Semi-arid Pasture Research Articles

The Relationship between the Sensitivity to Rill Erosion and Soil Physical Degradability Due to the Land Use Change in Semi-Arid Pastures

The Relationship between the Sensitivity to Rill Erosion and Soil Physical Degradability Due to the Land Use Change in Semi-Arid Pastures

Fitness benefits of grouping during foraging in beef cattle: Social behaviour or affinity to vegetation resources?

Grouping behaviour in gregarious species expresses a dynamic cost-benefit equilibrium. The balance between costs and benefits differs amongst individuals that were selected to maximize their individual fitness. In environments where resources are limited, benefits of grouping may come at the expense of increased competition over resources. This study aimed to test whether grouping behaviour during foraging in a free-ranging beef cattle herd is a social choice bearing fitness benefits for all participants, or reflects affinity to vegetation resources with possible differentiating fitness benefits. GPS location data were recorded in a herd of 60 beef cows grazing a semi-arid pasture in northern Israel. Pasture vegetation was chemically and spectrally analysed. GPS location data were used to investigate individual and shared foraging locations and the temporal sequence of initiating foraging movement. Co-travel function in ArcPro v3.0 was used to investigate the amount and variability of individual proximity associations and their correlation with fitness. Fitness proxies were conception result (yes/no) and the interval between calving and conception within the cows who conceived. A positive correlation was found between fitness and the individual number of proximity associations, but not with the variability in associations' partners. No significant correlations were found between fitness and vegetation biomass, N content and spectral properties measured by REEVI2 index in foraging locations. Individual sequence of arrival at shared foraging locations and foraging movement initiation sequence were also not correlated with fitness. Vegetation biomass in grouping locations was lower than in individually foraged locations, but no difference was found in N content between individual and shared foraging locations. No differences were found in vegetation biomass and N content between herd foraging locations and random locations, thus no evidence for herd foraging strategy aimed to increase biomass or N consumption was found. No further differences in pasture resources availability, i.e., water, shade, human or predator presence could explain grouping. Circular variance values implied the absence of preferred movement direction. Our results suggest that grouping during foraging is fitness beneficial and is not related to vegetation biomass or N content. Our results further suggest the absence of consistent leading individuals and no significant correlations between foraging movement initiation and fitness. This study provides insights into social and vegetation factors affecting cattle foraging behaviour in constrained pasture, and may allow ranchers to improve grazing management systems. We suggest that further research into pasture characteristics that affect beef cattle pasture location choice is needed.

Effect of Long-Term Semiarid Pasture Management on Soil Hydraulic and Thermal Properties

Semiarid pasture management strategies can affect soil hydraulic and thermal properties that determine water fluxes and storage, and heat flow in unsaturated soils. We evaluated long-term (>10 years) perennial and annual semiarid pasture system effects on saturated hydraulic conductivity (ks), soil water retention curves (SWRCs), soil water thresholds (i.e., volumetric water content (θv) at saturation, field capacity (FC), and permanent wilting point (PWP); plant available water (PAW)), thermal conductivity (λ), and diffusivity (Dt) within the 0-20 cm soil depth. Forage systems included: Old World bluestem (Bothriochloa bladhii) + legumes (predominantly alfalfa (Medicago sativa)) (OWB-legume), native grass-mix (native), alfalfa + tall wheatgrass (Thinopyrum ponticum) (alfalfa-TW), and annual grass-mix (annual) pastures on a clay loam soil; and native, teff (Eragrostis tef), OWB-grazed, and OWB-ungrazed pastures on a sandy clay loam soil. The perennial OWB-legume and native pastures had increased soil organic matter (SOM) and reduced bulk density (ρb), improving ks, soil water thresholds, λ, and Dt, compared to annual teff and alfalfa-TW (P < 0.05). Soil λ, but not Dt, increased with increasing θv. Grazed pastures decreased ks and water retention compared to other treatments (P < 0.05), yet did not affect λ and Dt (P > 0.05), likely due to higher ρb and contact between particles. Greater λ and Dt at saturation and PWP in perennial versus annual pastures may be attributed to differing SOM and ρb, and some a priori differences in soil texture. Overall, our results suggest that perennial pasture systems are more beneficial than annual systems for soil water storage and heat movement in semiarid regions.

