Dry Matter Yield Of Ryegrass Research Articles

Plant and Soil Effects of Alternative Sources of Phosphorous over Three Years of Application

Plant growth and food security depend heavily on phosphorous (P). Recovering and recycling P from animal, municipal, and food waste streams can significantly reduce dependency on traditional mineral P. This is particularly pertinent in the EU regions with limited native P supplies. The agronomic performance of including P-based recycling-derived fertilisers (two struvite and two ashes) or cattle slurry was compared to a conventional mineral P fertilisation programme along with no P and no fertiliser controls over three years. A field-scale experiment was set up to evaluate the perennial ryegrass dry matter yield (DMY), P uptake, and soil test P effects. Struvite, ash, and cattle slurry proved effective in replacing P mineral fertiliser and produced yields similar to those of the mineral fertiliser programme. Differences were observed in plant P recovery, with struvite-based programmes achieving a significantly higher P recovery than ash-based programmes, which had the lowest plant P recovery. Differences in Morgan’s soil test P were also noted, with potato waste struvite (PWS) and poultry litter ash (PLA) showing significantly higher soil test P values. The findings strongly indicate that a range of recycled bio-based fertilisers from the bioeconomy can be used to reduce reliance on conventional imported mineral P fertiliser, with some programmes based on recycled fertilisers even surpassing the performance of conventional linear economy mineral fertilisers.

UAV-based prediction of ryegrass dry matter yield

ABSTRACT Forage yield is traditionally measured by manual harvesting, drying, and weighing and has multiple uses, including plant breeding and pasture management. The goal of this paper was to determine the accuracy of unmanned aerial vehicle (UAV)-based prediction of ryegrass percentage cover, vegetation volume, and dry matter (DM) yield in Autumn from 300 rectangular 1.5 m2 plots at a height of 20 m above ground level, compared to the current manual method. The secondary goal was to evaluate the UAV-based method for the determination of dry matter yield from five different ryegrass cultivars. A photogrammetry-based technique combined with a spectral method to determine the soil level was used to determine the percentage cover and vegetation volume of ryegrass plots, which were then used to obtain calibration curves to predict DM yield per plot. Calibration curves were obtained for five different ryegrass cultivars, with concordance between calibration curves for four of the five cultivar populations. The relationship between predicted forage volume (m3) and measured DM (g per 1.5 m2 plot) for ryegrass Populations 1,2,4,5 had an R2 = 0.61. Population 3 was different to Populations 1,2,4,5, with a two-fold difference in DM yield for the same forage volume. This demonstrated that 61% of the variance in DM yield can be explained by forage volume determined by a UAV-based photogrammetry method. We also further tested the methodology from 70 rectangular 2.4 m2 ryegrass plots in a Spring trial. The relationship between the predicted DM yield per 2.4 m2 plot (based on the average predictions from forage volume and forage area models) and measured DM yield per plot had an R2 = 0.66. UAVs can therefore increase the acquisition of field data for research studies and the management of pasture in grazed farm systems.

Effect of Dairy Pond Sludge/Supernatant Application on Ryegrass Dry Matter Yield and Phosphorus Fractions in Soil

Pasture yield in dairy grazing systems is critical to supplying sufficient feed for milking cows and maintaining productivity. In the Australian dairy industry, ryegrass and clover are common grasses used in grazed pastures. Dairy shed effluent (DSE), the wastewater produced from washing down the dairy holding yards during and after milking, is generally managed through application to pasture as a fertilizer substitute/supplement following partial treatment in stabilization ponds. The aim of this study is to assess the benefits of applying sludge and supernatant collected from two-stage DSE pond systems to ryegrass pasture. A pot experiment was conducted which involved applying pond sludges and supernatant to soil seeded with ryegrass. The application rates of the pond by-products were set according to their labile (plant available) phosphorus content. Ryegrass yield and leachate generated from each of the pots were recorded, and samples were collected for analysis of nutrients and other parameters. The ryegrass grown in soil treated with pond sludge and supernatant yielded greater dry matter (DM) with higher nutrient content than untreated control pots. In addition, pots treated with pond sludge exhibited lower rates of phosphorus leaching from the soil compared with pots treated with supernatant. Thus, pond sludge retained more plant available phosphorus in soil than both the control and pond supernatant treatment. The potassium to calcium/magnesium ratios in the ryegrass in the pots treated with pond sludge and supernatant were below the recommended upper limit for grazing. Therefore, the application of pond sludges on the dairy paddocks was found to be superior to applying supernatant in terms of utilization and conservation of phosphorus within the dairy farm and presents low risks of groundwater pollution and grass tetany.

