Root Length Density Research Articles

Artificial humic acid promotes carbon sequestration in rice-soil system

Artificial humic acid (AHA) is a new exogenous organic material with enormous carbon sequestration potential. However, the effects and mechanisms of applying AHA under different irrigation regimes on carbon sequestration in rice-soil systems still need to be clarified. This study applied carbon isotope labeling technology to analyze the photosynthetic carbon sequestration capacity, the carbon transport capacity of the root, and greenhouse gas emission flux in the rice-soil system under different irrigation regimes and AHA application conditions. The results showed that as the amount of AHA applied increased, the leaf area and chlorophyll concentration gradually increased, the Rubisco activity first increased and then decreased under two irrigation regimes. In alternate wetting and drying irrigation with 300 mg kg-1 AHA treatment (DWI3), the photosynthetic carbon fixation ability was the highest, with Pn, Fv/Fm, and qP increasing by 65.35%, 214.85%, and 43.15% compared to alternate wetting and drying irrigation without applying AHA treatment (DWI0), respectively. Meanwhile, during DWI3 treatment, the organic acid concentration in root exudates, root biomass, root length, root surface area, and root length density were also the highest. In summary, among all treatments in this study, the content of 13C in soil under DWI3 treatment was highest, closely related to the strongest photosynthetic carbon fixation and root transport capacity under this treatment, as well as the lower greenhouse gas emission flux. Therefore, it is recommended to apply 300 mg kg-1 AHA with alternate wetting and drying irrigation for carbon sequestration, water conservation, and sustainable agricultural development.

Short-Term Effects of Incorporation Depth of Straw Combined with Manure During the Fallow Season on Maize Production, Water Efficiency, and Nutrient Utilization in Rainfed Regions

Diminishing soil fertility and crop productivity due to traditional intensive cultivation has prompted the use of straw and manure to improve soil health in Northeast China. However, few comparative studies have explored the influence of varying straw and manure incorporation depths on crop growth. A field experiment in the rainfed black soil regions of Gongzhuling and Keshan assessed the effects of deep (30 cm) and shallow (15 cm) incorporations of straw and manure on soil fertility, maize root growth, and maize productivity. Deep incorporations, via subsoiling tillage (DST) and deep-plow (DDT) tillage, enhanced soil water storage of 30–100 cm soil layer during periods of low rainfall, improved the availability of nutrients (nitrogen, phosphorus, and potassium) and soil organic matter content, especially in deeper soil, compared to shallow incorporation using rotary tillage (SRT). Both DST and DDT induced a larger rooting depth and a higher fine root (diameter class 0–0.5 mm) length density by 31.0% and 28.9%, respectively, accompanied by reduced root turnover. Furthermore, the sub-surface foraging strategies of roots under the DST and DDT treatments boosted the total nitrogen, phosphorus, and potassium uptake (6.5–17.9%) and achieved a higher dry mass accumulation during the later growth period, thus leading to notable improvements in the 100-kernel weight and yield (16.1–19.7%) and enhancing water- and nutrient-use efficiencies by 2.5–20.5%. Overall, compared to shallow incorporation, deep incorporation of straw and manure significantly enhances root growth and spatial distribution of soil water and nutrients, which has great potential for increasing maize yield in rainfed agricultural areas.

Rice Under Dry Cultivation-Maize Intercropping Improves Soil Environment and Increases Total Yield by Regulating Belowground Root Growth.

