Root Distribution

Although solutions of multidimensional transient water flow can be obtained by numerical modeling, their application may be limited in part as root water uptake is generally considered to be one‐dimensional only. The objective of this study was to develop and test a two‐dimensional root water uptake model, which can be incorporated into numerical multidimensional flow models. The two‐dimensional uptake model is based on the model by Raats, but is extended with a radial component. Subsequently, the root water uptake model was incorporated into a two‐dimensional flow model, and root water uptake parameters were optimized, minimizing the residuals between measured and simulated water content data. Water content was measured around a sprinkler‐irrigated almond tree (Prunus laurocerasus M.J.Roem) for a 16‐d period at 25 locations, following irrigation. To calibrate the flow and root water uptake model, a genetic algorithm (GA) was used to find the approximate global minimum of the optimi...

The mechanism of plant response to water availability is a crucial research area in ecosystem adaptation to dry environments. Global change in precipitation patterns exacerbates drought risks in many regions, necessitating investigations of tree responses to drought. However, compared with seasonal drought events, how water use characteristics respond to long-term rainfall reduction remains poorly characterized. Here, we assessed the effects of multi-year rainfall exclusion treatments (in the 4th and 5th years) on sap flow, canopy conductance (G C), and the response pattern to varying transpiration driving force (vapor pressure deficit (VPD)) and soil moisture conditions in a black locust (Robinia pseudoacacia) plantation in the China's Loess Plateau. The experimental platform includes paired plots of a 30% throughfall exclusion treatment and a control within the plantation. The reduction of soil water content (SWC), either as temporal variations or as a result of rainfall exclusion treatment, generally lowered sap flow, G C , and the sensitivity to VPD. The difference in each index between plots was substantially greater than that among temporal variations in SWC within a plot. The trees in the control plot showed strong responses of G C to temporal SWC changes, exhibiting an isohydric behavior. However, those subjected to long-term rainfall exclusion treatment had lower variations in G C and the sensitivity across different SWC, exhibiting an anisohydric behavior under limited water conditions. Additionally, rainfall exclusion treatment decreased basal area (BA) increment but increased water use efficiency (WUE). The transition to anisohydric behavior suggests an adventurous pattern of water use strategy that has risks of hydraulic damage and shoot mortality. These findings provide insights into the different adaptation strategies within a species to diverse intensity and duration of drought conditions, which is crucial for sustainable forest management under climate change conditions.

The concentration of 18O in atmospheric CO2 and H2O is a potentially powerful tracer of ecosystem carbon and water fluxes. In this paper we describe the development of an isotope model (ISOLSM) that simulates the 18O content of canopy water vapor, leaf water, and vertically resolved soil water; leaf photosynthetic 18OC16O (hereinafter C18OO) fluxes; CO2 oxygen isotope exchanges with soil and leaf water; soil CO2 and C18OO diffusive fluxes (including abiotic soil exchange); and ecosystem exchange of H218O and C18OO with the atmosphere. The isotope model is integrated into the land surface model LSM, but coupling with other models should be straightforward. We describe ISOLSM and apply it to evaluate (1) simplified methods of predicting the C18OO soil‐surface flux; (2) the impacts on the C18OO soil‐surface flux of the soil‐gas diffusion coefficient formulation, soil CO2 source distribution, and rooting distribution; (3) the impacts on the C18OO fluxes of carbonic anhydrase (CA) activi...

A field experiment was carried out to screen the best foliar concentration of salicylic acid (SA) out of 25, 50, 75 and 100 mg L-1 for its effect on various growth and yield parameters like number of leaves, plant height, number of fruits plant-1, fruit dimensions, leaf chlorophyll content and yield plant-1 in three chilli cultivars. The selected chilli cultivars included were Sky-Land-II, Sky-Land and 1130. The experiment was conducted in field area of the Department of Horticultural Sciences, The Islamia University of Bahawalpur, Pakistan during 2017. Results indicated that different levels of SA significantly increased plant growth and yield parameters, but the level of SA @ 75 mg L-1 highly improved the studied parameters in selected cultivars. Moreover, foliar spray of SA significantly increased growth in selected cultivars; however, Sky-Land-II performed better in response to different concentrations of SA. In conclusion, foliar spraying of 75 mg L-1 SA could be recommended to...

Landslides can have serious impact on natural and human environment and their prevention and mitigation is of global concern. The ability of a slope to resist a landslide depends on the materials and the properties of which it is composed. This project focuses on the increased landslide resistance of a slope due to vegetation. The properties of the soil-root composite were measured in laboratory and, from these results, calculation and graphically based evaluation was used to determine their qualities for resisting landslide. The results show that vegetation roots had a stabilising effect on the slope, limited to the rooting depth. Knowing the rooting depth (generally between 0.5 and 1.5 m) and dependent on the species, a correlation between the ratio of root weight to soil weight and the slope ability to resist landslide was implied from experimental results and a hypothetical design chart and equation were derived.