Efficiency of Phosphorus Fertilizers Derived from Recycled Biogas Digestate as Applied to Maize and Ryegrass in Soils with Different pH

Three phosphorus (P) fertilizer fractions recycled from biogas digestates were tested alone and in combination for their efficiency in two agricultural surface soils with different pH: a silty sandy loam and a clay loam. The experiments were carried out in pots under greenhouse conditions, using mineral triple superphosphate (TSP) as a reference. Maize was cultivated for 50 days, followed by ryegrass cultivation for an additional 84 days in the same soil, without additional fertilization. The variables investigated were above-ground plant biomass production, plant phosphorus concentration and content, and plant available phosphorus concentration in soil. The dry matter (DM) yield of maize was increased by the organic P fertilizers equal to or more than TSP in both soils. In the neutral soil, biomass was almost doubled compared to TSP when using one of the fractions (Struvite containing P-Salt) alone or in combination with dried solid fractions. P concentration in maize cultivated in the neutral soil was not significantly different between the P fertilization treatments. However, associated with biomass increase, the total P content in maize plants was equal to or higher than that with TSP. In the acidic soil, P concentration and total P content in maize plants, as well as the calcium-acetate-lactate extractable P (CAL-P) concentration in soil, were equal to or even higher than TSP. Ryegrass DM yield was unaffected by all P fertilizers, independent of the soil, although P concentration and total P content increased in the acidic soil with all fertilizers. Our results show that recycled P fertilizers from biogas digestates are effective P fertilizer alternatives to mineral TSP for maize cultivation under acidic and neutral soil conditions. The lack of growth effects in ryegrass indicates that recycled P fertilizers do not require changes in weed control. On the other hand, P extraction by ryegrass in overfertilized acidic soils as an option for soil remediation also works in soils fertilized with biogas digestate fractions.

Deterministic and stochastic modelling of impacts from genomic selection and phenomics on genetic gain for perennial ryegrass dry matter yield

Increasing the efficiency of current forage breeding programs through adoption of new technologies, such as genomic selection (GS) and phenomics (Ph), is challenging without proof of concept demonstrating cost effective genetic gain (∆G). This paper uses decision support software DeltaGen (tactical tool) and QU-GENE (strategic tool), to model and assess relative efficiency of five breeding methods. The effect on ∆G and cost ($) of integrating GS and Ph into an among half-sib (HS) family phenotypic selection breeding strategy was investigated. Deterministic and stochastic modelling were conducted using mock data sets of 200 and 1000 perennial ryegrass HS families using year-by-season-by-location dry matter (DM) yield data and in silico generated data, respectively. Results demonstrated short (deterministic)- and long-term (stochastic) impacts of breeding strategy and integration of key technologies, GS and Ph, on ∆G. These technologies offer substantial improvements in the rate of ∆G, and in some cases improved cost-efficiency. Applying 1% within HS family GS, predicted a 6.35 and 8.10% ∆G per cycle for DM yield from the 200 HS and 1000 HS, respectively. The application of GS in both among and within HS selection provided a significant boost to total annual ∆G, even at low GS accuracy rA of 0.12. Despite some reduction in ∆G, using Ph to assess seasonal DM yield clearly demonstrated its impact by reducing cost per percentage ∆G relative to standard DM cuts. Open-source software tools, DeltaGen and QuLinePlus/QU-GENE, offer ways to model the impact of breeding methodology and technology integration under a range of breeding scenarios.

