Cut Ryegrass Research Articles

Effect of By-product Feed-based Silage Feeding on the Performance, Blood Metabolites, and Carcass Characteristics of Hanwoo Steers (a Field Study).

This study was conducted to determine the effects of feeding by-product feed (BF)-based silage on the performance, blood metabolite parameters, and carcass characteristics of Hanwoo steers. The BF-based silage was composed of 50% spent mushroom substrate, 21% recycled poultry bedding, 15% cut ryegrass straw, 10.8% rice bran, 2% molasses, 0.6% bentonite, and 0.6% microbial additive (on a wet basis), and ensiled for over 5 d. Fifteen steers were allocated to three diets during the growing and fattening periods (3.1 and 9.8 months, respectively): a control diet (concentrate mix and free access to rice straw), a 50% BF-based silage diet (control diet+50% of maximum BF-based silage intake), and a 100% BF-based silage diet (the same amount of concentrate mix and ad libitum BF-based silage). The BF-based silage was fed during the growing and fattening periods, and was replaced with larger particles of rice straw during the finishing period. After 19.6 months of the whole period all the steers were slaughtered. Compared with feeding rice straw, feeding BF-based silage tended (p = 0.10) to increase the average daily gain (27%) and feed efficiency (18%) of the growing steers, caused by increased voluntary feed intake. Feeding BF-based silage had little effect on serum constituents, electrolytes, enzymes, or the blood cell profiles of fattening steers, except for low serum Ca and high blood urea concentrations (p<0.05). Feeding BF-based silage did not affect cold carcass weight, yield traits such as back fat thickness, longissimus muscle area, yield index or yield grade, or quality traits such as meat color, fat color, texture, maturity, marbling score, or quality grade. However, it improved good quality grade (1+ and 1++) appearance rates (60% for the control group vs 100% for the BF-based silage-fed groups). In conclusion, cheap BF-based silage could be successfully used as a good quality roughage source for beef cattle.

Response of perennial ryegrass (Lolium perenne L.) to soil contamination with zinc

Phytoremediation is one of the ways of removing toxic metals from soil. Phytoremediation relies on using plants which are highly capable of absorbing heavy metals to remove them from soil. In order to determine the effect of the degree of soil contamination with zinc on the production of biomass and concentration of zinc in ryegrass, a pot experiment was carried out, consisting of 6 treatments in which gradually increasing doses of zinc were used: control treatment (without zinc), 25, 50, 100, 200 and 400 mg Zn kg–1 off soil. The experiment was conducted on two types of soil, different in the cation exchange capacity: sand and sandy loam. The tested plant was perennial ryegrass cv. Nira. The toxic effect of zinc on the growth of ryegrass was much more pronounced in the case of plants grown on sand than on sandy loam. When ryegrass was grown on sand, the toxic effect of zinc was observable even when the lowest rate of zinc had been introduced to soil: the biomass of the first cut was considerably depressed. On sandy loam, the toxic effect of zinc was not manifested until the highest rate of the contaminant had been introduced to soil (400 mg Zn kg–1 of soil). The experiment has demonstrated the presence of a strong, statistically verified correlation between the content of zinc in soil extracted in 1 M HCl and the concentration and uptake of this metal in the following cuts of ryegrass. The concentration of zinc in grasses from the first cut was very high: 1660 mg Zn kg–1 d.m. on sand and 1200 mg Zn kg–1 d.m. on sandy loam. A one-year cultivation of perennial ryegrass only slightly lowered the content of zinc in soil. Although the concentration of zinc in harvested grass was very high, the total uptake was just a small percentage (1-2%) of the quantity of this metal introduced to soil. Perennial ryegrass cv. Nira is capable of accumulating very high amounts of zinc and is well tolerant to a high content of Zn in soil, which is why it can be used for sowing on land polluted with this heavy metal.

