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The response of grass for silage to sulphur application at 20 sites in Northern Ireland
Abstract
Twenty field site3 were selected for their potential sulphur-deficient status. The effect of sulphur at 10 kg S/ha per cut as gypsum or kieserite on the yield and composition of grass for silage given intensive fertilizer was measured at two or three cuts in 1985. Other incidental sulphur inputs in P and K fertilizers and organic manures were minimized. There were significant increases (P < 0·05) in dry-matter yield at ten harvests on five sites. At seven of the ten harvests gypsum and kieserite were equally effective, but at three harvests only kieserite gave significant yield increases. The drymatter yield increases occurred at all three cuts.
Using soil analyses to predict sulphur-deficient sites had limited success. The conclusions from this study were that soils with extractable sulphate values < 10 mg S/l had adequate reserves for three-cut silage while soils with values > 10 mg S/l had a 1 in 3 chance of being sulphur deficient. Using plant analyses to diagnose sulphur-deficient herbage had also limited success. In this study herbage with an N/S ratio > 14 was sulphur deficient while herbage with a ratio > 12 had a 1 in 2 chance of being deficient.
The proportion of sulphur responsive sites in this study is an overestimate for Northern Ireland as a whole. Most soils in this country have higher clay and organicmatter contents than the field sites. The application of organic manures in normal agricultural practice is likely to be an important source of sulphur to grass for cutting.
... c Treatments N 3 P 1 K 0 & N 3 P 1 K 3 in the NPK factorial experiment at cut 2 (Bailey et al., 1997b). d Control (S 0 ) & Kieserite (S 1 ) treatments; mean data for 20 sites (Stevens and Watson, 1986). e Standard errors of means at cut 2 in the NPK factorial experiment; df = 143 (Bailey et al., 1997b). ...
... The soil, fertiliser and herbage data used in the study were taken from selected sites in the series of 20 S experiments by Stevens and Watson (1986), carried out in 1985, and also (in 1997 from silage fields on selected farms participating in government-subsidised nutrient management schemes in both County Fermanagh and County Antrim. The farms selected were those on which accurate written records of fertiliser usage (type, rate and application date) had been kept for each field. ...
Perennial ryegrass is the most important species of forage grass in both continental Europe and the British Isles. An investigation
was carried out to see if the DRIS model developed for this species was able to diagnose crop nutrient sufficiency status,
at harvest time, using data for herbage samples collected 2 weeks earlier. A re-evaluation of P fertiliser recommendations
for silage, based on the ‘Olsen’ soil P-test, was then carried out using DRIS diagnoses of P sufficiency status as the criteria
with which to judge if swards had been adequately, under, or over-supplied with fertiliser P. The results confirmed that reliable
(DRIS) diagnoses of N, P, K and S sufficiency statuses of silage swards may be made from herbage clippings taken 2 weeks prior
to harvest. Current P recommendations for silage swards proved to be excessive for non-basaltic sandy textured soils at first
cut, correct for this group of soils at second cut, and more or less correct for non-basaltic clay textured soils at both
cuts. For basaltic soils, however, P recommendations at both cuts appeared to be unrelated to plant P status, and it was concluded
that the ‘Olsen’ soil P-test had provided an erroneous assessment of plant available P in these exceptionally iron-rich soils.
... The observed N/S ratio as an indicator of the S supply in plant material is in agreement with the identification of S deficiency (Dijkshoorn & van Wijk, 1967;Stevens & Watson, 1986). The N/S ratio in the herbage is considered to be a better indicator of the sulfur status than is the S percentage itself (Siman, 1996). ...
... Because there is an intrinsic correlation between the N and S supply in plants for amino acid and protein synthesis, it is suggested that an N/S ratio above 16 could be used as a diagnosis of S deficiency in grasslands. The critical N/S ratio has been reported to be 12Á14 (Metson, 1973;Stevens & Watson, 1986) and 14 (Bolton et al., 1976;Scott et al., 1983;Stevens, 1985) for silage grasses. According to Murphy and O'Donnell (1989) or Richards (1990) sulfur-deficient grass is usually associated with an N/S ratio higher than 17:1. ...