Under the one-season-a-year cropping pattern in Northeast China, continuous cropping is one of the main factors contributing to the degradation of black soil. Previous studies (on maize-soybean, maize-peanut, and maize-wheat intercropping) have shown that intercropping can alleviate this problem. However, it is not known whether intercropping is feasible for maize and rice under dry cultivation, and its effects on yield and soil fertility are unknown. A three-year field-orientation experiment was conducted at Jilin Agricultural University in Changchun city, Jilin Province, China, consisting of three cropping regimes, namely rice under dry cultivation-maize intercropping (IRM), sole rice under dry cultivation (SR), and sole maize (SM). All straw was fully returned to the field after mechanical harvesting. Rice under dry cultivation-maize intercropping with a land-equivalent ratio of 1.05 (the average of three years values) increased the total yield by 8.63% compared to the monoculture system. The aggressivity (A), relative crowding coefficient (K), time-area-equivalent ratio (ATER), and competition ratio (CR) value were positive or ≥1, also indicating that the rice under dry cultivation-maize intercropping had a yield advantage of the overall intercropping system. This is because the intercropped maize root length density (RLD) increased by 33.94-102.84% in the 0-40 cm soil layer, which contributed to an increase in the soil porosity (SP) of 5.58-10.10% in the 0-30 cm soil layer, an increase in the mean weight diameter of soil aggregates (MWD) of 3.00-15.69%, an increase in the geometric mean diameter of soil aggregates (GMD) of 8.16-26.42%, a decrease in the soil bulk density (SBD) of 4.02-7.35%, and an increase in the soil organic matter content (SOM) of 0.60-4.35%. This increased the water permeability and aeration of the soil and facilitated the absorption of nutrients and water by the root system and their transportation above ground, and the plant nitrogen, phosphorus, and potassium accumulation in the intercropping system were significantly higher than that in monoculture treatment, further promoting the total yield of intercropping. This suggests that rice under a dry cultivation-maize intercropping system is feasible in Northeast China, mainly because it promotes belowground root growth, improves the soil environment, and increases the total yield of intercropping.

Relationship between root characteristics and saturated hydraulic conductivity in a grassed clayey soil

Soil saturated hydraulic conductivity plays a crucial role in the fields of hydrology, geotechnical and geological engineering. This study investigated the relationship between root characteristics and soil saturated hydraulic conductivity in a grassed soil. The saturated hydraulic conductivity of soil specimens with varying soil dry densities and planting densities were experimentally determined. Root parameters of each specimen were measured, and the relationship between root parameters and soil saturated hydraulic conductivity was determined through the stepwise multiple regression analysis. Experimental results show that both soil dry density and planting density significantly influence root growth and the saturated hydraulic conductivity of the grassed soil. Root length ratio (>4 cm), root length, and root weight density exhibit a positive correlation with planting density, while root length density and root length ratio (>4 cm) are negatively correlated with dry density. Higher dry density leads to lower soil saturated hydraulic conductivity and the permeable effects become more pronounced with increased planting density. When planting density is higher, roots create more preferential flow channels in the soil, resulting in increased soil saturated hydraulic conductivity. Root length density exerts the most significant effect on soil saturated hydraulic conductivity (|r| = 0.82, p＜0.01), followed by root length ratio (>4 cm) and root weight density. This study provides insights into the relationship between root parameters and soil saturated hydraulic conductivity, and identifies key root parameters that govern the saturated hydraulic conductivity of soil. These findings hold significant implications for enhancing the understanding of slope protection using vegetation.

Plastic mulching enhances maize yield and water productivity by improving root characteristics, green leaf area, and photosynthesis for different cultivars in dryland regions

Uneven precipitation during the growing season and frequent seasonal droughts on the Loess Plateau in Northwest China adversely affect crop production and water use efficiency. While plastic mulching (PM) has been used to alleviate water stress, few studies have examined the traits maize cultivars need to adapt to the altered water environment under PM and achieve high yields. A two-year field experiment was conducted to assess the root characteristics and aboveground growth traits of three widely used high-yielding maize cultivars—Zhengdan 958 (ZD), Huanong 138 (HN), Heboshi 122 (HBS)—under no mulching (NM) and PM conditions. Among the three cultivars, HBS had the highest root system indices—root length density (RLD), root surface area density (RSD), and root biomass—in the topsoil (0–40 cm), followed by ZD and HN under both NM and PM conditions. Under NM, HBS_NM treatment exhibited strong water absorption, improving photosynthesis and yield, making it suitable for drought conditions. Under PM, topsoil moisture increased significantly, with root system indices increasing by 22.5–36.1 % for RLD, 30.2–36.1 % for RSD, and 25.2–36.5 % for root biomass across the cultivars compared to NM. While ZD_PM did not have the highest root system indices under PM, it exhibited higher green leaf area index (4.5–7.5 %), chlorophyll content (2.8–8.6 %), and photosynthetic rate (6.0–14.5 %), resulting in the highest aboveground biomass and yield among the treatments. These findings suggest ZD is better adapted to the enhanced soil moisture under PM. Future research should focus on breeding genotypes that thrive under PM conditions, emphasizing traits such as larger leaf areas and higher photosynthetic rates to boost crop productivity in rainfed areas.

