Interactions between N supply and N uptake by perennial ryegrass, 15N recovery and soil pH for four acid Scottish soils

The effects of NH₄⁺−N, NO₃⁻-N or urea-N addition on N uptake by perennial ryegrass ( Lolium perenne ), ¹⁵N recovery and pH of four limed and unlimed soils were determined in a pot experiment over 10 weeks. The best form of N in terms of herbage N uptake and fertilizer recovery differed between the soils. Recovery of applied ¹⁵N in herbage was greatest for the soil with the lowest pH and highest organic matter content, and overall recovery in the soil–plant system was influenced more by soil type than by N form. There was always an apparent mineralization of soil N when perennial ryegrass was present. Soil pH changes ranged from +0·11 to −0·58 units for the unlimed soils and from +0·03 to −1·06 units for the limed soils. The use of NO₃⁻-N rather than NH₄⁺-N or urea-N avoided further acidification. Lime increased herbage N only from the soils with the lowest pH values. Although the acidifying effect of NH₄⁺-fertilizer was alleviated, liming may increase nitrification and possibly N loss via denitrification and/or leaching in the field.
The major influence of soil type on herbage N uptake, pH response to the treatments and fertilizer recoveries implies that liming and fertilizer N management decisions should consider soil characteristics, such as organic matter, clay contents and pH.     

Effects of nitrification inhibitor and acid addition to cattle slurry on nitrogen losses and herbage yields

Cattle slurry was applied to grassland on two contrasting soils in autumn and spring between 1987 and 1990. Slurry was applied with or without the addition of acid, to lower the pH to 5·5, and, in autumn only, with or without a nitrification inhibitor. Ammonia volatilization, denitrification and apparent recovery of N by the cut herbage accounted for 61–86% of the ammonium nitrogen (NH₄⁺-N) applied in slurry. Estimates from lysimeter experiments indicated that nitrate leaching from autumn application may have accounted for an additional 1–2% only. Acidifying slurry reduced volatilization losses to 1–12% of the NH₄⁺-N applied, and the nitrification inhibitor halved denitrification losses from autumn applications. Reductions in nitrogen losses were reflected in significant increases in first-cut herbage yields which, for slurry applied in the autumn with acid and the nitrification inhibitor, were generally greater than those from 120 kg ha⁻¹ N as ammonium nitrate applied in the spring. There were no significant differences between treatments at subsequent cuts in each season but, owing to the large increases at first cut, total yields were significantly higher for autumn-applied slurry with acid and nitrification inhibitor.     

An evaluation of callus induction and plant regeneration in twenty-five turf-type tall fescue (Festuca arundinacea Schreb.) cultivars

In order to investigate the genetic variation in tissue culture response and to find the cultivars with high regeneration ability for genetic transformation, twenty-five turf-type tall fescue ( Festuca arundinacea Schreb.) cultivars, including many elite ones released recently, were evaluated for their callus induction and plant regeneration responses. Callus induction was initiated from mature seeds on a Murashige and Skoog (MS) medium containing 9·0 mg l^–1 2,4-dichlorophenoxyacetic acid (2,4-D). Induced calli were subcultured on the same medium with 2·0 mg l^–1 2,4-D and then transferred to a MS medium supplemented with 2·5 mg l^–1 6-benzylaminopurine (BAP) for plant regeneration. Significant differences were observed among the twenty-five cultivars in both callus induction and plant regeneration ( P  < 0·001). Callus induction rate of viable seeds varied from 4·4% to 51·9%. Callus regeneration rates ranged from 16·7% to 58·8%. Overall regeneration rates (number of regenerated calli over number of cultured viable seeds) ranged from 1% to 22%. Approximately 94% of the regenerants were green plantlets.     