The objective of our study was to assess the effect of soil application of sulfur in ammonium sulfate and gypsum and of either soil or foliar application of elemental sulfur on yield of grass forage and its qualitative parameters. The effect of various forms of sulfur on the yields of grass forage and its qualitative parameters was explored in the form of a small plot experiment in the Bohemian-Moravian Uplands in 2004–2006 involving the following variants: 1) sulfur unfertilised control; 2) ammonium sulfate; 3) elemental sulfur; 4) gypsum; 5) foliar elemental sulfur. Sulfurous fertilisers and foliar elemental sulfur were applied to the soil in doses of 40 kg and 8 kg S per ha, respectively. Nitrogen applied in ammonium sulfate was added to all the other variants in the form of ammonium nitrate. Application of the fertilisers was repeated at the beginning of each vegetation season. The stand was cut twice in the course of vegetation. In the harvested biomass we assessed the content of sulfur, nitrogenous substances, and net energy of lactation.The effect of various forms of sulfur on the grass biomass yields was not significant in either of the two cuts. Yields increased after sulfur fertilisation only in the 1st cut, especially after the application of sulfate sulfur and gypsum, and/or after foliar application of elemental sulfur. In the individual years the sulfur content in the biomass gradually increased significantly (0.17–0.23–0.29%). In the first year the sulfur content did not reach the critical deficiency limit (0.2%). Sulfur fertilisation increased the S concentration in grass forage in all the fertilised variants; the highest S content was detected in the variant where gypsum was applied (0.27%). No significant correlation was established between the values of water-soluble sulfur in the soil and the sulfur content in grass forage. Sulfur fertilisation had no significant effect on the N/S ratio, but was the highest in the variant not fertilised with sulfur and the lowest in the gypsum variant. The content of nitrogenous substances and net energy of lactation were significantly the highest after fertilisation with elemental sulfur and was related, among others, to the lowest yields of this variant. Sulfurous fertilisers did not significantly affect the exchangeable soil reaction and the highest content of water-soluble sulfur after the 2nd cut was seen in the gypsum-applied variant.
... Recognition of this problem has led to the use of nutrient ratio pairs in certain situations, e.g. N/K and N/S, rather than single nutrient concentrations, as more reliable diagnostic criteria (Stevens and Watson 1986;Dampney 1992). However, this latter approach only assesses the sufficiency status of a single nutrient (e.g. ...
... Admittedly the database used for model development was relatively small. However, the DRIS norms for the two nutrient ratios of known physiological and diagnostic importance, namely N/S and K/N, had norm values within the expected narrow ranges for higher plants, i.e. 11-13 for N/S, 0.6-0.9 for K/N (Elwali and Gascho 1984;Meldal-Johnsen and Sumner 1980;Stevens and Watson 1986;Amundson and Koehler 1987;Jones et al. 1990;Kelling and Matocha 1990;Dampney 1992;Marschner 1995) and relatively small CV's (≤26) in keeping with their diagnostic importance , thus giving credibility both to the database and to the DRIS model. Nitrogen and S are vital constituents of sulphur-containing amino acids and need to be present in quite specific proportions if the requisite proteins and proteincontaining structures are to be synthesized by plants (Marschner 1995). ...
Critical leaf nutrient concentrations have often been used to diagnose the nutritional causes of crop underperformance. Unfortunately,
these diagnostic criteria are not available for mature, tuber-bearing sweet potato plants (the word ‘tuber’ being used to
describe a swollen root rather than a swollen stem). The Diagnosis and Recommendation Integrated System (DRIS), however, provides
a reliable means of linking leaf nutrient concentrations to the yield of sweet potato tubers, and may be developed for this
crop using existing data from regional crop surveys. In the present study, tuber yield and leaf nutrient concentration data
from a survey of sweet potato gardens conducted in the Papua New Guinea (PNG) highlands in 2005 were used to establish DRIS
N, P, K, and S norms and statistical parameters for sweet potato. Although the database was relatively small, the norms derived
for nutrient ratios of key biological significance, i.e. N/S and K/N, were within the expected narrow ranges for higher plants,
giving credibility to both the database and the DRIS model. Data from future surveys and field trials may subsequently be
used to enlarge the database allowing the refinement of model parameters and hopefully an expansion of diagnostic scope to
include other macro and micro-nutrients. As it stands, though, this preliminary DRIS model for sweet potato is possibly the
best diagnostic tool currently available for evaluating the N, P, K and S statuses of sweet potato crops in the pacific region.
... Stevens and Watson (1986),6 Ryant and Skládanka (2009),7 Dampney (1992),8 Pegtel et al. (1996),9 Lawniczak et al. (2009). SE = standard error of the mean, Min. ...
Background and Aims
High mountain areas often show high soil heterogeneity that allows for the close coexistence of plant species and communities with contrasting resource requirements. This study investigates the nutritional factors driving the mosaic distribution of Nardus stricta L. grasslands and chalk grasslands dominated by forbs in the subalpine southern Pyrenees (Spain).