Soil density specification ranges to optimise plant water use and root growth for phytocapping and urban greening projects

Soil density or compaction is one of the key variables that need to be specified for designed soil profiles as part of urban greening. Examples include land rehabilitation (mining), waste containment (phytocapping), stormwater infrastructure (bioretention basins) and green infrastructure (green roofs and street trees). This study investigates the impact of a range of specified soil densities on plant water use and root development. Native Australian plant species selected for the study include: the C4 and C3 grasses, Themeda triandra and Microlaena stipoides respectively; the Eucalyptus trees, E. camaldulensis and E. cladocalyx; and the nitrogen-fixing pioneer trees, Acacia mearnsii and Allocasuarina verticillata. The plants were established at four soil density (compaction) levels: 72, 77, 82, and 87 % MDD (maximum dry density) in tall cylinders with weekly plant water use measurement over 8 months. Root growth was analysed using WinRhizo image analysis. The experimental results were used to create generalisable models for root length density (RLD), root diameter and plant water use. The models for RLD and plant water use were parabolic in nature, revealing clear optimum ranges that could be used to guide soil density specification. Root diameter provided additional insight into the allocation of resources to root thickening above a threshold soil density of 87 % MDD, indicating plant allocation of resources towards penetrating highly compacted soils. There were correlations between plant water use and RLD that were moderate and significant, particularly for grasses. Notably, T. triandra had the greatest mean RLD, thickest roots and plant water use at 16.8cm/cm3, 0.18 mm and 10mm/week, respectively. Findings demonstrate that RLD and plant water use can be optimised together within practically achievable soil density specification ranges that are sensitive to the pitfalls of both excessively low and excessively high soil densities. Recommended soil density specification ranges include: 75–82 % MDD with plant performance within 5 % of optimum (considered excellent), 74–84 % MDD with plant performance within 10 % of optimum (considered good) and 73–85 % MDD with plant performance within 15 % of optimum (considered fair). Within these ranges, plant water use and root growth performance is well balanced with practical achievement of the soil density ranges. Due to the use of %MDD, the modelled results can be usefully generalised for any soil type. Implementation of these specifications for urban greening and phytocap projects will optimise plant growth, transpiration and hydrological function while maintaining root networks essential for establishing and maintaining resilient living infrastructure.

Potato–Soybean Intercropping Increased Equivalent Tuber Yield by Improving Rhizosphere Soil Quality, Root Growth, and Plant Physiology of Potato

Potato–legume intercropping has been confirmed to increase productivity in modern agricultural systems. However, the physiological and ecological mechanisms of potato–soybean intercropping for promoting tuber yield formation in potato remain unclear. Field experiments were conducted in 2022 and 2023 to explore the responses of tuber yield formation, rhizosphere soil quality, root growth, and plant physiology of potato in potato–soybean intercropping. The soil at the experimental site is Cambisols. The treatments included sole cropping potato, sole cropping soybean, and potato–soybean intercropping. Our results indicated that potato –soybean intercropping decreased the water content, increased the total K content and activities of urease and catalase in rhizosphere soil, and enhanced the root mean diameter, root projected area, and root length density in the 0–5 cm and 15–20 cm soil layers of potato. Moreover, potato–soybean intercropping improved the plant photosynthetically active radiation and light transmittance rate of the middle and lower layers as well as the leaf area index, enhanced the leaf chlorophyll b content and ribulose-1,5-diphosphate carboxylase/oxygenase activity, and increased the leaf net photosynthetic rate and organ dry matter accumulation amounts of potato. The changes in the above parameters resulted in an increased tuber weight per plant (19.4%) and commercial tuber number (42.5%) and then enhanced the equivalent tuber yield of potato (38.2%) and land equivalent ratio (1.31 in 2022 and 1.33 in 2023). Overall, potato–soybean intercropping greatly increased the equivalent tuber yield by improving the rhizosphere soil quality, root growth, and plant physiology of potato and then achieved a higher land equivalent ratio.

