Maximum Rooting Depth Research Articles

Riparian restoration in sandy zones with alfalfa as pioneer plant in initial stage of soil and water bioengineering

As Nature-Based and Bio-based Solutions, soil and water bioengineering (SWB) provides several benefits to humans and nature. It has been widely used for erosion control, vegetation recovery and ecosystem restoration in riparian zones. Nevertheless, studies on riparian restoration in sandy zones with alfalfa as pioneer plant in initial stage of SWB are still rare, which are important for understanding the role of pioneer plants during the initial stage of SWB and also for choice of the appropriate measures. Here, three commonly applied SWB measures (vegetation geobag / VGB, grass-planting concrete block / GCB, and untreated flat area / NTF) are established in sandy riparian zones to explore the growth characteristics structural mechanics and reinforcement of pioneer plant (alfalfa) root, and also the factors influencing biomechanical properties in initial stage of SBE. Our results show that: (1)NTF demonstrated superior overall growth compared to GCB and VGB, underscoring the limitations that geobags and steep slopes impose on initial SWB vegetation establishment. In all treatments, alfalfa roots were able to penetrate soil layers below 60 cm, with NTF exhibiting the highest root biomass and diameter (NTF > GCB > VGB). GCB's higher root-to-shoot ratio may reflect a drought-resistant strategy. In contrast, VGB showed greater root length, maximum rooting depth, and a smaller crown width, indicating a focus on root growth to overcome geobag constraints (2) Differences in root growth distribution among the three treatments resulted in varying biomechanical impacts. Specifically, NTF exhibited significantly lower soil-root bond strength than GCB, while both NTF and GCB had higher maximum pull-out forces compared to VGB. Root diameter showed a significant negative correlation with Young's modulus and root tensile strength, but a positive correlation with root tensile force (p < 0.05). Although no significant correlations were found between root water content and root tensile strength, root tensile strength was positively correlated with Young's modulus. (3) In the comprehensive evaluation of root reinforcement performance, the scores ranked as VGB > GCB > NTF. Result of this study could provide valuable insights into the practical applications of SWB in sandy riparian restoration. Furthermore, it underscores the importance of pioneer plants in the fragile and critical initial stages of SWB, and also benefit both researchers and practitioners in effectively transitioning from the scientific research to practical solutions for riparian restoration.

Modeling the impact of long-term land use changes on deep soil hydrological processes in the Loess Plateau, China

Land use change can significantly affect soil hydrology in arid and semi-arid regions, making it crucial to understand the relationship between vegetation roots and soil moisture. Current models often fail to predict root growth and its impacts on water dynamics accurately. Our work presents a novel model that seamlessly integrates the Community Land Model (CLM) with the Soil & Water Assessment Tool (SWAT). Furthermore, it enhances the root module within the CLM, enabling more accurate simulations of dynamic root depth and distribution across varying tree ages. This improvement particularly considers the crucial processes of dormancy and plant maturity. Soil moisture and root patterns under apple trees of varying ages and in wheat fields on the Loess Plateau was analyzed. Our findings indicate that our dynamic root depth model outperforms traditional static models, and can accurately reflect soil moisture levels with high precision (R2 = 0.80–0.81; Nash-Sutcliffe efficiency (NSE) = 0.65–0.75). In contrast to methods that utilize fixed root depths, dynamic root simulation can provide new insights. As apple orchards mature, the roots of 22-year-old apple trees have been found to reach a depth of 21 m in the soil. Conversely, the maximum root depth of wheat is limited to 1.9 m. This latter finding aligns more closely with the measured root depths, highlighting the accuracy of dynamic simulations. This model reveals that older apple orchards show decreased soil moisture at greater depths (>20 m), contrasting with wheat fields that affect moisture mostly within the top 2 m. Our results underscore the crucial role of dynamic modeling in comprehending root-soil water interactions. Furthermore, they imply that extended orchard cultivation practices can lead to a substantial depletion of deep soil moisture. Specifically, over a period of 1 to 22 years, a water deficit of up to 85 mm yr−1 has been observed. For a 22-year-old forest, the D-D (dynamic distributions of coarse and fine roots) method calculates a significant cumulative deep Soil Water Storage loss. Over the course of 22 years, this loss amounts to 1664 mm, which is almost three times compare to the annual rainfall recorded. Such a large loss has the potential to significant impact on groundwater recharge. This highlights the need for careful consideration in future afforestation efforts to prevent increased soil aridity.

