Field Capacity Conditions Research Articles

Field capacity: Methodological approach by static and dynamic criteria

Field capacity (FC) is one of the most cited soil physical parameters and is relevant for the management of agricultural systems. In the search for alternatives to the estimation of FC, several researchers have proposed methods based on dynamic and static criteria. Evaluating these methods within a range of soil textural classes is important for prospects of their uses with higher water use efficiency. Based on the hypothesis that FC for a certain soil textural class is exclusively associated with an equivalent pore diameter, D-threshold, which separates structural and textural porosity, and that textural pores define the FC conditions, this study aimed to: 1) estimate the equivalent pore diameter (D-threshold) which defines FC in each soil textural class in situ and, with the change of density, from the alterations in its water characteristic curve - WCC; 2) estimate the water content at FC in each soil textural class in situ and, with the change of density, from the alterations in its WCC. To obtain the water content corresponding to FC in situ, instantaneous profile-type experiments were conducted in five soil textural classes. To estimate FC and D-threshold based on the change in pore volume (CPV), soil water characteristic curves were used considering two situations: before and after compaction. Correlation and regression analyses were carried out between D-threshold and sand percentage, between water content at FC and the fitting parameters α and n of the model of van Genuchten (1980), and between the value of the tangent at the inflection point of the soil WCC and the parameter α. By comparing D-threshold values obtained by the field and CPV methods, it was possible to observe that for the range of textural classes analyzed, in general, D-threshold values obtained by CPV were different from those obtained in situ. Therefore, the methodological procedure CPV does not represent the actual D-threshold of the FC found under field conditions. The values of water content corresponding to FC obtained by the CPV protocol are not due to the physical aspect conceived in the method's proposal. Thus, since these values were not due to the D-threshold, this protocol cannot be indicated because it became evident that there was no clear cause-effect relationship. It was concluded that: 1) the principle of the method of estimating FC must be consistent with processes occurring in the soil. Since FC is dependent on soil processes, and associated with a drainage rate, there is no good reason why the CPV method correctly estimates the attribute; 2) the water content at FC in a certain soil textural class is not exclusively associated with only one equivalent pore diameter, D-threshold, so the hypothesis assumed in the study has not been confirmed; and 3) protocols based on soil water dynamics should preferentially be used to estimate FC, to the detriment of methods based on static criteria.

Putrescine Effect on Physiological, Morphological, and Biochemical Traits of Carrizo Citrange and Volkameriana Rootstocks under Flooding Stress

ABSTRACTWater stress problems including drought stress and flooding are the most important factors limiting in citrus growth, development and production. The main purpose of this study was to investigate the effects of putrescine on reducing negative effect of flooding of Carrizo Citrange (Citrus sinensis Osb. × Poncirus trifoliata Raf.) and Volkameriana (Citrus volkameriana) rootstocks under flooding condition. Three concentrations of putrescine [0.0, 1.0 and 2.0% (w/v)] were sprayed on all the leaves of two mentioned rootstocks in a factorial experiment in a completely randomized design under flooding and field capacity conditions. In comparison to the field capacity condition, growth vegetative indicators, RWC, SPAD unit, stomatal conductance (gs), chlorophyll a and b content, chlorophyll fluorescence yield (Fv/Fm), and CO2 assimilation rate (AcO2) decreased in the flooded seedlings whereas intercellular CO2 concentration (Ci), SOD, and CAT antioxidant enzymes activities increased. Putrescine foliar application particularly in 2 mM concentration, resulted in a decrease in the intercellular CO2 concentration and an increase in the other study values. Overall, putrescine could help seedlings against flooding stress through increasing growth, improving physiological statuses, and reducing oxidative damages.