The influence of surface and sub-surface application methods for pig slurry on herbage yields and nitrogen recovery

Experiments were conducted on a grassland site at Wrest Park, Silsoe, Bedfordshire between 1987 and 1989, to compare herbage yields from slurry applied by deep and shallow injection, low trajectory and conventional vacuum tanker methods. Slurry application rates for all spreaders were calibrated at 86 ± 5 t ha^-1, an equivalent of c. 200 kg NH₄⁺-N ha^-1 applied in autumn or in spring.
As expected, herbage yields following spring applications were higher than from autumn applications, with average mineral fertilizer equivalents of 122 and 89 kg N ha^-1 respectively. Yields from the conventional and low trajectory spreaders showed no consistent differences. However, in both years, first cut yields from plots were significantly lower ( P < 0·05) where slurry had been injected than where surface applications had been used by an average of 0·7 t DM ha^-1. Subsequent cuts in 1988 demonstrated higher residual effects from injection so that annual total yields were similar from all slurry applications irrespective of spreader type.
Analysis of N content revealed high N levels in herbage from deep injection plots. Mean concentrations of N in the herbage, expressed as a percentage of the dry matter, were 1·43 for surface treatments and 1·79 for deep injection in 1988, and 1·84 for surface treatments, 2·13 for shallow injection and 2·68 for deep injection in 1989.     

不同氮素形态、pH对茶树元素吸收及有机酸含量影响

以茶树龙井43为材料,利用营养液水培试验研究了不同氮素形态、pH对茶树体内阴阳离子和有机酸的影响,初步明确茶树养分吸收与氮素形态及pH的关系。结果表明,与NO_3^--N处理相比,NH_4^+-N处理提高-的含量以及根中N、SO_4^2-含量,但是NH_4^+-N处理降低了茶树对Ca、Mg、B、Mn、Zn的吸收,也减少了成熟叶中SO_4^2-、根中H_2PO_4^-的累积量。与其他处理相比,NO_3^--N处理提高了成熟叶中苹果酸、草酸、柠檬酸浓度。茶树对养分的吸收、积累也与介质pH有关,尤其是pH与氮素互作时。在NO_3^--N处理下,pH 6.0显著提高了茶树对B、Mn、Zn的吸收和根中K、Ca、Mg浓度。茶树中有机酸含量受pH影响较大,与pH 4.0和pH 5.0相比,pH 6.0提高了茶树成熟叶中苹果酸、柠檬酸、草酸浓度以及根中草酸浓度。茶树对养分的吸收、积累与自身体内有机酸浓度有较好的相关性,茶树中全氮含量与柠檬酸、草酸浓度具有显著负相关性,而阳离子Zn²⁺、Ca²⁺、Mg²⁺、Mn²⁺含量与柠檬酸、草酸浓度具有显著正相关性。     

Opportunities for reducing the environmental impact of dairy farming managements: a systems approach

Dairy farming systems are important sources for the emission of a number of materials that include various forms of nitrogen (NO₃⁻, N₂O and NH₃) with potential environmental impact. The present paper is a systems synthesis study and assesses the likely impact of changes in management on N flows and losses. These include tactical fertilizer adjustment, slurry injection, maize silage production and the use of white clover as an alternative to fertilizer N. Implications for greenhouse gases (N₂O and CH₄) and support energy have also been considered. Substantial reductions in inputs and total and proportional losses by all die options considered were predicted by this study. Thus, using a tactical approach to fertilizer application and injecting slurry or using 50% maize silage reduced overall N losses from 160 (under conventional management) to 86 and 109kg Nha⁻¹ respectively. Combining both possibilities reduced losses further to 69 kg ha⁻¹. Although use of white clover, especially at low contents in the sward, was the most effective regime to reduce losses, this was at some cost to production so that losses per livestock unit (LU) did not always differ from those under other managements. Changing the N management had consequences for greenhouse gas emission with an estimated maximum 70% reduction in N₂O release. The effects on CH₄ emissions were relatively small. Substantial reductions in support energy costs were also obtained: these arose mainly from the reduction in fertilizer N use, which represented 66% of the total support energy in the original system.     

Changes in stubble carbohydrate content during regrowth of defoliated perennial ryegrass (Lolium perenne L.) on two nitrogen levels

Changes in stubble carbohydrate content during the regrowth of ryegrass ( Lolium perenne L.) grown under hydroponic conditions at two nitrogen levels were studied as a function of time by high-performance liquid chromatography. Experimental data showed that regrowth at a non-limiting nitrogen level (1·0 mol m⁻³ NH₄NO₃) involved two different physiological periods. The first occurred during the first 6 d and was characterized by the mobilization of 60 to 90% of the soluble carbohydrates (i.e. glucose, fructose, sucrose, oligofructans and polyfructans). During the second period (6.28 d of regrowth) carbohydrate contents rose to the values observed prior to cutting (20% of dry matter at the 28th d of regrowth).
The effect of low nitrogen conditions (0·2 mol m⁻³ NH₄NO₃) was observed only during the second phase. Plants regrown in a nitrogen-starved medium accumulated 2·3-fold more polyfructans than plants regrown in a non-limiting nitrogen medium. Their fructose and glucose contents remained at 2% of dry matter from the end of the first phase of mobilization.
The experimental results are interpreted and discussed in terms of the existence of two distinct fructan synthetic pathways.     