Rainfed-based production of Megathyrsus maximus in sub-Saharan Africa: the case of the semi-arid environment of Sudan

The performance of rainfed-based Megathyrsus maximus (syn. Urochloa maxima and Panicum maximum) was investigated in the semi-arid pastures of Sudan. Split-plot complete design experiments with three replications were applied for two consecutive seasons (2020–2021). The treatments were two in situ rainwater harvesting systems [i.e. ridges plus terraces (RD) and terraces (TR)], three seeding rates (i.e. 1.5, 2.5 and 3.5 kg ha−1) and two urea fertilisation rates [0 kg ha−1 (Z) and 95 kg ha−1 (F)]. These treatments were compared to a control (a flat, unfertilised and zero-tillage plot). Hydrological, biological and chemical indicators were used in the assessment. The results showed that the adopted RWH improved semi-arid pastures, with the RD treatment providing the best results for sustaining biomass production, water use efficiency, nutritional quality and soil quality. The highest plant density (112 000 plants ha−1) was associated with the RD3.5 treatment. The FSR1.5-RD treatment resulted in the greatest plant length (63.5 cm) and number of leaves per plant (34.59), whilst the FSR3.5-RD resulted in both the highest fresh biomass (25.9 t ha−1) and dry biomass (6.3 t ha−1). The chemical compositions of M. maximus (i.e. crude protein, organic matter and nitrogen contents) were also substantially improved by fertilisation. The water use efficiency of M. maximus was plant-, management- and climate-dependent.

Location assessment for producing biodiesel fuel from Jatropha Curcas in Iran

Biofuels are considered renewable sources of energy which can replace fossil fuels using naturally extracted fuels from the environment to fulfil growing demands for energy in developing countries. This paper aims to select a suitable province for producing biodiesel from Jatropha plants in new climate conditions of Iran using the additive ratio assessment method (ARAS). Previous feasibility studies lack the environmental factor when considering the cultivation of Jatropha plants in Iran. In this work, the relevant main selecting criteria were identified through using a literature review. Then, the most effective criteria were chosen and categorised as environmental, social and economical factors. The weighting of the criteria was determined by Shannon entropy method and using expert opinions. Next, the ARAS method was used for prioritizing the provinces in Iran. From the results, it is observed that the environmental factor is the key parameter for selecting biodiesel plant location. Furthermore, Golestan province was selected as the best candidate location in Iran for establishing a biodiesel plant using Jatropha plants. Using the semi-arid pastures of Golestan province (about 402,000 Hectares), 1,930,000 tons biodiesel can be produced annually for supplying the fuel to 600,000 diesel cars.

On-farm evaluation of regenerative land-use practices in a semi-arid pasture agroecosystem in West Texas, USA

ABSTRACT Continually rising scarcity in water and nutrient resources, especially in semi-arid agricultural systems, combined with increased frequency of extreme weather events such as drought, contribute to a growing need for resilient and regenerative agricultural ecosystems. However, evaluating a myriad of combinations of producer-led sustainable management practices in on-farm research remains challenging. Few studies have elucidated spatial variability in measured soil properties across the study area due to logistical and economic constraints. As such, this study aimed to: 1) establish [...]

Compost and legume management differently alter soil microbial abundance and soil carbon in semiarid pastures