This field experiment aimed to evaluate the impact of two distinct levels of irrigation, specifically drip irrigation, on a pear orchard to conserve water without compromising production. Kosovo boasts conducive conditions for tree cultivation; however, water scarcity, particularly during the vegetation period, necessitates supplementary irrigation. The study was carried out in the Dukagjini plain on a 10-hectare pear orchard, using a nested experimental design.. Per two levels of irrigation, for 13 rows with tress were used with 100% of evapotranspiration as control and 13 rows with 50% of deficit irrigation. One row were length 90 m and width 40 cm, in total area where applied irrigation were 936 m 2 . Using ANOVA, we detected significant fluctuations in total yield, the number of fruits, and fruit weight. With this technology in 100% irrigation have been achieved a total 7497 kg/900 trees or an average of 8.33 kg/tree while in 50% irrigation have been achieved 4590 kg/900 trees or 5.10 kg/tree. In classification of fruits 85.41% (100% irrigation) were extra class while 92.30% in 50% of irrigation. Our results confirmed that drip irrigation combined with a moderate water stress increase all productive parameters especiallity in total yield, too with significant water saving.

Soil erosion and embankment failures are serious challenges confronting our environment. In the face of these challenges, different possible solutions are been studied at different levels with special consideration on the implementation cost of such solutions. Hence, this work studied agronomical stabilization of Umuda-Isingwu erosion site using vetiver grass. The principal objective of this study was to determine the stability of an engineered slope by computing the factor of safety (FS) of the samples collected from the embankment on the erosion site. To ascertain the factor of safety, the soil samples collected from the study area were analyzed to determine its gradation by mechanical sieving and hydrometer method, while the density bottle was used to estimate the density of the samples which when multiplied by acceleration due to gravity of 9.81m/s 2 gave the unit weight of samples. The results showed that the soil samples are coarse sand and loamy sand, unit weight of bare and Vetiver rooted samples as 17.40KN/m 3 and 16.62KN/m 3 respectively, average shear strength of the bare soil samples and Vetiver rooted soil samples as 68.52KN/m 2 and 132.32KN/m 2 respectively and the factor of safety of the samples; bare and Vetiver rooted soils were computed to be 1.72 and 2.98 respectively. These computed factors of safety showed that Vetiver rooted samples are about 1.73 times more stable than the bare soil. Hence, Vetiver grass is a good embankment and erosion site stabilizer and should be put to effective use in the area erosion control and slope stabilization in Nigeria.

Roots play a major role in reinforcing and stabilizing steep hillslopes. Most studies in slope stability implement root reinforcement as an apparent cohesion by upscaling the behavior of static individual roots. Recent studies, however, have shown that much better predictions of slope stability can be made if the progressive failure of bundles of roots are considered. The characteristics of progressive failure depend on interactions between soil deformation and root bundle geometric and mechanical properties. We present a detailed model for the quantitative description of the mechanical behavior of a bundle of roots under strain‐controlled mechanical forcing. The Root Bundle Model explicitly considers typical values of root‐size spatial distribution (number and dimension of roots), geometric factors (diameter‐length proportion, tortuosity, and branching characteristics), and mechanical characteristics (tensile strength and Young's modulus) and interactions under various soil con...

Modelling the root zone water dynamics in a tree crop agroforestry system is a useful approach to understanding small-scale effects in tree crop systems and may be helpful for optimizing tree spacing in agroforestry system planning. The agroforestry system in this study consists of the species Theobroma grandiflorum ͑Willd ex Spreng͒ Schum ͑Cupuaçu͒, Bactris gasipaes H.B.K. ͑peach palm͒ and the cover crop Pueraria phaseoloides ͑Roxb.͒ Benth ͑Pueraria͒. The soiltype is an oxisol. Calibration was conducted for each of the three species separately. Calibration results show good conformity between simulated and measured data. Simulated scenarios examine the influence of different spacing between trees on root water uptake, evaporation and drainage. Mean interception and crop factors of the whole flow region vary with spacing or are held constant to examine below-ground effects only. Also a fictitious scenario of an older agroforestry system with deeper roots is calculated. In order to overcome restrictions of the computer program Hydrus-2D, correction factors in the root zone were introduced and a calculation scheme for root water uptake of a flow subregion was developped. Below-ground effects of spacing between trees are not or almost not present, but the depth of the tree roots has a significant influence on root water uptake, evaporation and drainage. When mean interception and crop factor vary, drainage increases and root water uptake decreases slightly with spacing. The modelling approach has been found promising for optimizing agroforestry systems although it can only be seen as a first beginning. In an agroforestry systems under drier conditions differences in results will probably be larger.

