Unfertilized Grass Research Articles

Growth Curve and Biomass Production of Mestizo Blend Grass (Brachiaria Hybrid) Fertilized with Bokashi-Type Compost

The forage rejected by sheep and goats together with manure, can be considered a problem for the producer when there is no effective strategy to reuse it, in addition, the use of chemical fertilizers to improve the production of forage is a source of environmental pollution. The transformation of these residues into organic fertilizers can be an efficient strategy to re-place the use of chemical fertilizers and maintain forage production. Thus, a field experiment was carried out to evaluate the growth curve and the biomass production of Mestizo blend grass fertilized with Bokashi-type compost. Bokashi was made using waste from sheep and goats as a source of manure and stubble. In a Mestizo grass meadow, apply Bokashi, a dose of 2 T /Ha. With these data, the growth curve was constructed and determined biomass production. An ef-fect of fertilization with Bokashi was found on the growth and biomass accumulation of Mestizo blend grass, being greater from day 14 after fertilization compared to unfertilized grass. On day 49, the grass fertilized with bokashi reached a height of 40 cm and produced 1.795 T/Ha, while the grass without fertilizer grew 31.1 cm and produced 1.231 T Ha-1. Therefore, it is concluded that, under the experimental conditions, the application of Bokashi at a rate of 2 tons per hectare is an effective strategy to increase the biomass production of Mestizo blend grass.

Bermudagrass mite (Acari: Eriophyidae) infestation worsens in response to increasing nitrogen fertility and decreasing irrigation volume but not mowing height.

Severe bermudagrass mite (Aceria cynodoniensis Sayed) infestation stunts turfgrass growth and reduces the aesthetic and recreational value of managed bermudagrass. Management practices, such as fertilization, mowing, and irrigation, may impact bermudagrass mite infestation and damage, but empirical evidence is lacking. Two 20 wk experiments were conducted with potted bermudagrass in a greenhouse or nursery to evaluate the effect of varying nitrogen rates (0, 24.5, or 49 kg N/ha), mowing heights (1.3, 2.5, 3.8, or 5 cm), and irrigation rates (60%, 100%, or 140% evapotranspiration [ET] rate) on the densities of witch's brooms (i.e., stunted and deformed terminals symptomatic of infestation) and bermudagrass mites. Increasing nitrogen fertility from 0 to 49 kg N/ha increased witch's broom and bermudagrass mite densities by 292% and 339%, respectively. Bermudagrass fertilized with nitrogen maintained higher turf quality than unfertilized grass despite greater mite damage. Decreasing irrigation from 140% to 60% of the ET rate also increased witch's broom densities by 124%. Mowing height did not consistently affect witch's broom or mite densities. Witch's broom and mite densities were positively correlated and followed a general trend with greater densities in April-August and a decline in densities in August-October. These findings suggest that nitrogen fertilization and water stress influence bermudagrass mite damage. Thus, limiting nitrogen fertilization to a level necessary to maintain turfgrass health and quality (0.5 kg N/ha) and minimizing turfgrass water stress can complement current chemical control strategies as part of an integrated pest management program.

Acceptability of Pennisetum purpureum by West African dwarf rams as influenced by manure application rates

The present study evaluated the chemical composition and acceptability of Pennisetum purpureum by West African dwarf (WAD) rams as influenced by manure application rates. The experiment was a completely randomized design replicated three times. Grasses that have been fertilized with 5 and 10 t ha-1 of swine manure and unfertilized (control (0 t ha-1)), were harvested from the experimental site 9 weeks after planting from 15 cm above ground level and evaluated for proximate and fibre composition. The harvested grasses were also offered to nine WAD rams on cafeteria basis, to assess the acceptability indices of the grass based on treatments. Results showed that the grass with manures consistently had higher (p<0.05) crude protein (CP) contents than the control (unfertilized plants) while all the grasses with different manure rates had similar (p>0.05) neutral detergent fibre (NDF). Consumption, co-efficient of preference and relative palatability of P. purpureum by WAD rams were improved by manure application, where highest values of acceptability indices was recorded in grass with manure rate of 5 t ha-1 over 10 t ha-1 manured grass. Percentage consumption, co-efficient preference and relative palatability index were in the order 5 t ha-1 > 10 t ha-1 > 0 t ha-1 (unfertilized). From the result, it can be concluded that P. purpureum with manure had a better chemical composition profile (higher CP) and better acceptability than unfertilized grass. Enhancing P. purpureum with manure at 5 t ha-1 had higher ash content and improved acceptability by WAD rams than grass with 10 t ha-1 manure application rate.