The characteristics of soil water and gas transport under different land use patterns in the water-wind erosion crisscross region

Understanding the effects of land use patterns on soil water and gas transport in the water-wind erosion crisscross region can provide guidance for high-efficiency use of limited soil and water resource in the ecological rehabilitation process on the Loess Plateau. To investigate the cha-racteristics of soil water and gas transport under different land use patterns and to study the relationships between soil saturated hydraulic conductivity (Ks), air permeability (Ka) and relative gas diffusivity (DP/D0), we collected soil samples (0-5 cm depth) from Caragana korshinskii land, abandoned land, alfalfa land, cropland, and bare land. Ks was measured by constant-head method. DP/D0 was measured by gas chamber method. Ka under field capacity (FC) was measured using the soil gas permeability meter. Results showed that soil bulk density (ρb) ranked as alfalfa land>bare land>abandoned land>C. korshinskii land >cropland, with that of abandoned land, bare land and alfalfa land being significantly different from that of cropland. Total soil porosity (Φ) ranked as cropland>C. korshinskii land>abandoned land>bare land>alfalfa land. Compared with cropland, Φ of alfalfa land, bare land and abandoned land was lower by 7.5%, 4.7% and 3.1%, respectively. Air filled porosity (ε100) ranked as cropland>abandoned land>C. korshinskii land>bare land>alfalfa land. ε100 of alfalfa land, bare land, C. korshinskii land and abandoned land was lower by 38.3%, 33.6%, 12.8% and 10.1%, respectively, as compared with cropland. Soil Ks ranked as abandoned land>C. korshinskii land>alfalfa land>bare land>cropland, with that of the abandoned land being significantly higher than the other four land use patterns. Soil Ka ranked as abandoned land>alfalfa land>C. korshinskii land>bare land>cropland, with that of abandoned land being significantly diffe-rent with cropland. Soil DP/D0 ranked as abandoned land> C. korshinskii land> alfalfa land>cropland>bare land, in which DP/D0 of C. korshinskii land and abandoned land was significantly higher than cropland by 36.8% and 61.6%, respectively. There were significant correlations between Ks and Ka, DP/D0 under FC conditions. Land use patterns significantly changed soil permeability. Farmland, abandonment, C. korshinskii, and alfalfa plantation improved hydraulic and gas transport parameters of the surface soil. In contrast, farmland and bare land had poor capability of soil water and gas transport.

Fortified fertilizer application in wheat (Triticum aestivum L.) grown under water stress condition

Abstract Water stress is a major threat against wheat growth. The effects of induced stress can be reduced after by fortified fertilizer treated by Plant Growth Promoting Bacteria (PGPB). With the objective to combat the water stress, two different experiments under net house and field condition were conducted. Three different states of fertilizer [F0: Control (no fertilizer application); F1: PGPB-coated fertilizer (urea and phosphorous) &F2: uncoated fertilizer (urea and phosphorous)]. In a pot experiment, wheat plants were applied fertilizer in raised and well-watered (60 percent of field capacity) and water stressed (40 percent of field capacity) conditions in soil filled pots. In experiment-II (field study), similar treatments of fertilizer were revised, but well-watered and water stress treatments/plots were irrigated for 60 seconds and 30 seconds respectively. At maturity plants were harvested and various morphological (number of tillers/plant, number of spikelet/spike, number of grains/spike, weight of grains, biological yield, economic yield and harvest index) and biochemical parameters (leaf nitrogen, phosphorous & potassium contents) of crop were recorded. Leaf chlorophyll and relative water contents of crop were also measured 60 days after sowing. In this study, it was demonstrated that the water stress adversely affected all the above mentioned parameters. The PGPB coated fertilizer application in wheat significantly increased (p<0.01 for pot and p<0.05 for field study) morphological and biochemical parameters in the presence and absence of water stress both under net house and field conditions. We can conclude from these findings that application of PGPB coated fertilizer is valuable strategy to mitigate the water stress impact on wheat with improved yield. Keywords: Coated fertilizer; Un-coated fertilizer; PGPB; Chlorophyll; Harvest inde http://dx.doi.org/10.19045/bspab.2019.80037

Does biochar mitigate the adverse effects of drought on the agronomic traits and yield components of soybean?