Degradation of endophyte alkaloids in field-dried cut ryegrass herbage

The stability of endophyte alkaloids was investigated in ryegrass herbage cut and then dried in the field under a simulated hay drying regime in early and mid-summer. Ryegrass (Lolium perenne) infected with typical 'wild-type' and the 'AR37' strain of endophyte (Neotyphodium lolii) was measured for peramine, ergovaline and lolitrem B for wild-type, and epoxy-janthitrems for AR37. Despite very contrasting weather conditions, relative decline in alkaloid concentrations was similar in both early and mid-summer. Concentrations had halved within 5 to 7 days, except for lolitrem B in mid-summer which had no decline until after 4 days of drying. Ergovaline showed quite variable and erratic responses over time possibly due to the low concentrations in the cut herbage. At least in the mid-summer experiment, if herbage had been conserved at the time of normal haying making, alkaloid concentrations would have been similar to those of the herbage at the time of cutting. Keywords: endophyte, Neotyphodium lolii, Lolium perenne, peramine, lolitrem, ergovaline, janthitrems

In vitro studies on microbial efficiency from two cuts of ryegrass ( Lolium perenne, cv. Aberdart) with different proportions of sugars and protein

An in vitro study investigated effects on microbial efficiency of feeding ryegrass diets differing in water soluble carbohydrates (WSC) and crude protein (CP) levels. A 1st cut of a diploid ryegrass (Aberdart) with high WSC-low CP (Cut1), a 2nd cut with low WSC-high CP (Cut2) contents and the two cuts, supplemented with mainly casein or fructans + sucrose (Cu1P and Cut2S) to achieve similar WSC and CP levels, were used. Dietary levels of WSC, CP and neutral detergent fibre (NDFom) were (in g/kg dry matter): 298, 100, 464 (Cut1), 101, 179, 484 (Cut2), 290, 181, 401 (Cut1P) and 290, 181, 351 (Cut2S), respectively. The in vitro system (SIMCO) was a repeatedly fed semi-continuous culture allowing stratification of vessel contents and selective retention of feed particles. The estimated NDFom in sacco degradation rate (h −1) and indigestible NDFom (INDFom) was 0.042 and 0.117 for the 1st cut and 0.086 and 0.270 for the 2nd cut. Digestibility of NDFom in SIMCO tended to be higher in the 1st cut than in the 2nd cut diets. Fermentation patterns were in normal rumen ranges. Ribonucleic acid (RNA) and volatile fatty acid (VFA) efficiencies (g/kg truly digested organic matter) differed among treatments (P=0.005 and P=0.018, respectively). Statistical significance at P<0.05 was only achieved for Cut1P vs Cut2 and Cut2S (RNA efficiency) and for Cut1P vs Cut2S (VFA efficiency). Molar proportions of acetate were lower and propionate higher in 1st cut, compared to 2nd cut diets (P<0.05). Mean retention time (MRT) of the liquid fraction was fixed at 10.4 h, but MRT of INDFom was long, varying from 95 to 303 h and strongly influenced by the daily supply of INDFom in the different diets, which was approximately twice as high in the 2nd as compared to the 1st cut diets. This resulted in a strong negative relationship between RNA efficiency and MRT. Microbial N and VFA efficiency in the SIMCO system is likely to be more dependent on solids retention time than on the relatively wide range of WSC and CP levels used in this study. To evaluate diets with respect to microbial efficiency, fermentation system must have the possibility to separate effects substrates from digesta retention under near rumen-like conditions.