Ryegrass yield and nutrient status after biochar application in two Mediterranean soils

ABSTRACTThis study was conducted to evaluate whether biochar, produced by pyrolysis at 300°C from rice husk and grape pomace (GP), affects plant growth, P uptake and nutrient status. A 3-month period of ryegrass (Lolium perenne L.) cultivation was studied on two Mediterranean agricultural soils. Treatments comprised control soils amended only with compost or biochar, and combinations of biochar plus compost, with the addition of all nutrients but P (FNoP) or without any fertilization at all (NoF). Application of both types of biochar or/with compost, in the presence of inorganic fertilization except P, significantly increased (P < 0.05) dry matter yield of ryegrass (58.9–77.6%), compared with control, in sandy loam soil, although no statistically significant increase was observed in loam soil. GP biochar and GP biochar plus compost amended loam soil harvests gave higher P uptake than control, in the presence of inorganic fertilization except P, whereas in sandy loam soil, a statistical increase was recorded only in the last harvest. In addition, Mn and Fe uptake increased with the addition of the amendments in both soils, while Ca increased only in the alkaline loam soil. Biochar addition could enhance ryegrass yield and P uptake, although inorganic fertilization along with soil condition should receive special attention.

Evaluation of the agricultural production systems simulator simulating Lucerne and annual ryegrass dry matter yield in the Argentine Pampas and south-eastern Australia

Modelling plant growth provides a tool for evaluating interactions between environment and management of forage crops for pasture-based livestock systems. Consequently, biophysical and farm systems models are becoming important tools for studying production systems that are based on forage crops. The Agricultural Production Systems Simulator (APSIM) is a model with the potential to compare the growth of annual forage crops and perennial pastures. However, information is limited about how accurately the Lucerne and Weed modules represent the growth and development of forage crops and pastures under different managements, soil types and environments in South America. This study evaluated the capacity of APSIM to simulate the growth rates and predict the dry matter (DM) yield of Lucerne (Medicago sativa L.) and annual ryegrass (Lolium multiflorum Lam.) in contrasting climatic regions of Argentina. In addition, at several Australian locations, DM yields of both crops were simulated to ensure that possible changes to the model not interfere with the robust APSIM performance that was already shown in south-eastern Australia. Initial simulations for Lucerne and ryegrass were made with original Lucerne and Weed modules of APSIM, respectively. Simulated DM yield was then compared with field data collected from the same crops grown in five locations in the Argentine Pampas and seven locations in south-eastern Australia over 5 of years. APSIM predicted DM yield of Lucerne at each harvest with reasonable accuracy [0.59, 0.77 and 0.77 for R2, correlation coefficient and concordance correlation coefficient (CCC), respectively]. However, these statistics improved when the DM yield was analysed by annual accumulation, with values of 0.87, 0.93 and 0.92 for R2, correlation coefficient and CCC, respectively. APSIM, generally, over-predicted DM yield of annual ryegrass at the first harvest. Nonetheless, when the Weed module was modified through changes in phenology and transpiration efficiency, performance improved (values of 0.89, 0.94 and 0.93 for R2, correlation coefficient and CCC, respectively). This study showed that annual DM yield of Lucerne can be successfully modelled by the APSIM Lucerne module without any modifications, using a crop modelling approach. However, successfully modelling of Lucerne DM yield by harvest will require further development of the model. Moreover, modification of model parameters associated with phenology and transpiration was required to enable the Weed module of APSIM simulate growth and yield of annual ryegrass in a range of geographic locations within the Argentine Pampas.

GROWTH AND DRY MATTER YIELD OF MAIZE (ZEA MAYS L.) AND RYEGRASS (LOLIUM PERENNE L.) PLANTS AS AFFECTED BY THE APPLICATION OF LIQUID AND SOLID ORGANIC AMENDMENTS IN A CU CONTAMINATED SOIL

The main objective of this study was to evaluate the effect of the application of two solid and one liquid organic amendments (OA), i.e., turkey manure, vineyard compost, and compost-derived humic acids (HA), on the growth and dry matter (DM) yield of maize and ryegrass plants grown in pots (5 L and 2 L) using a contaminated soil. Maize and ryegrass plants were consecutively cultivated during the experimental period (140 days) using a complete random design. Amendments were applied 10 days before the first crop (maize), at three different application rates, and both plant species were chemically fertilized (NPK). Control treatments with and without chemical fertilization were also included. Aerial dry matter (DM) yield of maize was enhance by manure and compost addition in comparison to the fertilized control, while HA had a negative impact on the DM production due to increased soil electrical conductivity (EC). In average, compost and manure applications increased maize DM about 1.2 and 2.7 fold over the control, respectively. DM yield of ryegrass was proportionally increased by the C rate for the three amendments, with few significant differences (p<0.05) among them at the higher application rates. In average, compost, manure and HA applications increased ryegrass DM about 1.5, 1.9, and 1.4 fold over the control. Significant modifications (p<0.001) of the soil available Cu were noted. Correlation analyses indicated that the lower DM production of plants was related to a higher damage of root membranes (malon-dialdehyde [MDA] test) induced by the higher levels of DTPA-Cu. The observed differences in DM would be also explained by the input of different nutrients (like N-NH4) contained in the OA, especially in the manure. Using a stepwise procedure, a regression model was generated for predicting the total maize + ryegrass DM production as a function of soil properties. This model incorporated as predictive variables: TPA-Cu and FA-C.

