Deep Vertical Rotary Tillage: A Sustainable Agricultural Practice to Improve Soil Quality and Crop Yields in China

Abstract

Deep vertical rotary tillage (DVRT) is an innovative soil tillage technology that has been widely adopted in China and shown significant potential in enhancing soil quality, optimizing water use efficiency, and increasing crop yields across diverse ecological and agronomic conditions. DVRT utilizes a vertical spiral drill bit for deep plowing, which preserves soil structure, reduces soil compaction, and improves water retention, making it particularly effective in regions facing climatic challenges such as drought. This review synthesizes the effects of DVRT on soil’s physical and chemical properties, crop root systems, photosynthesis, and water use efficiency, demonstrating its advantages in promoting robust root development and improving nutrient utilization. Although the technology has been applied successfully across various crops and regions, its nationwide adoption remains limited. This paper emphasizes the need for further research to refine the theoretical framework of DVRT and develop tailored strategies for different local conditions. Additionally, integrating DVRT with other agronomic practices and advancing machinery design, supported by policy measures, is essential for maximizing its benefits. In conclusion, DVRT presents a promising approach for sustainable agriculture in China, contributing to improved soil quality, increased crop yields, and enhanced food security.

1. Introduction

Deep vertical rotary tillage (DVRT) epitomizes an innovative soil tillage technology that has been extensively promoted across China over the past decade [1,2]. This technique utilizes a vertical spiral drill bit to finely grind and crush the soil, naturally forming ridges through meticulous fragmentation. It enables deep loosening, deep plowing, and land preparation in a single operation, all while preserving the vertical integrity of the soil structure (Figure 1), which streamlines tillage processes [3]. Initially, DVRT was deployed in sugarcane cultivation in Guangxi, where it significantly improved soil’s water retention from rainfall and minimized fertilizer loss, ensuring the availability of water and nutrients for crops during the dry season [4,5].

Currently, DVRT has been widely adopted for the cultivation of over 50 different crops across diverse climatic zones in China, including maize (Zea mays L.) [6,7], wheat (Triticum aestivum L.) [8,9], cotton (Gossypium hirsutum L.) [10,11], rice (Oryza sativa L.) [12,13], potato (Solanum tuberosum L.) [14,15], soybean (Glycine max L.) [16], tobacco (Nicotiana tabacum L.) [17,18], and peanuts (Arachis hypogaea L.) [19].

In recent years, the intensification of global warming has aggravated the uneven temporal and spatial distribution of rainfall, while the frequency of extreme weather events—such as typhoons, torrential rains, and unprecedented heatwaves—has surged [20,21]. These climatic shifts have directly impaired crop productivity, increased crop sensitivity to climate, reduced resilience, and consequently diminished overall grain yields (Figure 2). The interplay between climate stress, crop sensitivity, and resilience is key to adaptation and mitigation. As climate stress heightens crop sensitivity, boosting crop resilience through adaptive practices can mitigate impacts, ensuring sustainable agriculture and food security. Of these, extreme drought, high temperatures, frost events, and intense rainfall are widely acknowledged as having severe impacts on crop growth and development. Drought is widely regarded as one of the most severe threats to global food security, with its impact on crop yields potentially surpassing the combined effects of other extreme weather events. Consequently, enhancing storage capacity for natural rainfall and optimizing water use efficiency in agricultural production have become critical factors in boosting agricultural productivity. In response to this challenge, China has developed a range of methods for collecting and storing rainfall and enhancing the utilization of natural precipitation [21], such as the implementation of DVRT [4,5], alongside the use of plastic film [22] or straw mulching [23]. These interventions not only improve the absorption and utilization of water and nutrients by crops, but also promote their growth and development, ultimately resulting in increased yields and improved quality [24,25].

To address issues such as drought, soil compaction, and the shallowing of the plow layer, this paper provides a comprehensive review and summary of the impact of DVRT across different soil types and regions. It investigates the effects on soil’s physical properties—including soil compaction, bulk density, moisture content, porosity, and soil aggregates—alongside soil nutrient indicators, microbial populations, enzyme activity, and organic carbon content. This study focused on exploring the effects of DVRT on crop root systems, photosynthesis, yield, and water use efficiency, aiming to assess the technique’s advantages objectively. Additionally, this paper offers insights into future research directions for DVRT. In light of current trends aimed at improving arable land quality and promoting soil health through physical interventions, the following research areas and explorations are recommended for future consideration.