Brinjal (Solanum melongena) rootstocks improve photosynthetic rate, fruit yield and quality parameters in grafted tomato (Solanum lycopersicum)

The experiment was conducted during winter (rabi) seasons of 2021–22 and 2022–23 at ICAR-Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh to study the improvement in yield and quality parameters in tomato (Solanum lycopersicum L.) cultivar using brinjal (Solanum melongena L.) rootstock. Three improved cultivars of tomatoes i.e. Kashi Aman, Kashi Adarsh and Kashi Chayan were grafted over three brinjal rootstocks, IC-111056, IC- 354557, and Surya. Experimental findings revealed that brinjal rootstocks significantly affected photosynthetic traits, root architectures, fruit yields and quality traits of tomatoes. Maximum photosynthetic rate (23.8 µmol/m2/s) and stomatal conductance (492.74 mmol/m2/s) were recorded in Kashi Chayan grafted over Surya rootstock, whereas chlorophyll fluorescence yields (Fv/Fm) was significantly higher in Kashi Aman self-rooted plants (0.452–0.457). Grafting tomato onto brinjal rootstocks significantly enhanced most of the yield traits, such as fruit number, weight, size and yields. Surya + Kashi Chayan graft combination registered an enhancement in number of fruits and yields by 8.65% and 8.4%, respectively over self-rooted Kashi Chayan. Significantly higher root volumes were noticed in two graft combinations i.e. IC-354557 + Kashi Aman (28.53 cm2) and Surya + Kashi Chayan (27.98 cm2), while 63% and 44.5% higher root length density (RLD) were registered in graft combinations IC-354557 + Kashi Chayan and Surya + Kashi Chayan, respectively over self-rooted Kashi Chayan. Fruit quality such as lycopene and ascorbic acid contents were significantly affected in different rootstocks and scions, whereas fruit acidity was unaffected. From the present study it may be conclude that use of brinjal rootstock Surya significantly improved most of the physiological, yield, root architecture and fruit quality in Kashi Chayan tomato cultivars.

Optimizing nitrogen fertilizer for improved root growth, nitrogen utilization, and yield of cotton under mulched drip irrigation in southern Xinjiang, China

The root system plays a crucial role in water and nutrient absorption, making it a significant factor affected by nitrogen (N) availability in the soil. However, the intricate dynamics and distribution patterns of cotton (Gossypium hirsutum L.) root density and N nutrient under varying N supplies in Southern Xinjiang, China, have not been thoroughly understood. A two-year experiment (2021 and 2022) was conducted to determine the effects of five N rates (0, 150, 225, 300, and 450 kg N ha−1) on the root system, shoot growth, N uptake and distribution, and cotton yield. Compared to the N0 treatment (0 kg N ha−1), the application of N fertilizer at a rate of 300 kg N ha−1 resulted in consistent and higher seed cotton yields of 5875 kg ha−1 and 6815 kg ha−1 in 2021 and 2022, respectively. This N fertilization also led to a significant improvement in dry matter weight and N uptake by 32.4% and 53.7%, respectively. Furthermore, applying N fertilizer at a rate of 225 kg N ha−1 significantly increased root length density (RLD), root surface density (RSD), and root volume density (RVD) by 49.6–113.3%, 29.1–95.1%, and 42.2–64.4%, respectively, compared to the treatment without N fertilization (0 kg N ha−1). Notably, the roots in the 0–20 cm soil layers exhibited a stronger response to N fertilization compared to the roots distributed in the 20–40 cm soil layers. The root morphology parameters (RLD, RSD, and RVD) at specific soil depths (0–10 cm in the seedling stage, 10–25 cm in the bud stage, and 20–40 cm in the peak boll stage) were significantly associated with N uptake and seed cotton yield. Optimizing nitrogen fertilizer supply within the range of 225–300 kg N ha−1 can enhance root foraging, thereby promoting the interaction between roots and shoots and ultimately improving cotton production in arid areas.

Artificial macropores improve maize performance at the seedling stage under poor aeration.

Maize is susceptible to hypoxia stress in soils with poor aeration, but the macropores have the potential to improve soil aeration. We studied the impact of artificial macropores on maize performance under poor aeration. Three levels of air-filled porosity (5%, 10% and 15%) were established, and soil columns with (28 vertical artificial macropores with 0.5 mm diameter) or without macropores were created for each level of air-filled porosity with a bulk density of 1.3 g cm-3. Root-macropore interactions were visualized using CT scanning (41 μm in resolution). Our results showed that root length density significantly increased by 114%, as air-filled porosity increased from 5% to 15%. However, when artificial macropores were present, an increase in air-filled porosity had no significant effect on root length density. The treatment of 5% air-filled porosity with macropores significantly increased root length density and root biomass by 108% and 65%, respectively, relative to the treatment of 5% air-filled porosity without macropores, whereas there was no significant difference in root growth between the treatments of 15% air-filled porosity with and without macropores. Compared to the treatment of 5% air-filled porosity with macropores, there was a significant reduction of 49% in the number of macropores colonized by roots under the treatment of 15% air-filled porosity with macropores. Our results demonstrate that macropores provide preferential paths for the colonization of maize roots, thereby promoting root growth under poor aeration. Creating macropores with bio-tillage can serve as a crucial strategy for enhancing crop performance in poorly aerated soils.

