Nutrient redistribution by grazing cattle drives patterns of topsoil N and P stocks in a low-input pasture ecosystem

Nutrient cycles in grassland often involve net transfers from some areas to others. Here, we analyse patterns of N and P transfers by cattle in two grazing periods, and their relationships to soil P and N stocks in an unfertilised old pasture with a history of >50 years grazing. Net transfers were assessed from spatial patterns of nutrient ingestion and excretion. Total soil N and P were determined at 0–5, 5–10, 10–30 and 30–60 cm. All analyses were performed with a spatial resolution of 10 × 10 m² or higher. Data were geostatistically interpolated. Nutrients accumulated in the flat crest zone and were depleted in the steeper areas. Nutrient ingestion was less and excretion higher in the accumulation zone (and vice versa in the depletion zone) revealing that both components of grazer-driven net transfers of nutrients promoted the development of accumulation/depletion zones. Topsoil stocks of N and P were closely correlated with excreta density and net transfers of N (P < 0.001), whereas N and P at 30–60 cm displayed only weak or no correlation. Redistribution involved a small fraction of the soil stocks: nutrients grazed in two periods were equivalent to 0.8% of N and 0.2% of P of the whole pasture (0–60 cm). These factors suggest that topsoil nutrient distribution was modified by long-term stable patterns of net transfers of nutrients. The excess of N in the accumulation zone (N in accumulation zone minus N in depletion zone, in 0–60 cm) was 11 times larger than that of annual (i.e. short-term) net transfers; but for P, it was 30 times larger. This contrast likely derived from leaching/volatilization losses of N in the accumulation zone and only small inputs of biologically fixed N in the depletion zone. The nitrogen status of vegetation (Nitrogen Nutrition Index) had a strong effect on herbage production throughout the pasture, while the Phosphorus Nutrition Index indicated no limitation, except in urine patches.     

Yield and P uptake by wheat as affected by residual and applied P

The effect of residual (built up in continued fertilizer experiments) and applied P in Fatehpur loamy sand and Jodhan sandy loam soils of two long term experiments on its availability and uptake by wheat (Triticum aestivum L.) was studied using³²P in greenhouse experiment. Dry matter yield increased significantly with carry over P. Response in the absence of residual P was observed up to a direct application of 134 kg P ha^?1, whereas, in the presence of carry over P, the response was confined upto 67 kg P ha^?1 at site A. The response was however, observed up to 67 kg P ha^?1 irrespective of carry over P at site B. Total P uptake by wheat was significantly increased at all levels of residual P. However, it did not differ signficantly among levels of residual P when these were high. The uptake of soil P (residual) increased signficantly with increase in the dose of directly applied P, indicating that addition of inorganic P fertilizer tends to mobilize the native soil P. Per cent utilization of fertilizer P was enhanced in soils having residual P from continuous application of both inorganic and organic P sources.     

Phosphorus transformations as affected by sampling date, fertilizer rate and phosphorus uptake in a soil under pasture

A phosphorus (P) fertilization study was conducted in the southeast of the Buenos Aires province in Argentina, to determine the effect of P fertilizer rate and sampling date on microbial biomass P, and of organic and inorganic P extractable with 0.5M NaHCO₃, in a soil under pasture. In addition, Bray-P, dry-matter production and P uptake were measured. Soil was sampled at different times over one year, and two to three years after application of 0, 50, 100 and 200 kg P ha ^–1. The addition of P fertilizer significantly increased total soil P and the labile fraction of P extractable with NaHCO₃, with the greatest change in the labile inorganic P form, but had no effect on microbial biomass P. Fractions of P showed different patterns of seasonal variation. Microbial biomass P had a peak in winter and a lowest value in summer, the opposite occurring with NaHCO₃-extractable organic P, while NaHCO₃-extractable inorganic P remained relatively constant throughout the year. The cumulative dry-matter yield after three years was 31% higher in the fertilized than in the unfertilized treatments; the highest being 27660 kg ha^–1 for 200 kg P ha^–1. Concentration of Bray-P increased by 0.18 mg P kg ^–1 for each additional kg P ha^–1 added, but remained relatively constant over the year. A significant correlation was found between available Bray-P and microbial biomass P (r = 0.53), and NaHCO₃-extractable organic P (r = 0.47), suggesting that these organic fractions may contribute to plant nutrition.     