While very little is yet known about the root system depth of sugar cane, the study set out to model the potential root extraction ratio in soil (PRER), by counting root intersections (RI) obtained using the trench?profile method (TPM), to infer the spatial distribution of sugar cane root length densities (RLD) and root distances (RD). The experiment was conducted in a deep clayey cambisol in Reunion. RI values were counted using a grid with a 5 x 5 cm mesh, down to a depth of 4 m over a 1.5 m wide soil profile. The results revealed: i) wide variability in root distribution between the soil surface and root front (4 m), with many competing roots and other rootless zones over distances of more than 5 cm, ii) the PRER, calculated as the ratio of the volume of soil available to a root for water uptake to the volume of soil assigned to that root, ranged from 80% near the surface to values between 30% and 1% between 1 and 3 m, iii) if RLD mean values were used to estimate usable water, a...

A better understanding of the effects of agronomic management on soil resource accessibility is needed to improve upland rice cropping systems. Here we investigated a new indicator: the potential root extraction ratio (PRER) which takes into account the overall spatial variability of root distribution in soil profiles.

THE SUGARCANE root system depth is crucial as it determines the potential depth of soil available for water and nutrient uptake by the crop. It was reported in an early publication that these roots could grow quite deep (6 m), but otherwise very little data are available on the root system depth. The present study was carried out in three countries: Cote d'Ivoire (var. NCo376), Brazil (var. RB72454) and Reunion, France (var. R570) at various sugarcane growth stages. There were no shoot or root growth constraints (deep soil with enough water). For plant cane, the root front growth (RF in cm) was linear. In Cote d'Ivoire, from 45 to 160 days after planting (DAP), RF = 0.81 DAP; R2 = 0.91. On the island of Reunion, from 100 to 280 DAP, sugarcane root front growth was: RF = 0.56 DAP; R2 = 0.70. When DAP was replaced by thermal time (TT: sum of degree-days), the root front growth patterns were quite similar in Reunion and Cote d'Ivoire (RF = 0.045 and 0.049 TT, respectively)....

We present the findings of a study testing the PRER (Potential Root Extraction Ratio) model (Leifi et al., 2011) to estimate the maximum available soil water (MASW) depending on the sugarcane root system in a deep soil of La Reunion. The aim is to optimize sugarcane irrigation, especially deficit irrigation (DI), by adjusting irrigation rates and intervals according to root distribution in the soil. The experiment was conducted in a deep Cambisol in La Reunion. Sugarcane cultivar was R570. Measurements where done in a ratoon crop nine months after harvest of the previous crop. Root spatial distribution was studied using the trench-profile method by counting and mapping root intersections (RI) in four soil profiles to a depth of four metres using a grid with a 5 x 5 cm mesh. From RI, we inferred root length densities (RLD) (Chopart et al., 2008) and root distances (RD) (Newman, 1969).The PRER (%) is the ratio of volume of soil potentially accessible to a root for water uptake (Vu) an...

Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/23/4-1-3/5 The XXIII International Grassland Congress (Sustainable use of Grassland Resources for Forage Production, Biodiversity and Environmental Protection) took place in New Delhi, India from November 20 through November 24, 2015. Proceedings Editors: M. M. Roy, D. R. Malaviya, V. K. Yadav, Tejveer Singh, R. P. Sah, D. Vijay, and A. Radhakrishna Published by Range Management Society of India

Soil water conservation through tillage is widely accepted as one of the appropriate ways of addressing soil moisture constraints in rainfed agriculture. A field experiment was conducted for 6 seasons (2007 to 2009) to evaluate the effects of 3 tillage practices namely ox-plough (OP), subsoiling-ripping (SR) and tied-ridge (TR) on soil physical and hydro-physical properties of a sandy loam soil. Soil surface roughness, bulk density (BD), total porosity, crust strength, saturated hydraulic conductivity, steady infiltration rates and soil water storage were evaluated. Results showed that, mean inter-row BD (1.51 Mg m -3 ) and crust strength (3.05 MPa) with SR tillage were 7 and 15% greater (P ≤ 0.05) than with OP, respectively. Inter-row infiltration rates for OP (7.9 cm h -1 ) were more than two fold greater than for SR (3.6 cm h -1 ). Soil surface roughness with TR was significantly greater than with OP and SR tillage systems. Soil water storage for TR (222 mm) exceeded (P ≤ 0.05) that for OP and SR by 30 mm (16%) and 32 mm (17%), respectively. This study concluded that, ripping soil along planting line that are prone to surface crusting without disturbing the soil between crop rows was not effective as a conservation tillage method.

Aims To determine soil water diffusivity, D(θ), on undisturbed field soil at medium to low water content (suction range from 10 to 150 m of water), for the purpose of modeling the uptake of water by plant roots. Methods The method is based on the analysis of onestep outflow induced by a turbulent stream of dry air over the exposed end of a soil core, with the other end of the core enclosed. The outflow is measured through time as the change in the weight of the core as it sits on a recording balance. D(θ) is calculated by deconvoluting the measured outflow function. Results Over the suction range of 10 to 150 m of water, D(θ) calculated on the undisturbed soil ranged from 20×10 -9 to 10×10 -9 [m 2 s -1 ], substantially higher than other published estimates over this range in suction. Conclusions These unusually large values cast doubt on the view that flow of water to roots limits uptake of water from the targeted subsoil.