Species mixtures enhance fine root biomass but inhibit root decay under throughfall manipulation in young natural boreal forests

Fine roots play crucial roles in terrestrial biogeochemical cycles. Although biodiversity loss and changes in precipitation are two major drivers of global change, our understanding of their effects on fine root biomass (FRB), root functional traits, and fine root decay (FRD) remains incomplete. We manipulated precipitation in young boreal forests dominated by Populus tremuloides, Pinus banksiana, and their relatively even mixtures using 25 % addition, ambient, and 25 % reduction in throughfall during the growing season. We collected root samples using soil core and trunk-traced methods to quantify FRB and root traits, and we simulated fine root decay using an in-situ experiment over 531 days. We found that compared to the average of single-species-dominated stands, species mixtures increased FRB by 41 % under ambient throughfall, by 89 % under throughfall reduction and by 71 % under throughfall addition. Root surface area, fine root volume, and root length density responded to species mixtures similarly to FRB. Meanwhile, species mixtures reduced FRD across all water treatments. There was a positive relationship between the effect of species mixtures on the FRD of absorptive roots and those on the FRB. Our results highlight that species mixtures could modify carbon cycling by enhancing fine root biomass accumulation and reducing its decomposition of young boreal forests under changing precipitation.

Incorporation of undissolved lime from previous applications can ameliorate subsoil acidity promptly and improve crop performance on sandy soils of the semi-arid regions of Western Australia

Abstract Background and aims Repeated surface application of lime for managing subsoil acidity is slow and ineffective, resulting in an accumulation of undissolved lime (carbonate) in the topsoil. We investigated the impact of the incorporation of undissolved lime into the subsoil to improve acidity and crop performance. Methods The undissolved lime in 2-cm layers of topsoil (0–10 cm) from three long-term experiments in Western Australia was measured. Both limed and unlimed topsoil with the acidic subsoil of the same profile was incubated at eight incorporation rates for six weeks, followed by growing barley and wheat in the incubated soil for two weeks to assess the impact on soil acidity and crop root architecture, respectively. Furthermore, a three-year-long field experiment was conducted following strategic tillage in limed and control plots to assess the impact on soil acidity and performance of wheat, canola and barley. Results A significant amount of undissolved lime was concentrated in the topsoil, amounting to 1.7, 1.8 and 1.3 t/ha for the limed plots at Wongan Hills, Northam and Merredin, respectively. Incubation of 5–25% topsoil after incorporation with the acidic subsoil was enough to ameliorate subsoil acidity and to improve root length density by up to 13-fold depending on undissolved lime content in topsoils and soil type. In the field experiment, the incorporation of undissolved lime also significantly improved subsoil acidity and canola performance. Conclusion We concluded that the incorporation of topsoil containing sufficient undissolved lime with acidic subsoil may offer a quick amelioration of subsoil acidity.

Growth, Photosynthesis and Yield Responses of Common Wheat to Foliar Application of Methylobacterium symbioticum under Decreasing Chemical Nitrogen Fertilization

Current agriculture intensifies crop cultivation to meet food demand, leading to unsustainable use of chemical fertilizers. This study investigates a few physiological and agronomic responses of common wheat following the inoculation with plant growth-promoting bacteria to reduce nitrogen inputs. A field trial was conducted in 2022–2023, in Legnago (Verona, Italy) on Triticum aestivum var. LG-Auriga comparing full (180 kg ha−1) and reduced (130 kg ha−1) N doses, both with and without foliar application at end tillering of the N-fixing bacterium Methylobacterium symbioticum. Biofertilization did not improve shoot growth, while it seldom increased the root length density in the arable layer. It delayed leaf senescence, prolonged photosynthetic activity, and amplified stomatal conductance and PSII efficiency under the reduced N dose. Appreciable ACC-deaminase activity of such bacterium disclosed augmented nitrogen retrieval and reduced ethylene production, explaining the ameliorated stay-green. Yield and test weight were unaffected by biofertilization, while both glutenin-to-gliadin and HMW-to-LMW ratios increased together with dough tenacity. It is concluded that Methylobacterium symbioticum can amplify nitrogen metabolism at a reduced nitrogen dose, offering a viable approach to reduce chemical fertilization under suboptimal growing conditions for achieving a more sustainable agriculture. Further research over multiple growing seasons and soil types is necessary to corroborate these preliminary observations.