Methods
The concentrations of C, N, P, S, K, Ca and fiber fractions were analyzed in herbage in relation to soil nutrient availability, soil β–glucosidase, urease, phosphatase and arylsulfatase activity and plant species and functional type composition.
Results
The chalk grassland showed higher N:P ratios in herbage and higher enzyme demand for P relative to N in the soil, which indicate a greater limitation of P versus N compared to the Nardus grassland. This limitation was related to the higher soil and plant Ca levels in the chalk grassland, where the calcareous bedrock lies close to the soil surface. In the Nardus grasslands, the alleviation of P limitation translated into higher productivity and replacement of forbs with taller graminoids rich in structural carbohydrates, which was accompanied by greater β–D–glucosidase activity. The plant N:K and P:K ratios indicated potential K deficiency in both grasslands, which resulted from a decreased uptake of K due to competition from Ca, as indicated by the correlation between plant K and the soil K⁺:Ca²⁺ ratio.
Conclusions
Our results highlight the effect of the heterogeneity of soil nutrient constraints, as mediated by their stoichiometry and controlled by local topography, on the biodiversity of high mountain ecosystems.
... Recognition of this problem has led to use of nutrients ratio pairs in certain situations, e.g. N/K and N/S, rather than single nutrient concentrations, as more reliable diagnostic criteria (Stevens and Watson, 1986, Walworth and Sumner 1986, Dampney 1992). However, this approach only assesses the sufficiency status of a single nutrient (e.g. ...
... It is difficult to determine at what point it becomes economically beneficial to correct a nutrient deficiency in herbage, since this depends on a number of variables including the amount and type of extra fertiliser to be applied, and uses of crops. Data from a new NPK factorial field experiment and from a previous series of field S experiments (Stevens and Watson, 1986) are used to calibrate and validate the model; data from separate harvests and/or treatments being used for the calibration and validation procedures. Tissue analysis is considered a more direct method of plant nutritional status evaluation than soil analysis, but that method must necessarily involve a well-defined plant part analysis (Hallmark & Beverly, 1991). ...
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production techniques for sustainable development of agriculture for food and nutritional
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science, agronomy, ecology, and the environmental sciences.
... Recognition of this problem has led to use of nutrients ratio pairs in certain situations, e.g. N/K and N/S, rather than single nutrient concentrations, as more reliable diagnostic criteria (Stevens and Watson, 1986, Walworth and Sumner 1986, Dampney 1992). However, this approach only assesses the sufficiency status of a single nutrient (e.g. ...
... Das Ergebnis zeigt Abb. 3. Es bestand eine lineare Beziehung zwischen der Zunahme des N:S-Verhältnisses und einer verringerten Ertragsleistung und zwar in der Weise, daß bei einem N:S-Verhältnis von etwa 12:1 die Regressionsgerade die Null-Linie schneidet, ab Werten >15:1 zehnprozentige und ab >20:1 zwanzigprozentige Mindererträge im Vergleich zu ausreichend versorgten Beständen zu verzeichnen waren. Damit werden ähnliche Berechnungen (COWLING & JONES 1971) und Befunde (DIJKSHOORN & VAN WIJK 1967, STEVENS & WATSON 1986, RICHARDS 1990) bestätigt. (1974), die ebenfalls einen positven Einfluß der S-Düngung auf die Verdaulichkeit fanden, vermuteten eine höhere mikrobielle Aktivität im Pansen als Ursache für diesen Effekt. ...
This study was conducted to evaluate the effects on dry matter (DM) yield and chemical composition of sulphur fertilization (0 or 50 kg S ha-1 year-1) of a perennial ryegrass (Lolium perenne L.) sward cut four times per year as related to nitrogen fertilizer level (200 or 400 kg N ha-1 year-1). Sulphur fertilization had no effect on DM yield when 200 kg N were applied, whereas DM yield increased significantly at 400 kg N ha-1 year-1. Dry matter yield response varied among growths and 70% of the increase in DM yield could be attributed to the first regrowth. Other effects of sulphur fertilization were increased yields of nitrogen and sulphur and higher concentrations of sulphur and crude fibre and lower concentrations of crude protein in the grass. Sulphur fertilization also affected the amino acid pattern of the crude protein of the grass and increased the proportion of true protein at the expense of nonprotein-nitrogen components and lowered the nitrate concentration. Sulphur fertilization had no effect on the selenium contents of the grass.