Growth and water relations of field-grown tall fescue as influenced by drought and endophyte

Field plots were established in autumn 1992 in which endophyte [ Neotyphodium coenophialum Glenn. Bacon, Price and Hanlin (formerly Acremonium coenophialum )]-infected (E⁺) and endophyte-free (E⁻) isolines of three tall fescue [ Festuca arundinacea Schreb.) genotypes were planted. Plants were subjected to three water-withholding periods in 1993 and one in 1994, or were kept well watered throughout the experiment. There were no consistent endophyte effects for leaf elongation, tiller density or dry weight per tiller. There were genotype X endophyte interactions ( P <001) for tiller density and shoot dry weight per area and genotype X water X endophyte interactions ( P <005) for cumulative leaf elongation in 1993. These interactions indicated the highly specific effect of host genotype-endophyte association on the expression of plant growth. Leaf rolling in the stressed treatments was more severe in E⁻ than in E⁺ plants in 1993, but there were no differences in 1994, and stomatal conductance tended to be lower in E⁻ than in E⁺ plants in 1993. Fractional water content of the lower 3 cm of the youngest fully developed leaf sheath was usually greater, and never less, in E⁺ than in E⁻ plants. The leaf rolling and stomatal conductance results suggest that E⁻ plants were more severely stressed in the summer after planting. Thus, the endophyte may induce greater water retention in the leaf sheath and therefore better protect the internal growing zone from lethal desiccation.     

Intake, rumen fermentation, degradability and digestion kinetics in beef cattle offered autumn grass herbage differing in regrowth interval

The effects of a 10-d increase in regrowth interval (35 and 45 d) of a predominantly perennial ryegrass sward harvested in two periods in the autumn in Ireland on feed intake, rumen fermentation, in situ degradability and rumen digesta kinetics was examined using six ruminally cannulated Holstein–Friesian steers in three replicates of a 2 × 2 crossover design. The longer regrowth interval had a higher grass dry-matter (DM) yield of herbage by 615 kg DM ha⁻¹ and a lower crude protein (CP) concentration of herbage by 27 g kg⁻¹ DM. There was no effect of regrowth interval on DM intake, rumen pH, total volatile fatty acid concentration or the molar proportions of acetate, propionate or butyrate in the rumen but the concentration of rumen ammonia (NH₃-N) was lower on the longer regrowth interval. The longer regrowth interval had a lower apparent total tract digestibility of DM, organic matter (OM), N and neutral-detergent fibre (NDF). There was no effect of regrowth interval on the in situ degradability of DM, OM, N or NDF. The passage rates ( k _p) of DM and OM were higher while the rate of digestion ( k _d) of DM and NDF was lower with the longer regrowth interval. The results indicated that, although increasing the regrowth interval by 10 d in autumn reduced the apparent digestibility of the grass herbage, there was no adverse effect on DM intake, rumen fermentation pattern or in situ rumen degradability. The reduction in rumen NH₃-N concentrations, reflecting the lower herbage CP concentration in herbage for the longer regrowth interval, may potentially reduce nitrogen excretion to the environment.     

Effect of season, soil type and fertilizer on the biomass production and chemical composition of five tropical shrub legumes with forage potential

The biomass production and the nutritive value of three tropical shrub legumes with condensed tannins (CT) ( Calliandra calothyrsus , Flemingia macrophylla , Leucaena leucocephala ) and two without CT ( Cratylia argentea , Desmodium velutinum ) as nitrogen-rich feed supplements for ruminants were assessed in two field experiments in Colombia. In one experiment, conducted on two different typical tropical soils (mollisol vs. oxisol; pH, 7·8 vs. 5·0; P content, 43 vs. 2 mg kg DM⁻¹), the effects of low and high levels of fertilizer application with P, K, Ca, Mg and S were tested in both the dry and rainy seasons. In a second experiment on the oxisol, the effect of a lower level of application of either P or S fertilizer was assessed. On the oxisol, C. calothyrsus and F. macrophylla had the highest biomass production (93 and 100 g DM plant⁻¹ in 9 weeks respectively) but the dry season caused extremely low DM yields in all species tested. Leucaena leucocephala did not grow on the oxisol but had the highest biomass production on the mollisol (454 g DM plant⁻¹ in 9 weeks). On the oxisol, the mineral concentrations of the forage were below the requirements of ruminant livestock. Fertilizer treatment had no clear effects on the nutrient composition of the forage. The non-CT shrub C. argentea had the highest concentrations of most minerals in its forage.     