The Combined Effect of Taproot and Fibrous Roots of Herbaceous Plants and Shrubs on the Distribution of Soil Water-Stable Aggregates

Soil aggregation, an important indicator of soil restoration in degraded ecosystems, is a fundamental unit of soil structure. However, research on the influence of grass–shrub composites on the distribution of >0.25 mm soil water-stable aggregates (macroaggregates) is scarce. Therefore, this study focuses on the hill and gully region of the Loess Plateau, where vegetation has been well restored since the return of farmland to forests and grasslands. The study investigated the root and macroaggregate distribution characteristics and interrelationships of three widely distributed mixed vegetation types of Caragana korshinskii and Agropyron cristatum (C-AC), C. korshinskii and Bothriochloa ischaemum (C-BI), and C. korshinskii and Artemisia gmelinii (C-AG) in this area. The results indicate that soil macroaggregates decrease with increasing depth. Due to the spatial differences in the distribution of shrub root, the content of macroaggregates at 50 cm from the shrub base was higher than that at the shrub base, with an increase of 25.98%–34.27% in different vegetation associations. In this study, the root length density and root diameter better reflected the influence of roots on the distribution of macroaggregates, and the product of the two had a good power function relationship with the content of macroaggregates (R2 ≥ 0.82, p < 0.01). Grey correlation analysis showed that the influence of root length density on the distribution of large aggregates was greater than that of root diameter. The content of macroaggregates in the vegetation association of taproot herbaceous plants and shrubs was higher than that of fibrous root herbaceous plants. The average soil macroaggregate content in the C-AG was 15.79%–248.6% higher than that in the C-BI and C-AC. In this study, the spatial distribution differences in root caused by shrub growth were the main reason for the spatial heterogeneity of soil macroaggregate content distribution. The improvement ability of soil macroaggregates was higher in the combination of taproot herbaceous plants and shrubs than in the combination of fibrous root herbaceous plants and shrubs. The results of this study can, to some extent, reveal the influence and mechanisms of plant roots on soil aggregates in grass–shrub vegetation association.

Partial root zone irrigation and K application improves summer maize production and salt resistance in saline soil

Irrigation patterns and K fertilization are the key measures used to improve the salt tolerance of crops in saline land. A pot experiment was carried out to assess the effects of partial root-zone irrigation and K fertilization on maize in saline land. For the study parameters, we used a split plot design with three irrigation treatments (conventional irrigation (CI), fixed root-zone irrigation (FRI) and alternate root-zone irrigation (ARI)) and two K application rates (0 (K0) and 120 (K1) kg K2O ha−1). Compared with the CI treatment, the FRI and ARI treatments reduced the transpiration rate (Tr) and MDA content but increased the root length density (RLD), root surface density (RSD), root volume density (RVD), root dry weight density (RDWD), proline content, plant K/Na ratio, photosynthetic rate (Pn), yield, water use efficiency (WUE) and K use efficiency (KUE). Compared with the FRI treatment, the ARI treatment increased RLD, RSD, RVD, RDWD, the Tr, the proline content, the plant K/Na ratio and the Pn but decreased the MDA content; these factors increased yield, WUE and KUE. K application decreased the MDA content; improved root growth; and increased the stomatal conductance, Tr, proline content, Pn, yield and WUE. Of all the treatments, the ARI-K1 treatment maximized RLD, RSD, RVD, RDWD, the Pn and yield while minimizing the MDA content. Therefore, ARI combined with K application can maximize resistance to salt stress and osmotic stress, delay senescence, and improve photosynthesis, yield and WUE.