... The DRIS norms for K/N (0.7) a nutrient ratios of known physiological and diagnostic importance had norm values within the expected narrow ranges for higher plants, i.e. 0.6-0.9 (Elwali and Gascho 1984;Meldal-Johnsen and Sumner 1980;Stevens and Watson 1986;Amundson and Koehler 1987;Jones et al. 1990;Kelling and Matocha 1990;Dampney 1992;Marschner 1995), thus giving another proof of credibility both to the database and to the DRIS model. Potassium is known to have a key role in N uptake and translocation (Minotti et al. 1968;Cushnahan et al. 1995), and therefore both N and K need to be present in quite specific proportions whether N accumulation and subsequent assimilation into proteins is to take place at optimal rates. ...
The use of critical concentration approach to diagnosis the nutrient status of plants is somewhat erroneous in that ‘critical nutrient concentrations’ are not independent diagnostics, but can vary in magnitude as the background concentrations of other nutrients increase or decrease in crop tissue. The Diagnosis and Recommendation Integrated System (DRIS), an alternative is sometimes less sensitive than the sufficiency range approach to differences caused by leaf position, tissues age,
climate, soil conditions, and cultivar effect because it uses nutrient ratios. The DRIS provides a reliable means of linking leaf nutrient concentrations to the yield of groundnut, and may be developed for this crop using existing experimental data. The present study was carried out in the Upper Catchment of Benin in 2001 and 2002, and grain yield and leaf nutrient concentration data from organic and inorganic trials were used to establish DRIS norms for N, P, K, Mg, Ca, S and Zn and statistical parameters for groundnut. The DRIS norms from this study were K/Ca: 1.4, K/S: 15.8, K/N:0.7, Mg/Ca: 0.2, Mg/K: 0.2, Mg/P: 2.1, Mg/Zn: 159.8, N/Ca: 2, N/S: 23.9, Zn/N: 0.0008, P/K: 0.1, P/N: 0.1, P/S: 1.3, P/Ca: 0.1, P/Zn: 76.1, S/Ca: 0.1, and Zn/Ca: 0.002. Although the database was relatively small, the norms derived for nutrient ratios of key biological significance, i.e. N/S and K/N, were within the expected narrow ranges for higher plants, giving credibility to both the
database and the DRIS model. Data from future surveys and field experiments may subsequently be used to enlarge the database allowing the refinement of model parameters and hopefully an expansion of the diagnostic scope such as to include other micro-nutrients. The nutrient status assessment using the selected DRIS norms shows a good nutrient level for N, P, K, Ca, S and Zn in the groundnut leaves for high yielding as their value was similar to those presented in the literature. As it stands, this preliminary DRIS model for groundnut offers a good diagnostic tool for evaluating the N, P, K, Ca, S and Zn status of groundnut crops in Benin.
... Recognition of this problem has led to the use of nutrient ratio pairs (e.g. N:K and N:S) in certain situations, rather than single nutrient concentrations, as more reliable diagnostic criteria (Stevens and Watson 1986;Walworth and Sumner 1986;Dampney 1992). However, this latter approach only assesses the sufficiency status of a single nutrient (e.g. ...
... Die Schwefeldüngung bedingte jedoch eine deutliche Verengung des N/S- Verhältnisses, wie es auch von Jahns und Taube (2001) in Grasbeständen festgestellt wurde. Der von Saalbach (1966) für Kleearten und von Stevens und Watson (1986) für Grasbestände ermittelte Grenzwert für das N/S-Verhältnis hinsichtlich einer ausrei- ...
In a field experiment at the Experimental Farm for Organic Farming in northern Germany, the effect of sulphur fertilisation in the form of MgSO4 to a red clover-grass mixture was conducted in the year 2011. At the beginning of the vegetation period in the Spring plots were fertilised with 30 and 60 kg S ha-1 and were compared to an unfertilised treatment. The sulphur fertilisation resulted in significantly higher fresh weight and dry matter yields and otherwise in a lower dry matter content. The content of crude protein and sulphur were significantly increased by sulphur fertilisation. The N/S-ratios in the fertilised plots showed values below the threshold of 15 for an adequate supply of sulphur. The N-withdrawals added up over the three cuts increased in the fertilised plots by over 55%. S-withdrawals increased from 8 kg S ha-1 in the unfertilised plots by more than 10 kg S ha-1. In the comparison of the 30 and 60 kg S ha-1 fertilisation level there was no significant effect on yield level, but on N/S-ratio and N uptake. Therefore, a sulphur fertilisation level of 30 kg ha-1 can be considered sufficient.
... The lowest content was found in maize silage and cereals, with values achieving about 10 µg kg -1 DM. The observed N/S ratio as an indicator of S supply in plant material is in agreement with the identification of S deficiency (Dijkshoorn & van Wijk, 1967;Stevens & Watson, 1986). Because there is an intrinsic correlation between N and S supply in plants for amino acid and protein synthesis, it is suggested that a N /S ratio above 16:0 could be used as a diagnosis of S deficiency in grasslands. ...