Yield and P uptake by wheat as affected by P fertilization and soil moisture regime

The influence of different moisture regimes and the method of phosphate application on the availability and uptake of native and fertilizer P by wheat (Triticum aestivum L.) was studied in a field experiment on sandy loam soil low in available P. Phosphorus application up to 39 kg ha^?1 signficantly increased wheat yield irrespective of the method of application. Wheat yield with drill application of 26 kg P ha^?1 was almost equal to that with broadcast application of 39 kg P ha^?1. A mean increase of 230 kg ha^?1 grains was obtained, when P fertilizer was drilled below seed. The relative efficiencly of placement was found to be 1.4 times that of broadcast method. The increase in IW/PAN-E ratio from 0.6 to 1.0 significantly increased grain yield. Scheduling of irrigation at narrow IW/PAN-E ratio but with fertilizer placed gave almost the same yield as was obtained with irrigation scheduled at IW/PAN-E equal to 1.0 and P fertilizer broadcast. Total P uptake by wheat was greater under wetter moisture regimes. The uptake of applied P decreased with increase in soil moisture regime, while that of soil P tended to increase with frequent irrigation. The uptake of soil P was a linear function of moisture supply and under conditions of this experiment P uptake by wheat beyond a P dressing of 20 kg ha^?1 was limited by soil water.     

Nitrogen and phosphorus uptake,yield and agronomic traits of oat cultivars as affected by fertilizer N rates under diverse environments

Oat has been gaining renewed interest due to its role in human healthy diet. A field study was conducted across three diverse locations in Canada to determine N and P uptake, agronomic traits and yield performance of 10–12 cultivars under four fertilizer N rates. Our data showed that ‘SA060123’ and ‘OA1331-5’ were the highest-yielding cultivars, and ‘Dieter’ and ‘Morrison’ the lowest, across sites-years. Yield components were altered to adapt to soil-environmental conditions, specifically, panicles m^?2 mostly accounted for yield variation at Melfort, seeds panicle^?1 and 1000-seed weight at Normandin, and lodging index was an additional yield-determining factor at Ottawa. It was noted that severe crop lodging that occurred mainly at Ottawa, was logically associated with greater accumulation of straw N and plant biomass under high N supply conditions, and that crop lodging displayed a strong correlation with straw P content. Relationship of lodging index and straw P was best-fit into a split-line model with a change-point of 13.6 kg P ha^?1, below which lodging rarely occurred. We speculate that high straw P content, induced by external N supply, may have exhibited similar behavior as N in weakening the strength of stem base and anchorage system, leading to crop lodging. This study also demonstrated an interactive genotype-by-environment effect on all traits except for the seed number panicle^?1. Multidimensional preference analysis revealed the best performance of ‘SA060123’ for outstanding yield and 'Minstrel' for harvest index, respectively.     

Biomass and nutrient uptake ofAilanthus excelsa as affected by N and P fertilization on an aridisol

A field experiment was conducted on a coarse sand soil having pH 8.8 and organic matter 0.06% in Indian arid region, to study the influence of N and P fertilizers on growth, biomass and nutrient content ofAilanthus excelsa, which is an important fodder species of arid and semi arid regions. Three levels of nitrogen (0, 9 and 18 g N tree^–1 as Urea) and of phosphorus (0, 3 and 6 g P₂O₅ tree^–1 as Single Superphosphate) in factorial combinations were taken in triplicate and the experiment was laid in Randomised Block Design. Application of 9 g N plant^–1 improved tree height by 15 to 25%, collar circumference by 30 to 37% and crown diameter by 18 to 26% in the initial 3 years. Total biomass increase due to 9 g N plant^–1 was 76% and 59%, respectively, after 1 and 2 years of planting. Application of 3 g P₂O₅ tree^–1 increased tree height by 8 to 18% and collar circumference by 17 to 24% during initial three years, and total biomass by 70% at 1 year and 30% at 2 years of age. Combined application of 18 g N and 3 g P₂O₅ tree^–1 (N₁₈P₃) was the best treatment which increased tree height by 49%, 85% and 35% and collar circumference by 56%, 10% and 11% at 1, 2, and 3 years of age, respectively. N₁₈P₃ treatment increased the total biomass by 181% at 1 year and 185% at 2 years of age. N and P applications improved considerably the branching of roots and root length and enhanced root biomass by 2 to 3 folds. N₁₈P₃ treatment increased the nitrogen uptake by 304% (4.02 g tree^–1) at 1 year and 211% (42.56 g tree^–1) at 2 years of age. The P uptake was maximum (290.4 mg tree^–1) due to N₁₈P₃ treatment in 1 year old and 11.37 g tree^–1 due to N₉P₆ treatment in 2 year old plantation.     