Commercial maize hybrids have smaller root systems after 80 Years of breeding

Roots have gained attention for their role in improving plant function in high-stress environments and providing ecosystem services such as soil organic carbon storage. An important step in breeding for enhanced root phenotypes is understanding how root traits have changed historically due to selection for yield and other aboveground traits. However, among the few era panel studies focused on roots, there are conflicting findings about how breeding has altered traits such as root system length and biomass, while other traits such as root depth distribution, root size class distribution, and tissue quality remain largely unexplored. Our aim was to assess breeding-driven changes in root traits that are relevant to resource acquisition and soil carbon sequestration. We grew twelve maize (Zea mays L.) hybrids from the Corteva/Pioneer ERA panel, spanning from 1936 to 2014, in 1.5 m deep mesocosms. At the eight-leaf stage, intact root systems were imaged and analyzed using a custom root phenotyping platform, and roots and shoots were subjected to carbon and nitrogen analysis and Diffuse Reflectance FTIR to assess variation in tissue composition. We found that the newest hybrids produced 40% less root biomass and 36% less root length than the oldest hybrids, with declines of 0.024 g year−1 (s.e.: 0.005, p < 0.01) and 0.86 m year−1 (s.e.: 0.23, p < 0.01) with no changes in maximum rooting depth, which averaged 113 cm (±5.62). , and no directional shifts in chemical composition. We also found a decline in the root-to-shoot ratio from 0.58 g g−1 to 0.46 g g−1 (s.e.: 0.0006, p < 0.05). Our results suggest that selection for yield has indirectly decreased root system size over 80 years of maize breeding. Smaller root systems of modern hybrids may contribute to the higher optimum plant populations and higher yields of modern maize hybrids.

Fine Root Density Dynamics and Carbon Stock of Eucalyptus spp.: Interplay of Age, Genotype, and Edaphoclimatic Conditions.

Roots play a fundamental role in forest ecosystems, but obtaining samples from deep layers remains a challenging process due to the methodological and financial efforts required. In our quest to understand the dynamics of Eucalyptus roots, we raise three fundamental questions. First, we inquire about the average extent of the roots of two contrasting Eucalyptus genotypes. Next, we explore the factors that directly influence the growth and depth of these roots, addressing elements such as soil type, climate, and water availability. Lastly, we investigate how the variation in Eucalyptus species may impact root growth patterns, biomass, and carbon stock. In this study, we observed that the maximum root depth increased by an average of 20% when genotypes were grown on sites with higher water availability (wet site). E. urophylla stands had a higher biomass and carbon stock (5.7 Mg C ha-1) of fine roots when cultivated on dry sites (annual rainfall~727 mm) than the wet sites (annual rainfall~1590 mm). In E. grandis × E. camaldulensis stands, no significant differences were observed in the stock of fine root biomass (3.2 Mg C ha-1) between the studied environments. Our results demonstrated that genotypes with greater drought tolerance (E. grandis × E. camaldulensis) tend to maintain higher stocks of fine root biomass (3.2-6.3 Mg ha-1) compared to those classified as plastic (E. urophylla), regardless of the edaphoclimatic conditions of the cultivation site. Finally, our research helps understand how Eucalyptus trees adapt to their environment, aiding sustainable forest management and climate change mitigation. We also provide a practical tool to estimate underground biomass, assisting forest managers and policymakers in ensuring long-term forest sustainability.

Tree water uptake patterns across the globe.