Drought and low amounts of organic matter are two main constraints when considering agriculture in arid and semiarid regions. The two constraints and their adverse effects on soils and plants may be alleviated by biochar (B). Therefore, this study aimed to evaluate the influence of 0 (0B), 1.25 (1.25B), 2.5 (2.5B) and 5% wt (5B) cattle-manure biochar on the agronomic and physiological traits of soybean under field capacity (FC), 0.7FC and 0.55FC conditions. Drought was observed to reduce water use efficiency (WUE), leaf area, stomatal conductance (SC), harvest index (only for 0.55FC), straw fresh matter yield (SFMY), straw dry matter yield (SDMY), pod yield, grain yield, pod lenght, and plant height by nearly 15–16%, 23–36%, 23–47%, 11–12%, 42–64%, 36–52%, 44–65%, 41–64%, 5–11%, and 33–60%, respectively as compared with those of control (FC conditions), whereas drought increased the greenness index (GI) of soybean leaves by 11–20% compared with control. In general, drought decreased all traits of studied soybean variety. However, pod yield, grain number, SFMY and plant height were more negatively influenced. The most unfavorable effect of drought on SC was observed at the late reproductive stage (90 days after planting, DAP); whereas, drought effects on leaf area were similar at different growth stages. Harvest index (HI) and WUE was the lowest at severe drought (0.55FC) and there was no significant difference between these traits at non-drought (FC) and moderate drought (0.7FC) conditions. Therefore, keeping soil moisture to near 0.7FC not only did not change the WUE and HI, but also reduces water consumption. All B treatments increased the leaf area (at the beginning, 60 DAP and middle reproductive stages, 75 DAP), GI and SC by 6–36%, 11–20%, and 46–80%, respectively. The application of 1.25B increased WUE, SFMY, SDMY, the pod length and plant height by 26%, 35%, 27%, 5%, and 16%, respectively, whereas higher percentages of B were ineffective, i.e. 2.5B did not significantly affect the WUE, SDMY and pod length and 5B reduced the values of the grain and pod yield and 1000-grain weight. Low level of biochar (1.25B) had positive influences on almost all traits; whereas, higher levels (2.5B and 5B) due to the excessive salinity not only had no positive effects but also adversely influenced almost all traits. Furthermore, positive effects of the effective biochar treatment (1.25B) on almost all traits were most pronounced at the moderate or severe drought conditions compared with non-drought conditions. In conclusion, high levels of B due to salinity related negative influences on plant cannot be suggested. While, application of 1.25B due to mitigating the adverse effects of drought and consequently increasing WUE, the growth and yield components of soybean may be recommended.

PERTUMBUHAN PADI GOGO DI MEDIUM ULTISOL DENGAN PEMBERIAN CAMPURAN FOSFAT ALAM DAN COCOPEAT PADA DUA KONDISI KADAR AIR

The main problem of upland rice cultivation in Ultisol are fixation of P, solubility and saturation of Al are the height and water content is low. The research aim to study the effect of interaction of application of mixture of cocopeat with rock phosphate (RP) on growth of upland rice in Ultisols medium at two water content condition. The research was conducted at the Green House of the Faculty of Agriculture, University of Riau, Pekanbaru from February to July 2017. This research in form factorial experiment was arranged in a completely randomized design. The first factor was mixture of RP with cocopeat consist of 7 levels (0, 30, 45 and 60 kg P2O5/ha each dose + cocopeat dose 10 tons/ha and 30, 45 and 60 kg P2O5/ha without cocopeat). The second factor was water content consists of 2 levels (field capacity and 25% under field capacity), each combination repeated 3 times. The results show the application of rock phosphate dose of 30 kg P2O5/ha + 10 tons cocopeat/ha or without cocopeat increased the growth of upland rice include plant high, number of maximum tiller and productive tiller and dry weight of straw compared to without RP both on the field capacity and 25% below field capacity condition, the increasing of RP dose to 45-60 kg P2O5/ha tended to increase each parameter.Key words : rock phosphate, water content, cocopeat, upland rice.