Characterization of the effect of high salinity on roots of Chloris gayana Kunth: carbohydrate and lipid accumulation and growth

Branched nodal roots comprise the largest portion of the root system mass in Chloris gayana Kunth and the effects of high salinity on nodal root appearance and elongation rates were analysed in cv. Boma in greenhouse experiments. Roots from salt-treated plants (0·2 mol l^–1 NaCl) were smaller than controls, and accumulated higher concentrations of soluble sugars and reserve lipids. The number of nodal roots was reduced by the saline treatment. Leaf, tiller and nodal root appearance were delayed by salinity but the correlation among these processes was maintained, indicating that the developmental pattern was not altered by this level of salinity, only its rate. Initial nodal root growth rates varied as a function of plant size and were decreased by salinity only after 2 weeks of treatment. When shoots of non-salinized plants were cut, a drastic reduction in nodal root appearance was observed, suggesting emerging leaves were stronger sinks than roots for available reserves. However, when the shoots of salt-treated plants were cut, the already depressed root appearance rate was not further reduced. This suggests that, under salinity, alterations in root ability to metabolize reserves could have been more significant than reserve availability for controlling elongation.     

Sulphur concentration of soils and plants and its requirement for ruminants in the Inner Mongolia steppe of China

The sulphur status of four soils and 122 forage plants from the Inner Mongolia steppe was determined. The organic sulphur concentration ranged from 17 μg g^–1 in the 0·2–0·4 m soil layer to 397 μg g^–1 in the topsoil. The mean sulphate-S concentrations were <10 μg g^–1; greater concentrations were found only in the chernozem soil. Biomass-S accounted for 0·018–0·028 of total S in four soils. Three-quarters of plant samples examined had <1·6 g kg^–1 S, and >0·80 of them had an N:S ratio >14:1. More than 0·80 of the plants were deficient in S. There was a close relationship between plant-available soil sulphur concentrations and total plant sulphur concentrations. It was concluded that sulphur deficiency is widespread in the Inner Mongolia steppe and that sulphur fertilizer requirements should be evaluated.     

Reseeding in the Falkland Islands: seed rate and fertilizers for establishment

Five experiments were carried out to measure the effects of seed rate and fertilizers on the establishment and early growth of reseeded grass mixtures in the Falkland Islands.
Experiments 1 and 2 compared seed rates within the range 7·5-35kg ha⁻¹. Experiment 3 assessed the effects of three levels of each of nitrogen (N), P₂O₅, K₂O and CaCO₃ applied as seedbed fertilizers. Experiments 4 and 5 were similar in intent to Experiment 3, but treatments consisted of either nil or a very heavy application of the same fertilizer elements. In all experiments, the grass seed mixtures were sown in late summer after rotavation and burning of Cortaderia pilosa dominant indigenous vegetation on peaty soils. Percentage ground cover was estimated in the following spring and dry matter production through the first year was determined by sample harvests.
Initially, heavier seed rates resulted in higher percentage ground cover of sown species, but dry matter production over the season following sowing showed a significant increase only between the 25 and 35 kg ha⁻¹ rates in Experiment 2. The modest levels of seedbed fertilizers applied in Experiment 3 had no significant effect on either percentage ground cover of sown species or dry matter production. Even at the higher levels used in Experiments 4 and 5, only N consistently increased dry matter yields, although a significant positive response was also obtained from CaCO₃ in the final harvests.
The implications of the results to farmers in the Falkland Islands who may be contemplating reseeding are discussed.     