Yield and nitrogen uptake by rice as affected by variety,method of planting and new nitrogen fertilizers

A field experiment conducted for two years (1977 and 1978) at the Indian Agricultural Research Institute, New Delhi showed that yield and nitrogen uptake by rice was more in the case of medium duration (135 days) variety Improved Sabarmati than in the case of the short duration (105 days) variety Pusa-33. Highest yield and nitrogen uptake by rice was recorded when it was transplanted and lowest when rice was direct-seeded (drilled in moist soil). Broadcasting sprouted seeds on puddled seed bed gave yield and nitrogen uptake in between transplanting and direct-seeding and provides a reasonably acceptable method of planting. Rice responded well to nitrogen and the economic optimum dose was found to be 160–170 kg N ha^–1. Urea briquettes gave the highest yield and nitrogen uptake by rice and was superior to sulphur-coated urea or neem-cake-coated urea with respect to N-uptake. All these new nitrogen fertilizers were superior to urea and therefore hold considerable promise in rice culture.     

Effects of predator fecal odors on feed selection by sheep and cattle

The effectiveness of predator fecal odors in modifying feeding selection by sheep and cattle was investigated in two trials. In trial 1, animals could select from feed bins contaminated with coyote, fox, cougar, or bear fecal odor, and oil of wintergreen, or select the control feed. All odors were rejected (P<0.01) by sheep and cattle, except bear odors by sheep. In trial 2, animals could select feed during 10-min periods in an open 11-m × 16-m arena. Fecal odor did not influence approaches to feed bins, or head entries into bins. Only coyote fecal odor reduced (P<0.05) the time spent feeding in the contaminated bin, and increased (P<0.05) consumption from the control bin by both cattle and sheep. Some animals on some test days refused to feed from either feed bin, although cattle and sheep closely inspected bins. Results suggest that fecal odors may not prevent livestock from entering a treated area but may reduce the time spent grazing in such an area.This research was supported in part by the Utah Agric. Exper. Sta., Utah State University, Logan, Utah 84322. Approved as journal article no. 3721     

Phosphorus and potassium cycling in a long-term no-till integrated soybean-beef cattle production system under different grazing intensities insubtropics

Long-term integrated crop-livestock system enables constant and more efficient nutrient cycling because animal, pasture and crop residues release nutrients at different rates. Therefore, appropriate management of these systems is needed to maximize benefits from nutrient cycling. The objective of this study was to evaluate how grazing intensity affected the release rates of phosphorus (P) and potassium (K) in pasture, dung and soybean residues in a no-till long-term integrated crop-livestock system. The experiment was established in 2001 on a clayey Oxisol after soybean harvest. Treatments consisted of pasture with sward heights maintained at 1020, 30 and 40 cm by different cattle stocking rates and a non-grazed (NG) treatment. Decomposition and release rates of nutrients in the pasture and dung were determined using litter bags, which were installed at soybean seeding and pasture seeding during two pasture-crop cycles (2009–2011). Lighter grazing intensities resulted in greater P release rate from pasture and dung residues. Pasture and dung residues released K at a very high rate and were not influenced by grazing intensity. The P and K released from soybean residue were not affected by grazing intensity; however, decomposition of soybean leaves was greater than of stems. Greatest rates of total P and K released were from pasture and dung residues under lighter grazing intensities and in the NG areas. Large amounts of P (~25 kg ha^?1) and K (~130–180 kg ha^?1) were cycled in a complete soybean-beef cattle integrated system and must be considered in the fertilization management.     

Nanofluidization as affected by vibration and electrostatic fields

In this paper we investigate the behavior of a fluidized bed of silica nanoparticles under the influence of externally applied vibrations and an electrostatic field. We have observed that the application of these fields separately has opposite effects on bed expansion. On one hand, vertical vibrations enhance bed expansion as the vibration intensity is increased up to a critical value. On the other hand, an electrostatic field applied in the horizontal direction, hinders bed expansion. In previous research papers, it has been suggested that the size of nanoparticle agglomerates could be affected either by vibration or by the action of the electric field. Using the modified Richardson-Zaki method to analyze our experimental data we find that vertical vibration tends to decrease the average agglomerate size in agreement with previous research. However, in this work we look further into the physical mechanisms which affect the response of the fluidized bed. Our results suggest that both vibration and the electric field produce a significant perturbation to the flow of agglomerates within the fluidized bed. Vibration transmits a vertical motion to the agglomerates that enhances bed expansion until the vibration velocity becomes of the order of the expected rising velocity of macroscopic bubbles. At this critical point, bubble growth is stimulated by vibration. A horizontal electrostatic field produces a drift of the charged agglomerates toward the walls that gives rise to fluidization heterogeneity and bed collapse. When both fields are simultaneous applied, these opposed effects can be practically compensated.     