Nitrate leaching under spring barley is influenced by the presence of a ryegrass catch crop: Results from a lysimeter experiment

The influence on nitrate leaching of ryegrass (Lolium perenne L.) used as a catch crop in spring barley (Hordeum vulgare L.) was investigated during three successive years in a lysimeter experiment on a sandy loam soil. Four treatments were included with combinations of time of tillage (November/March) and handling strategy of the aboveground ryegrass biomass (return/ removal). Reference plots tilled in March were sown to spring barley alone. The four fertilization levels initiated 15 years earlier were continued with barley either left unfertilized, or receiving 11 g N m � 2 year � 1 (1N) in mineral fertilizer or with 1N or 1ΩN (16.5 g N m � 2 year � 1 ) in pig slurry. The ryegrass reduced nitrate leaching by 1.4‐4.3 g N m � 2 year � 1 when incorporation took place in November. If incorporation was carried out in March, reductions in nitrate leaching were 2.1‐5.6 g N m � 2 year � 1 . The herbage cut of ryegrass had accumulated 1.0‐2.4 g N m � 2 year � 1 and 0.9‐2.1 g N m � 2 year � 1 in November and March, respectively. Nitrate leaching losses increased with higher rates of N both with and without a catch crop. At the highest N rate (1ΩN in slurry), the incorporation of the herbage cut of the ryegrass raised nitrate leaching compared with removal. At the other three fertilization levels, return of the herbage did not significantly affect nitrate leaching. Grain yield and N uptake of the spring barley were unaffected by a catch crop and the management strategy did not interact with N fertility level. The study showed that growing a ryegrass catch crop repeatedly for three years was effective in reducing nitrate leaching losses, but the retained N did not have any immediate beneficial effect on spring barley grain yield. # 2005 Elsevier B.V. All rights reserved.

Lactation responses of dairy cows to whole-crop wheat or ryegrass silages

Feed intake and milk production responses to whole-crop wheat or ryegrass silages were measured in a replicated 3 × 3 Latin square experiment using nine (six multi- and three primiparous) Holstein cows. Each experimental period lasted for 3 weeks, with measurements performed in the last 7 days. Iso-nitrogenous diets contained (dry matter, DM, basis) 550 g kg −1 of a standard dairy cow concentrate (crude protein: 245 g kg −1 DM; starch: 255 g kg −1 DM) and 450 g kg −1 of one of the following silages: ryegrass (RGS; Lolium multiflorum Lam., cv. Promenade), Tigre wheat (TWS; Triticum aestivum L., cv. Tigre) and Arpan wheat (ARWS; T. aestivum L., cv. Arpan). All whole-plant forages were direct cut, on the same date, chopped to a length of ca. 5 cm and ensiled in bunker silos. Because RGS was harvested at a late stage of maturity, it contained 81 g crude protein kg −1 DM and 638 g neutral detergent fiber (NDF) kg −1 DM. The starch contents of TWS and ARWS were, respectively, 91 and 111 g kg −1 DM. The whole-crop wheat silages had higher acid detergent lignin contents and lower DM and NDF in sacco disappearance than RGS. The type of ensiled forage did not significantly affect feed intake or milk production and composition. Plasma urea concentration increased ( P < 0.01) with the decrease in in sacco disappearance of silages, suggesting differences between dietary treatments in synchrony between N and energy supply to rumen microbes. This study showed no benefits of whole-crop wheat silages over late single cut ryegrass silage as base forage for lactating dairy cows.

PA—Precision Agriculture: Development of a Model to predict Drying Rates of Cut Ryegrass

A mathematical model was developed to describe the rates of drying of perennial ryegrass across a number of different treatments at mowing and after mowing and different weights of grass per unit area. In the experiment, weight change of grass in wire-mesh trays was measured in the field over 2 d (32 h). Weight change was used to assess water loss and hence drying rate of the grass. The effects on drying rate of five weights of grass per unit area (1·5, 3, 6, 12 and 24 kg [fresh material] m−2), three treatments at mowing (no treatment, mower-conditioned, flail-treated) and three treatments after mowing (no treatment, inverted, mixed) were examined in a 5×3×3 factorial experimental design. The experiment was replicated twice on each of 16 occasions in 1992 at the Agricultural Research Institute of Northern Ireland. This gave a total of 32 replicates per treatment. The trays were weighed at 2-h intervals from 09·00 to 17·00 h each day. Three potential evaporation parameters (net/solar radiation, the Penman equation) were compared for use in a final empirical model. Drying rate parameters were calculated for each of the individual treatments. Relationships were developed between drying parameters and weight of grass per unit area for each of the treatments at and after mowing. Inclusion of a rainfall correction factor made the prediction of grass dry matter concentration more complex. The final empirical model reliably predicted dry matter concentration of grass in trays in the field over 32 h across the wide range of weather conditions and mechanical treatments that were studied. This final model which incorporated a single evaporation parameter (solar radiation) was shown to describe the pattern of grass drying in the field as accurately as a final model based on the Penman equation. However, further work is required to establish the extent of any differences between grass drying rates in the wire-mesh trays used in the current work and grass drying rates from commercial-type swaths.