OsAMT1.1 Expression by Nitrate-Inducible Promoter of OsNAR2.1 Increases Nitrogen Use Efficiency and Rice Yield

Nitrate(NO₃^-) and ammonium(NH₄⁺) are two main inorganic nitrogen(N) sources during crop growth.Here,we enhanced the expression of OsAMT1.1,which encodes a NH₄⁺ transporter,using the NO₃^--inducible promoter of OsNAR2.1 and an ubiquitin promoter in transgenic rice plants.Under field condition of 120 kg/hm² N,agronomic N use efficiency,N recovery efficiency and N transport efficiency,and grain yield o...     

Nitrate leaching from cut grassland as affected by the substitution of slurry with nitrogen mineral fertilizer on two soil types

A field experiment was conducted to find out whether there is any difference in risk of N leaching to groundwater when cattle slurry and/or mineral fertilizer-N was applied to cut grassland. The experiment was carried out over two consecutive years on two sites (one with a relatively wet sandy soil and one with a relatively dry sandy soil). Treatments were mineral fertilizer-N at annual rates of 0–510 kg N ha⁻¹ year⁻¹ and combinations of sod-injected cattle slurry (85, 170, 250 and 335 kg N ha⁻¹ year⁻¹) and mineral fertilizer-N (289, 238, 190 and 139 kg N ha⁻¹ year⁻¹). Yield responses indicated that in the short run, 0·44–0·88 (average 0·60) of the slurry-N was as available as mineral fertilizer-N. The total N input from mineral fertilizer and slurry was a worse predictor of nitrate leaching (     0·11) than the N surplus (i.e. the difference between total N input and harvested N) (     0·60). The effective N surplus, based on the difference between the summed inputs of the plant-available N and harvested N, proved to be the best indicator of leaching (     0·86). Annual N application rates of up to 340 kg plant-available N ha⁻¹ complied with the target nitrate concentration in groundwater of 11·3 mg N L⁻¹ set by the European Union in both years on the wet sandy soil, whereas on the dry sandy soil none of the treatments did.     

Influence of different forage grasses on nitrate capture and leaching loss from a pumice soil

Nitrogen (N) uptake and loss in leachate from a pulse of ¹⁵N-labelled synthetic cow urine applied to a pumice soil were compared in a glasshouse lysimeter experiment among the grass species, Agrostis capillaris , Dactylis glomerata , Phalaris aquatica , Lolium multiflorum , L . perenne and a L . multiflorum/A. capillaris mixture. In addition, four L. perenne treatments investigated the effect of infection by Neotyphodium lolii strains. Leachate volumes and leachate nitrate concentrations were measured. At final harvest 24 weeks after sowing, dry matter (DM) mass of shoots and roots, plant N and ¹⁵N contents, soil residual mineral N, and root diameters and lengths were measured. Endophyte had no effect on plant or nitrate variables. Lysimeters planted with L . perenne (pooled endophyte treatments) leached 48 mg of NO₃-N compared with <3 mg N for the other grasses. Recovery of ¹⁵N was highest in A. capillaris (0·99), followed by D. glomerata and P. aquatica (0·89), the L . multiflorum / A. capillaris mixture (0·87), L . multiflorum (0·60) and L . perenne (0·44). Low ¹⁵N recoveries and high leaching losses from L . perenne were associated with low plant and root masses of DM and low rooting depth. High aerial mass of DM, root systems extending below 20 cm and high root masses of DM in lysimeters with A. capillaris , P. aquatica and D. glomerata contributed to a high rate of nitrate interception by these species and low leachate losses. The L . multifloru m/ A. capillaris mixture was intermediate between the two species for most of the variables measured.     

Soil acidification induced by leguminous crops

Solution culture and greenhouse studies have both clearly demonstrated the ability of legumes to acidify their rooting medium. Furthermore, research workers comparing the pH beneath undisturbed sites versus all-legume pastures or all-grass versus all-legume (or grass-legume) pastures have observed a lower soil pH under the leguminous pastures. The processes leading to legume-induced soil acidification are reviewed and discussed.
The growth of legumes which are fixing atmospheric N₂ involves the excess uptake of nutrient cations over anions from soil solution. This results in the net efflux of H₃O⁺ ions from plant roots into the rhizosphere.
When virgin lands are sown with legumes the accumulation of soil organic matter, with a consequent increase in cation exchange capacity and exchange acidity, is an important contributing factor to the long-term decline in surface soil (0–10 cm) pH. Nonetheless, such a phenomenon does not explain the decrease in pH below 10 cm soil depth nor the lower pH below leguminous than all-grass pastures. The efflux of H₃O⁺ ions from the legume roots may have an important effect on the soil pH under such conditions. The loss of symbiotically fixed N; from the system through leaching of NO₃⁻ - N may also contribute to soil acidification under leguminous pastures.     