2. Progress in DVRT Research

2.1. Forms of DVRT

Two primary tillage methods have been developed and tailored to the diversity of crop root types (deep-rooted, shallow-rooted, taproot, and fibrous-rooted) along with cultivation practices, local climates, and terrain characteristics, as depicted in Figure 3 [26,27]. The tillage method shown in Figure 3a involves tilling the entire plow layer, making it particularly suitable for crops like wheat and rice. Unlike traditional plowing, this technique conducts deep tillage across the entire field while preserving the relative positioning of soil layers. Additionally, it allows for precise adjustment of tillage depth tailored to the specific requirements of different crops’ root growth. The ridge and furrow planting method shown in Figure 3b is well suited for wide-row crops like sugarcane and watermelon, or for use in orchards. Its advantage lies in tilling only a portion of the soil, leaving the rest fallow, thus significantly reducing tillage costs. Moreover, it minimizes water and nutrient losses resulting from soil tillage on sloped land.

2.2. Soil Properties

Various tillage practices directly impact soil’s physical and chemical properties, influencing crop growth, development, and yield. Research has shown that within the 0–40 cm soil profile, DVRT decreases soil’s bulk density while increasing soil’s porosity [26,27,28,29,30]. Due to the combined effects of soil’s water-holding capacity and vegetation’s water consumption, soil water storage under DVRT is significantly greater than that under conventional rotary tillage [31]. DVRT has been demonstrated to elevate soil’s surface temperatures and increase the proportion of >0.25 mm aggregates [12,32,33], enhance the mean weight diameter (MWD) and geometric mean diameter (GMD) of both mechanically and water-stable aggregates, improve the stability of water-stable aggregates (WSARs), and decrease the percentage of aggregate destruction (PAD). As a result, these changes increase soil permeability, improve soil structure, promote the mineralization of soil nutrients, and enhance crop nutrient use efficiency [34,35,36].

With increasing tillage depth and planting years, significant increases have been observed in soil’s total nitrogen, microbial biomass nitrogen, organic matter, available phosphorus, rapidly available potassium, and urease activity [14,36,37,38,39,40,41]. These changes accelerate the decomposition of soil’s organic matter, enhance the release and uptake of available nutrients, and improve nutrient utilization efficiency [21,42].

2.3. Roots

Selecting the appropriate tillage method is crucial for optimizing soil structure, as well as the size, number, distribution, and healthy growth and development of roots [43,44,45]. Recent studies have shown that deep vertical tillage fosters the healthy growth and development of crop roots [4,12,46,47]. For maize, DVRT has been demonstrated to stimulate root growth compared to traditional tillage methods, increasing the root–crown ratio, total root length, root surface area, root volume, and average root diameter, which promotes root development and facilitates nutrient transfer to aboveground plant parts, ultimately enhancing yield [47,48]. Tian et al. [46] investigated the combined effects of DVRT depth and irrigation levels and found that cotton root density increased vertically with tillage depth, showing corresponding increases across all soil layers. The root-length distribution ratio for each treatment was concentrated in the 40–60 cm soil layer, with cotton root density, root length distribution ratio, and root activity all increasing with tillage depth and irrigation levels. Shi et al. [12] observed that compared to traditional tillage, DVRT promoted maize root development, with ridge tillage treatments showing average increases of 39.29% in root diameter, 35.25% in volume, and 17.14% in root vitality. Shan et al. [49] reported that, compared to traditional rotary tillage, cauliflower under DVRT exhibited a higher root growth rate, with greater accumulation of root dry matter, resulting in larger and more uniformly sized cauliflower heads at harvest.

2.4. Photosynthesis

Photosynthesis transforms light energy into chemical energy, synthesizing organic matter and providing the fundamental material basis for plant growth and development. Dry matter accumulation (DMA) underpins crop yield formation, with photosynthesis functioning as its core mechanism. Enhancing the photosynthetic rate is pivotal for achieving high yields. Li et al. [50] reported the effects of DVRT on the photosynthetic physiological characteristics of sugarcane. Their findings revealed that, compared with conventional tillage, DVRT significantly enhanced the chlorophyll content (SPAD), net photosynthetic rate (Pn), stomatal conductance (Cn), and transpiration rate (Tr) in sugarcane. This approach facilitated the accumulation of photosynthetic products, reduced light transmittance, and boosted the light-use efficiency of photosynthetically active radiation. DVRT also elevated the activity of photosynthesis-related enzymes (NADP-MDH, PEPC, and RuBPC), increased maximum photochemical efficiency (Fv/Fm), and enhanced both the primary light energy conversion efficiency and actual photochemical efficiency of PSII reaction centers (φPSII). These factors collectively enhanced the photosynthetic capacity of plant leaves [51]. Similar results regarding photosynthesis under DVRT have also been observed in sweet sorghum [52], wheat [9], maize [6], and peanuts [19].