Plant water uptake from the soil is a crucial element of the global hydrological cycle and essential for vegetation drought resilience. Yet, knowledge of how the distribution of water uptake depth (WUD) varies across species, climates, and seasons is scarce relative to our knowledge of aboveground plant functions. With a global literature review, we found that average WUD varied more among biomes than plant functional types (i.e. deciduous/evergreen broadleaves and conifers), illustrating the importance of the hydroclimate, especially precipitation seasonality, on WUD. By combining records of rooting depth with WUD, we observed a consistently deeper maximum rooting depth than WUD with the largest differences in arid regions - indicating that deep taproots act as lifelines while not contributing to the majority of water uptake. The most ubiquitous observation across the literature was that woody plants switch water sources to soil layers with the highest water availability within short timescales. Hence, seasonal shifts to deep soil layers occur across the globe when shallow soils are drying out, allowing continued transpiration and hydraulic safety. While there are still significant gaps in our understanding of WUD, the consistency across global ecosystems allows integration of existing knowledge into the next generation of vegetation process models.

Do newer maize hybrids grow roots faster and deeper?

AbstractUnderstanding historical changes in root depth attributes is needed for crop productivity and sustainability assessments, but such information is rare. We explored whether newer maize (Zea mays L.) hybrids grow roots faster and deeper than older hybrids and quantified the role of management and environment on root trait expression. We measured root front velocity (RFV) and maximum root depth in 11 Bayer Crop Science legacy hybrids released from 1983 to 2017 across five environments in the US Corn Belt during 2021 and 2022. Root depth was measured weekly during vegetative stages with manual probes and the maximum root depth at crop harvest with a Giddings probe. Results indicated that the RFV and maximum root depth slightly increased with the year of hybrid release (0.13% per year, p = 0.1) at 8.7 plants m−2. Historical increases in plant density from 4.7 to 8.7 plants m−2 lowered RFV and maximum root depth, but the new hybrids compensated for this loss, resulting in 4% higher RFV and 3% higher maximum depth when comparing systems from 1983 to 2017. The environment strongly influenced root trait expression (&gt;41%). Rain anomaly and soil bulk density explained a portion of this variation. We found a linear relationship between root depth and leaf number (R2 = 0.95) and a nonlinear relationship between RFV and maximum root depth (R2 = 0.77), which can stimulate crop model improvements. Faster and deeper roots were not correlated with maize yields in our environments. This study enhances our understanding of maize breeding impacts on root traits.

Dynamic root growth in response to depth-varying soil moisture availability: a rhizobox study

Abstract. Plant roots are highly adaptable, but their adaptability is not included in crop and land surface models. They rely on a simplified representation of root growth, which is independent of soil moisture availability. Data of subsurface processes and interactions, needed for model setup and validation, are scarce. Here we investigated soil-moisture-driven root growth. To this end, we installed subsurface drip lines and small soil moisture sensors (0.2 L measurement volume) inside rhizoboxes (length × width × height of 45 × 7.5 × 45 cm). The development of the vertical soil moisture and root growth profiles is tracked with a high spatial and temporal resolution. The results confirm that root growth is predominantly driven by vertical soil moisture distribution, while influencing soil moisture at the same time. Besides support for the functional relationship between the soil moisture and the root density growth rate, the experiments also suggest that the extension of the maximum rooting depth will stop if the soil moisture at the root tip drops below a threshold value. We show that even a parsimonious one-dimensional water balance model, driven by the water input flux (irrigation), can be convincingly improved by implementing root growth driven by soil moisture availability.

How do leaf functional traits and age influence the maximum rooting depth of trees?

How do leaf functional traits and age influence the maximum rooting depth of trees?

Compacted soil adaptability of Brassica napus driven by root mechanical traits

Soil compaction due to mechanized farming operations is a recurrent issue affecting crop growth and yield. Yet, how soil compaction affects plant functions and ecological strategies is poorly known. With Brassica napus, i.e. a widespread crop species as study object, we aim to understand (i) how soil compaction impacts root and shoot traits related to the plant’s well-being, nutrient acquisition of Brassica napus with different mechanical robustness, as well as their trade-offs, and (ii) how such impacts vary among different cultivars. To do this, we cultivated six cultivars of Brassica napus in non-compacted (control) and compacted (treatment) soils, respectively, in a sand culture system. After harvesting, a series of mechanical, morphological and chemical traits of roots and/or shoots were measured. Results showed that soil compaction significantly limited root penetration depth and root system establishment in morphological traits, leading further to significant reduction in nutrients acquisition and plant biomass accumulation. However, soil compaction significantly increases the average root diameter and root/shoot ratio, and facilitate more root exudates secretion (e.g. organic acids and polysaccharides) of Brassica napus cultivars. The Brassica napus cultivars with large root mechanical traits (e.g. root tensile force, root tensile strength and modulus of elasticity) had higher root cellulose and lignin concentrations and showed a stronger response in maximum root depth and specific root length compared with Brassica napus cultivars with small root mechanical traits in compacted treatment, which resulted in the greater fine root length and more root exudates secretion at root-soil interface. Furthermore, deep rooting enhanced nutrients acquisition and further biomass accumulation in compacted soil. Totally, the Brassica napus cultivars with large root mechanical traits with more fine roots and root exudates were critical for Brassica napus root penetration into a deep soil layer in compacted soil.