Optimizing Ridge–Furrow Ratio to Improve Water Resource Utilization for Wheat in the North China Plain

The shortage of water resources seriously limits sustainable production in agriculture, and the ridge–furrow planting pattern is an effective water-saving cultivation pattern. However, the mechanism of the ridge–furrow planting pattern that drives the efficient utilization of field water resources in the North China Plain (NCP) is still unclear. A two-year field experiment was conducted in the NCP from 2021 to 2023. The ridge–furrow planting patterns followed a randomized block design as follows: ridge–furrow ratios of 50 cm:50 cm (M2), 75 cm:50 cm (M3), and 100 cm:50 cm (M4). A traditional planting pattern was used as the control (M1). These were used to investigate the effects of different treatments on water use and roots. The results showed that M3 reduced the amount of irrigation, improved water distribution after irrigation, increased water use efficiency (WUE), and promoted root growth. Compared with other treatments, M3 increased soil water consumption at a 0–100 cm soil depth by 6.76–21.34% (average values over two years), root length density by 8.46–20.77%, and root surface area density by 7.87–22.13%. On average, M3 increased grain yields by 3.96–9.80%, biomass yields by 5.32–10.94%, and WUE by 4.5–9.87%. In conclusion, M3 is an effective planting pattern for improving the yield and WUE of wheat in the NCP.

Effects of phosphorus fertilizer type and dripline depth on root and soil nutrient distribution, nutrient uptake, and maize yield under subsurface drip fertigation

ContextSubsurface drip irrigation can potentially increase nutrient uptake by altering the spatial distribution of nutrients and roots, but the efficiency enhancement potential of different phosphorus (P) sources combined with varying dripline depths still requires further evaluation. MethodsWe established a 2-year field experiment with spring maize in 2021 and 2022 to determine the regulatory effects of three P sources [P1, monoammonium phosphate (MAP); P2, ammonium polyphosphate (APP); and P0, no P] and three dripline depths (D0, surface drip irrigation, 0 cm; D15, subsurface at 15 cm depth; and D30, subsurface at 30 cm depth) on the soil NO3-N, NH4-N and Olsen-P distribution, root distribution, nitrogen (N) fertilizer partial factor productivity (PFPN) and P use efficiency (PUE), and grain yield. ResultsWe found a significant coupling effect between the P source and dripline depth, both of which significantly impacted soil nutrients and root distribution, grain yield, PFPN, and PUE. In P1D15 and P2D15, the highest soil NO3-N and Olsen-P contents were observed at soil depths of 0–30 and 10–20 cm and at 0–30 and 10–30 cm, respectively. Similarly, in P1D30 and P2D30, which were 20–40 and 20–40 cm, and 20–40 and 30–60 cm, respectively. Compared to the other treatments, P2D15 and P1D30 exhibited considerable increases in root length density at the 30–60 cm soil depth of 37∼52 % and 28∼58 %, respectively. Regardless of the dripline depth, P0 resulted in the lowest yield during both growing seasons. P1D30 and P2D15 were found to be the optimal combinations for achieving higher grain yield, PFPN, and PUE, as they were able to achieve a high degree of coordination between soil available N and Olsen-P, as well as root distribution. ConclusionsThe recommended approach for optimizing nutrient and root spatial distributions under subsurface drip irrigation systems involves the use of poly-P fertilizer (APP) in conjunction with shallow dripline depth and ortho-P fertilizer (MAP) paired with deep dripline depth, which provides valuable guidance for co-fertigation practices involving N and P fertilizers.

Higher Seed Rates Enlarge the Effects of Wide-Belt Sowing on Root Length Density, Thereby Improving Nitrogen Uptake and Use Efficiencies in Winter Wheat.

The optimized sowing method and appropriate seed rate can improve wheat N use efficiency. However, the interactive effect of the sowing method and seed rate on N use efficiency, particularly N uptake and root length density, are unclear. A field experiment was conducted for two growing seasons in southern Shanxi province, China, using a split-plot design with the sowing method as the main plot (wide-belt sowing, WBS, and conventional narrow-drill sowing, NDS) and seed rate as the sub-plot (100-700 m-2). Our results showed that WBS had a significant and positive effect on N use efficiency (yield per unit of available N from the fertilizer and soil, by 4.7-15.4%), and the relatively higher seed rates (>300 or 400 m-2) enlarged the effects. The N use efficiency increases under WBS were mainly attributed to the increases in N uptake before anthesis, resulting from the promoted nodal roots per plant and per unit area, and root length density in the top layer(s). WBS promoted N translocation and the N harvest index, resulting in equivalent grain protein concentration and processing quality compared to NDS. Thus, adopting higher seed rates (>300 m-2) combined with WBS is recommended for achieving greater N efficiencies while maintaining the grain protein concentration and processing quality of winter wheat.

