as fruit quality, tree vitality, and soil nutrient dynamics could yield comprehensive insights into the multifaceted benefits of intercropping strategies [58].
The financial benefit of intercropping strategies in R. roxburghii orchards emerges as a notable outcome of our study, particularly when compared to conventional clean tillage practices.In this context, intercropping R. roxburghii with crops such as Z. mays, C. annuum, and L. perenne yields promising financial benefits, while the presence of natural grass demonstrated a propensity to diminish overall profits.This observation underscores the pivotal role of judicious intercropping practices and effective weed management in maximizing the financial returns of R. roxburghii cultivation.
Within the realm of intercropping systems, C. annuum emerges as a standout, boasting the highest level of profitability.Z. mays and L. perenne follow, each presenting positive financial returns.In stark contrast, the clean tillage and natural grass treatments yield negative profits, essentially incurring input costs without commensurate output.Importantly, the amplified profitability stemming from intercropping the 4-year-old R. roxburghii orchard with C. annuum and Z. mays compared to the intercropping of the 7-year-old R. roxburghii orchard with L. perenne can be attributed to two key factors.Primarily, the larger intercropping area in the 4-year-old orchard enhances the scale of financial benefits.Furthermore, the higher unit prices commanded by C. annuum and Z. mays in comparison to L. perenne contribute significantly to the observed disparity.These observations elucidate the intricate interplay between orchard age, intercropping area, and crop unit prices.
In light of these insights, the selection of intercropping crops should be underpinned by a comprehensive understanding of local market dynamics and crop unit valuations.This strategic approach will enable cultivators to align their intercropping choices with prevailing market demands and capitalize on the most financially advantageous options.Finally, the efficient intercropping patterns we screened have the opportunity to be sustainably and widely promoted [59].
Our research significantly contributes to the existing knowledge regarding orchard intercropping and its positive repercussions on both fruit yield and financial benefits [19,[60][61][62].Moreover, our observations regarding the advantageous impacts of R. roxburghii orchard intercropping on soil nutrient enrichment, microbial activity, and enzyme dynamics align with findings from previous studies [63,64].However, we acknowledge the nuanced nature of intercropping effects on profitability, which could be influenced by diverse variables such as climatic conditions, soil attributes, management protocols, intercrop species, and intercropping duration.Further comprehensive research is imperative to thoroughly explore these factors, facilitating the broad adoption of R. roxburghii intercropping methodologies and promoting the sustainable growth of fruit orchard agriculture.
It is essential to recognize the limitations of our study.The relatively short duration of intercropping in our investigation might have restrained the full manifestation of its potential yield-promoting effects.This finding aligns with similar observations reported in related studies [57].For a more robust evaluation of intercropping's impact, future studies should consider prolonged intercropping periods and delve into the intricate agronomic and agroecological mechanisms underlying the enhanced productivity observed in older R. roxburghii orchards (7 years old compared to 4 years old).
The residents near our experimental site like to eat C. annuum and Z. mays, so the financial benefits are better.At the same time, these two crops have strong adaptability in the local area, so they are selected as intercrops.In addition, the local aquaculture industry is relatively developed, and the demand for forage is large.Intercropping forage grass in R. roxburghii orchards can reduce nutrient loss caused by soil erosion and help to maintain soil fertility in orchards, thus promoting the growth of R. roxburghii trees and laying a foundation for high yield and high financial benefits.This shows that the selection of intercrops should take into account the needs of local residents so that the products produced can be sold well.Such intercropping modes can continue to develop.
Guesmi-Mzoughi et al. [65] reported that some intercrops, such as potato, tomato, and cucumber, generated an environment more advantageous to plant-parasitic nematodes infecting olive trees in Tunisia.Therefore, in order to test whether the intercrops host dangerous nematodes, the structure and diversity of plant-parasitic nematodes in R. roxburghii intercropping should be investigated.Intercropping with aromatic plants improved soil health by increasing soil organic matter in pear orchards [66], and hindered the occurrence of insects, such as Proagopertha lucidela, Serica orientalis, and Maladera verticalis [67].A large number of beetle species love to feed on the twigs of R. roxburghii in summer, especially during drought periods, which led to reduction in R. roxburghii yield to a greater extent.Hence, it is necessary to study the biocontrol effect of intercropping aromatic plants on beetles in R. roxburghii orchards in the future.It is difficult to achieve high fruit yield by relying solely on intercropping crops to provide nutrients for R. roxburghii trees.It has been found that orchard intercropping grass resulted in the reduction in soil total phosphorus and available potassium [68], which suggests that orchard intercropping systems should also be given reasonable fertilization, especially of available nitrogen, phosphorus, and potassium compound fertilizer.Therefore, it is necessary to carry out fertilization experiments in combination with the age of R. roxburghii trees and soil background fertility to find a reasonable amount of fertilizer under intercropping.According to the growth of natural grass in orchards, weeding should be carried out in time.Timely cutting of the aboveground parts of the natural grass is necessary to use it as organic fertilizer for R. roxburghii orchards.Tougeron et al. [69] revealed that flower strips in an apple orchard provided a favorable condition to two parasitoid species, Aphidius matricariae and Ephedrus cerasicola, which effectively enhanced the control of rosy apple aphids.Future studies are needed to test which intercrops in R. roxburghii orchard are conducive to the survival of natural enemies of insects.In our study, R. roxburghii in the intercropping system was in the fruiting period, and it is necessary for us to study the intercropping mode of R. roxburghii saplings.Since the financial benefits of intercropping may change over time, in order to obtain higher financial benefits of intercropping systems, fruit growers should choose suitable intercropping crops in R. roxburghii orchards according to the future market demands for those crops.