Root trait variation along water gradients in the Cape Floristic Region

AbstractQuestionsRoots are responsible for essential plant functions including water uptake. However, the extent to which root traits (size and structure) determine plant presence in water‐limited environments is still poorly understood. Here we investigated how root traits vary across water availability gradients within a dry South African biome.LocationSouth Africa.MethodsWe measured six below‐ground (root) and eight above‐ground (leaf + stem) traits of 124 individuals of nine dominant woody shrub species from wetter and drier sites (600–700 vs 250–300 mm annual precipitation) in the Fynbos biome of the Cape Floristic Region. Within sites, we sampled from recently burnt and unburnt/more mature vegetation and at three locations along topographical gradients.ResultsDrier regions showed greater maximum rooting depth, length, root dry matter content and root to shoot ratio. These trait patterns were consistent at an intraspecific level, along locally drier topographical locations and in post‐fire environments. Roots accounted for significant whole‐plant trait variation. Additionally, in drier conditions, we found increased root allocation deviating from expected global allometric relationships. Our study also demonstrates that the combination of fire and drought in the driest locations results in poor above‐ground vegetation recovery in terms of plant size, cover and individual counts with only resprouters persisting.ConclusionsOur research suggests that root investment in Fynbos shrubs will likely be key for coping with a drier and warmer future and should be a focus of more research for dryland biomes.

Molecular identification and mapping of mixed root samples to species and individuals.

This article is a Commentary on Osborne et al. (2023), 238: 1305–1317.

Analysis of extreme values of soil ecosystem services predicted from associated soil properties and weather conditions

AbstractSoils provide services that can increase food security and mitigate global warming. Simulation modelling of biophysical processes is one approach used to estimate values of soil ecosystem services (SES) based on soil properties and climate conditions. The SES are usually investigated using statistical approaches that assume that values of SES are normally distributed. This assumption, however, ignores atypical values of SES, which deviate strongly from average values. Classic approaches have, therefore, failed to identify such atypical values of SES. To address this issue, we applied extreme value theory (EVT) as a statistical tool to identify thresholds above which SES can be considered as ‘extreme’. EVT was applied to a dataset of four SES—climate regulation, groundwater recharge, water‐to‐plant provision and plant biomass provision—estimated by biophysical soil and crop modelling based on a dataset of 64 cultivated soils located in northwestern France under a single climate observed over 30 years (1988–2018) and a single crop management of a maize and wheat rotation. Extreme values of the SES considered in our study were identified, and soil properties associated with these values were characterised. For instance, soils with extreme minimum values of climate regulation service had the highest pH, clay and organic carbon contents and maximum rooting depth. Applying EVT also enabled identification of the ‘return period’, which is the amount of time after which an extreme value of SES is likely to occur again. For instance, under the maize and wheat rotation simulated and weather conditions equivalent to those from 1988 to 2018, storage of organic carbon in the soil of 1000 kg C ha−1 year−1 is expected to be exceeded by at least one of the 64 of soils once every 2 years. This approach can thus be useful for decision making in natural resource management by identifying atypical values of SES and predicting how frequently they may occur.Highlights Extreme value theory identified soils with extreme values of ecosystem services (SES). Some soil properties differed significantly among samples of extreme values of SES. Soils in extreme samples of SES were identified as a function of their parent material. The mean extreme maxima of the SES were expected to be exceeded every 2 years.

Effect of Sulphur, Potassium and PSB on Growth Parameters, Root Architecture and Quality of Mustard (Brassica juncea L.)