How good are the predictions of mobility of aged polychlorinated biphenyls (PCBs) in soil? Insights from a soil column experiment

A column leaching experiment was performed to evaluate the influence of some relevant environmental factors (soil/water contact time, temperature, saturation) on mobility of aged polychlorinated biphenyls (PCBs) in soil together with transport mediated by dissolved organic carbon (DOC) and mobile organic carbon (OC) coated fine particles/colloids. Consecutive fractions of leachates were collected after a variable pre-equilibration time (2, 5, 7, 48 days), using leaching solutions with different DOC content (tap water vs. Aldrich humic acid), in saturated vs. field capacity conditions and at different temperatures (25 °C vs. 15 °C). The data obtained were compared to the predicted values using a multimedia model (SoilPlusVeg) to evaluate model behaviour. Contact time and temperature determined a relevant effect on DOC and particle/colloid availability, with significant variations in leachate concentrations (up to 1 order of magnitude), typically overlooked by most environmental fate models. Results obtained at different temperatures show a modulation of the DOC/particles production with temperature and therefore the role of temperature changes in the environmental scenarios (e.g. seasonal variations). Transport of PCBs enhanced by Aldrich DOC was not linearly correlated to chemical hydrophobicity but revealed a threshold to ~Log KOW 6.5, likely because of the slow sorption kinetics of more hydrophobic chemicals. Additionally, variation of the saturation conditions (e.g. drying-wetting cycles) can determine contamination peaks at the beginning of an irrigation/rainfall event because of the soil/water equilibration. Model simulations, even when including DOC in the water phase, but not accounting for the particle/colloidal transport and sorption/desorption kinetics, mismatched the ratio of dissolved vs. DOC-associated and particle-associated PCBs and substantially underpredicted concentrations, especially for the high chlorinated congeners. The results indicated that some of the common assumptions and paradigms in fate modelling of such hydrophobic compounds should be revisited and models updated.

Multi-surface modeling of Ni(II) and Cd(II) partitioning in soils: Effects of salts and solid/liquid ratios

Metal partitioning in soils is a key process controlling metal bioavailability and mobility and is greatly influenced by the solid/liquid ratio. However, metal partitioning is difficult to describe either by a simple partition coefficient or by isotherm adsorption equations. This study investigated the solubility of Ni(II) and Cd(II) in 19 soils as a function of three extraction reagents (water, 0.01 M NaNO3, and 0.01 M CaCl2), five solid/liquid ratios (5–400 g/L) and field condition extracted by Rhizon samplers. Thermodynamically based multi-surface models (MSMs) that included generic parameters were used to describe metal partitioning under the studied conditions. The results showed that Ni/Cd solubility depended on the soil type, extraction reagent, and solid/liquid ratio. Soil major background cations (especially Ca2+, Mg2+, Fe3+ and Al3+) had a significant effect on the model's prediction ability. The MSM was able to predict the extractable metal in 0.01 M CaCl2 in various soils at different solid/liquid ratios when soil background cations were included in the calculation; without the background cations, the model was able to predict metal partitioning only at solid/liquid ratios of <100 g/L. In addition, the model failed to predict water-extracted and 0.01 M-NaNO3-extracted Ni/Cd if background cations were not included, but could reasonably do so if they were included. More importantly, after the background cations were included, MSMs relatively well predicted the Ni/Cd content in soil pore water under 80% field capacity conditions with water as the solution matrix.

Arsenic effects on some photophysical parameters of Cichorium intybus under different radiation and water irrigation regimes

The presence of arsenic (As) in groundwater is a major problem in several parts of Latin America. In the present work, non-destructive approaches to monitor the effects of As on plants of Cichorium intybus, an herbaceous Asteraceae, were explored. In this sense, the effects of As at different levels of water and radiation were evaluated on these crops. Plants were grown in a greenhouse, watered daily with As solutions and exposed to different water and/or light conditions for four months, using a three-factor (As, water, radiation) and two-level resource (As vs non As, field capacity vs half-field capacity condition, light vs shade condition) factorial design. The parameters most affected by this treatment were the area under the first derivative of the reflectance spectrum in the blue region, chlorophyll concentration, the Fred/Ffar-red fluorescence ratio and the quantum yield for the photophysical decay. These changes indicated the ability of this plant species to be a biomonitor for the presence of arsenic in irrigation water. Interestingly, it was further proved in this work that the biomonitoring capacity was enhanced in the presence of sunlight.