Recovery efficiency of nitrogen from liquid and solid fractions of pig slurry obtained using different separation technologies

AbstractThe characteristics of solid (SF) and liquid (LF) fractions resulting from solid–liquid separation of pig slurry depend on the separation technique used. It can be assumed that the separation technique will also affect the nitrogen (N) availability to plants. A pot experiment was performed with ryegrass to compare the N‐recovery efficiency of SFs and LFs obtained with four frequently used separation techniques (centrifugation [Cent], sediment settling during 20 h [Sed], enhanced settling during 20 h by addition of cationic polyacrylamide [Sed+PAM], sieving [Siev], sieving followed by treatment of the resulting liquid fraction by PAM addition [Siev+PAM]) with the untreated slurry (US) and an unfertilized control. Increases (2–17%) of ryegrass dry matter yield (DMY) were obtained in LF treatments relative to US. However, this increase was statistically significant only for the Siev+PAM‐L treatment. A significant decrease of ryegrass DMY was observed in SF treatments relative to US. All treatments with SFs led to similar values of DMY while only small differences were observed between treatments receiving LFs. A significant correlation (R2 = 0.968) was observed between the total DMY and the NH$ _4^+ $ ‐ N : Ntot ratio of the fraction applied suggesting that this is a major parameter to be considered when comparing separation techniques. Overall, the separation techniques showed only a weak effect on the dry matter yields and on the N ‐ recovery efficiency from LF and SF although they strongly affected the nutrient concentration and speciation in each fraction.

Compost-Sewage Effluent Integration for Ryegrass Production

This study evaluated effects of integrated application of compost and secondary treated sewage effluent (STSE) on net N mineralization (NMnet) and ryegrass production. Soil incubation and pot (glasshouse) trials were carried out on two soil types, sandy loam and clay loam. NMnet was significantly higher (p < 0.05) in clay loam than in sandy loam soil. Increasing contribution of compost in integrated compost and STSE resulted in N immobilization. Experimental data on ryegrass dry matter (DM) obtained in pot trial was consistent with NMnet trend observed in soil incubation. In pot trial, ryegrass DM yield and N use efficiency reduced with increasing contribution of N from compost. For every unit addition of compost (25%), DM yield of ryegrass declined by 573 and 462 kg DM−1 in sandy loam and clay loam, respectively.

An evaluation of the effectiveness of nonconventional p fertilizers derived from Zimbabwe phosphate rock using ryegrass as a test crop

Zimbabwe and many other African countries lack high-quality phosphate ores for the production of conventional phosphate fertilizers. The objective of this study was to investigate the agronomic potential of an igneous phosphate rock derived from Dorowa (Zimbabwe) in agreenhouse experiment using rye grass (Lolium perenne) as test crop on a Hartsells silt loam. Three phosphate fertilizer materials: finely ground (0.150-mm screen) Dorowa phosphate rock (DPR);DPR partially acidulated with 50 % of the sulfuric acid required for complete acidulation (PADPR); and a compacted mixture of DPR + triple superphosphate + urea + potassium chloride (DTUK)with half of phosphorus from DPR and half from TSP were made from Dorowa rock and their agronomic effectiveness compared with that of single superphosphate. The relative agronomic effectiveness of the fertilizers based on dry matter yield of ryegrass followed the orders:DTUK=SSP>PADPR>DPR=Check and SSP>DTUK=PADPR>DPR=Check during the first 12 weeksand the second 12 weeks, respectively. For phosphorus uptake by ryegrass, the orders were: DTUK>SSP>PADPR>DPR=Check, DTUK=SSP>PADPR>DPR=Check, and SSP>DTUK>PADPR>DPR=Check during the first six, second six, and last 12 weeks, respectively. The results confirmed that the effectiveness of DPR could be greatly enhanced by partially acidulatingDPR or compacting DPR with TSP, urea, and KCl.