Availability of Nitrogen in 15N‐Labeled Ruminant Manure Components to Successively Grown Crops

AbstractTo improve crop N use efficiency of animal manures, the availability of N in individual manure components must be better understood. This microplot field study quantifies crop offtakes of N in four similar batches of ruminant manure containing 15N‐labeled urine, feces, or straw, or unlabeled components only. The urine and feces were from a sheep first fed unlabeled hay and then 15N‐labeled hay. Manures (≈ 19 g total N m‐2) were incorporated into two coarse‐textured soils before planting to spring barley (Hordeum vulgare L.) undersown with perennial ryegrass (Lolium perenne L.). Manures with one 15N‐labeled component were supplemented with unlabeled NH4NO3 (7.3 g N m‐2), while unlabeled manure was given 15NH415NO3. Labeled and unlabeled N were determined in the spring barley at maturity and in six cuts of ryegrass taken during the succeeding 2.5 yr. The homogeneity of feces and urine 15N‐labeling was high. Dry matter yields and crop N offtakes were similar in all treatments. Barley (grain and straw) recovered 40, 26, 10, and 6%, respectively of 15N added with mineral fertilizer, urine, straw, and feces. Weighted mean recovery of the combined manure and fertilizer dressing was 22% of the added 15N. Crop recovery of urine and feces 15N was smaller and that of straw 15N higher than reported in previous studies on individual components, indicating that the N mineralization‐immobilization turnover (MIT) of the manure components interacted. In the second and third growth seasons, 2.7 to 4.4% and 1.1 to 2.0% of the 15N was recovered in grass cuts, respectively. Total recovery ranged from 84 to 95% of the added 15N, suggesting small N losses from this cropping system.

Nitrogen transformations after the spreading of pig slurry on bare soil and ryegrass using 15N-labelled ammonium

A short field experiment (27 days) was carried out in summer 1995, to study the effect of an actively growing grass sward on nitrogen transformations of a pig slurry. The ammonium fraction of the slurry was labelled with ( 15NH 4) 2SO 4. The slurry was spread manually on microplots in mid-June, at the rate of 3 l/m 2, on a cut ryegrass sward, and compared with bare soil. Absorption of 15N-labelled NH 4 by the grass occurred very rapidly, attaining 41% after 13 days and showing no further change at 27 days. The gaseous losses, mainly through volatilization of ammonia, were considerable. 15N recovery in soil and plant material on day 27 was 42.5% (±1.2) on the bare soil, versus 57.4% (±3.1) on the ryegrass. The grass sward significantly reduced: (i) volatilization, as shown by the difference of 14.9% in 15N recovery, on the 6th day; (ii) immobilization, which was 25% (±2.2) on day 27 on bare soil and 16.4% (±2.9) in the presence of ryegrass. 15N-labelled inorganic nitrogen was completely depleted beneath the ryegrass, 27 days after application, whereas ammonium was depleted and the nitrate was equal to 16.4% (±1.6) of the applied NH 4 on the bare soil. It is clearly apparent that the ammonia from the slurry is more efficiently used when applied to an actively growing sward, rather than to bare soil, even though a significant portion of the plant is involved in internal recycling.