Availability and Transformations of Phosphorus in Calcareous Sandy Soil as Affected by Farmyard Manure and Elemental Sulfur Applications

An incubation experiment was conducted to study the effects of farmyard manure (FYM) and elemental sulfur (S) on availability, fractionation and transformation of phosphorus in calcareous sandy soil. Soil samples were treated with FYM at levels: 0 (FYM0), 2.5 (FYM1), 5 (FYM2) and 7.5 (FYM3) g pot−1 and S at levels: 0 (S0), 0.1 (S1), 0.2 (S2) and 0.3 (S3) g pot−1. The soil was incubated for ten weeks under field capacity conditions. Additions of FYM caused significant increases in the amount of available P (Olsen−P) from 34.57 to 44.54 mg kg−1. The S with FYM application significantly increased Olsen−P of this soil at S1FYM1 from 42.95 to 52.70 mg kg−1. Significant reduction in Olsen−P was observed at S2 and S3 levels, but the addition of S at S1 level led to its insignificant increase. FYM application transformed HCl-Pi, NaOH II-Pi and residual P to NH4Cl-P, NaHCO3-Pi, NaHCO3-Po, NaOH I-Pi, NaOH I-Po and NaOH II-Po fractions. Application of S converted the NH4Cl-P, NaOH I-Pi and HCl-Pi fractions to NaHCO3-Pi, NaHCO3-Po, NaOH I-Po, NaOH II-Pi, NaOH II-Po and residual P fractions. It’s recommended adding FYM to calcareous sandy soils as well as adding S combined with FYM to improve the soil properties.

Legume Plant Growth at Various Levels of Drought Stress Treatment

A strategic alternative step for the development of cultivation of feed crops is to optimize the use of dry land that has the potential for agricultural and livestock business. One of the forage plants that has good adaptation to less good soil condition and is a pioneer plant, Pueraria javanica legume, so it can be considered as a potential alternative forage as animal feed. The research aims at determining the effect of various levels of drought stress treatment on the plant hight, fresh matter production, dry matter production and root biomass of Pueraria javanica legume. The experiment was conducted in the Greenhouse of the Agriculture Faculty of Universitas Sumatera Utara. The experiment was carried out using a completely randomized design (CRD) with 3 treatments and 4 replications. The treatments were A1 (25% field capacity (FC)=144 ml/polybag, A2 (50% FC)=288 ml/polybag and A3 (100% FC)=576 ml/polybag. The results show that Pueraria javanica legume can survive and grow up to severe drought stress (25% FC) but the crop production does not increase when compared to the field capacity condition; besides, the legume cannot survive longer in drought condition. The volume of water supplied corresponding to the field capacity makes the plant growth better.

Cattle manure biochar potential for ameliorating soil physical characteristics and spinach response under drought

ABSTRACTDrought and low amounts of organic matter are two main constraints in arid and semiarid regions and their adverse effects on soils and plants can be alleviated by biochar (B). Therefore, the influence of 0 (0B), 1.25 (1.25B), 2.5 (2.5B) and 5% (5B) cattle-manure biochar on the growth and physiological traits of spinach and physical characteristics of postharvest soil under field capacity (FC), 0.7FC and 0.55FC conditions was evaluated. Drought decreased stomatal conductance (SC), water use efficiency (WUE), shoot dry matter yield (SDMY), soil water repellency (WR) and saturated hydraulic conductivity (Ks) by 13–45%, 3–17%, 27–51%, 48–60% and 26–36%, respectively. Whereas, all B treatments increased SC, Ks and total porosity by 11–63%, 82–221% and 2–12%, respectively. Application of 1.25B increased SDMY and WUE, whereas higher B levels were ineffective, i.e. 2.5B did not significantly affect the measured parameters and 5B reduced them. At all B levels, drought reduced SDMY. However, the lowest decrease in SDMY was observed by 1.25B. Despite their positive influence on soil’s physical quality, high B levels induced excessive salinity. Therefore, a low B level (1.25B) may be recommended since it provides positive impacts on the plant’s growth and yield while mitigating the adverse effects of drought.