Enhanced efficiency nitrogen formulations for bermudagrass–white clover pastures

AbstractNitrogen fertilizer use is generally restricted in bermudagrass [Cynodon dactylon (L.) Pers.]–white clover (Trifolium repens L.) forage systems because it stimulates grass growth and increases competition with the clover, compromising forage nutritive value and prospective forage accumulation. Enhanced efficiency fertilizer nitrogen (N) products hold potential to improve white clover persistence in bermudagrass–clover pastures while providing supplemental N required by the grass. This study evaluated the effect of different enhanced efficiency N formulations (Environmentally Smart Nitrogen [ESN]; methylene urea; SuperU; and 75% ESN, 25% urea blend) and untreated urea on forage accumulation, nutritive value, and legume persistence in a ‘Wrangler’ bermudagrass and ‘Durana’ white clover mixture. Nitrogen was applied at four rates (0, 112, 224, and 448 kg N ha−1) in two equal applications each year. By the second year, white clover stands were lesser at the greatest N rates. All enhanced efficiency N sources maintained white clover similar to the unfertilized grass–clover control, but only ESN improved white clover persistence over urea. Total season forage accumulation increased linearly with increasing N rates within all three growing seasons, but dry weather conditions in the last 2 yr resulted in less forage accumulation. Nutritive value decreased with maturity throughout the growing season, but ESN maintained clover in the pasture resulted in overall less fiber components and greater digestibility. Although there was no effect of N source on forage accumulation, the ability of ESN to maintain clover could make it a viable option for fertilization in bermudagrass–white clover mixtures.

EFFICIENCY OF FERTILIZER APPLICATION ON LONG YEARS HERBAGES

The article presents the results of a study of the long-term herbage of the 71st year of using the
 herbage in the Central Region of the Non-Chernozem Zone of Russia, which over the past 25, against an
 unfertilized background and with an unbalanced fertilization with fertilizers, was transformed into a
 pasture type with a content of grassland grains up to 50%. Against the background of the influence of
 mineral fertilizers (NPK), the grass stand of the hay type remains, in which the content of foxtail reaches
 74%, and with a higher dose of nitrogen fertilizers (N 180) of awnless rump up to 70%.
 The productivity of pasture-type herbage was 55.9 gJ / ha MA, or about 4.5 thousand fodder.
 units from 1 ha 200 - 850 kg / ha of crude protein (CP). The productivity of the hay type increased to 80.4
 GJ / ha MA, or about 6.5 thousand fodder. units from 1 ha, 756 - 1206 kg / ha JV on average for 1993-
 2017 The collection of essential nutrients is in direct proportion to the productivity and quality of the feed
 with different fertilization systems.
 The consumption of nutrients by unfertilized grass stands is provided due to the natural fertility of
 sod-podzolic medium loamy soils on pasture grass stands fertilized with nitrogen fertilizers, nitrogen
 collection increased up to 1.8 times. On grass stands of hay type - 2.6-4.3 times compared to unfertilized
 grass stand. The utilization rate of nitrogen fertilizers on pasture-type herbage was 37 - 65%, phosphorus
 fertilizers - 22-24%, potash fertilizers - 51-100%, on hay-type grass stands, respectively, 48-84, 24-53 and
 106-120%.