Fertilizer placement distance at which sugarcane utilizes fertilizer optimally was determined in terms of its growth parameters (root distribution, stem height, stalk thickness, and leaf count). Three placement distances (4, 8 and 12 cm) were used as treatment and ...

Summary 1 Although plants of Equisetum spp. are generally thought to be of little value to ecosystems, a study of a cold‐temperate Alaskan shrub wetland showed that they acquired and cycled phosphorus and other nutrients more efficiently than other plant community members. While Equisetum plants represented only 5% of the above‐ and below‐ground biomass in the community, they contained 16% of the P and 24% of the K. 2 Equisetum plants accounted for 29% of the P and 39% of the K in annual community foliage litterfall. Over a 2‐year period, losses from Equisetum litter contributed 55, 41, and 75% of the P, K and Ca litter inputs into soil nutrient pools. 3 The ability of different species of Equisetum to acquire nutrients is linked to their deep rooting habit. While the majority of their roots and rhizomes, and particularly the fine roots, were located in the C horizon, the majority of roots and rhizomes of other species were located in the overlying O horizon. The biomass of Equisetu...

Four shrub/tree species, Alchornea cordifolia, Pennisetum purpureum, Chromolaena odorata, and Calliandra calothyrsus were evaluated for their potential contribution to soil fertility restoration after two years fallow. Standing biomass, root distribution, nutrient content in the biomass, decomposition and nutrient release patterns, and association with mycorrhizae were the evaluation parameters. Alchornea and Pennisetum produced thehighest above-ground biomass, 66 t and 54 t/ha respectively. Pennisetum had more than 19 t/ha of root, 92% of which was in the 20 cm top soil. Alchornea had 74% of it roots in this soil layer, mostly as coarse roots while Calliandra had a deeper root system. Alchornea fallow accumulated more N and Ca, and Pennisetum fallow, more K than others, and mycorrhizae were mostly associated with Alchornea roots. The ranking of the different species for the decomposition rate was: Chromolaena > Pennisetum > Calliandra = Alchornea. Also release of nutrients du...

The present paper shows the effects of various irrigation methods on the distribution of roots in the Golden Delicious apple cultivar grafted on MM 106 rootstock under the specific conditions of the hilly region of Pitesti-Maracineni, Southern Romania. The results obtained here showed that a higher influence was induced by the different irrigation treatments to the active tree root cross-sectional area (TRCSA) versus the total TRCSA. A direct, linear and distinctly significant correlation was found between the sum of the total TRCSA and the fruit yield on the one hand, and between the total TRCSA and the annual growth in tree trunk cross-sectional area on the other hand. This study also revealed, from the TRCSA point of view, that in apple tree farming microsprinkler irrigation and drip irrigation would be the best methods to be used under the natural and technological conditions discussed here. They are fully recommended as the best irrigation methods in apple growing extension und...

My sincere gratitude to Prof. John D. Tenhunen under whose wise guidance and invaluable support I have been able to carry out research and write this thesis. His suggestions, constructive criticism and continuous encouragement have immensely contributed to the writing of a precise piece of work that is presented here. Prof. E. Steudle for his advice during the greenhouse experiments and constructive discussions and interpretation of the results. I am dearly indebted to Mr. Markus M. Schmidt who created an atmosphere of comradeship, introduced me to the equipment, worked tirelessly with me during field experiments and was always there to solve arising technical problems in the field and in the lab. His help with data processing and constructive discussions enabled the interpretation of data to make meaning out of otherwise jargon. I am grateful to Dr. Eva Falge for her constructive discussions, Marga Wartinger, Annette Suske, Barbara Scheidler, Frederike Rothe and Ralf Geyer for their support, Drs. Bärbel Heindl-Tenhunen and Pedro Gerstberger for plant identification, Dr. Jinchen Liu for his help with data as well as equipment. This work would have not been possible without the full support and understanding from my wife Mollyne, sons Tom and Brian Otieno. Thanks to family members and friends who offered the much needed support and encouragement throughout the program. Prof. J.I. Kinyamario of the University of Nairobi who helped identify suitable field site in Kenya as well as his support during the fieldwork. Members of the Kibwezi Arid and Semi-Arid Research Station, especially the station manager Mr. Abeid Kagondu and security team headed by Mr. Kisilu Richard. The director of Kenya Forestry Research Institute (KEFRI) Dr. P.K.A. Konuche for allowing me to carry out my fieldwork under the Institute and more so to the head of Kibwezi Station, Dr. Jackson Mulatya for his valuable support during the fieldwork in Kenya. The Portuguese team (Instituto Superior de Agronomia) under Prof. J.S. Pereira, especially Dr. Cathy Kurz-Besson, Ms. Raquel Vale-Lobo do, Dr. Teresa David and Mr. Joao Banza for their support and comradeship during the Mitra/Evora field campaigns. Special thanks to KAAD-Germany, for offering me the scholarship, which saw me through this program. Ms. Simone Saure and Dr. Thomas Scheidtweiler of KAAD for their regular contacts and readiness to solve arising problems.