Environmental Factors Moderate Glyphosate-induced Antagonism of POST Herbicides on the Rapid Response Biotype of Glyphosate-Resistant Giant Ragweed (Ambrosia trifida)

AbstractIn the rapid response (RR) biotype of glyphosate-resistant (GR) giant ragweed (Ambrosia trifidaL.), exposure to glyphosate elicits H2O2production in mature leaves, resulting in foliage loss and reduced glyphosate translocation. When glyphosate is applied with POST herbicides intended to improve control ofA. trifida, the RR to glyphosate has the propensity to antagonize these herbicide combinations. This research documents how transient changes in air temperature, soil moisture, and light intensity during a 6-d period surrounding herbicide application regulate induction of the RR and the effect on POST herbicide interactions with glyphosate. Air temperature had the greatest influence on H2O2accumulation in leaf disks following treatment with glyphosate, as plants at 30 C produced more than twice the amount of H2O2at 2.5 h after treatment compared with 10 C. Plants under field capacity conditions accumulated nearly 50% more H2O2than those at one-third field capacity, while those under no shade had only 18% more H2O2compared with those in a shaded environment. Despite these initial results, dry weight reduction at 21 d after treatment never differed by more than 8% between levels of environmental factors, thus indicating a negligible influence on glyphosate efficacy. The magnitude of glyphosate-induced antagonism was generally greater at 30 C (12% to 21% less than expected control) versus 10 C (11% to 16%) on atrazine, cloransulam, dicamba, and topramezone and was greater at field capacity (20% to 24%) versus one-third field capacity (11% to 15%) on cloransulam and topramezone. These results indicate air temperatures and soil moisture levels conducive to optimal plant growth accelerate the RR to glyphosate, thereby increasing the likelihood of glyphosate-induced antagonism on several translocated herbicides.

Effect of Biochar Application on Hydraulic Properties of Sandy Soil under Dry and Wet Conditions

Core Ideas High doses of biochar increased water retention of sandy soil in both dry and wet conditions. Larger sized biochar decreased water retention at field capacity (FC). High‐pyrolysis biochar could increase water retention at FC and in dry conditions. We investigated the impact of biochar application on the evaporation rate of sandy soil. Knowledge of soil hydraulic properties under dry (below permanent wilting point) and wet (from saturation to permanent wilting point) conditions is helpful for evaluating soil physical quality and modeling the movement of the substances (water and nutrients) in biochar‐amended soils. To investigate the effect of biochar application on hydraulic properties of sandy soil under dry and wet conditions, water retention in wet conditions and soil drying curves from wet to dry conditions were measured under different application rates (1, 3, and 5%, w/w), particle sizes (&lt;0.25, 0.25–0.5, 0.5–1, and 1–2 mm), and pyrolysis temperatures (300, 450, and 600°C) of wheat (Triticum aestivum L.) straw‐derived biochar. Results showed that when higher rate biochar (3 and 5%) was applied into the sandy soil, water retention became higher under dry and wet conditions. Biochar application with a larger particle size (0.5–1 and 1–2 mm) increased water retention under saturation and dry conditions but decreased water retention at field capacity. Sandy soil amended with biochar at the higher pyrolysis temperatures (450 and 600°C) had higher water retention under field capacity or dry conditions. Increasing biochar application rate, particle size, and pyrolysis temperature decreased the evaporation rate of sandy soil under dry conditions. Our findings suggested that hydraulic properties of the sand–biochar mixture were mainly determined by biochar properties under dry conditions and were highly related to the interpores between particles under wet condition.