AbstractEstablishment of improved perennial pasture systems for livestock production has been demonstrated to improve soil health in the semiarid Texas Southern High Plains (SHP). Use of waste products from other components of the animal production chain, such as applying composted manure from feedlot operations to grazed pastures, may provide an additional means of improving soil health and sustainability of these systems. However, few studies have examined the impact of composted animal manure on the changes in soil microbial communities, although they are important indicators of soil health. We investigated the effects of a one‐time composted cattle manure application at 3.36 Mg ha−1 on soil microbial community size and structure, soil organic C (SOC), total N (TN), and soil organic matter (SOM) up to 1.5 yr after application. We compared pastures consisting of either WW‐B. Dahl Old World bluestem grass [Bothriochloa bladhii (Retz.) S.T. Blake] alone or in mix with alfalfa (Medicago sativa L.). Results showed that compost application significantly increased SOC by about 4.4 g kg−1 soil within 1.5 yr after application. In N‐fertilized grass‐only pastures, compost addition increased microbial phospholipid fatty acid abundance, SOC, TN, and SOM, but no significant differences were observed between compost treatments in unfertilized pastures containing legumes. Our results show that even a one‐time compost addition at a relatively low rate can augment SOC in this semiarid pasture system after 1.5 yr, and that stimulation of soil microbial abundance and soil C and N from compost is more pronounced in fertilized grass‐only pastures compared with those with legume establishment.

A Practical Satellite-Derived Vegetation Drought Index for Arid and Semi-Arid Grassland Drought Monitoring

In semi-arid pasture areas, drought may directly influence livestock production, cause economic losses, and accelerate the processes of desertification along with destructive human activities (i.e., overgrazing). The aim of this article is to analyze the disadvantages of several drought indices derived from remote sensing data and develop a new vegetation drought index (VDI) for monitoring of grassland drought with high temporal frequency (dekad) and fine spatial resolution (1 km). The site-based soil moisture data from the field campaign in 2014 and the fenced biomass values at nine sites from 2000 to 2015 were adopted for validation. The results indicate that the proposed VDI would better reflect the extent, severity, and changes of drought compared with single drought indices or the vegetation health index (VHI); specifically, the VDI is more closely related to site-based soil moisture, with R human increasing to approximately 0.07 compared with the VHI; and with normalized fenced biomass (NFB) values, with average R human increasing to approximately 0.11 compared with the VHI. However, the correlations between VHI and VDI with NFB values are relatively lower in desert steppe regions. Furthermore, regional drought-affected data (RDA) are used to ensure spatial consistency of the evaluation; the VDI map is in good agreement with the RDA map based on field measurements. The presented VDI shows reliable and stable drought monitoring ability, which will play an important role in the future drought monitoring of inland grassland.

Phosphorus mineralization in response to organic and inorganic amendment in a semi-arid pasture soil

Phosphorus deficient soil was amended with compost (C) (organic source of phosphorus) and inorganic P (KH2PO4 as inorganic phosphorus) at different rates and incubated for 28 days. Six treatments were used including i) Control ii) Inorganic P (0.79 mg per 30 g of soil sample) iii) 100 % C (0.13 g) iv) 75% C (0.1 g) + 25% P (0.2 mg) v) 50% C (0.065 g) + 50% P (0.4 mg) vi) 25% C (0.03 g) + 75% P (0.6 mg). Soil respiration was recorded using Infra-red CO2 gas analyzer. MBC was determined by using fumigation extraction method. Resin P and MBP extraction was carried out by anion exchange membranes and was determined colorimetrically. P pools were determined by using DeLuca method. Cumulative respiration microbial biomass significantly increased in organic amended soil with higher increase in soil emended with 75% C +25% P rate followed by 50% C and 50% P rate. It was concluded that compost amended with high inorganic P stimulated the formation of P labile pools which supply long term slow release of P for plants and microbes.