Particulate and active soil nitrogen fractions are reduced by sheep grazing in dryland cropping systems

Sheep (Ovis aries L.) grazing, a cost-effective method of weed control compared to herbicide application and tillage, may influence N cycling by consuming crop residue and weeds and returning N through feces and urine to the soil. The objective of this experiment was to evaluate the effect of sheep grazing compared to tillage and herbicide application for weed control on soil particulate and active soil N fractions in dryland cropping systems. Our hypothesis was that sheep grazing used for weed control would increase particulate and active soil N fractions compared to tillage and herbicide application. Soil samples collected at the 0–30 cm depth from a Blackmore silt loam were analyzed for particulate organic N (PON), microbial biomass N (MBN), and potential N mineralization (PNM) under dryland cropping systems from 2009 to 2011 in southwestern Montana, USA. Treatments were three weed management practices [sheep grazing (grazing), herbicide application (chemical), and tillage (mechanical)] as the main plot and two cropping sequences [continuous spring wheat (Triticum aestivum L.; CSW) and spring wheat–pea (Pisum sativum L.)/barley (Hordeum vulgare L.) mixture hay–fallow; W–P/B–F] as the split-plot factor arranged in randomized complete block with three replications. The PON and MBN at 0–30 cm were greater in the chemical or mechanical than the grazing treatment with CSW. The PNM at 15–30 cm was greater in the chemical or mechanical than the grazing treatment in 2009 and 2011 and at 5–15 cm was greater with W–P/B–F than CSW in 2010. From 2009 to 2011, PON at 0–30 cm and PNM at 15–30 cm reduced from 2 to 580 kg N ha^?1 year^?1 in the grazing and chemical treatments, but the rate varied from ?400 to 2 kg N ha^?1 year^?1 in the mechanical treatment. Lower amount of labile than nonlabile organic matter returned to the soil through feces and urine probably reduced soil active and coarse organic matter N fractions with sheep grazing compared to herbicide application and tillage for weed control. Reduction in the rate of decline in N fractions from 2009 to 2011 compared to the herbicide application treatment, however, suggests that sheep grazing may stabilize N fractions in the long-term if the intensity of grazing is reduced. Animal grazing may reduce soil N fractions in annual cropping systems in contrast to known increased fractions in perennial cropping systems.     

Polyester composite water uptake and organic contaminant release affected by carbon nanofiber reinforcements

The incorporation of carbon nanofiber (CNF) into glass fiber (GF) composites is a potential route to extend polymer composite service‐life and enhance mechanical properties. Under nonstatic conditions, only limited information concerning water uptake and contaminant release properties of nanocomposite materials is currently available. Polyester composites containing GF and oxidized CNF were immersed in water for 30 days under nominal pressure at 23 °C, below the polymer's glass‐transition temperature. Water was analyzed and changed every three days to simulate water chemistry regeneration similar to exposures in flowing systems. Composites with oxidized CNF had greater water sorption capacity and leaching rates than CNF‐free composites. The total mass of organic contaminant released correlated with the amount of water sorbed by each composite (r² = 0.91), although CNF dispersion was found to vary greatly within composites. The greatest and least contaminant release rates were found for the polyester‐CNF and the polyester‐GF composites, respectively. While volatile aromatic resin solvents and stabilizer compounds were detected, their concentrations declined over the 30 day exposure period. We hypothesize that the hydrophilic nature of the oxidized CNF increased the water sorption capacity of the polyester composites. Additional studies are warranted that examine the impact of this phenomenon on composite mechanical and long‐term durability properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43724.     

CO2, CH4 and N2O fluxes in an alpine meadow on the Tibetan Plateau as affected by N-addition and grazing exclusion

Nutrient Cycling in Agroecosystems - Limited understanding of the effects of enhanced nitrogen (N) addition and grazing exclusion (E) on greenhouse gases fluxes (GHGs: CO2, CH4, and N2O) in...     