Burn effects on soil properties associated to heat transfer under contrasting moisture content

The aim of this work is to investigate the topsoil thickness affected by burning under contrasting soil moisture content (field capacity versus air-dried conditions). A mollic horizon of an Aleppo pine forest was sampled and burned in the laboratory, recording the temperature continuously at the topsoil surface and at soil depths of 1, 2, and 3cm. Changes in soil properties were measured at 0–1, 1–2, 2–3, and 3–4cm.Both the maximum temperature and the charring intensities were significantly lower in wet soils than in air-dried soils up to 3cm in depth. Moreover, soil heating was slower and cooling faster in wet soils as compared to dry soils. Therefore, the heat capacity increase of the soil moistened at field capacity plays a more important role than the thermal conductivity increase on heat transfer on burned soils. Burning did not significantly modify the pH, the carbonate content and the chroma, for either wet or dry soil. Fire caused an immediate and significant decrease in water repellency in the air-dried soil, even at 3cm depth, whereas the wet soil remained hydrophilic throughout its thickness, without being affected by burning. Burning depleted 50% of the soil organic C (OC) content in the air-dried soil and 25% in the wet soil at the upper centimeter, which was blackened. Burning significantly decreased the total N (TN) content only in the dry soil (to one-third of the original value) through the first centimeter of soil depth. Soluble ions, measured by electrical conductivity (EC), increased after burning, although only significantly in the first centimeter of air-dried soils. Below 2cm, burning had no significant effects on the brightness, OC, TN, or EC, for either wet or dry soil.

Improvement of drought tolerance in Tobacco (Nicotiana rustica L.) plants by Silicon

ABSTRACTAmeliorative effect of silicon (Si) (2 mM as sodium silicate (Na2SiO3)) was studied in tobacco (Nicotiana rustica L.) plants grown under control at 100% field capacity (FC), mild drought (60% FC), and severe drought (30% FC) conditions. Si-treated plants had higher biomass of particularly above-ground parts both under drought and control conditions. Plants with Si supply had significantly higher net assimilation rates but lower transpiration rates. Silicon supply enhanced osmotic potentials only in the leaves, but not in the roots. A considerable rise in the concentrations of soluble sugars was observed particularly in the leaves under both drought and Si treatments. Soluble proteins, free α-amino acids, and proline concentrations increased in Si-treated plants under all watering treatments. Si enhanced the activity of antioxidative enzymes and decreased hydrogen peroxide (H2O2) concentrations. Results indicate that Si supplementation alleviates drought stress via improvement of water relation parameters, enhancement of photosynthesis, and elevation of antioxidant defenses.

Susceptibility of peruvian watergrass and rice cutgrass to glyphosate under soil moisture variations

Peruvian watergrass and rice cutgrass are important grass weeds in paddy rice in southern Brazil, mainly due to the low efficacy of non-selective herbicides against these species. The objectives of this study were (1) to evaluate the susceptibility of peruvian watergrass to glyphosate under soil moisture variations, (2) to investigate the effect of soil moisture variations in the control efficiency of glyphosate on peruvian watergrass and rice cutgrass, and (3) to determine the leaf blade and stem anatomical features of both species under flood conditions. Three experiments were conducted, two in a greenhouse and one in laboratory conditions. The first experiment was conducted using three soil water contents (field capacity, saturated and flood conditions) and nine doses of glyphosate to evaluate peruvian watergrass control and dry biomass reduction. The same factors and evaluations were used in the second experiment, however with the addition of the rice cutgrass species. Plants of both species, grown under flood conditions, were collected for histological analysis in the third trial. The susceptibility of these grass weeds was greatly reduced under flood conditions, particularly peruvian watergrass. There were anatomical differences between the two species, but these may not influence the efficacy of the chemical control. Their morphological differences are therefore expected to be involved in their tolerance to glyphosate.

Parthenium weed (Parthenium hysterophorus L.) and climate change: the effect of CO2 concentration, temperature, and water deficit on growth and reproduction of two biotypes.