Forage mass, nutritive value, and economic viability of cowpea overseeded in tall fescue and sorghum‐sudangrass swards

AbstractCowpea (Vigna unguiculata L. Walp) (CW) is being considered as an alternative feed source in the southern U.S. Legume–grass mixtures are known to provide greater forage mass compared with unfertilized grass monocultures; however, research is needed to evaluate alternatives for increasing forage availability during the summer. The objective of this study was to quantify forage mass, nutritive value, and economic viability of CW overseeded in tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] (TF) and sorghum × sudangrass hybrid [Sorghum bicolor (L.) Moench × Sorghum sudanese (P.) Stapf] (SS) swards seeded at different rates. Two experiments were established in Spring Hill, TN, one with TF and the other with SS, from June to September of 2016 and 2017. Inoculated CW seeds were drilled into TF and SS plots at 25, 50, or 75 lb acre−1 and compared with control treatments that were without CW. There were no differences in total and average forage mass of TF or SS with the addition of CW, regardless of the seeding rate, likely due to the competitiveness of the grasses. No differences among seed rates were observed in the concentration of crude protein (CP) for TF swards mixed with CW in either year while in vitro dry matter digestibility (IVDMD) was less for the control treatment in 2017. Meanwhile, the nutritive value of the SS and CW mixture was improved as the CW seeding rate increased in both years. Data from this study suggest that the addition of CW to TF or SS does not justify its cost given the minimal benefit provided.

Diazotroph Diversity and Nitrogen Fixation in Summer Active Perennial Grasses in a Mediterranean Region Agricultural Soil.

Summer-growing perennial grasses such as Panicum coloratum L. cv. Bambatsi (Bambatsi panic), Chloris gayana Kunth cv. Katambora (Rhodes grass) and Digitaria eriantha Steud. cv. Premier (Premier digit grass) growing in the poor fertility sandy soils in the Mediterranean regions of southern Australia and western Australia mainly depend upon soil N and biological N inputs through diazotrophic (free living or associative) N fixation. We investigated the community composition and diversity (nifH-amplicon sequencing), abundance (qPCR) and functional capacity (15N incubation assay) of the endophytic diazotrophic community in the below and above ground plant parts of field grown and unfertilized grasses. Results showed a diverse and abundant diazotrophic community inside plant both above and below-ground and there was a distinct diazotrophic assemblage in the different plant parts in all the three grasses. There was a limited difference in the diversity between leaves, stems and roots except that Panicum grass roots harbored greater species richness. Nitrogen fixation potentials ranged between 0.24 and 5.9 mg N kg−1 day−1 and N fixation capacity was found in both the above and below ground plant parts. Results confirmed previous reports of plant species-based variation and that Alpha-Proteobacteria were the dominant group of nifH-harboring taxa both in the belowground and aboveground parts of the three grass species. Results also showed a well-structured nifH-harboring community in all plant parts, an example for a functional endophytic community. Overall, the variation in the number and identity of module hubs and connectors among the different plant parts suggests that co-occurrence patterns within the nifH-harboring community specific to individual compartments and local environments of the niches within each plant part may dictate the overall composition of diazotrophs within a plant.

Legume Proportion in Grassland Litter Affects Decomposition Dynamics and Nutrient Mineralization