Study of oil uptake and some quality attributes of potato chips affected by hydrocolloids

The use of coating agents is one effective way to reduce oil absorption in fried products. Reducing the fat content of fried foods by application of coatings is an alternative solution to comply with both health concerns and consumer preferences. The aim of this study was to analyze the effect of hydrocolloids as coating agent on the quantity of oil uptake and on sensory attributes of potato chips. The effect of the coating composition showed that the minimum fat content was related to 1% carboxymethyl cellulose (CMC), 0.5% xanthan, 0.3% guar and 1% xanthan with 21.2, 21.7, 22.4 and 24.8%, respectively, and the highest of fat content was related to blank sample (non-coated), 2% tragacanth, 0.5% guar gum with 49.4, 41.7 and 33.2% of oil content, respectively (p <0.05). The most effective coating agent reduced the oil uptake by 57.03, 55.94, 54.67 and 49.71%, respectively (p <0.05). Sensory evaluation showed that the best color was related to 1% CMC, 0.3% guar and 2% tragacanth, and with respect to flavor evaluation the best flavor was observed in tragacanth 2%, CMC 0.5% and CMC 0.1%, and the best texture referred to tragacanth 2%, CMC 0.5% and CMC 1%. In sensory evaluation, all coated chips got high scores compared with blank (non-coated chips) samples (p <0.05).     

Nitrate in upper groundwater on farms under tillage as affected by fertilizer use,soil type and groundwater table

Indicators are needed to check whether policies on protection of groundwater are effective and if regulations are complied with. We evaluated various indicators at different scales, both in space and in time, and at different degrees of complexity. Groundwater was sampled on 34 arable farms for 3 years. Nitrate concentration in upper groundwater was low on clay soil. On sandy soil, peat layers reduced the nitrate concentration with about 80 mg/l on average. Sandy soils with high groundwater tables had nitrate concentrations that were less than half of those at sandy soils with low groundwater tables. The relationship between different fertilization variables and nitrate in groundwater was investigated for sandy soils without peat layers. N surplus poorly correlated with nitrate concentrations in groundwater when individual sampling points were studied, but clearly increased when data were averaged at the farm level. Soil mineral nitrogen correlated best with nitrate concentrations in groundwater. The relationships show that especially on well drained soil drastic measures will be inevitable to reach good water quality.     

Sunflower oil quality and quantity as affected by rhizopus head rot

Sunflower seed (Helianthus annus L.) from plants infected with head rot caused byRhizopus spp. exhibited serious oil quality problems. Free fatty acid content of this oil was 19.4%, compared with 0.8% for oil from seed of healthy plants. Oil from diseased seed was also higher in palmitic, stearic, arachidic, behenic and lignoceric fatty acids. In addition, diseased plants yielded only 81% as much seed and only 55% as much oil.     

Photooxidation of soybean oils as affected by triacylglycerol composition and structure

The photooxidation of soybean oil was determined and correlated with triacylglycerol composition and structure. Purified triacylglycerols were photooxidized at room temperature under fluorescent light. Rates of peroxide formation and total headspace volatiles were related positively (P<0.5 significance) to oxidizability (r=0.75, r=0.76); content of linolenic acid (r=0.80, r=0.85) and linoleic acid (r=0.61, r=0.57); linoleic acid on carbon 2 (r=0.64, r=0.64); and average number of double bonds (r=0.76, r=0.76). Negative correlations were observed with respect to oleic acid (r=−0.70, r=−0.70). Soybean oil stability was decreased by linolenic acid-containing triacylglycerols and increased by oleic acid-containing triacylglycerols. Trilinoleoylglycerol and dilinoleoyl-oleoylglycerol were the most important oxidation product precursors. However, for high-linolenic acid soybean oil, dilinoleoyl-linolenoylglycerol and trilinoleoylglycerol were the most important oxidation product precursors. The most abundant volatile produced from thermal decomposition at 140°C of photooxidized triacylglycerols was 2-heptenal, except for high-linolenic acid oils, where the most abundant volatile was propanal. The photooxidative stability of soybean oil triacylglycerols with respect to composition and structure is of interest for the development of soybean varieties with oils of improved odor and flavor stability. Presented at the 20th ISF World Congress 83rd Annual American Oil Chemists’ Society Meeting, May 10–14, 1992, Toronto, Canada.