Studies were conducted to examine changes in soil (Ys) and plant water status during summer in a 16-year old Quercus suber plantation in southern Portugal. Continuous measurements were conducted between May 2003 and August 2004, while discontinuous measurements were conducted on a monthly basis between May and September 2003 and repeated between March and September 2004. Intensive measurements were conducted on five trees with mean height and DBH of 5.3 m and 11.6 cm, respectively, growing at close proximity to each other. Weather conditions and soil water potential (Ys) at the rhizosphere of each of the trees measured at 0.3 and 1 m soil depth were continuously monitored. Predawn (Ypd) and midday (Ymd) leaf water potentials were determined every month. Soil and plant samples were also collected in June and September from different locations within the study site for d 18 O isotope composition analysis. Pressure-volume (p-v) curves were constructed from plant shoots at different times during the vegetative period to determine osmotic potential at full saturation (P 100 ), water potential at turgor loss point (Y tlp ), relative water content at turgor loss point (R* tlp ) and bulk modulus of elasticity (e). Significant P < 0.05 decline in Ys occurred between May and September, the lowest value recorded being -2.0 MPa. Decline in soil moisture affected tree water status, but decline in leaf water potential varied significantly (P < 0.05) among the trees. At the end of summer drought, lowest Ypd measured was -1.7 MPa while the highest measured during this time was -0.8 MPa. Differences among trees were attributed to differences in rooting depth, as shown by regression analysis of 18 O isotopes. Radial stem growth ceased when Ys within the upper 0.3 m depth approached -1.5 MPa. The upper soil layers contributed approximately 33% of the total tree water requirement, between spring and mid summer when drought was experienced by trees. Deep soil layers however, supplied most of the water required during drought and no growth was recorded during this time. Stressed trees increased solute concentration of their tissues by a Magnitude of 0.7 MPa while bulk tissue elastic modulus increased by about 17 MPa. The study emphasizes the significance of roots as determinants of tree productivity and survival in the Mediterranean ecosystems.

The deciduous tropical dry forest at Chamela (Jalisco, Mexico) occurs in a seasonal climate with eight rainless (November through June) and four wet months (700 mm annual precipitation). The forest reaches a mean height of 10 m. Tree density in the research area was 4700 trees per ha with a basal area at breast height of 23 m 2 per ha. The above-and below-ground biomass of trees, shrubs, and lianas was 73.6 Mg ha-and 31 Mg ha -1, respectively. A root:shoot biomass ratio of 0.42 was calculated. Nearly two thirds of all roots occur in the 0-20 cm soil layer and 29% of all roots have a diameter of less than 5 mm.

Wetland restoration is a pressing conservation priority, but there are few replicated field studies that provide a scientific foundation for these activities. We conducted a 3-year, replicated field experiment to examine the effectiveness of initial site preparation techniques (combinations of solarization, herbicide, tilling, and thermal weed control) in restoring native plant biodiversity to an agricultural field in a former wetland prairie in Oregon, USA. Posttreatment, plots were sown with a typical restoration mix of native graminoids and forbs. Treatments were compared to three high-quality managed reference wetlands and the adjacent agricultural field. Site preparation treatments varied in their effectiveness in suppressing extant vegetation and eliminating the residual seed bank. After 1 year, the solarization and fall herbicide application treatments were the most effective at reducing exotic cover. However, after 3 years, plant community composition converged in all treatments due to a loss of annual species and increasing dominance of native perennial bunchgrasses. Plant community composition became more similar to the reference wetlands each year, but diversity and richness diverged, apparently due to a trade-off between the cover of the dominant native bunchgrasses and diversity. Successional theory offers insights into how priority effects and competitive inhibition may influence community trajectories, and offers a useful model for restoring plant communities with high native diversity and dominance. Finding ways to mitigate the tradeoff between native plant cover and diversity by actively managing successional trajectories is an important challenge in wetland restoration that deserves further investigation.