Effect of sulfur additions on the yield and elemental composition of red clover and ryegrass

Abstract Experiments were conducted in a growth chamber using three soils testing low in extractable sulfate (SO4), and two crops, red clover (Trifolium pratense L.) and annual ryegrass (Lolium multiflorum L.). The study's objectives were to determine how the three soils compared in plant available sulfur (S) and to test the effects of various rates of potassium sulfate (K2SO4) and gypsum on the elemental composition, nitrogen:sulfur (N:S) ratio, and dry matter yield of two cuts of forage taken from each of the two crops. Of the three soils used, the Queens sandy loam tested lowest in extractable S and the plants grown in this soil were lowest in tissue S and S uptake. There was no yield response to S amenments except for the second cut of ryegrass grown in the Queens soil. In terms of S uptake and the N:S ratio of the forage, ryegrass was more responsive than red clover to S amendments from either source. Gypsum was as effective as K2SO4for supplying plant available S.

Effect of organic matter on the distribution, extractability and uptake of cadmium in soils

SUMMARYDistribution and plant uptake of soil Cd as influenced by organic matter and soil type were investigated in a greenhouse experiment. Three soils (a sand, sandy loam and clay loam) were used. The rates of organic matter in its moist state added were 0,20,40, 80, 160 and 320 g kg‐1 of the air‐dried soil on mass basis. Ryegrass (Lolium multörum L.) was used as a test crop. Soil Cd was analysed by a sequential extraction technique and by extraction with 1 M NH4NO3 and 0.005 M DTPA. The exchangeable fraction of Cd as determined by 1 M MgCl2 in the sequential extraction procedure increased, whereas the Fe‐Mn oxidebound fraction decreased, with increasing levels of organic matter addition in all three soils. The dry matter yields of ryegrass were not affected by the addition of organic matter, but the Cd concentrations in both cuts of ryegrass decreased with increasing amounts of organic matter added. The plant Cd was highly but negatively correlated to soil CEC. At any level of organic matter addition, the decrease in Cd concentration of ryegrass was in the order: sand &gt; sandy loam &gt; clay loam.

Extractable phosphorus to predict agronomic effectiveness of ground and unground phosphate rocks

The reactivity of 11 phosphate rocks (PRs), both in their finely ground and unground forms, and containing up to 12% of CaCO3 were estimated from the P extracted with 2% citric acid, 2% formic acid and neutral ammonium citrate. With the neutral ammonium citrate, PRs were also extracted sequentially. To determine the relative agronomic effectiveness (RAE) of PRs a greenhouse experiment was conducted using three soils of different P retention, and growing ryegrass as the test plant. PRs were applied at three rates plus control. Ground Sechura PR was employed as the standard PR and single superphosphate was included to determine maximum dry matter production. Three cuts of ryegrass were taken over 4 months in 2 soils, and 8 cuts over 10 months in one soil. RAE of the PRs was calculated from dry matter yields obtained at a fertiliser P rate where superphosphate gave 90% of the maximum attainable yield, and also from the yield and P uptake values averaged over rates of application. Amount of P extracted by the different reagents correlated closely with each other (R2 0.82–0.99). Chemical extractable P integrated the effect of particle size as well as the inherent chemical reactivity of PRs. Formic P expanded the scale and thus was the most sensitive indicator to rank PRs. The ranking of PRs were similar between soils. RAEs between soils correlated significantly (R2 = 0.88–0.91). For predicting the agronomic potential of PRs, RAEs calculated from 4 cuts of ryegrass over 4 months appeared to be as good as those calculated from 8 cuts, over 10 months. The total P of PRs was smaller in the large and very small size fractions than in the intermediate ones. With unground rocks the extractable P decreased with increasing particle size mainly due to their decreasing specific surface area. Practical implications of these results are discussed. Extractable P did not decline with increasing total P in the different size fractions of PRs. End-over-end shakers, unlike wrist-action shakers, gave consistent extractable P values. Formic-P was the best predictor of the agronomic effectiveness of PRs even when the data from ground and unground PRs, and from 3 soils of differing P retention were treated as one population (R2 = 0.87–0.92).