2.5. Water Use Efficiency (WUE)

Water use efficiency (WUE) refers to the dry matter or economic yield produced per unit of water consumed by plants under specific water supply conditions. It reflects water utilization efficiency and serves as a critical indicator for assessing agricultural water use effectiveness. Tillage practices can significantly influence a crop’s water absorption and utilization through regulation of the soil environment. Jiang et al. [53] observed that compared to traditional rotary tillage, DVRT significantly improved the physical structure of the soil’s tillage layer. DVRT increased the thickness of the tillage layer, reduced soil’s bulk density, enhanced soil infiltration rates, and broke the soil’s plow pan, which expanded soil’s water storage capacity. This effectively regulated soil water distribution and improved crop drought resistance, consistent with findings from Zhang et al. [54] and Zhang et al. [55]. Wang et al. [15] reported that DVRT can increase soil’s moisture content and WUE, with WUE increasing by 54.76–71.85% as the tillage depth increases. Similar results were observed for maize [6,7]. This improvement was primarily achieved through the use of a vertical spiral drill, which deeply engaged the soil, breaking soil particles into finer fragments and restructuring the soil. The soil surface post-DVRT typically appears rough, reducing surface runoff during rainfall and allowing for greater water infiltration into the soil.

2.6. Yield

Previous studies have demonstrated that DVRT has been employed for cultivation and soil improvement across various soil types, such as sandy, clay, and loamy soils, as well as in diverse ecological environments, including plateaus, degraded low-yield grasslands, saline–alkali lands, and sloping terrains. This technique has been utilized across a wide spectrum of crops, including grains, vegetables, fruits, medicinal herbs, and fodder crops. Proper application of DVRT, as compared to RT, can significantly enhance crop yields (

Table 1. Yield and WUE of crops grown with DVRT compared with RT/SS.

Tillage Method	Control Method	Crop	Experimental Site	Soil Type	Increase in Yield (%)	Increase in WUE (%)	References
DVRT20	RT	Potato	Ningxia	Sandy loam	8.56	54.76	[15]
DVRT40					12.31	70.32
DVRT50					13.21	71.85
DVRT	RT	Potato	Ningxia	Sandy loam	23.3	29.7–39.8	[56]
DVRT	RT	Maize	Ningxia	Sandy loam	13.6	19.6	[6]
DVRT30	SS/RT	Maize	Hebei	Loam	4.21–9.80	21.65–31.11	[7]
DVRT50					7.04–12.78	19.07–28.33
DVRT	PT	Cotton	Xinjiang	Sandy loam	49.5	-	[10]
DVRT	RT	Rice	Guangxi	Clay	23.87	-	[13]
DVRT	RT	Wheat	Henan	Sandy loam	34.13	-	[8]
DVRT20	RT	Sugarcane	Guangxi	Silt loam	2.49–24.89	-	[57]
DVRT40	SS				3.71–8.73	-
DVRT25	RT	Peanut	Henan	Loam	10.45–14.64	-	[19]
DVRT40					21.42–21.67	-
DVRT20	RT	Sweet Potato	Jiangxi	Loam	89.18	-	[53]
DVRT30					104.33	-
DVRT40					116.88	-
DVRT20	RT	Tobacco	Hunan	Loamy sand	7.59	-	[58]
DVRT30					17.06	-
DVRT40					13.16	-
DVRT30	RT	Sorghum	Ningxia	Loam	8.30	-	[39]
DVRT50					8.70	-
DVRT40	RT	Cassava	Guangxi	-	29.22–63.78	-	[4]

DVRT, deep vertical rotary tillage, with numbers indicating tillage depth; RT, traditional rotary tillage at 20 cm depth; SS, deep tillage at 40 cm depth.

). For instance, compared with RT, potato yields with DVRT increased with tillage depth by 8.56–13.21% [15], 27.43–38.29% [14], and 23.3% [56]. Wei et al. [5] found that rice yields increased by 23.87% under DVRT in paddy fields compared to conventional rotary tillage. Zhao et al. [57] reported that DVRT increased sugarcane yields by 2.49–24.89% and 3.71–8.73% compared to traditional rotary tillage and deep plowing, respectively. Cui et al. [2] reviewed the research on DVRT in China, emphasizing its successful application, particularly in addressing issues of shallow tillage layers, low water and fertilizer utilization, and reduced crop yields. The higher crop yields achieved with DVRT compared to traditional rotary tillage are primarily attributed to its capacity to alter the soil structure, regulate the water–salt environment, and enhance soil’s moisture and nutrient contents.