Potassium-(K) and water-stratification in conservation tillage, rain-fed agroecosystems may reduce soybean [Glycine max (L.) Merr.] performance. A split-pot experiment with two soil-K levels [80 mg Kg -1 (Low-K) and 164 mg Kg -1 (Optimum-K)] and two soil-water contents [insufficient (Dry): variable between 55 to 85% field capacity (FC); sufficient (Wet): constant at 85 to 95% FC] was imposed to determine the effect of synchronous and asynchronous availability of localized K and soil water on soybean roots, nutrient uptake, and shoot growth. Asynchrony of soil water and K had no impact on soybean dry matter accumulation or nutrient uptake. Optimum soil K levels were relatively more important than soil water content to increase K availability and K tissue concentration and accumulation. Shoot-and root-growth responded more to water-than to K-stress. Shoot-K accumulation increased concomitantly with sufficient water availability and greater root surface area (RSA), but RSA was more important relative to water for K accumulation. Optimum-K with sufficient-water increased K accumulation by 50% compared to the insufficient-water treatment. Since enhanced K uptake occurred with greater RSA, and roots proliferated in response to water availability and not localized K, K should be placed in the soil fraction that provides sufficient water availability. K stratification . Root distribution . Root response to localized K and water . K uptake rate . Split root system . Soil water availability, soil solution phase-K . Soil exchangeable K Abbreviations C min minimum soil solution concentration below which no net plant uptake can occur FC field capacity K exch 1 M NH 4 OAc-extractable-K (exchangeable potassium) ΔK exch change in K exch K sol solution-phase potassium Dry insufficient water treatment

Background: Vetiver grass (Chrysopogon zizanioides L. Roberty) is one of the most studied and applied species in soil bioengineering techniques all over the world, but there are technical information related to its root system deserving a better comprehension provided by different methodologies' . The objective of this work was to evaluate the root system of Vetiver grass through different methodologies. The trench method evaluated 50 images in 10 × 10 cm squares in its vertical face. The volumetric ring method uses a metallic ring with a volume of 50 cm 3 (diameter ≅ 4.6 cm and height ≅ 3.0 cm) to collect samples in the same trench's vertical face. A hand auger hole method worked with soil samples and roots removed from the surface up to 0.50 m depth. The monolith method comprises a 0.50 m wide, 0.50 m long, and 1 m deep monolith. A spatial correlation between root volume and root area was observed in the kriging maps by the volumetric ring method. The root area values for both the volumetric ring method and the hand auger hole method were similar, up to 0.10 to 0.20 m. On the analyzed variables, the root area showed the best correlation coefficient among the root methods, especially those that use the limited spatial distribution by its sampling collection, such as the volumetric ring method and the hand auger hole method (r = 0.526, p < 0.05). The studied methods can be separated in different groups, such as those that provide more detailed information on the behavior and distribution of the root system, like trench and monolith methods and the methods that better describe the morphological characteristics of the features, like the volumetric ring method. Both require greater spatial coverage, and therefore have greater precision.

A single, mature and 12 smaller honey mesquite (Prosopisglanduloso Ton. var. glandulosa) trees were partinlly excavated during 1986 to examine root distributional pntterns. The mature tree bad an extensive lateral ruut system and P large tap root that subdivided into 3 smaller tap roots at P depth near 1 m. The lateral root system of all trees was concentrated in the upper 0.3 m of the soil profile. Results from the excavations provide evidence in support of honey mesquite's classification as P facultative pbreatopbyte.

By influencing belowground processes, streamside vegetation affects soil processes important to surface water quality. We conducted this study to compare root distributions and dynamics, and total soil respiration among six sites comprising an agricultural buffer system: poplar (Populus × euroamericana' Eugenei), switchgrass, cool-season pasture grasses, corn (Zea mays L.), and soybean (Glycine max (L.) Merr.). The dynamics of fine (0-2 mm) and small roots (2-5 mm) were assessed by sequentially collecting 35 cm deep, 5.4 cm diameter cores from April through November. Coarse roots were described by excavating 1 × 1 × 2 m pits and collecting all roots in 20 cm depth increments. Root distributions within the soil profile were determined by counting roots that intersected the walls of the excavated pits. Soil respiration was measured monthly from July to October using the soda-lime technique. Over the sampling period, live fine-root biomass in the top 35 cm of soil averaged over 6 Mg ha -1 for the coolseason grass, poplar, and switchgrass sites while root biomass in the crop fields was < 2.3 Mg ha -1 at its maximum. Roots of trees, cool-season grasses, and switchgrass extended to more than 1.5 m in depth, with switchgrass roots being more widely distributed in deeper horizons. Root density was significantly greater under switchgrass and cool-season grasses than under corn or soybean. Soil respiration rates, which ranged from 1.4-7.2 g C m -2 day -1 , were up to twice as high under the poplar, switchgrass and cool-season grasses as in the cropped fields. Abundant fine roots, deep rooting depths, and high soil respiration rates in the multispecies riparian buffer zones suggest that these buffer systems added more organic matter to the soil profile, and therefore provided better conditions for nutrient sequestration within the riparian buffers.