Core Ideas Grass reduced lag phase and increased legume decomposition in mixtures relative to monocultures. Factors besides litter chemical composition, such as microbial diversity, affected decomposition. Legume treatments were enriched and grass monoculture depleted in δ13C during decomposition. Availability of C, and to a greater extent N, decreased during decomposition. ABSTRACTThe impact of legume inclusion on the decomposition of aboveground plant litter in grasslands is not well understood. Our objective was to quantify litter decomposition and nutrient disappearance from ‘Pensacola’ bahiagrass (Paspalum notatum Flügge) as affected by N fertilizer or proportion of ‘Florigraze’ rhizoma peanut (Arachis glabrata Benth.) in litter. Five litter treatments (unfertilized bahiagrass [BG], bahiagrass receiving 60 kg N ha−1 [BGN], rhizoma peanut and bahiagrass mixtures in 33–67% and 67–33% proportions [RP33 and RP67, respectively], and pure rhizoma peanut [RP]) were incubated for 128 d during each of 2 yr. Decomposition followed a logistic curve with a linear decay between initial and final lag phases. Litter treatment did not affect decomposition rate, but RP33 litter decomposed to a greater extent than BG (35 and 43% remaining biomass, respectively) due to a longer linear decay period for RP33. At the end of incubation, only 25% of the initial rhizoma peanut component litter mass remained for RP33, whereas 35 and 39% remained for RP67 and RP. Bahiagrass decomposition was not affected by the presence of legume. Bahiagrass monocultures showed δ13C depletion, and all legume‐containing treatments showed δ13C enrichment during incubation. After incubation, there was less N in legume litter treatments despite similar chemical characteristics to BGN, indicating that other factors, such as microbial diversity, affected mixture decomposition. Recalcitrance of C and especially N increased during decomposition. We conclude that N return from mixed legume–grass litter is superior to that of unfertilized grass and equal or superior to that of moderately N‐fertilized grass.

Actual Evapotranspiration of Unirrigated Grass in a Smart Field Lysimeter

Core Ideas Small smart lysimeters make high‐quality research of low and dense crops easy. FAO 56 can estimate well the reference crop ET on non‐ or mildly stressed sites. Weather station grass (not water stressed) has lower ET than the reference crop. Lysimeters are basic instruments for evapotranspiration measurement. This study characterized the actual evapotranspiration of unirrigated and unfertilized grass in a warm region of the Czech Republic on a Chernozem loamy soil. An SFL‐300 weighing lysimeter (diameter 0.3 m, depth 0.3 m) was used for this purpose. The suction at its bottom was maintained at the same level as in the native soil nearby. We selected 585 rainless days with regular records for the analysis of daily differences. On most days, the lysimeter‐measured actual evapotranspiration, ETa, was smaller than the Penman–Monteith FAO 56 reference crop evapotranspiration, ET0. The FAO 56 procedure was found to be a reasonable estimator of the unstressed evapotranspiration in a moderately stressed environment. The ETa/ET0 ratio and the canopy surface resistance, rs, depend on the soil water content and suction measured at 5 cm. These graphs break down into horizontal unstressed parts and declining (for ETa/ET0) or inclining (for rs) water‐stressed parts. The ratio ETa/ET0 is about 85% and rs is about 250 s m−1 when the grass is not under water stress. The annual curve of the unstressed crop coefficient has a sine shape. An energy balance criterion suggests that advection of heat is important in winter but not so much in summer. The study provides parameters of evapotranspiration for a canopy that can be found on many standard weather stations and demonstrates that high‐quality research into evapotranspiration of low, dense, and shallow‐rooting crops is possible with small lysimeters of this type.

Managing competitive interactions to promote regeneration of native perennial grasses in semi-arid south-eastern Australia

Treatments to reduce available soil nitrogen and achieve specified levels of weed control were evaluated for their capacity to promote regeneration of native perennial grasses in a degraded semi-arid woodland in central-western New South Wales. Treatments were factorial combinations of nitrogen-reduction levels and weed-control levels. The four levels of nitrogen reduction were no intervention, and oversowing of an unfertilised summer crop, an unfertilised winter crop or an unfertilised perennial grass. The three weed-control levels were defined by the outcome sought rather than the chemical applied and were nil, control of annual legumes and control of all annual species (AA). Regeneration of perennial grasses, predominantly Enteropogon acicularis, was promoted most rapidly by the AA level of weed control with no introduction of sown species. Sown species negated the benefits of weed control and limited but did not prevent the regeneration of native perennials. Sown species also contributed substantially to biomass production, which was otherwise severely limited under the AA level of weed control, and they were effective in reducing soil nitrogen availability. Sown species in combination with appropriate herbicide use can therefore maintain or increase available forage in the short–medium term, permit a low rate of native perennial grass recruitment, and condition the system (by reducing soil mineral nitrogen) for more rapid regeneration of native perennials should annual sowings be discontinued or a sown grass fail to persist. Soil nitrate was reduced roughly in proportion to biomass production. High levels of soil nitrate did not inhibit native perennial grass regeneration when biomass was suppressed by AA weed control, and may be beneficial for pastoral production, but could also render sites more susceptible to future invasion of exotic annuals. The need for astute grazing management of the restored grassland is thus emphasised. This study was conducted on a site that supported a remnant population of perennial grasses. Use of the nitrogen-reduction techniques described may not be appropriate on sites where very few perennial grass plants remain.