Field experiments were conducted to Studies effect of sulphur, potassium and PSB on growth parameters, root characterstics and quality of mustard during rabi season of 2019-20 and 2020-21 at students instructional farm, Chandra Shekhar Azad University of Agriculture &amp; Technology, Kanpur. The experiment consists of 9 treatments combinations in randomized block design with three replications. Mustard variety Varuna (T-59) was grown with the recommended agronomic practices. On the basis of results emanated from investigation it can be concluded that among the growth parameters viz. The maximum plant height (137.72 cm) and number of leaves (8.62) were recorded in the treatment T9 [K60 + S40 + PSB] during the second year (2020-21) of experimentation. Similarly among the root characterstics, maximum root depth (72.49 cm), no. of roots plant-1 (14.92) and dry weight of roots (28.37 g) were associated with the treatment T9 [K60 + S40 + PSB] during the second year (2020-21) of experimentation. Maximum oil content (38.65 %) and oil yield (841.80 kg ha-1) were recorded in the treatment T9 [K60 + S40 + PSB] during the second year (2020-21) of experimentation.

Precipitation predictability affects intra- and trans-generational plasticity and causes differential selection on root traits of Papaver rhoeas.

Climate forecasts show that in many regions the temporal distribution of precipitation events will become less predictable. Root traits may play key roles in dealing with changes in precipitation predictability, but their functional plastic responses, including transgenerational processes, are scarcely known. We investigated root trait plasticity of Papaver rhoeas with respect to higher versus lower intra-seasonal and inter-seasonal precipitation predictability (i.e., the degree of temporal autocorrelation among precipitation events) during a four-year outdoor multi-generation experiment. We first tested how the simulated predictability regimes affected intra-generational plasticity of root traits and allocation strategies of the ancestors, and investigated the selective forces acting on them. Second, we exposed three descendant generations to the same predictability regime experienced by their mothers or to a different one. We then investigated whether high inter-generational predictability causes root trait differentiation, whether transgenerational root plasticity existed and whether it was affected by the different predictability treatments. We found that the number of secondary roots, root biomass and root allocation strategies of ancestors were affected by changes in precipitation predictability, in line with intra-generational plasticity. Lower predictability induced a root response, possibly reflecting a fast-acquisitive strategy that increases water absorbance from shallow soil layers. Ancestors' root traits were generally under selection, and the predictability treatments did neither affect the strength nor the direction of selection. Transgenerational effects were detected in root biomass and root weight ratio (RWR). In presence of lower predictability, descendants significantly reduced RWR compared to ancestors, leading to an increase in performance. This points to a change in root allocation in order to maintain or increase the descendants' fitness. Moreover, transgenerational plasticity existed in maximum rooting depth and root biomass, and the less predictable treatment promoted the lowest coefficient of variation among descendants' treatments in five out of six root traits. This shows that the level of maternal predictability determines the variation in the descendants' responses, and suggests that lower phenotypic plasticity evolves in less predictable environments. Overall, our findings show that roots are functional plastic traits that rapidly respond to differences in precipitation predictability, and that the plasticity and adaptation of root traits may crucially determine how climate change will affect plants.

Soil moisture-vegetation interaction from near-global in-situ soil moisture measurements

Although the interactions between soil moisture (SM) and vegetation dynamics have been extensively investigated, most of previous findings are derived from satellite-observed and/or model-simulated SM data, which inevitably include multiple sources of error. With the effort of many field workers and researchers in in-situ SM measurement and SM data integration, it is now possible to obtain the integrated in-situ SM dataset in the global range. Here we used the in-situ SM dataset of the International Soil Moisture Network to analyze the anomaly correlation between SM and leaf area index (LAI). We found that positive (negative) correlations exist between SM (LAI) and temporally lagged LAI (SM). The peak correlation and lagging time to reach it (often less than 3 months) depends on climate, land cover and rooting depths. The high SM-LAI anomaly correlation prevails in water-limited regions, e.g. dryland, where plant physiology has strong sensitivity to subsurface water stress. Dynamics of vegetation with deeper maximum rooting depths are not always correlated with SM in deeper soil layers, and vegetation dynamics with shallower maximum rooting depth may strongly correlate with SM in deeper soil layers. Overall, we highlight the potential of the global in-situ SM observation network to analyze the interactions between SM and vegetation dynamics.