Besides aboveground interactions, pruning of trees may also modify their rooting pattern for which a better understanding is needed for the optimisation of agroforestry systems. Thus, variation in fine root (d ≤ 2 mm) distribution of pruned trees and crops were assessed during three cropping seasons by sampling soil layers at 10 cm intervals up to 50 cm and at four distances from tree trunk. Three crown pruning treatments (totally-pruning, half-pruning and no-pruning) were applied to karité (Vitellaria paradoxa) and néré (Parkia biglobosa). In 1999, 59% (0.477 cm cm −3) and 69% (0.447 cm cm −3) of fine roots for karité and néré respectively occurred in the upper 20 cm with a significant decrease in root length density with soil depth. However, in 2000, totally-pruned trees of néré and karité showed 32% (0.051 cm cm −3) and 34% (0.078 cm cm −3) of their density in the upper 20 cm whereas root distribution in 2001 was similar to that of 1999. Thus, pruning to reduce belowground competition for the benefit of associated crops can be recommended in the light of the temporary reduction of root density in crop rooting zone and consequently the increase in crop production.

We tested several hypotheses to explain the superior growth and nitrogen (N) status of lodgepole pine (Pinus contorta Dougl. ex Laws. var. contorta) compared with Sitka spruce (Picea sitchensis (Bong.) Carrière) on a N-poor site by comparing N distribution, N retranslocation, rooting distribution, and mycorrhizal fungi in plots of 11-year-old trees on a cedar-hemlock cutover. Aboveground N content was nine times greater in pine than in spruce of the same age, and thus, we conclude that pine acquired more N during the 11 years than spruce. Greater N acquisition by pine was not related to rooting depth, as both species rooted primarily in the residual forest floor. There were differences in mycorrhizal fungal associates: a high proportion of pine roots were infected with Suillus-like fungi. Pine produced more aboveground biomass per unit N (388 compared with 292 g•g-1 in spruce) and distributed more N to young foliage. Nitrogen retranslocation efficiency (based on foliar N contents in July and October) was higher in pine (50-52%) than in spruce (24-36%). These characteristics all appear to contribute to pine's abilities to both acquire more N and use it more efficiently and, thus, outperform spruce on this N-poor site. Résumé : Nous avons testé plusieurs hypothèses pour expliquer pourquoi le pin lodgepole (Pinus contorta Dougl. ex Laws. var. contorta) a une meilleure croissance et un meilleur bilan de l'azote (N) que l'épinette de Sitka (Picea sitchensis (Bong.) Carrière) sur un site pauvre en N. Des parcelles ont été établies dans un peuplement de cèdre et de pruche coupé à blanc où les arbres étaient âgés de 11 ans afin de comparer la distribution de N, la translocation de N, la distribution des racines et les champignons mycorhiziens. Le contenu en azote épigé était neuf fois plus élevé chez le pin que chez l'épinette du même âge. Par conséquent, nous concluons que le pin a emmagasiné plus de N que l'épinette au cours des onze années de croissance. La plus forte accumulation de N par le pin n'était pas liée à la profondeur de l'enracinement car le système racinaire des deux espèces se développait principalement dans la couverture morte résiduelle. Les champignons mycorhiziens associés aux deux espèces étaient différents. Une forte proportion des racines de pin étaient infectées par des champignons apparentés à Suillus. Le pin produisait plus de biomasse épigée par unité de N (388 comparativement à 292 g•g-1 pour l'épinette) et distribuait davantage de N vers le jeune feuillage. L'efficacité de la translocation de N, basée sur le contenu en N en juillet et octobre, était plus élevée chez le pin (50-52%) que chez l'épinette (24-36%). Ces caractéristiques semblent toutes contribuer à l'acquisition de plus de N et à son utilisation plus efficace par le pin qui déclasse l'épinette sur ce site pauvre. [Traduit par la Rédaction] Bothwell et al. 1279

Nitrogen (N) content in the soil and in the herbaceous biomass were monitored during spring of 2004e2006 to determine how the herbaceous layer development influences soil N availability in the montado ecosystem of southern Portugal. Highest (246.6 AE 52.7 g m À2) and lowest (123.2 AE 89.5 g m À2) peak biomass occurred in 2006 and 2005 respectively. Total soil N within the top 20 cm soil profile ranged between 0.2 AE 0.1% in February and 0.41 AE 0.2% in May, while available soil N was lowest (5 AE 2 mg g À1 soil) in February but increased three-to-five fold in March and was >17.5 mg g À1 soil at senescence in May. Significant (p < 0.001) increase in total N in the aboveground pool occurred between February and May. There was however, no decay in soil N content. Instead, the herbaceous vegetation enhanced soil N input and N retention in the ecosystem. Most of the herbaceous plants were annuals with large reserves of organic N at senescence, which returned to the soil as detritus. The herbaceous vegetation is a critical component of the montado that contributes to N recharge and cycling within the ecosystem.