Predicting potassium fertilizer requirement using exchange isotherm approach in relation to soil characteristics

Determining potassium (K) fertilizer requirement using sorption isotherms is considered more accurate than conventional soil K tests. A total of 59 surface soil samples were used to establish K exchange isotherm. To evaluate K requirement sorption test, a glasshouse experiment using perennial ryegrass (Lolium perenne, cv. Roper) was carried out on 10 soil samples. The experiment was laid out as a completely randomized design with four replications and four K levels (K0, K20, K40, K80). Concentrations of K in solution established by adding K in the pots estimated from the sorption curve ranged from 20 to 80 mg K l−1 including check treatment (no K). Dry matter yield of ryegrass in most soils approached maximum as adjusted K levels were increased to 20 mg K l−1. The amounts of K required to bring the soils to 20 mg l−1 in soil solution varied among soils and ranged from 99 to 399 mg kg−1, on average 205 mg kg−1 soil. It was found that a useful regression model for the prediction of standard K requirement (K20) included the combination of plant available K extracted by NH4OAc (Av-K) and clay content: K20 = −41 − 0.63 Av-K + 9.0 Clay (R2 = 0.61, p < 0.001, n = 59).

Sea salmon sludge as fertilizer: effects on a volcanic soil and annual ryegrass yield and quality

Abstract. To evaluate the effect of sea salmon sludge on soil and ryegrass yield and quality, five treatments were tested (30, 60 and 90 t ha−1 of sludge, inorganic fertilizer and control). The sludge contained 16% dry matter (DM), 0.13% total N and 1.6% P. The sludge increased ryegrass DM yield, P and Na content, but decreased K concentrations in soil and plants. Sludge can be applied successfully on to land, but its addition should be complemented with inorganic nutrients (N, K). The high Na content of the sludge may limit repeated application, but the main benefit is its P content.

Long-term performance of white clover varieties grown with perennial ryegrass under rotational grazing by sheep with different nitrogen applications

Three experiments were carried out to investigate the dry matter production of nine white clover (Trifolium repens L.) varieties grown with the same variety of perennial ryegrass (Lolium perenne L.) and subjected to rotational grazing by sheep over a period of 10 years. The experiments differed only in the nitrogen fertilizer added: no nitrogen, 100 kg/ha per year and 200 kg/ha per year. Dry matter (DM) yields of white clover and perennial ryegrass components of the sward were recorded at approximately 6-week intervals during the growing season.Without applied nitrogen, 10-year mean white clover annual DM yields ranged from 2·89–4·54 t/ha. Mean clover content for all varieties ranged from 31–50% for the first 9 years, declining to 20% in the 10th year. The most consistently high yielding variety, AberVantage, gave yields greater than 3·5 t/ha in every year. Similar results were observed for the variety Aran. The 10-year mean annual DM yield of the perennial ryegrass companion (variety Talbot) ranged from 4·41–5·57 t/ha depending on the white clover variety in the mixture. Variation in perennial ryegrass DM yield was of a similar range and pattern as for white clover.In the experiment in which 100 kg N/ha per year was added, 10-year mean white clover annual DM yields ranged from 2·27–3·87 t/ha. The varieties AberVantage and Aran showed yields that fell below 3 t/ha per year in only 1 or 2 years, respectively. Mean clover content for all varieties ranged from 26–38% for the first 9 years, declining to 17·5% in the 10th year. There was no consecutive annual decline in white clover DM yields. The 10-year mean annual DM yields of the perennial ryegrass companion ranged from 6·03–7·57 t/ha.With applied nitrogen fertilizer of 200 kg N/ha per year (Experiment 3), 10-year mean white clover annual DM yields ranged from 1·21–2·67 t/ha. Mean clover content ranged from 12–27% for the 10 years. AberVantage and Aran showed yields consistently above 2 t/ha. No general decline in white clover DM yields was observed although some varieties showed consecutive annual reductions in years 8, 9 and 10. The 10-year mean annual DM perennial ryegrass yields ranged from 7·27–8·68 t/ha.The results show that, under rotational grazing by sheep, white clover can give reliably high yields over a 10-year period. With moderate to high applications of nitrogen fertilizer white clover yields were lower than without nitrogen but they were consistent and sufficient to make a considerable impact on forage quality. There was no evidence for a general decline in clover content until the 10th year of the experiment and no cyclical pattern of annual variation in white clover yield was observed. The implications of these results for the role of white clover in UK agriculture are discussed.