2.7. Others

Due to undulating changes in the surface after DVRT, the surface area can increase by 10–20%. Additionally, as tillage depth significantly increases, it reduces surface runoff, soil erosion, and nutrient loss caused by rainfall [59,60,61]. Moreover, DVRT disrupts the plow pan, increases the tillage layer, and interrupts soil capillary pores, reducing soil water evaporation and capillary salt accumulation. With irrigation and rainfall, soil water infiltration rates increase by 30–50%, leaching salts from the topsoil to the subsoil, which effectively improves saline–alkali soils in China [11,62,63,64]. Furthermore, DVRT activates soil enzyme activity and microbial community diversity, creating a novel ecological environment promoting robust root growth and deep rooting [65,66,67,68].

3. Prospects

3.1. Continuing to Improve the Theoretical Framework of DVRT

DVRT technology has demonstrated promising results in experimental trials across various regions of the country. However, the nationwide adoption of DVRT technology remains considerably low. In-depth research is essential to refine the theoretical framework of DVRT by selecting appropriate tillage methods tailored to local soil conditions, climatic environments, crop types, and planting histories. This approach ensures compatibility with local conditions [1]. For instance, the appropriate tillage depth and width should be chosen based on the crop sowing method (broadcast sowing or row sowing) and root system type. Tillage intervals and methods (full-field tillage or interval tillage) should be selected according to crop growth characteristics (annual or perennial) and local climate conditions. Additionally, tillage types (contour tillage or slope tillage) should be chosen based on soil types (saline–alkali soil or grassland) and terrain slopes. By considering these factors, DVRT can be effectively adapted to various regional conditions, enhancing its practical application and promoting sustainable agricultural development [69].

3.2. Integration of DVRT with Other Agronomic Measures

The benefits of deep vertical rotary tillage can be synergistically integrated with other agronomic measures to achieve cumulative positive impacts. For instance, combining deep vertical rotary tillage with agronomic and soil conditioning practices—such as plastic film mulching [14], drip irrigation with fertilization [46], wide–narrow row planting, and straw return [69]—can enhance farmland quality. This integrated approach can promote increased crop yields and improved efficiency. By leveraging the complementary benefits of these combined techniques, farmers can optimize soil health, enhance water and nutrient management, and ultimately achieve greater productivity and sustainability in agricultural practices.

3.3. Applicability and Promotion Strategies of DVRT

Given the complexity of China’s terrain and the diversity of its crop species, it is imperative to expand the pivotal role of DVRT in the nation’s agricultural green development, tailored to regional characteristics. It is crucial to fully acknowledge the significance of DVRT in enhancing farmland quality, boosting soil’s ecological functions, and ensuring food security. Efforts should be intensified in regional macro-agricultural planning, the adjustment of planting structures, and agricultural technological innovation, with augmented policy and financial support. In regions where conditions permit, efforts should be expedited to research and demonstrate DVRT technology systems, establish regional, characteristic, and multifunctional models of DVRT, and formulate comprehensive technical solutions and promotion strategies [1].

3.4. Development and Advancement of Machinery for DVRT

Existing DVRT machinery consumes a substantial amount of power, which is directly proportional to the depth of operation. To fully leverage the advantages of DVRT, it is sometimes necessary to increase the operating depth. Therefore, further improvements in the design of DVRT machinery are necessary to align with the characteristics of agricultural and rural production in China, reduce operating consumption, and enhance lightweight flexibility [70,71]. Additionally, more policy support is essential. Firstly, DVRT should be included in relevant agricultural machinery subsidy policies, with increased subsidies for its purchase. Secondly, subsidies for deep tillage operations using DVRT machinery should be increased, and nationwide promotion should be conducted to enhance the soil quality of farmland in China.

4. Conclusions

DVRT is a promising and sustainable agricultural practice with significant potential to enhance soil quality, optimize water use efficiency, and increase crop yields across diverse ecological and agronomic conditions in China. By altering soil structure, improving soil properties, and promoting robust root development, DVRT effectively addresses the challenges of soil compaction, shallow plow layers, and uneven water distribution prevalent in traditional tillage methods. Although its extensive application across various crops and regions demonstrates adaptability and efficacy, the relatively low nationwide adoption rate highlights the need for further research to refine its theoretical framework and develop tailored strategies that align with local conditions. Integrating DVRT with other agronomic practices, such as plastic film mulching, drip irrigation, and straw return, can further optimize soil health and agricultural sustainability. Advancing DVRT machinery design, supported by policy measures like subsidies and nationwide promotion, is essential for reducing energy consumption and enhancing operational efficiency. In conclusion, DVRT offers a viable pathway towards sustainable agriculture in China, contributing to improved soil quality and enhanced crop yields, and ensuring food security, with continued research, innovation, and policy support being crucial for its broader adoption and success.