Evaluating potential groundwater recharge in the unsteady state for deep-rooted afforestation in deep loess deposits

Groundwater recharge reduces due to high transpiration from shallow-rooted to deep-rooted afforestation. However, reaching a steady state in recharge process is challenging and no methods are available for assessing potential groundwater recharge under unsteady state. Hence, this study developed a new method to quantify groundwater recharge in the unsteady state by (1) calculating the water age (A2) at maximum root depth (D2) for deep-rooted afforestation using the chloride accumulative age method; (2) determining the soil depth (D1) corresponding to A2 under shallow-rooted vegetation using the multi-year average pore water velocity multiplied by A2; (3) calculating the reduction in groundwater recharge (∆R) from shallow- to deep-rooted afforestation as the depth difference multiplied by the average water content between D1 and D2, divided by stand age. The average groundwater recharge for deep-rooted afforestation is equal to the average annual groundwater recharge under shallow-rooted vegetation minus ∆R. Soil cores with >25 m soil profiles below four land-use types of Hippophae rhamnoides Linn. (H. rhamnoides), Platycladus orientalis (L.) Franco (P. orientalis), Robinia pseudoacacia L. (R. pseudoacacia), and grassland were collected to measure soil water content, root distribution, and chloride and tritium contents. The results revealed that: (1) maximum root depths were 11.0 ± 0.5, 20.2 ± 1.2, and 22.6 ± 0.8 m, with soil water deficits of 373.48, 823.65, and 1847.92 mm under H. rhamnoides, P. orientalis, and R. pseudoacacia, respectively; (2) groundwater recharge following land-use change has not reached a steady state; (3) an average annual groundwater recharge was 89.12 mm yr−1 under grassland, amounting to 16 % of the average annual precipitation; deep-rooted afforestation did not significantly differ, with 83.55, 84.91, and 85.65 mm yr−1 under H. rhamnoides, P. orientalis, and R. pseudoacacia, respectively. This study contributes to a rational assessment of groundwater resources under unsteady state during land-use change.

Maximum Rooting Depth of Pinus thunbergii Parl. Estimated with Depth at the Center Point of Rotation in a Tree-Pulling Experiment in a Coastal Forest in Japan

Tree resistance to uprooting can be estimated as the critical turning moment in tree-pulling experiments. The depth at the center point of rotation (Dcp) in tree-pulling experiments is measured as an indicator of below-ground traits and is related to this critical turning moment. However, few researchers have investigated the relationship between the Dcp and maximum root depth. Our objective in this study was to clarify whether the Dcp in tree-pulling experiments can be estimated as the maximum root depth of Pinus thunbergii Parl. in sandy soils. We also estimated which position of displacement of the center of rotation (Cp) can be applied as the Dcp. We conducted tree-pulling experiments, and compared the Dcp obtained from images with the measured maximum root depth. We found significant positive correlations between the Dcp and maximum root depth. The Cp displacement concentrated immediately below the stem when the maximum critical turning moment was reached. This position should be measured as the Dcp, which is related to the maximum root depth. We found that the Dcp can serve as a parameter, preventing the need for uprooting, when tree-pulling experiments are performed to obtain an important below-ground trait for understanding the critical turning moment.

Root architecture and leaf photosynthesis traits and associations with nitrogen-use efficiency in landrace-derived lines in wheat