Studies on the effectiveness of various sulfur fertilizers under controlled conditions

Three factorial experiments with four replications were conducted in a greenhouse to examine the effectiveness of gypsum, elemental sulfur (ES powder) and three S containing N fertilizers, viz., ammonium sulfate (AS), urea + ES, and Ureas (20% AS and 80% urea). All experiments were conducted twice in different years. In the first experiment with uncropped soil, the effects of soil type, leaching rate (2.3 and 6.9 mm water per day) and urea addition on sulfate leaching losses were studied. Leaching losses decreased in the order Ureas > ammonium sulfate (AS) > gypsum ≫ urea + ES. Increasing the leaching rate greatly increased sulfate losses from both soils. Losses were greater in the sandy Typic Hapludoll than in the clayey Oxic Paleustalf. Sulfate adsorption was found to decrease strongly with rising the pH in both soils. Hydrolysis of urea temporarily raised the pH of the soil, thereby increasing the sulfate leaching losses. In the second experiment the effects of S rate (0–65 mg per kg soil), split application and leaching rate (0 and 2.3 mm per day) on sulfate leaching losses and ‘apparent S recovery’ (ASR) by three successive cuts of ryegrass (Lolium perenne L.) were studied. Herbage yield more than doubled when S was applied. The effectiveness of the sulfate fertilizers was greater when S was split-applied than given all at once. With split applications the ASR decreased in the order: Ureas > AS > gypsum > urea + ES > ES powder. ES fertilizers were least effective, because the oxidation rate of ES to sulfate was clearly too slow. In the third experiment the effects of S rate (0–40 mg per kg soil) and split application on sulfate leaching losses and ASR in the grain of wheat (Triticum aestivum L.) were studied under leaching conditions (2.3 mm per day). Grain yield increased strongly due to S application. Split application greatly increased the effectiveness of the sulfate fertilizers and appeared to be an effective tool in satisfying the S need of the crop under leaching conditions. Again, ES fertilizers were least effective, because the oxidation rate of ES was too slow to meet the S demand of the crop. In all experiments leaching losses of sulfate from the ES fertilizers were smaller than from the sulfate fertilizers.

The effect of fertiliser type and application rate on denitrification losses from cut grassland in Northern Ireland

Denitrification losses were measured using the acetylene inhibition technique adapted for a coring procedure. Two soils under a cut ryegrass sward were used. One soil was a freely-drained clay loam receiving under 900 mm rainfall annually, the other soil being a poorly-drained silty clay receiving over 1100 mm rainfall annually. Swards at each site received up to 300 kg N ha−1 yr−1 of calcium ammonium nitrate (CAN), urea or a new fertiliser mixture GRANUMS (30% ammonium nitrate, 30% urea, 10% ammonium sulphate, 30% dolomite). For both soils the rate of denitrification exceeded 0.1 kg N ha−1 day−1 only when the air-filled porosity of the soil was 2 mg N kg−1 in the top 10cm of the profile and when soil temperature at 10 cm was > 4°C. When the soils dried such that their air-filled porosity was > 30% v/v, denitrification rates decreased to < 0.08 kg N ha−1 day−1. Highest rates (up to 3.7 kg N ha−1 day−1) were observed on the clay soil following application of 94 kg N ha−1 CAN to soil near field capacity in early summer 1986. Losses from CAN were approximately 3 times those from urea for a given application. Denitrification losses from the GRANUMS treatment were, overall, intermediate between those from CAN and urea but the daily losses more closely resembled those from the CAN treatment. The impeded drainage on the clay soil, where soil moisture contents remained close to field capacity throughout the year, showed denitrification losses roughly 3 times those observed on the more freely drained clay-loam for any given treatment. Over a 12-month period, N losses arising from denitrification were 29.0 and 10.0 kg N ha−1 for plots receiving 300 kg N ha−1 CAN and urea, respectively, on the well drained clay-loam and 79.0 and 31.1 kg N ha−1 respectively, for identical plots on the poorly drained clay soil. Annual denitrification losses from control plots were < 1 kg N ha−1 on both soils.