Climate change will have a considerable impact upon the processes that moderate weed invasion, in particular to that of parthenium weed (Parthenium hysterophorus L.). This study evaluated the performance of two Australian biotypes of parthenium weed under a range of environmental conditions including soil moisture (100 and 50% of field capacity), atmospheric carbon dioxide (CO2) concentration (390 and 550ppm), and temperature (35/20 and 30/15°C/day/night). Measurements were taken upon growth, reproductive output, seed biology (fill, viability and dormancy) and soil seed longevity. Parthenium weed growth and seed output were significantly increased under the elevated CO2 concentration (550ppm) and in the cooler (30/15°C) and wetter (field capacity) conditions. However, elevated CO2 concentration could not promote growth or seed output when the plants were grown under the warmer (35/20°C) and wetter conditions. Warm temperatures accelerated the growth of parthenium weed, producing plants with greater height biomass but with a shorter life span. Warm temperatures also affected the reproductive output by promoting both seed production and fill, and promoting seed longevity. Dryer soil conditions (50% of field capacity) also promoted the reproductive output, but did not retain high seed fill or promote seed longevity. Therefore, the rising temperatures, the increased atmospheric CO2 concentration and the longer periods of drought predicted under climate change scenarios are likely to substantially enhance the growth and reproductive output of these two Australian parthenium weed biotypes. This may facilitate the further invasion of this noxious weed in tropical and sub-tropical natural and agro-ecosystems.

Selenium Supplementation Affects Physiological and Biochemical Processes to Improve Fodder Yield and Quality of Maize (Zea mays L.) under Water Deficit Conditions.

Climate change is one of the most complex challenges that pose serious threats to livelihoods of poor people who rely heavily on agriculture and livestock particularly in climate-sensitive developing countries of the world. The negative effects of water scarcity, due to climate change, are not limited to productivity food crops but have far-reaching consequences on livestock feed production systems. Selenium (Se) is considered essential for animal health and has also been reported to counteract various abiotic stresses in plants, however, understanding of Se regulated mechanisms for improving nutritional status of fodder crops remains elusive. We report the effects of exogenous selenium supply on physiological and biochemical processes that may influence green fodder yield and quality of maize (Zea mays L.) under drought stress conditions. The plants were grown in lysimeter tanks under natural conditions and were subjected to normal (100% field capacity) and water stress (60% field capacity) conditions. Foliar spray of Se was carried out before the start of tasseling stage (65 days after sowing) and was repeated after 1 week, whereas, water spray was used as a control. Drought stress markedly reduced the water status, pigments and green fodder yield and resulted in low forage quality in water stressed maize plants. Nevertheless, exogenous Se application at 40 mg L-1 resulted in less negative leaf water potential (41%) and enhanced relative water contents (30%), total chlorophyll (53%), carotenoid contents (60%), accumulation of total free amino acids (40%) and activities of superoxide dismutase (53%), catalase (30%), peroxidase (27%), and ascorbate peroxidase (27%) with respect to control under water deficit conditions. Consequently, Se regulated processes improved fodder yield (15%) and increased crude protein (47%), fiber (10%), nitrogen free extract (10%) and Se content (36%) but did not affect crude ash content in water stressed maize plants. We propose that Se foliar spray (40 mg L-1) is a handy, feasible and cost-effective approach to improve maize fodder yield and quality in arid and semi-arid regions of the world facing acute shortage of water.

Effects of arsenic and moisture regime on nutrient content and their uptake by NERICA rice

A pot experiment was carried out in the net house of Bangladesh Institute of Nuclear Agriculture (BINA) to study nutrient content and their uptake by different rice varieties (NERICA-1, NERICA-10 and BRRI dhan48) in response to different levels of arsenic (As) under varying moisture regimes. Three levels of As were added viz. 0, 30, 60 ppm to the pot soil from sodium arsenate (Na2HAsO4. 7H2O). After establishment of crops the moisture level of soil was adjusted to maintain flooded, 50% and 100% field capacity condition during crop growing period. The experiment was laid out in a Completely Randomized Design (CRD), with three replications. The amount of N, P, K, S and Zn was calculated as per their rate of application and was applied to the individual pot. Higher levels of As adversely affected the nutrient content and their uptake by rice except N contents. Nitrogen content increased with the increase of As level. Higher amount of nutrient content and uptake was recorded in BRRI dhan48 and flood condition enhanced higher nutrient content as well as uptake by rice. This study suggests the possible management of moisture regime and considering less As susceptible variety, which might reduce the toxic effects of As on nutrient uptake.J. Bangladesh Agril. Univ. 12(2): 291-296, December 2014