Conclusions
Our investigation underscores the potential advantages of intercropping as a financially viable practice for R. roxburghii orchards.The inclusion of clean tillage and natural grass as control treatments provided a comparative baseline, revealing their inadequacy in enhancing R. roxburghii yield.On the other hand, intercropping with C. annuum, Z. mays, and L. perenne significantly improved both the yield and financial benefit of R. roxburghii cultivation when compared to clean tillage practices.This knowledge holds immense value for researchers and farmers, both in China and globally, who are engaged in orchard intercropping.The adoption of intercropping strategies can improve orchard conditions, elevate fruit yield, and ultimately, augment the financial benefits of R. roxburghii cultivation, which may contribute to the financial benefit of the R. roxburghii fruit industry.
While our study provides insightful contributions to this field, we recognize certain experimental limitations, such as fewer test repeats, the two-year experimental span, and the selection of intercropping crops based on regional availability.Future endeavors should set more repetitions to minimize the deviation in research results caused by soil heterogeneity in the field, and consider long-term studies to assess the persistent effects of intercropping on R. roxburghii yield and financial benefits across multiple cropping seasons.Moreover, exploring alternative intercropping combinations and crop rotations, alongside comprehensive cost-benefit analyses, may unveil insights into the most suitable intercropping strategies for diverse R. roxburghii orchards and regional scenarios.Further research could also delve into the ecological interactions between intercropped species to better understand and demonstrate the sustainability aspect of intercropping systems in R. roxburghii orchards.

Figure 5 .Figure 5 .
Figure 5.Total financial benefits of R. roxburghii orchards under different intercropping modes and duration.Total financial benefits of R. roxburghii between three intercropping modes (a) under 4 and 5-year-old in Gujiao orchard, and (b) under 7 and 8-year-old in Xima orchard, and total financial benefits of R. roxburghii (c) between 4 and 5-year-old under three intercropping modes in Gujiao orchard, and (d) between 7 and 8-year-old under three intercropping modes in Xima orchard.n.s., Figure 5.Total financial benefits of R. roxburghii orchards under different intercropping modes and duration.Total financial benefits of R. roxburghii between three intercropping modes (a) under 4 and 5-year-old in Gujiao orchard, and (b) under 7 and 8-year-old in Xima orchard, and total financial benefits of R. roxburghii (c) between 4 and 5-year-old under three intercropping modes in Gujiao orchard, and (d) between 7 and 8-year-old under three intercropping modes in Xima orchard.n.s., *, **, and *** denote no significant difference, p < 0.05, p < 0.01, and p < 0.001, respectively.CT, clean tillage; ZM, Z. mays; CA, C. annuum; NG, natural grass; LP, L. perenne.

Table 1 .
Investment unit price of R. roxburghii cultivation.