A physically based model was developed to simulate changes in plant water use and soil water distribution over time. It was built from two main submodels which dealt with soil water flow and plant water uptake. The soil water flow submodel employed the Richards equation combined with vapour flow procedures to predict soil water distribution, deep drainage, and soil evaporation. The plant water uptake submodel used a potential driven approach in that it depended on the water potential gradient between the roots and soil matrix. The model was used to analyse the effects of rooting patterns on deep drainage, which is one of the main differences in plant properties between trees and annual crops or grasses. Root distribution affects plant water uptake, soil water distribution, and deep drainage. The deep drainage rate under Armidale (NSW, Australia) weather conditions is episodic in character and root distribution influences deep drainage during wet periods. From discussion of the optimal root distribution for an agroforestry system it was concluded that to prevent too much deep drainage, it may not be necessary to have only deep-rooted species present. Simulation can indicate the appropriate ratio of deeprooted trees to shallow-rooted crops or grasses in an agroforestry system where the aim is to minimise deep drainage while maximising the percentage of productive shallowrooted crops or grasses.

A physically based model was developed to simulate changes in plant water use and soil water distribution over time. It was built from two main submodels which dealt with soil water flow and plant water uptake. The soil water flow submodel employed the Richards equation combined with vapour flow procedures to predict soil water distribution, deep drainage, and soil evaporation. The plant water uptake submodel used a potential driven approach in that it depended on the water potential gradient between the roots and soil matrix. The model was used to analyse the effects of rooting patterns on deep drainage, which is one of the main differences in plant properties between trees and annual crops or grasses. Root distribution affects plant water uptake, soil water distribution, and deep drainage. The deep drainage rate under Armidale (NSW, Australia) weather conditions is episodic in character and root distribution influences deep drainage during wet periods. From discussion of the optim...

Determining fine‐root dynamics is fundamental to forest soil nutrient management yet root development of fast‐growing loblolly pine (Pinus taeda L.) is poorly documented. The objectives of this study were to (i) investigate the spatial and temporal root development of loblolly pine; (ii) evaluate the relationship between root length, number of roots exiting a trench face, and root mass densities; and (iii) determine if there is a relationship between fine root and foliage mass as well as root and shoot mass during the early stages of stand development. Thirteen forest sites in southeastern Georgia covering ages 1 to 4 yr old were used. Roots temporal and spatial distributions were investigated using a trench method. The value of NX (# roots cm−2) was measured in August/September during the first 4 yr of stand development. Root density depth distributions fit a natural logarithm relationship with soil depth. An empirical model for root development over time was developed. A two‐dimen...

The Australian Centre for International Agricultural Research (ACIAR) was established in June 1982 by an Act of the Australian Parliament. ACIAR operates as part of Australia's international development cooperation program, with a mission to achieve more productive and sustainable agricultural systems, for the benefit of developing countries and Australia. It commissions collaborative research between Australian and developing-country researchers in areas where Australia has special research competence. It also administers Australia's contribution to the International Agricultural Research Centres. Where trade names are used this constitutes neither endorsement of nor discrimination against any product by ACIAR. ACIAR MONOGRAPH SERIES This series contains the results of original research supported by ACIAR, or material deemed relevant to ACIAR's research and development objectives. The series is distributed internationally, with an emphasis on developing countries.

Most of the sandy land areas in northwest China belong to semi-arid
area and the average annual rainfall is about 250-500 mm. Sandy land
has the potential to reverse itself when man-made pressure is removed.
The specific permeability structure of sandy soil showed heterogeneous
anisotropy in the horizontal direction (x or y) of the soil surface (0-10cm)
and showed interlayer homogeneity and isotropy in the vertical direction
(z) of the underlying of soil surface, which formed rainfall infiltration
process of the special combination of both channel flow and capillary
flow percolation systems in sandy soil.

Inoculation of large-scale plant root culture reactors can be carried out by briefly homogenizing bulk root tissue, followed by aseptic transfer as a slurry to the reactor. Uniform root distribution can be achieved in bioreactors by entrapment of the growing root inoculum onto process packing elements (e.g. distillation packings), randomly distributed within the reactor, in a bubble column operation. These two techniques have been successfully used to inoculate a 14 L pilot-scale reactor which is subsequently operated as a trickle bed reactor.

Two field experiments were conducted at Evboneka in Edo State, Nigeria to determine the optimum fertilizer requirement of white guinea yam ( Dioscorea rotundata Poir) and to develop an efficient fertilization strategy for yam production in the rainforest locations of Nigeria. We examined the dry matter production and yield, besides growth parameters under five levels of NPK in 2005 and 2006. The treatments (0, 100, 200, 300, and 400 kg 15:15:15 NPK ha–1) were arranged in a randomized complete block design with three replications. Leaf area index (LAI) and dry matter content increased significantly as the quantities of fertilizer applied increased. LAI values ranged from 1.24 to 5.73 at 16 week after planting (WAP) and 2.77 to 6.37 at 24 WAP respectively for the unfertilized and 400 NPK kg ha–1 plots. The corresponding values for dry matter accumulation were 1.29 to 3.70 t ha–1 and 6.0 to 8.77 t ha–1 at 16 and 24 WAP respectively. These parameters resulted in higher crop growth rate ...

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