A three-year experiment was carried out at three different sites in northern Germany to investigate the effects of combined sulphur (S, up to 50 kg S ha −1 year −1 ) and nitrogen (N, up to 300 kg N ha −1 year −1 ) fertilization on dry matter (DM) yield and forage quality. There was an interaction effect of site, year, S and N fertilization. The greatest DM yield increment relative to yield at the start of the experiment (1997) with no S and N applied was 10.2 t DM ha −1 at Ostenfeld (arable grassland). Cattle slurry when applied to provide 50 kg N ha −1 and 10 kg S ha −1 did not noticeably increase yield. The S content in forage decreased significantly over the years without S fertilization. At 300 kg N ha −1 and 0 kg S ha −1 , crude protein (CP) contents achieved 173 g kg −1 DM and were diluted due to higher DM yields with S fertilization. The true protein content (TP% of CP) differed significantly at 300 kg N ha −1 . TP achieved 93% with 50 and 87% with 0 kg S ha −1 year −1 , respectively. In conclusion, with N fertilizer intensities in the range of 300 kg N ha −1 , it is necessary to apply 25 kg S ha −1 to improve forage yield and quality. On the other hand, with N fertilization levels below 300 kg N ha −1 , S fertilization could be omitted.
... Admittedly, the database used for model development was relatively small. However, the DRIS norms for the two nutrient ratios of known physiological and diagnostic importance, namely N/S (10.0) and K/N (0.7), had norm values within the expected narrow ranges for higher plants, that is, 11 to 13 for N/S, 0.6 to 0.9 for K/N (Elwali and Gascho, 1984; Meldal-Johnsen and Sumner, 1980;Stevens and Watson, 1986;Amundson and Koehler, 1987;Jones et al., 1990;Kelling and Matocha, 1990;Dampney, 1992;Marschner, 1995), thus giving credibility both to the database and to the DRIS model. Nitrogen and Sulphur are vital constituents of sulphur-containing amino acids Table 4. DRIS norms selected and comparison to the norms proposed by Arogun (1978). ...
The Diagnosis and Recommendation Integrated System (DRIS) is a potential method for interpreting plant foliar nutrient composition. It provides a reliable means of linking leaf nutrient concentrations to the yield of sorghum, and has been developed for this crop using experimental data from organic and inorganic trials carried out in the Upper Catchment of Benin. Grain yield and leaf nutrient concentration were used to establish DRIS norms for N, P, K, Mg, Ca, S and Zn and statistical parameters for sorghum. The DRIS norms provided by this study were N/P: 6.5, K/N: 0.7, N/Ca: 4.6, S/N: 0.1, N/Zn: 712.2, K/P: 4.7, P/Ca: 0.7, S/P: 0.4, Zn/P: 0.01, K/Ca: 3.3, S/K: 0.1, K/Zn: 510.1, S/Zn: 39.0, Ca/Zn: 164.0, and S/Ca: 0.3. Although the database was relatively small, the norms derived for nutrient ratios of key biological significance, that is, N/S and K/N, were within the expected narrow ranges for higher plants, giving credibility to both the database and the DRIS model. Data from future surveys and field experiments may subsequently be used to enlarge the database allowing the refinement of model parameters and hopefully an expansion of the diagnostic scope such as to include other micro-nutrients. As it stands, this preliminary DRIS model for sorghum offers a good diagnostic tool for evaluating the N, P, K, Ca, S and Zn status of sorghum crops in Benin.
Key words: DRIS norms, grain yield, sorghum, Benin.
... Admittedly, the database used for model development was relatively small. However, the DRIS norms for the two nutrient ratios of known physiological and diagnostic importance, namely N/S (12.5) and K/N (0.59 ≈ 0.6), had norm values within the expected narrow ranges for higher plants, i.e. 11– 13 for N/S, 0.6–0.9 for K/N (Elwali and Gascho 1984; Meldal-Johnsen and Sumner 1980; Stevens and Watson 1986; Amundson and Koehler 1987; Jones et al. 1990; Kelling and Matocha 1990; Dampney 1992; Marschner 1995 ...