Botanical composition and aroma compounds of semi‐arid pastures in Algeria

AbstractThis study aims to determine the botanical composition of different pastures in a semiarid region of Algeria and investigate the aromatic profile of the characteristic plant species grazed by goats and sheep. At three pastures (1: montane area with spontaneous vegetation ‘never cultivated before’, 2: previously cultivated but set at rest, 3: cultivated, under cereal production), plants were sampled twice during April–May to determine plant composition. Based on dominance of fresh aerial biomass of each plant per pasture and consumption by dairy goats, 10 species (Atractylis humilis, Calendula arvensis, Filago pygmaea, Globularia alypum, Hordeum vulgare, Malva sylvestris, Plantago sp., Scolymus hispanicus, Sonchus asper and Thymus algeriensis) were selected and sampled once at flowering stage to characterize their aromatic profile. The odour‐active compounds (OACs) of the selected species were extracted using steam distillation, then detected and identified using gas chromatography/mass spectrometry/olfactometry (GC/MS/O). The analysis of botanical composition revealed the presence of 70 species (29 in mountain, 40 in set at rest, 11 in cultivated pasture) belonging to 62 genera and 22 families, with dominance of Asteraceae species. A total of 86 different OACs were identified, including mainly terpenes (21) and aldehydes (18). Among the OACs, 19 different compounds have various odour notes including herbaceous, floral, sweet spicy, fried, mint, cooked, fruity, sulphur, sweet and unpleasant notes. The number of OACs and individual chemical classes differed significantly between selected species. Atractylis humilis contained more OACs than Scolymus hispanicus and Plantago sp., whereas Globularia alypum had higher number of OACs compared to Plantago sp. This study gave a general overview on plant aroma profile of semiarid pastures in Algeria and suggests that the aromatic profile of grazed plants in the pasture is determinant of the aromatic quality of dairy‐derived foods which depends also on animal feed selection.

Improvement of Sowing Units to Strengthen the Feeding of Aridic Livestock Breeding

This article provides information on arid and semi-arid pasture fields. They are the main feeding for grassland farming. Pastures' yield capacity needs to be maintained through improvement. The Heavy workload requires mechanization of the improvement process. Here you can see the specifications for combined sowing units to improve the arid pastures.

Fatty acid, volatile and sensory profiles of milk and cheese from goats raised on native semiarid pasture or in confinement

The fatty acid (FA), volatile and sensory profiles of cheese and milk, obtained from goats grazing native pastures (PS) of semiarid region of Brazil or kept under confinement (CS), were evaluated. Milk and cheese from native pasture-fed animals contained higher amounts of oleic acid, stearic acid, total polyunsaturated, cis-monounsaturated and trans FA, and lower amounts of medium chain FA, total saturated FA and rumenic acid compared with milk and cheese from confined goats. Two terpenes (α-terpineol and β-caryophyllene) were exclusively detected in PS milk and cheese. Milk from the PS group presented higher intensity for herbaceous flavour and lower butter aroma, butter flavour and residual persistence compared with CS milk. Both PS cheese and milk presented higher overall acceptability compared with CS counterparts.

Pollinator Abundance in Semiarid Pastures as Affected by Forage Species

The semiarid Texas High Plains has a declining water supply for irrigated crop production because of unsustainable pumping from the Ogallala aquifer. Conversion of land from annual crops to limited‐irrigated perennial forages is an option for profitable land use. ‘WW‐B.Dahl’ old world bluestem [Bothriochloa bladhii (Retz) S.T. Blake, OWB] is a well‐adapted grass known for deterring some soil‐dwelling insects, but effects of OWB on insect pollinators are unknown. The aim of this study was to determine whether adapted forage types (species or mixtures) affected insect pollinator abundance in pastures. Foraging insects were collected using bee bowls and compared among OWB alone, OWB mixed with alfalfa (Medicago sativa L.), alfalfa, and a native grass mix. Twenty‐one families from four orders of insects were recovered over 3 yr. Sweat bee (Hymenoptera: Halictidae) was the most abundant family, with 59% of the total number of insects collected. Honey bees (Hymenoptera: Apidae) constituted an additional 17% of the total number of insects collected, with hover flies (Diptera: Syrphidae) and skippers (Lepidoptera: Hesperiidae) found in lesser abundances. Interactions between forage type and years restricted consistent forage‐type effects. In general, the lowest abundances of foraging insects were commonly found in OWB growing alone, especially of the native, ground‐nesting sweat bee, whereas greater abundances were more commonly found in native grass and alfalfa pastures. Widespread adoption of WW‐B.Dahl OWB may reduce local numbers of foraging insects in the Texas High Plains, which could negatively affect pollinators in managed grasslands.