Mineral sources of potassium to plants for seven soils from south-western Australia

This investigation was conducted with surface horizon samples from 7 south-western Australian soils and their 3 size fractions (sand, silt, and clay). The K release of these materials was measured for several extractants; the highest amounts of K were released from the clay (&lt;2 μm) fraction. The presence of sand-size feldspars and incomplete removal of attached organic matter resulted in sand releasing significant amounts of K. The proportions of total K released in boiling 1 m HNO3 by the sand, silt, and clay fractions ranged from 0.4 to 3.4%, 2.6 to 36.3%, and 11.2 to 51.4%, respectively, and from 2.0% to 22.9% for the whole soils. Cumulative K uptake by 6 harvests of ryegrass over 260 days ranged from 0.26 to 1.23 cmol/kg soil.The clay fraction released higher proportions of total K to acid compared with the sand and silt size fractions because of the high specific surface area of the clay and because it contained proportionately higher amounts of illite, which releases K by both ion exchange and dissolution, whereas K release from feldspars requires congruent dissolution of the silicate structure. The differences in contents of StepK (relatively available fraction of the non-exchangeable K) and CRK (constant rate K) for 1 m HNO3 dissolution of these soils and size fractions reflect differences in mineralogical composition between the soils and size fractions. The low contents of StepK for the sand fraction indicated that K was strongly retained by feldspars. The soils with high CRK values had significant amounts of illite in the clay fraction. Values of CRK were positively related to cumulative K uptake and cumulative dry matter yield of ryegrass.

COMPETENCIA ENTRE BALLICA PERENNE Y TREBOL BLANCO EN CONDICIONES DE BAJO SUMINISTRO DE NITROGENO DEL SUELO

With the objective to evaluate the competition between perennial ryegrass and white clover under low soil nitrogen supply a glasshouse experiment was conducted. The soil sampled from Valdivia soil series was initially lowered in its nitrogen content by extraction with oat by several months. After extraction, the soil was put in boxes in a completely randomized design with four replicates for treatment. The treatments were: no competition, shoot competition only, root competition only and shoot and root competition. Additionally, two treatments with N fertilization (equivalent to 300 kg N ha-1) were included: no competition and total competition. The treatments were evaluated during five cuttings and the following parameters were measured: dry matter yield and cutting height of perennial ryegrass and dry matter yield and stolons length on white clover The study allowed to establish that N affect perennial ryegrass competitive ability and it does not affect white clover competitive ability. Moreover, white clover in conditions of a low supply is capable to depress the perennial ryegrass dry matter yield and height because of its higher competitive ability just after cutting. It is suggested that is possible to maintain an adequate balance between perennial ryegrass and white clover when the soil N supply is low if cutting is properly managed.

Microbial biomass phosphorus and its significance in predicting phosphorus availability in red soils

Red soils are widespread in Southern China and other subtropical regions in the world. An improved management of phosphorus (P) is crucial for sustainable agriculture and environmental quality in red soil regions. Plant‐availability of P in red soils mainly depends on fertilization and biological cycling. Both laboratory analyses and greenhouse experiments were conducted to examine the relationships between plant P uptake, chemical index of P, and microbial biomass P in red soils with different fertility levels. Microbial biomass P ranged from 2.1 to 43 mg kg‐1 in the red soils and was significantly correlated with total P (r=0.84*), organic P (r=0.87*), or Bray I extractable P (r=0.94**). Extractable P plus organic carbon accounted for >85% of the variation in microbial biomass P in the red soils. The significant relationship between microbial biomass P and extractable P suggests that microbial biomass P has a great potential in predicting P‐supply ability in soil. Greenhouse experiments showed that there were close relationships between ryegrass dry matter yield, plant P uptake or tissue P concentration and microbial biomass P in the red soils. The corresponding correlation coefficients were 0.79*, 0.90*, and 0.91*, respectively. These results imply that microbial biomass P plays an important role in the availability of P to plants, and is a potential biological index of P availability in the red soils.