Growth rate and nutritive value of sown tropical perennial grasses in a variable summer‐dominant rainfall environment, Australia

AbstractGrowth rate, proportion of leaf and stem and nutritive value of sown tropical perennial grasses have not previously been documented for the dryland, frost‐prone summer‐dominant rainfall region of eastern Australia. An experiment was conducted in northern inland New South Wales with Chloris gayana (Rhodes grass) cv. Katambora and Digitaria eriantha (digit grass) cv. Premier, and compared to Sorghum bicolor ssp. bicolor x S. bicolor ssp. drummondii (forage sorghum). The grasses were harvested every 2 or 6 weeks and fertilized at five rates of nitrogen (N; 0–300 kg N ha−1) over two growing seasons (September–May), 2006–2007 and 2007–2008. Growing season rainfall was below median for both years of the experiment and growth rate was highly variable, reflecting variable rainfall. Sorghum generally had the highest growth rate. Digit grass generally had higher growth rates than Rhodes grass, was more responsive to growing season rainfall, commenced growth earlier and had a longer growing season. Nitrogen application extended the growing season of both perennial grasses. Growth response to N application was minimal when rainfall was low and response following significant rainfall was higher for fertilized than unfertilized grasses. In general, the proportion of green leaf was greater than green stem, although the proportion of stem increased when defoliation interval increased. Nutritive value of the perennial grasses was higher in leaf than stem and declined during the growing season. Differences between the grasses were slight, but indicated that fertilized digit grass defoliated at 2‐week intervals had higher growth rate and nutritive value than Rhodes grass.

Exploring the potential ofin situhyperspectral data and multivariate techniques in discriminating different fertilizer treatments in grasslands

Optimizing the productivity of native rangelands has received considerable attention in range management. Rangeland fertilizer application has emerged as a popular intervention for improving rangeland quality. To achieve optimal range quality from such intervention, there is a need for quick and accurate methods of assessing the effects of different fertilizer combinations. The utility of in situ hyperspectral data and multivariate techniques in distinguishing 12 complex ammonium nitrate, ammonium sulfate, lime, and phosphorus fertilizer combinations on a grassland is assessed. Partial least squares regression discriminant analysis (PLS-DA) and discriminant analysis (DA) classification results derived using hyperspectral grass reflectance that were (1) fertilized using 11 combinations of ammonium sulfate, ammonium nitrate, phosphorus, and lime and (2) unfertilized experimental plots were compared. Results illustrate the strength of in situ hyperspectral data and multivariate techniques in detecting and discriminating grasses with different fertilizer treatments. Specifically, four bands within the red edge (731 and 737 nm) and the shortwave infrared (1310 and 1777 nm) regions of the electromagnetic spectrum demonstrated a high potential for discriminating the effects of fertilizer treatments on grasslands. DA outperformed PLS-DA in discriminating complex combinations of ammonium nitrate, ammonium sulfate combined with lime and phosphorus, as well as unfertilized grasses. Overall, spectroscopy and DA offer great potential for discriminating complex fertilizer combinations.