Soil health indicators as affected by diverse forage species and mixtures in semi-arid pastures

‘WW-B.Dahl’ Old World bluestem [OWB, Bothriochloa bladhii (Retz) S.T. Blake] is a persistent pasture grass in the semi-arid Texas High Plains. Some growers are transitioning their irrigated continuous cotton (Gossypium hirsutum L.) land to dryland or low-irrigation production of WW-B.Dahl owing to diminished water supply. This grass strongly deters soil-dwelling ants (Hymenoptera: Formicidae), presumably via release of unidentified phytochemical repellants in the soil. Our aim was to determine whether the inhibitory effects of OWB extend to soil microbial community structure and function in relation to other adapted forages. We compared soil chemical and microbial properties in a Pullman clay-loam soil for OWB relative to OWB-alfalfa (Medicago sativa L.), alfalfa, and native mixed-grass pastures at 0–5 cm and 10–15 cm depth in June and December of 2016. The pastures ranged in age from 7 to 17 yr. Most measurements of organic forms of C and N showed greatest amounts in OWB-alfalfa; however, not always significantly. Enzyme activities linked to C, N, and S transformations were greatest (P ≤ 0.03) with OWB-alfalfa. This trend was similar for alkaline phosphatase activity, involved in P cycling, but not always significantly. Soil organic C in OWB was 1.2–1.4 fold greater than in the native mix depending on soil depth and sampling date, whereas SOC in OWB-alfalfa was 1.4–1.6 fold greater than in the native mix. Enzyme activities and microbial biomass N (MBN) were likewise greater in OWB and OWB-alfalfa than in the native mix, likely because the latter received no irrigation or N inputs. The microbial community structure demonstrated greater total FAMEs, bacterial markers for Gram+, Gram−, and actinomycetes in OWB-alfalfa compared to OWB, alfalfa, and native mix. Similar results were found in fungal markers for arbuscular mycorrhizal fungi (AMF) and saprophytic fungi. Protozoan indicators were found only in December, of which the native mix had the highest levels in the 0–5 cm depth. In general, selected soil properties, soil microbial biomass, community and enzyme activities were greater in December than in June except AMF, which was greater in June. The stimulating effect of OWB growing with alfalfa on the soil microbial community suggested this forage combination as favorable for soil health in relation to OWB, alfalfa alone, and native mixed-grass pastures. The previously reported inhibitory effect of OWB on soil-dwelling ants did not carry over to a depressing effect on the soil microbial component.

Combined use of in situ hyperspectral vegetation indices for estimating pasture biomass at peak productive period for harvest decision

Since the typical destructive methods for measuring aboveground biomass (AGB) have many limitations, a variety of non-destructive techniques have been developed. In this paper, the potential of ground-based hyperspectral remote-sensed data for non-destructive assessment of semi-arid pasture AGB at the peak productive period was investigated. The reflectance spectrometric and AGB data were sampled at the end of the growing season (almost peak biomass) over two locations at pastures in the southern Horqin sandy land, eastern Inner Mongolia, China. All combinations (two-band and three-band) of narrow bands in the forms of simple ratio vegetation index (SRVI), normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI) and enhanced vegetation index (EVI) were used in a linear regression analysis against AGB. The predictive performance of the stepwise multiple linear regression (SMLR) using 4 best VIs as input variables was compared with the performance of multivariate partial least squares regression (PLSR) using all reflectance bands as input variables to estimate AGB. It was observed that the relationship between AGB and single band spectral reflectance was low, while the estimation performance of the best VIs based on all available wavebands was improved considerably. In addition, the best VIs based on all available wavebands had considerably better fitting performance than those based on traditionally used wavebands for estimating AGB. In comparison to PLSR using the full individual reflectance as input variables, SMLR using the best VIs as input variables performed much better, with the maximum decrease in RMSECV of 37% and the relative mean absolute errors always below 12.5%. The study demonstrated the high potential to estimate pasture AGB, which is a proxy for pasture forage yield, at the peak productive period using a hyperspectral technique.

Grazing alters net ecosystem C fluxes and the global warming potential of a subtropical pasture.