RELEASE OF POTASSIUM FROM THE SILT AND SAND FRACTION OF LOESS-DERIVED SOILS

The objective of this investigation was to examine whether the silt in loess-derived soils represents a major K+ source for plants. The experiment was carried out with 14 arable loess-derived soils (Alfisols) from which, in one series, the clay was removed and in which, in another series, complete soils were used. In this work, the latter are denoted as whole soils, whereas the soils without clay are labeled silt + sand fractions, of which the silt proportion was about 80%. Potassium was extracted from whole soils and from silt + sand fractions by electroultrafiltration (EUF). Potassium quantities extracted from the silt + sand fractions were about half the K+ quantities extracted from whole soils. Potassium rates extracted and plotted on extraction time yielded curves that fitted the Elovich equation. Dry matter yield of ryegrass (Lolium perenne) grown in pots on whole soils did not differ significantly from dry matter yields obtained from grass grown in pots on silt + sand fractions. Thus, it is suggested that the K+ present in the silt + sand fraction was readily available to the grass. Close correlations between K+ uptake of the grass and K+ soil parameters were obtained with the EUF extraction at 400 V and 80°C, with which the interlayer K+ was mainly obtained. The b values of the Elovich equation reflect the K+ release rates of interlayer K+. The data provide evidence that in loess-derived soils, the silt fraction, presumably because of its high mica concentration, is of great importance for the supply of K+ to plants.

Effect of composted sewage sludge amendment on soil nitrogen and phosphorus availability

Municipal sewage sludge previously composted with sawdust (CSS) was applied to an eutric sandy cambisol at rates of 7.5, 15.0, 22.5, and 30 g#lbkg‐1. Incubation and pot experiments were conducted to evaluate CSS effectiveness on nitrogen (N) and phosphorus (P) soil availability and on plant nutrition. The CSS rates did not increase soil mineral N and had little effect on organic P and on labile forms of P. Efficiency of total applied P was 17% for the soil labile forms and 4.8% for the resin extractable fraction. In contrast, CSS significantly increased hydroxide extractable inorganic P and nonextractable soil P fraction. The major portion of the increment on nonextractable forms was at the expense of HC1 extractable P fraction [calcium (Ca)‐bounded], dominant on the original CSS. Thus, chemical rather than biological reactions lead to the redistribution of CSS‐borne P to more firmly held forms after its application to the soil. Ryegrass dry matter yield, N content, and N uptake did not increase in CSS‐treated soils. Plant P content increased at the second harvest, but the effect was nil in the subsequent harvest. Total P uptake increased from 14.1 to 20.2 mg#lbpot‐1, but percentage P recovery by ryegrass was modest, averaging 2.5% of the CSS‐borne P. Results suggest that moderate application of CSS to agricultural systems are inadequate for crop growth but may contribute to nutrient recycling without environmental risks related to N and P loss.

Determination of available phosphorus in soils from northern Greece by the electro‐ultrafiltration (EUF) and other methods of soil analysis

Abstract The suitability of electro‐ultrafiltration (EUF) and other methods of soil analysis, commonly practised worldwide, for the assessment of available phosphorus (P) in 21 soils taken from various locations of northern Greece, as defined by P uptake and dry matter yield of ryegrass grown in pots, was studied. Significant correlations were found to exist between the quantities of P uptake by ryegrass and those of P extracted by the various methods. Phosphorus uptake by ryegrass correlated best with the P‐resin contents (r = 0.91***), while the poorest correlation was observed with the organic P fraction (r = 0.53*). The correlation between EUF‐P at 20°C and P uptake by ryegrass was highly significant (r = 0.84***) and became even higher when the values of the quotient EUF‐P 80°C/EUF‐P 20'C, i.e. the P reserves, were taken into account. Of all the methods tested, the Olsen‐P method proved least sensitive to changes in pH, texture, cation exchange capacity (CEC), and percent base saturation.