Effectiveness of buffer strips without added fertilizer to reduce phosphorus loads from flat fields to surface waters

AbstractBuffer strips with no added fertilizers are a mitigation measure to reduce P loads from agricultural land to surface water. However, the experimental evidence on their effectiveness (BSE) has been from sloping locations with shallow flow and surface runoff. The aim of this experimental study was to quantify BSE for P on flat agricultural lowland, predominantly with deep flow. We selected sites characteristic of five major hydrogeological classes in the Netherlands and in each experimental field installed paired 5‐m‐wide unfertilized grass (BS) and reference treatments (REF) that abutted the ditch. The REF treatments were managed similar to the adjacent grass or maize field, but BS treatments were only harvested. Each treatment had a reservoir in the ditch to collect and measure discharge and flow‐proportional P concentration for 3 or 4 yr. We also measured net P withdrawal, the P status of the soil and P concentration in upper groundwater. We found a significant BSE for P of 61% on the site with the shallowest flow and steepest slope (2%). At the other sites, BSE was low and statistically insignificant. We conclude that harvested unfertilized buffer strips reduce P loads from flat fields only in specific areas with high surface runoff and/or shallow flow, especially in combination with a high original soil P status.

Effectiveness of Unfertilized Buffer Strips for Reducing Nitrogen Loads from Agricultural Lowland to Surface Waters

Unfertilized buffer strips (BS) are widely accepted to reduce nitrogen (N) loads from agricultural land to surface water. However, the relative reduction of N load or concentration (BS effectiveness, BSE), varies with management and local conditions, especially hydrogeology. We present novel experimental evidence on BSE for 5-m-wide grass BS on intensively drained and managed plain agricultural lowland with varying hydrogeology. We selected characteristic sites for five major hydrogeological classes of the Netherlands and installed paired 5-m-wide unfertilized grass (BS) and reference (REF) treatments along the ditch. The REF was managed like the adjacent field, and BS was only harvested. Treatments were equipped with reservoirs in the ditch to collect and measure discharge and flow proportional N concentration for 3 or 4 yr. In addition, N concentration in upper groundwater was measured. We found a statistically significant BSE of 10% on the peat site. At the other sites, BSE for N was low and statistically insignificant. Low BSE was explained by denitrification between adjacent field and ditch, as well as by the site-specific hydrologic factors including low proportion of shallow groundwater flow, downward seepage, low residence time in the BS, and surface runoff away from the ditch. We emphasize that a REF treatment is needed to evaluate BSE in agriculture and recommend reservoirs if drainage patterns are unknown. Introduction of a 5-m-wide BS is ineffective for mitigating N loads from lowland agriculture to surface waters. We expect more from BS specifically designed to abate surface runoff.

Nitrogen excretion of adult sheep fed silages made of a mixed sward or of pure unfertilised grass alone and in combination with barley

Four adult rumen-fistulated wether sheep were fed silages combined with barley. The silages consisted of 48% grasses, 28% legumes and 24% other forbs (GCF) or of pure grass (G). The swards received no mineral fertiliser. The dry matter (DM) and fibre contents were lower in GCF than in G. Crude protein content of DM in GCF and G were 145 g/kg and 102 g/kg respectively. DM content as ash, lipids and non-fibrous carbohydrates were rather similar in both silages. About 40g DM were offered per kg BW0.75 and day either as silage alone or as a mixture of silage and barley (60:40). Faecal N excretion was greater with GCF than with G. The proportion of faecal bacterial and endogenous debris N reached 75 and 73% when GCF or G was fed, respectively. Undigested dietary N represented about 20%, and water soluble N accounted for 5–6% of faecal N. GCF caused more urinary N than G. Barley reduced urinary N excretion when supplemented to GCF. No dietary influence on urinary non-urea nitrogenous compounds was shown. GCF caused higher urinary urea N excretion than G and barley reduced this fraction when replacing part of GCF. Based on the urinary urea N proportions, it is concluded that N intake exceeded N requirement for any of the four diets fed. Dietary supplementation of ruminally fermentable carbohydrates can reduce urinary N excretion and this improves the efficiency of utilisation of N in N-unfertilised biodiverse grassland/ruminant farming systems.