Effects of irrigation, N fertilizer, cutting frequency and pesticides on ryegrass, ryegrass–clover mixtures, clover and lucerne grown on heavy and light land

SummaryThe effects of irrigation, nitrogen fertilizer, cutting three or six times per year and a combined pesticide treatment that included aldicarb, phorate, benomyl and methiocarb on ryegrass (Lolium perenne) cv. S.23, either alone or in mixtures with white clover (Trifolium repens) cvs S.I00 or Blanca, and on lucerne (Medicago sativa) cv. Vertus grown on a silty clay–loam at Rothamsted and a sandy loam at Woburn were studied in 1977–81.Benefits from irrigation were greater for six-cut than three-cut swards, with pesticides than without, for ryegrass with clover S. 100 than ryegrass with Blanca and at Woburnthan at Rothamsted. Lucerne did not benefit.Responses of ryegrass to fertilizer N were best fitted by the model y = a + b/1+cx+dx2; and those of ryegrass–clover by the model y = a+bx (where y = yield, x = amount of N; a, b, c and d are constants). Without N, yields of ryegrass–Blanca clover mixtures considerably exceeded those of ryegrass–S.100. The former gave yields equivalent to those of ryegrass given 270 kg N/ha at Rothamsted and 330 kg N/ha at Woburn.Lucerne without irrigation, N or pesticides gave yields in excess of all other unirrigated crops, even when these received pesticides and maximum N. Yields from three cuts of ryegrass greatly exceeded those from six cuts but yields of ryegrass–Blanca were greater from the six-cut regime.Pesticides substantially improved the yields of ryegrass and clover, whether grown separately or mixed, but not those of lucerne. Pesticides not only controlled pests and diseases but also increased the incidence of vesicular–arbuscular mycorrhizas. The relative magnitude of yields of the different swards at the two sites differed, depending on treatment with irrigation, N fertilizer and pesticides. Differences between sites were removed or reversed by appropriate combinations of treatments.Ryegrass–Blanca given no N fertilizer and cut six times removed 300 kg N/ha, an amount that was increased by irrigation and decreased by less frequent cutting; ryegrass–S.100 clover contained less N. Removals of P and K. often exceeded 35 and 300 kg/ha, respectively, each year. Herbage containing Blanca clover had much more Ca than that containing S.100 but at comparable yields all swards contained similar amounts of Mg.

Fate of fertilizer nitrogen.

SUMMARYResults are presented from a three year lysimeter investigation, employing single (15NH4NO3) and double (15NH415NO3) labelled ammonium nitrate to study the uptake of soil and fertilizer nitrogen by cut ryegrass at 250, 500 and 900 kg N ha−1 a−1. Average annual recoveries of nitrogen were equivalent to 99,76 and 50% of the nitrogen added at 250, 500 and 900 kg N ha−1, respectively.At 250 kg N ha−1 the difference between the overall nitrogen recovery and the fertilizer recovery was almost entirely attributable to pool substitution resulting from mineralization/immobilization turnover (MIT). At 900 kg N ha−1 both the low overall recovery of nitrogen and the low fertilizer recovery reflected the large excess of available nitrogen over crop requirements. No evidence of ‘priming’ was obtained.Analysis of the results from single and double labelled lysimeters using simultaneous equations indicated that at 250 kg N ha−1,∼70% of the nitrogen in the crop was derived from the ammonium pool. At 500 kg N ha−1 this dropped to 64%, while at 900 kg N ha−1 the figure was 59%. There was a suggestion that at the lower application rates, preferential uptake of ammonium was occurring but that as N supply exceeded crop requirements, nitrate was the major N source.Despite the preferential exploitation of the ammonium pool, at 250 and 500 kg N ha−1 pool substitution resulting from MIT resulted in lower recoveries of fertilizer ammonium compared with fertilizer nitrate.