Interaction Effects of Water and Nitrogen Practices on Wheat Yield, Water and Nitrogen Productivity under Drip Fertigation in Northern China

Water resource shortage and unreasonable application of nitrogen (N) fertilizer have been problems in wheat production of northern China. However, the interaction effects of water regimes and N practices on wheat root growth, grain yield, soil water, and inorganic N changes as well as water-N use efficiency are still unclear under drip irrigation. A field experiment was conducted during the 2020–2021 and 2021–2022 winter wheat (Triticum aestivum) growing seasons. In this study, three irrigation schedules (i.e., irrigation was applied up to 80% [D1], 75% [D2], and 70% [D3] as soon as the soil water content decreased to 65%, 60% or 55% of field capacity) and two N practices (i.e., N applied at the base, jointing, booting stages were 90, 72, 48 kg ha−1 [N1], and the base, jointing, booting, filling stages were 90, 40, 40, 40 kg ha−1 [N2], respectively) were considered. The decease in irrigation water amount was offset by the increase in soil water consumption. In addition, N practices significantly interacted with irrigation on soil NO3−–N accumulation (2021–2022), NH4+–N accumulation, SPAD value (2020–2021), N content in stems and grains at maturity, and average root length and weight density at the flowering stage. Irrigation, rather than N practices, significantly affected grain yield, total N uptake, crop N transformations (NT), the contribution of NT to grain (NTPC), water and N productivity, in which, for the value of these two seasons, D2 increased total N uptake by 18.1% (p < 0.05), and NT by 39.4% (p < 0.05) under N1 as compared to D3. Additionally, the highest WUE and ANUE were found in D2 during 2021–2022. Heavy irrigation water amount caused high a LAI; further analysis proved that the LAI was the key factor affecting grain yield, and positively and significantly correlated to yield. However, no significant difference in the LAI between D1 and D2 was found. N1 was beneficial to prevent N leaching and increase water and N use efficiency, biomass, and N transformation amount. This study recommends that D2 + N1 might be a promising system for manipulating irrigation and fertilization practices under sub-surface drip irrigation systems to improve water and N use efficiency and grain yields in semi-arid regions.

Straw return under deep tillage increases grain yield in the rice-rotated wheat cropping system

ContextStraw return under rotary tillage has been used for two decades in the rice-rotated wheat cropping system in the lower Yangtze region of China, but it has become prone to reduce wheat emergence and yield in recent years, and alternative tillage methods are required to ensure the high wheat yields. AimsTo determine whether straw return under deep tillage can improve wheat yield and under what mechanisms. We hypothesize that straw return under deep tillage can increase wheat seedling number by reducing rice stubble and straw coverage, and expand the nutrient pool and root system of the plow soil profile to keep post-anthesis viability for increasing wheat yield. MethodsA field study was conducted during two consecutive years and included four treatments: rotary tillage after straw removal (RT); rotary tillage after straw return (RTS); shallow rotary tillage followed by straw mulch (STS) and deep tillage after straw return (DTS). Wheat seedling number, yield, aboveground nutrient uptake, growth period, root characteristics, and soil nutrients were measured. ResultsCompared to RT, seedling number under RTS and STS decreased by 8.3 % and 13.4 %, respectively, while DTS increased by 14.7 %. Wheat yield under RTS and STS decreased by 3.0 % and 7.3 %, respectively, while DTS increased by 8.2 %. The reduction in seedling number under RTS and STS would be partially offset in wheat yield by an increase in effective tiller number per plant and grain weight. Consequently, the variation in wheat yield among treatments was less than the variation in seedling number. Aboveground N and P accumulation in wheat under DTS were higher than the other treatments. Among four treatments, DTS had the highest root distribution and soil N and P contents in the middle and deep soil layers, thus prolonged grain filling duration. Wheat nutrient uptake at maturity and yield were significantly correlated with root weight density and root length density in both middle and deep soil layers. ConclusionsStraw return under deep tillage can increase nutrient supply capacity and root distribution in deep soil while ensuring wheat emergence, enabling better filling of post-anthesis wheat and yield. It is therefore an effective alternative tillage method suitable for the rice-rotated wheat cropping system.