Root system architecture (RSA) is important in optimizing the use of nitrogen. High-throughput phenotyping techniques may be used to study root system architecture traits under controlled environments. A root phenotyping platform, consisting of germination paper-based pouch and wick coupled with image analysis, was used to characterize root seedling traits in 30 landrace-derived bread wheat genotypes and the bread wheat parent Paragon under hydroponic high N (HN) and low N (LN) conditions. In addition, two glasshouse experiments under HN and LN conditions were carried out to measure whole plant performance including flag-leaf photosynthetic rate, N uptake and biomass per plant for 13 wheat genotypes of which eight were common with those in the root phenotyping hydroponic experiment. There were significant differences in RSA traits between genotypes for seminal root number per plant, lateral root number per plant, seminal root length per plant and seminal root angle, with transgressive segregation for landrace-derived lines above the elite parental cultivar Paragon under HN and LN conditions. In the glasshouse experiments, genetic variation in flag-leaf photosynthesis rate was found in landrace-derived genotypes in the range 25.9–33.3 µmol m−2 s−1 under HN and in N uptake in the ranges 0.37–0.48 g N plant−1and 0.21–0.30 g plant−1 under HN and LN conditions, respectively (P < 0.05), with transgressive segregation above Paragon. Plant Nitrogen Nutrition Index also showed transgressive segregation in the landrace-derived lines above Paragon under HN and LN conditions. Greater maximum root depth and more lateral roots per plant in the hydroponic screen were each correlated with increased biomass per plant under LN conditions. Results from this study demonstrated genetic variation for seedling RSA traits in landrace-derived lines above the elite parental cultivar Paragon, which potentially could be utilized to improve N-use efficiency in breeding programmes.

The evaluation of drought-tolerance rice genetic resources

About 70% of the rice consumed in Ghana is imported. The state of self-insufficiency in rice production can be attributed to the lack of adequate or continuous water supply. Rice, being an aquatic plant, is not tolerant to drought, which is known as the most threatening abiotic factor causing as much as 64% yield reduction. Therefore, this study was conducted to identify drought-tolerance genotypes among 24 rice collections and to estimate their heritability. A total of 24 traits were assessed in this study, and three treatments were applied, including stress free, mild stress, and severe stress, each of which involved three replications. The results showed that most of the parameters under investigation, including panicle length, fertile panicle rate, shoot, and root dry weight, and maximum root depth, decreased considerably as the level of drought stress increased. In addition, five of the accessions showed considerable tolerance to drought, eight accessions were high yielding, and eight accessions combined high yields and drought tolerance. The study concluded that 80% of the rice accessions offer promising lines to be used as parents in the development of drought-tolerant varieties and in genetic improvement programs aimed at such a purpose. The study recommended that molecular studies and morphological characterization should be done on the collections to understand their genetic makeup, similarities, and differences.

Suitability of Idi-Apa Oke-Oyi Soil for Groundnut Cultivation

Soil supplies most of the mineral nutrients for plant growth through the plant’s root system. The need to determine the soil nutrient supplying capacity of the soil at Idi-Apa, Oke-Oyi area of Kwara State, Nigeria for groundnut cultivation is of major concern before embarking on large-scale cultivation of groundnut to avoid great loss. The project was therefore conducted to analyse the soil at Idi-Apa, Oke-Oyi area based on the fertility for the cultivation of groundnut.&#x0D; Soil samples were taken at depths 0–30 cm and 30–60 cm (which is the maximum rooting depth for groundnut) from the land. The samples which were collected through the random method were sent to the laboratory and analysed for chemical parameters: pH; organic carbon (OC); organic matter (OM); calcium (Ca); magnesium (Mg); sodium (Na); potassium (K); and nitrogen (N). Physical properties (textural class) and other properties such as sodium adsorption ratio (SAR); exchangeable sodium percentage (ESP); base saturation (BS) and cation exchange capacity (CEC) were determined.&#x0D; The result of the analysis showed that the pH (7.1-7.8), OM (2.36-6.93%), OC (1.37-4.98%), Na (0.04-0.15%), ESP (1.04 – 1.28%) and BS (95.37-95.85%) were found to be in the range of the requirements for groundnut production, while the other analyses parameters were outside the required range.&#x0D; Generally, some of the major nutrients like and potassium needed by the crop have deteriorated while some others like calcium are available in sufficient quantities. This calls for the application of fertilizer to the soil to provide the lost nutrients and proper monitoring of the soil before the cultivation of groundnut. An integrated approach that involves the cultivation of nutrient-efficient varieties of groundnut on nutrient-deficient soils is suggested. In the absence of magnesium-efficient varieties, the application of magnesium as fertilizer is recommended.&#x0D; There were no significant differences (p &gt;.05) in the results between the two soil layers for all chemical properties considered except for organic where OM was significantly higher in the subsoil than in the topsoil.