Denitrification loss from a grassland soil in the field receiving different rates of nitrogen as ammonium nitrate

SummaryDenitrification loss from a loam under a cut ryegrass sward receiving 0, 250 and 500 kg N ha−1 a−1 in four equal amounts was measured during 14 months using the acetylene‐inhibition technique. The rate of denitrification responded rapidly to changes in soil water content as affected by rain. Mean rates of denitrification exceeded 0.2 kg N ha−1 day−1 only when the soil water content was &gt;20% (w/w) and nitrate was &gt;5μ N g−1 in the upper 20 cm of the profile and when soil temperature at 2 cm was &gt;5–8°C. When the soil dried to a water content &lt;20%, denitrification decreased to &lt;0.05 kg N ha−1 day−1. Highest rates (up to 2.0 kg N ha−1 day−1) were observed following application of fertilizer to soil at a water content of about 30% (w/w) in early spring. Denitrification in the control plot during this period was generally about a hundredth of that in plots treated with ammonium nitrate. High rates of N2O loss (up to 0.30 kg N ha−1 day‐1) were invariably associated with high rates of denitrification (&gt; 0.2 kg N ha−1 day−1). However, within 2–3 weeks following application of fertilizer to the plot receiving 250 kg N ha−1 a−1 the soil acted as a sink for atmospheric N2O when its water content was &gt;20% and its temperature &gt;5–8°C. Annual N losses arising from denitrification were 1.6, 11.1 and 29.1 kg N ha−1 for the plots receiving 0, 250 and 500 kg N ha−1 a−1, respectively. More than 60% of the annual loss occurred during a period of 8 weeks when fertilizer was applied to soil with a water content &gt;20%.

Uptake of fluoride by ryegrass grown in soil treated with sewage sludge

Ryegrass was grown in pots of soil treated with a fluoride-rich sludge which had been implicated in an outbreak of fluorosis on a farm where it was used as a fertiliser. Results showed an approximately linear relationship between fluoride applied to soil in sludge and concentrations of fluoride in ryegrass tissue. Applications in excess of 8·7 t dry matter (dm)/ha of the sludge tested (equivalent to 290 kg/ha of fluoride) produced potentially toxic concentrations of fluoride in the first cut of ryegrass but plant tissue concentrations of fluoride decreased progressively in two later cuts. Every 100 mg/kg increase in the concentration of fluoride in soil resulting from treatment with sludge produced an increase in the concentration of fluoride in ryegrass of 18 mg/kg dm at cut 1, 8 mg/kg at cut 2 and 5 mg/kg at cut 3. In field conditions, direct ingestion of sludge and soil by grazing cattle may be as important a source of dietary fluoride as that ingested in herbage.

The sulphate status of soils from north scotland

AbstractIn a survey of soils from 125 farms in northern Scotland, calcium phosphate extractable sulphate values ranged from 4 to 55 mg S kg soil−1. In 46% of the samples the values were below 14 mg S kg−1, a limit which in countries such as Australia and USA is regarded as representing marginal soils likely to respond to added sulphur. Low values occurred throughout the area examined. Five soils representative of the group and varying in extractable sulphate from 5 to 18 mg S kg soil−1 were studied in a pot experiment to assess the sulphur supplying power. The first cuts of ryegrass contained &lt;0.2% S in the dry matter and had N:S ratios upwards of 15:1, both indicative of inadequate sulphur. Addition of sulphur improved the nutrition of the plants and increased yields, but in some cases N:S values in excess of 15:1 were still obtained. A similar result was found in the second cut, indicating that under these conditions the five soils were unable to provide an adequate supply of sulphur to the crop.

Measurement of available phosphate content of some Spanish soils

Eight Spanish and seven English soils were used to examine methods of determining available soil phosphate. The reference value for the amount of phosphate available was that taken up by six successive cuts of ryegrass grown in a pot experiment.