Transient responses to increasing CO2 and climate change in an unfertilized grass–clover sward

Mechanisms controlling transient responses to elevated CO2 concentration and climate change in an unfertilized grassland on the Swiss Plateau were examined in light of simulations with PROGRASS, a process-based model of grass-clover interactions. Daily weather for a series of tran- sient climate scenarios spanning the 21st century were developed for the study site with the help of the LARS-WG weather generator. Changes in the length of dry and wet spells, temperature, precip- itation and solar radiation defining the scenarios were obtained from regional climate simulations carried out in the framework of the PRUDENCE project. Compared to 1961-1990, the latter indicated that for 2071-2100 there would be a noticeable increase in temperature (roughly 3°C in winter and 5°C in summer), a significant drop in summer precipitation (of the order of -30%) and a nearly 2-fold increase in the length of dry spells. Assuming that clover is less drought-tolerant than grass, we examined whether clover abundance would decrease as a consequence of increasing heat and water stress, or be promoted on account of CO2 stimulation. Results indicated that: (1) at our site, climate change alone did not curtail biological N2 fixation to the point as to alter the composition of the sward but nevertheless entailed a decrease in grassland productivity; (2) increasing CO2 clearly promoted clover growth (via feedbacks on nitrogen acquisition) and grassland productivity; and (3) even with CO2 stimulation, the additional N input from symbiotic N2 fixation was not sufficient to substantially improve the mineral N status of the system and promote grass competitiveness.

Feeding Preferences in Greylag Geese and the Effect of Activated Charcoal

ABSTRACT Greylag geese (Anser anser) can cause serious damage to agricultural fields near wetlands that are attractive for resting and nesting but not for feeding. Alternative plantings or spraying fields may prevent goose damage. We randomly designed 64 plots in spring 2004 and prepared plantings of white clover (Trifolium repens), white clover with perennial ryegrass (Lolium perenne; mixture), fertilized perennial ryegrass (grass), or unfertilized perennial ryegrass. We measured goose‐dropping densities in plots as a measure of feeding preference in autumn 2004 (7 weeks), spring 2005 (6 weeks), and autumn 2005 (7 weeks) following removal of a protective fence and vegetation sampling for content analysis in 2004. We also sprayed activated charcoal (20 kg/ha) in a suspension on 32 plots (8/planting) to deter geese in autumn 2004 only. In a second experiment we examined pairs of greylag geese in cages for preferences between grass treated with or without activated charcoal. Charcoal did not deter geese in either experiment. However, dropping density averaged highest for clover (1.01/m2), followed by the mixture (0.65/m2), then fertilized (0.23/m2) and unfertilized grass (0.16/m2). Preferences were consistent in all 3 experimental periods. Fertilized grass reached 31.8 cm in height on average in spring, whereas clover measured 15.4 cm. Crude protein and water‐soluble carbohydrate content (g/kg dry matter) was 294 and 49, respectively, in white clover and 183 and 139, respectively, in fertilized grass. We found a positive partial correlation independent of vegetation type between dropping densities and crude protein and a negative correlation with water‐soluble carbohydrate content. Thus, to prevent grazing damage to agricultural fields, we recommend planting white clover, strongly preferred by feeding geese, in areas (fallow agricultural or nonagricultural) adjacent to their habitat and not in agricultural fields under production.

Residual effect and nitrate leaching in grass‐arable rotations: effect of grassland proportion, sward type and fertilizer history