Critical leaf nutrient concentrations have often been used to diagnose the nutritional causes of crop under performance. The Diagnosis and Recommendation Integrated System (DRIS), however, provides a reliable means of linking leaf nutrient concentrations to the yield of cotton, and may be developed for this crop using existing experiment data. In the present study, carried out in the Upper Catchment of Benin, fiber yield and leaf nutrient concentration data from an organic and inorganic trials were used to establish Diagnosis and Recommendation Integrated System norms for nitrogen (N), phosphorus (P), potassium K, magnesium (Mg), calcium (Ca), sulphur (S) and zinc (Zn) and statistical parameters for cotton. The Diagnosis and Recommendation Integrated System norms provided by this study were as followings: N/P = 9.65; K/N = 0.59; N/Mg = 10.55; S/N = 0.08; P/K = 0.19; Ca/P = 5.79; Mg/P = 0.96; Zn/P = 0.01; Ca/K = 1.08; Mg/K = 0.18; Zn/K = 0.001; Ca/Mg = 5.77; S/Ca = 0.14; Mg/Zn = 143.84. Although the database was relatively small, the norms derived for nutrient ratios of key biological significance, i.e. N/S and K/N, were within the expected narrow ranges for higher plants, giving credibility to both the database and the Diagnosis and Recommendation Integrated System model. Data from future surveys and field experiments may subsequently be used to enlarge the database allowing the refinement of model parameters and hopefully an expansion of diagnostic scope to include other micro-nutrients. As it stands, this preliminary Diagnosis and Recommendation Integrated System model for cotton is a good diagnostic tool currently available for evaluating the N, P, K, Mg, Ca, S and Zn status for cotton crops in Benin.
... The lowest content was found in maize silage and cereals, with values achieving about 10 µg kg -1 DM. The observed N/S ratio as an indicator of S supply in plant material is in agreement with the identification of S deficiency (Dijkshoorn & van Wijk, 1967;Stevens & Watson, 1986). Because there is an intrinsic correlation between N and S supply in plants for amino acid and protein synthesis, it is suggested that a N /S ratio above 16:0 could be used as a diagnosis of S deficiency in grasslands. ...
A three-year experiment was carried out at three different sites in northern Germany to investigate the effects of combined sulphur (S, up to 50 kg S ha�1 year�1) and nitrogen (N, up to 300 kg N ha�1 year�1) fertilization on dry matter (DM) yield and forage quality. There was an interaction effect of site, year, S and N fertilization. The greatest DM yield increment
relative to yield at the start of the experiment (1997) with no S and N applied was 10.2 t DM ha�1 at Ostenfeld (arable grassland). Cattle slurry when applied to provide 50 kg N ha�1 and 10 kg S ha�1 did not noticeably increase yield. The S content in forage decreased significantly over the years without S fertilization. At 300 kg N ha�1 and 0 kg S ha�1, crude
protein (CP) contents achieved 173 g kg�1 DM and were diluted due to higher DM yields with S fertilization. The true protein content (TP% of CP) differed significantly at 300 kg N ha�1. TP achieved 93% with 50 and 87% with 0 kg S ha�1 year�1, respectively. In conclusion, with N fertilizer intensities in the range of 300 kg N ha�1, it is necessary to apply 25 kg S ha�1 to improve forage yield and quality. On the other hand, with N fertilization levels below 300 kg N ha�1, S fertilization could be omitted.
... Of particular interest are the changes that take place in soils previously exposed to high rock P and Ca additions (a worst case scenario) after treatment with materials that may cause an immense down shift of up to 3 (or more) pH units in a matter of months. To this end, an experiment was conducted in southern England with three forms of sulfur utilized in agriculture but newly applied in habitat restoration: pelletized elemental sulfur, liquid ferric sulfate, and dried ferrous sulfate (S 0 , Fe (II) SO 4(aq) , and Fe (III) SO 4(s) , respectively), at rates approximately two orders of magnitude higher than conventional agricultural application (e.g., Stevens & Watson 1986;Malhi et al. 2000). The experimental work had three aims. ...
This paper deals with the complex issue of reversing long-term improvements of fertility in soils derived from heathlands and acidic grasslands using sulfur-based amendments. The experiment was conducted on a former heathland and acid grassland in the U.K. that was heavily fertilized and limed with rock phosphate, chalk, and marl. The experimental work had three aims. First, to determine whether sulfurous soil amendments are able to lower pH to a level suitable for heathland and acidic grassland re-creation (approximately 3 pH units). Second, to determine what effect the soil amendments have on the available pool of some basic cations and some potentially toxic acidic cations that may affect the plant community. Third, to determine whether the addition of Fe to the soil system would sequester PO4− ions that might be liberated from rock phosphate by the experimental treatments. The application of S0 and Fe(II)SO4− to the soil was able to reduce pH. However, only the highest S0 treatment (2,000 kg/ha S) lowered pH sufficiently for heathland restoration purposes but effectively so. Where pH was lowered, basic cations were lost from the exchangeable pool and replaced by acidic cations. Where Fe was added to the soil, there was no evidence of PO4− sequestration from soil test data (Olsen P), but sequestration was apparent because of lower foliar P in the grass sward. The ability of the forb Rumex acetosella to apparently detoxify Al3+, prevalent in acidified soils, appeared to give it a competitive advantage over other less tolerant species. We would anticipate further changes in plant community structure through time, driven by Al3+ toxicity, leading to the competitive exclusion of less tolerant species. This, we suggest, is a key abiotic driver in the restoration of biotic (acidic plant) communities.