The impact of grazing on C fluxes from pastures in subtropical and tropical regions and on the environment is uncertain, although these systems account for a substantial portion of global C storage. We investigated how cattle grazing influences net ecosystem CO2 and CH4 exchange in subtropical pastures using the eddy covariance technique. Measurements were made over several wet-dry seasonal cycles in a grazed pasture, and in an adjacent pasture during the first three years of grazer exclusion. Grazing increased soil wetness but did not affect soil temperature. By removing aboveground biomass, grazing decreased ecosystem respiration (Reco ) and gross primary productivity (GPP). As the decrease in Reco was larger than the reduction in GPP, grazing consistently increased the net CO2 sink strength of subtropical pastures (55, 219 and 187 more C/m2 in 2013, 2014, and 2015). Enteric ruminant fermentation and increased soil wetness due to grazers, increased total net ecosystem CH4 emissions in grazed relative to ungrazed pasture (27-80%). Unlike temperate, arid, and semiarid pastures, where differences in CH4 emissions between grazed and ungrazed pastures are mainly driven by enteric ruminant fermentation, our results showed that the effect of grazing on soil CH4 emissions can be greater than CH4 produced by cattle. Thus, our results suggest that the interactions between grazers and soil hydrology affecting soil CH4 emissions play an important role in determining the environmental impacts of this management practice in a subtropical pasture. Although grazing increased total net ecosystem CH4 emissions and removed aboveground biomass, it increased the net storage of C and decreased the global warming potential associated with C fluxes of pasture by increasing its net CO2 sink strength.

Nitrapyrin Reduced Nitrous Oxide Emissions from Beef Cattle Urine Patches on a Semiarid Tame Pasture

Core Ideas Limited data are available about mitigating N2O emissions from urine patches on semiarid pasture. Nitrapyrin reduced cumulative N2O emissions by 39% in a dry season. Nitrapyrin reduced cumulative N2O emissions by 58% in normal precipitation season. NBPT and NBPT plus DCD did not limit N2O emissions compared with untreated urine patches. N2O emission factors ranged from 0.03 to 0.21% over two grazing seasons Urease and/or nitrification inhibitors applied to urine patches or pastures may increase N retention in the soil–plant system, but how N2O emissions respond to these N stabilizers in semiarid regions is poorly understood. The objectives of this research were (i) to quantify N2O emissions and the associated emission factors, based on the percentage of applied urine‐N emitted as N2O–N, from beef cattle urine patches (urine) and (ii) to test the N2O reduction potential of three N stabilizers [2‐chloro‐6(trichloromethyl) pyridine (nitrapyrin), N‐(n‐butyl)‐thiophosphoric triamide (NBPT), and NBPT plus dicyandiamide (DCD)] on a semiarid tame pasture over two grazing seasons in western Canada. A deionized water control was also included. Nitrapyrin reduced cumulative N2O emissions by 39% and the N2O emission factor by 50% compared with untreated urine in a dry grazing season and reduced cumulative N2O emissions by 58% and the N2O emission factor by 68% compared with untreated urine in a grazing season with normal precipitation. The NBPT and NBPT + DCD had similar cumulative N2O emissions compared with untreated urine patches. The N2O emission factors ranged from 0.03 to 0.08% over 103 d in 2015 and from 0.06 to 0.21% over 119 d in 2016, all lower than the 2% Intergovernmental Panel on Climate Change default 365‐d value. Extrapolating over 1‐yr periods, N2O emission factors ranged from 0.11 to 0.64%. Based on the N stabilizers tested, nitrapyrin most effectively reduced N2O emissions from beef cattle urine patches on a tame pasture in a nonirrigated semiarid region of Canada.

Effects of endophyte-infected and non-infected tall fescue residues on aggregate stability in four texturally different soils