Salinity effects on the early development stages of Panicum coloratum: cultivar differences

The Argentinean semiarid Chaco region is climatically suitable for cattle raising and has an average annual rainfall of 550 mm, concentrated from November to February. There, large areas are affected by high salinity; thus, perennial forages suitable for this region must combine adequate salt and drought tolerance. Panicum coloratum is a C₄ perennial grass adapted over a wide range of soil and rainfall conditions, and the purpose of this study was to evaluate the response of two cultivars (Klein Verde and Bambatsi) to salinity. Under controlled conditions, 100 and 200 mmol l⁻¹ NaCl delayed germination and significantly reduced germination percentages and seedling survival in both cultivars. However, in the field, factors other than salinity (possibly drought) had a large impact on plant survival. In short-term experiments under controlled environmental conditions, the vegetative growth of cultivar Klein Verde was less affected by salinity than Bambatsi. The cumulative growth over one year in a saline plot was also higher in cultivar Klein Verde. This cultivar also had higher shoot K⁺/Na⁺ ratios under salinity, as a result of higher K⁺ concentrations, and accumulated more triglycerides in roots. These features have been associated with salt tolerance in other species.     

Effects of an established sward of Lolium perenne L. on the growth and development of Rumex obtusifolius L. seedlings

Seedlings of Rumex obtusifolius L. were grown in gaps (11 cm diameter) in an established sward at Lolium perenne L., Root competition from the surrounding sward was controlled by PVC tubes and shoot competition was controlled by cutting the sward frequently. All combinations, with and without root competition and with and without shoot competition, were used.
Plants received either 40 or 80 kg N ha⁻¹ month⁻¹ and 0 or 300 kg K₂O ha⁻¹ and were harvested 39 d after emergence; a second harvest was made 12 d later, after shading to 20% of full sunlight.
The shoot dry weight per plant of R. obtusifolius was much more affected by root competition than by shoot competition, especially at low nitrogen applications. Potassium supply had no effect.
More dry matter was allocated to the leaf petioles under shaded conditions and the specific leaf area was greater. This morphological plasticity enabled R. obtusifolius to grow well under shading and to be affected only slightly by shoot competition from L. perenne.
The results suggest that competition for nitrogen was the main factor limiting the initial grown of R. obtusifolius in a ryegrass sward and that the morphological characteristics of R. obtusifolius make it less susceptible to competition for light in the early stages of its development.     

Long-term responses in the yield of Eastern Gamagrass [Tripsacum dactyloides (L.) L.] to nitrogen fertilizer under two harvest regimes in the United States

Eastern Gamagrass [ Tripsacum dactyloides (L.) L.] is a perennial C₄ grass with potentially high productivity. Intensive management through the application of nitrogen (N) fertilizer and frequency of cutting, however, may be required to maximize its potential for forage production. This study determined the long-term and residual responses of Eastern Gamagrass in terms of dry matter (DM) yield and tiller density to three annual application rates (0, 50 or 100 kg ha⁻¹) of a N-fertilizer solution applied by broadcasting or knife placement for 5 out of the 10 years of the study, and harvested using one-cut or two-cut regimes. Application of N-fertilizer increased total DM yield in the 5 years of N applications by 0·44 with the first increment of 50 kg N ha⁻¹, and by an additional 0·15 with the next increment of 50 kg N ha⁻¹. In the first year that directly followed N-fertilizer applications, DM yield was 0·175 higher than the no fertilizer treatment when 50 kg ha⁻¹ had been previously applied and a further 0·16 higher when 100 kg ha⁻¹ had been previously applied. Dry matter yields were greater from the one-cut than the two-cut regime only in years when no N-fertilizer was applied. Knife placement of N-fertilizer increased total DM yield only at 100 kg N ha⁻¹. Tiller densities were generally higher under the one-cut than the two-cut regime, particularly when N-fertilizer was broadcast. The application of N-fertilizer increased herbage production, especially when responses in the year subsequent to application are considered.