... During the last few decades, a decrease in sulphur (S) deposits and lower S supply through mineral fertilisation (Ceccotti, 1996) has led to sulphur deficient crops and cutting grasslands throughout Europe . A wide range of yield responses to sulphur fertilisation has been observed for grasslands, from 0.24 (Stevens and Watson, 1986) to 3.5 t DM ha −1 y −1 (Brown et al., 2000). Yield increases with S fertilisation were also observed in some of the highest S deposition areas in Europe (Tarrason et al., 2003) such as in Belgium (Mathot et al., 2008) and in the Netherlands (Bussink and Den Boer, 2000). ...
In Europe, during the last 30 years, the decrease in sulphur (S) atmospheric depositions has led to S deficient grasslands. Concern for S fertilisation resulted in research about S fertilisation advices and definition of S nutritional diagnostic tools for plants. However, for grasses, S nutrition indicators are still discussed. We propose a diagnostic tool based upon linear relationships linking the sulphur and nitrogen (N) content of grasses. This diagnostic tool is built thanks to data from field and pot trials treated with an algorithm (Bolides) and discriminant analyses. The relationships allow the characterisation of the grass sulphur nutritional status following four categories: certainly sufficient, probably sufficient, probably deficient and certainly deficient. This relation based and tested on a large dataset from literature and own field trials allowed diagnosing correctly 94% of the sulphur sufficient grasses and 71% of the sulphur deficient grasses.
... Recognition of this problem has led to the use of nutrient ratio pairs (e.g. N:K and N:S) in certain situations, rather than single nutrient concentrations, as more reliable diagnostic criteria (Stevens and Watson 1986;Walworth and Sumner 1986;Dampney 1992). However, this latter approach only assesses the sufficiency status of a single nutrient (e.g. ...
Population growth in the Paua New Guinea highlands is among the highest in developing countries. While the 2000 census reported a rate of 3%, more realistic estimates may be closer to 2%. Even if exact rates are unknown, the trend of expanding population will continue and could result in a doubling of the population to around 4 million in just over 3.5 decades. This will place unprecedented pressure on the land resource. However, it is still unclear if the resource-base ‘soil’ is indeed being depleted at a greater rate than it can be restored, given the potentially high productivity of the soils in the region. We surveyed farmers and assessed their gardens to evaluate if soil fertility and associated production of the most important staple food, sweetpotato, is indeed declining as a consequence of increasing land pressure, shortening fallow periods and a number of other factors, including pests and diseases. This survey included 95 farmers in four highlands provinces with an average of three districts in each province. Farmers’ perceptions on soil fertility decline and management options were obtained. They were then asked to show us one garden that had recently been brought back into production after fallow, the ‘new’ fertile garden, and another garden that was about to go into fallow, the ‘old’ run-down garden. Plant and soil samples were collected from these two gardens to quantify changes as a result of cropping over time.
The aim of the study was to compare sulfate fertilizers and mixtures of elemental sulfur (S0) and sulfate in terms of yield and nitrogen (N) and sulfur (S) status in perennial ryegrass. Mixtures of sulfate and S0 can reduce the consumption of sulfate alone. The plants were grown in soil cultures. The plants were supplemented with S0, K2SO4, MgSO4, and (NH4)SO4 or a mixture of these salts with So. Two sulfur doses were applied and the ryegrass was harvested three times. Fresh and dry weights of each swath, the N and S content, and their uptake were determined. The total fresh yield of sulfur-fertilized plants was 25 to 94% higher compared to unfertilized plants. The increases in dry matter were even more significant. Fertilizers, being a mixture of S0 and sulfate, showed the same efficiency as those containing sulfate alone. Sulfur fertilization resulted in a higher S content and its uptake, lowered N concentration in second and third swatch, and a decrease in total N uptake. In conclusion, to achieve high crop yields, soil sulfur deficiency should be corrected and fertilizers that are the mixture of elemental sulfur and sulfate are a beneficial and effective approach.