Fungal endophyte (Epichloë coenophiala) usually infects cool-season perennial forage grasses and enhances host plant resistance to biotic and abiotic stresses and, by potentially altering the litter quality and decomposition rate, can affect soil properties. Aggregate stability, as an important determinant of plant root growth and soil quality, may be affected by the endophyte status of plant residues. In this study, the effects of endophyte-infected (E+) and endophyte-free (E−) tall fescue residues (0%, 1% and 2%) on soil organic carbon (SOC), basal soil respiration (BSR) and aggregate stability were investigated in four texturally different soils in the laboratory. The aggregate stability indices were determined by the high energy moisture characteristic (HEMC) method. Moist soil samples were thoroughly mixed with either E+ or E− tall fescue residues before being incubated at 25°C. During the 2-month incubation period, the amended soil samples were subjected to ten wetting and drying cycles, after which soil properties were measured. The results indicated that SOC and aggregate stability were higher and that BSR was lower in the finer-textured soils. Furthermore, an increase in the application rate of plant residues significantly increased SOC, BSR and aggregate stability. Treating the soils with E+ tall fescue residues increased SOC and aggregate stability (i.e., stability ratio, SR, a dimensionless index defined as the ratio of the structural index for the fast wetting to the structural index for the slow wetting), and significantly decreased BSR due to the toxic effects of phenolic compounds on soil microbial communities and changes in the litter chemical quality. The interactive effect of soil type and endophyte status on the SOC and BSR values was significant but no clear trend was observed. Our findings indicated that tall fescue residues (especially E+ ones) can improve soil physical quality due to increased SOC storage and greater aggregate stability. Therefore, these plants have great potential for use in grassland reclamation and soil conservation plans in semi-arid pasture and agricultural lands.

Soil Quality of a Semi-Arid Pasture Irrigated with Reverse Osmosis Wastewater—A Case Study from Northern New Mexico

Soil quality indicators were assessed in two adjacent fields in northern New Mexico near a reverse osmosis (RO) facility. One field had been cleared of native vegetation, sowed with a pasture mix and irrigated with saline RO wastewater (electrical conductivity (EC) of 2.73 dS/m) (WW) for two years. An adjacent field of non-irrigated, undisturbed native vegetation (NV) that received only natural rainfall was sampled for comparison and assumed to be representative of baseline values. Measurements included mean weight diameter (MWD), dry aggregates > 2 mm (D > 2 mm), dry aggregates < 0.25 mm (D < 0.25 mm), wet aggregate stability, permanganate oxidizable carbon (POXC), soil organic matter, EC, pH, sand, silt and clay contents, and chemical parameters (NO3-N, P, Ca, Mg, Na, Zn, Fe, Mn and Cu). The wastewater irrigated field had more favorable soil quality indicators than the non-irrigated field, presumably due to the pasture mix and irrigation. However, the EC is higher in the WW irrigated field and will affect long-term utilization of the land for cropping, unless good soil salinity management is implemented.

Changes in soil pore network in response to twenty-three years of irrigation in a tropical semiarid pasture from northeast Brazil

Irrigation is a technique in agri-, vini- and horticulture which consists in the controlled supply of water and which has been used for many years in order to ensure agricultural productivity in many regions of the world. In regions where this water application technique is used there is the possibility of changes in soil properties; amongst others, soil structure, a physical attribute that is related to several other soil attributes such as density, porosity and aggregate stability. Soil structure is also greatly affected by wetting and drying cycles, which are provided by irrigation in these regions. This study aims at evaluating changes in the physical attributes of a soil caused by 23 years of irrigation. The study area is located on the Apodi Plateau, Ceará, Brazil. Two areas were evaluated, one irrigated by a central-pivot sprinkler system and a non-irrigated control. For the study, eight disturbed soil samples were collected in each area, in the layers of 0–20, 20–40 and 40–60cm, and four undisturbed soil samples, using cylinders of 5cm×5cm, in the layers of 0–20cm and 20–40cm. The analyzed physical attributes were: particle density, soil bulk density, particle size distribution, total porosity, macroporosity (pores with diameter≥50μm, applying matric potential of −6kPa), microporosity (pores with diameter<50μm, total porosity minus macroporosity), soil air permeability, soil resistance to penetration, aggregate stability and pore continuity indices. The results indicated that irrigation contributed to changes in soil physical attributes directly related to soil structure. Also, the consequent wetting and drying cycles were sufficient to improve aggregate stability; however, these cycles, combined with processes of translocation and compaction, have increased microporosity, causing the formation of less continuous and more tortuous pores and lower soil air permeability.