AbstractA key point in designing grass‐arable rotations is to find the right balance between the number of cultivations and the length of the grass phase. In a field experiment, we investigated the effect of cropping history (grazed unfertilized grass–clover and fertilized [300 kg N per hectare] ryegrass, proportion of grassland and previous fertilizer use) on crop growth and nitrate leaching for 2 years following grassland cultivation. In the final year, the effect of perennial ryegrass as a catch crop was investigated. The nitrogen fertilizer replacement value (NFRV) of grassland cultivation was higher at 132 kg N per hectare in the rotation with 75% grassland compared with on average 111 kg N per hectare in rotations with 25 and 38% grassland and the NFRV of ryegrass in the rotation was higher than that of grass–clover. Nitrate leaching following cultivation was not affected by the proportion of grassland in the crop rotation or sward type. However, there was a considerable effect of having a ryegrass catch crop following the final barley crop as nitrate leaching was reduced from 60 to 9 kg N per hectare. When summarizing results from the crop rotations over a longer period (1997–2005), management strategy adopted in both the grassland and arable phases appeared to be the primary instrument in avoiding nutrient losses from mixed crop rotations, irrespective of grass proportion. In the arable phase, the huge potential of catch crops has been demonstrated, but it is also important to realize that all parts of the grass‐arable crop rotations must be considered potentially leaky.

Soil Organic Carbon after Twelve Years of Various Crop Rotations in an Aridic Boroll

Eliminating summer fallow or establishing perennial grass elicited measurable gains in soil organic C (SOC) after just 6 yr in a crop rotation study on an Aridic Boroll in southern Alberta. This study was resampled after 12 yr to determine if SOC increases were continuing with time and to evaluate the impact of alternative crop rotation and fertilizer treatments on SOC. The crop rotation treatments included in this study were fallow‐wheat (FW), fallow‐wheat‐wheat (FWW), fallow‐flax‐wheat (FXW), legume‐wheat (LW), continuous wheat (W) and continuous grass (G). The gain in SOC due to the elimination of fallow was 1.5 Mg C ha−1 after 12 yr, no greater than that observed after 6 yr. Soil organic C was the same for all rotations that included fallow (FW, FWW, FXW). Fertilizer treatments that had the greatest benefit on grain yields of annual crops also tended to increase SOC, although differences were barely detectable. The gain in SOC of unfertilized grass compared to the FW rotation was no higher after 12 yr than after 6 yr (3 Mg C ha−1). Under fertilized grass, in contrast, SOC continued to increase at a rate of approximately 0.5 Mg C ha−1 yr−1 Accumulation of light fraction C accounted for most of the gains in SOC that occurred with elimination of fallow or establishment of grass. These findings suggest that much of the SOC gain due to adoption of C‐conserving practices in soils like those of this study may occur early, within the first decade, and consist primarily of decomposable soil fractions. If confirmed, this means that C sequestration in these soils may be comparatively short‐lived and vulnerable to future loss.

Reduced nitrate concentrations in shallow ground water under a non-fertilised grass buffer strip

In this paper the suitability of a buffer strip to reduce nitrate concentrations in the upper groundwater was tested for a sandy arable soil in The Netherlands during two consecutive leaching seasons. The bufferstrip was a 3.5 m wide unfertilised grass strip adjacent to a ditch on an arable field. In total 24 groundwater wells were installed in 4 transects perpendicular to the ditch to determine Cl, NO3 and δ15N concentrations. Piezometers were installed to assess the groundwater flow, which was in the direction of the ditch with small downward leakage across a peat layer at about 3 m depth. Nitrogen was dominantly present as nitrate (NO3). The NO3-N concentrations under the bufferstrip were significantly lower than under the adjacent arable field. The lower concentrations were due to dilution, uptake by grass and denitrification. Nitrate was actively removed in the bufferstrip, since the Cl/NO3 ratios were higher in the bufferstrip than in the remainder of the field. Furthermore, δ15N data indicated that denitrification occurred in the groundwater and increased with decreasing distance to the ditch. NO3-N loads to the ditch were estimated at 8.5 kg ha−1yr−1, which is relatively low for this area. We can, however, not determine whether these relatively low NO3-N loads were causally related to the reduced NO3-N concentrations in the bufferstrip. Nevertheless, the results of the present study are promising and justify additional research on the efficiency of bufferstrips to reduce NO3 concentrations in shallow groundwater, and subsequently reduce NO3 loading of surface water, under Dutch conditions.