The effects of sulphur (S) fertilization on forage production, sulphur content and N/S ratio of perennial timothy-meadow-grass (Phleum pratens L.- Festuca pratensis Hudson) and cocksfoot-dominant (Dactylis glomerata L.) swards cropped for one to three years were measured under a silage-cutting regime at six sites in Finland. Soil sulphur status ranged from poor/adequate (fine sand) to good (organic soils). Plant growth responses to supplementary sulphur were small, inconsistent and statistically insignificant. The supplementary S-fertilization increased the sulphur content of forage and decreased N/S-ratios at all sites. However, even in low-S fertilized plots the average sulphur content was very seldomly less than 0.2% on a dry matter (DM) basis, which has been assumed to be an adequate concentration in several foreign studies. High N/S ratios (> 14) were rare. The sulphur content of DM depended more significantly on growth stage and grass species than on supplementary sulphur. According to the results of these experiments, NPKS fertilizers contain sufficient amounts of sulphur to ensure both a good quality and a high yield of grass silage.
Perennial ryegrass was grown on a wide range of unlimed and limed soils in an attempt to identify plant‐soil factors which could explain the variable nature of lime responses in pastures. On most soils, lime responses appeared to be due either to enhanced soil nitrogen mineralization or to the alleviation of aluminium toxicity. On a small number of soils, however, the responses were not explicable by any known mechanism. On the basis of certain plant mineral compositional features it was proposed that these responses may have been due to improvements in the supply of calcium to shoot tissue as a result of liming. It was suggested that relatively low phosphorus/zinc ratios in grass shoots had stimulated the production of higher than normal concentrations of auxin, which in turn had increased the calcium requirement of growing tissue. Using selected data it was possible to show that relationships existed between the critical concentration of calcium in grass and the concentrations of phosphorus and zinc, and between the critical concentration of phosphorus in grass and the concentrations of calcium and zinc. The results suggested that the reputed phosphorus‐sparing effect of lime on grassland, may be due in part to the lower internal phosphorus requirements of grass grown on limed soils.
Combinations of treatments of cattle slurry, which have previously been shown to have lowered ammonia volatilization by 75% of that from whole slurry, were compared in a field experiment with perennial ryegrass at the Agricultural Research Institute, Hillsborough in 1990. Whole slurry and slurries obtained by separation through screens with mesh sizes of 5·0, 3·0, 1·1 and 0·4mm were acidified with 1·4% by volume of 10M nitric acid. Slurries separated through 5·0 and 0·4 mm meshes were diluted 100% and 50% respectively by volume with water and amended with calcium nitrate to supply the same amount of nitrogen as the nitric acid. All slurry combinations were surface-applied at 100 kg (NH 4 ⁺ -N + NO 3 ⁻ -N)/ha to different plots on three occasions during the growing season. Volatilization of ammonia was measured on adjacent plots using ventilated enclosures. By comparison with inorganic fertilizer treatments, assessments were made of the efficiency of slurry nitrogen for herbage production, the fertilizer value of phosphorus, potassium and sulphur in the slurry, and the effects of slurry on silage quality.
The mean ammonia volatilization over all applications of acidified slurries was 17% of that from whole slurry. The two separation plus dilution treatments, however, only lowered volatilization to about half of that from whole slurry. Within separation plus acidification treatments, the trend was for dry matter yield and nitrogen offtake to increase as mesh size decreased down to 1.1 mm. For slurries separated through 5·0 and 0·4 mm meshes, the effect of the additional dilution treatment on dry matter yield and nitrogen offtake was similar to the effect of acidification. Efficiency of nitrogen offtake over all three cuts, relative to inorganic fertilizer nitrogen, was 54% for acidified whole slurry and 88% for slurry separated through a 1·1 mm mesh and acidified. Denitrification in nitric-acid amended slurries and sward contamination from slurry solids may have been responsible for lowering nitrogen efficiency.
Chemical analyses of herbage showed that the concentrations of phosphorus, potassium and sulphur from the slurry treatments were comparable to those in herbage receiving the recommended rates of inorganic fertilizers and were sufficient for optimum yield. Slurry application had a detrimental effect on the fermentation quality of the ensiled herbage. Chemical analyses indicated that fermentations from two slurry treatments at the first cut and all slurry treatments at the third cut were poorer than those on treatments receiving the equivalent rate of inorganic fertilizer nitrogen.
Virtually all of the indigenous sulphate (SO4) in a range of UK soils with moderately high pH values (> 6) was found to be present in the soil solution and, as a consequence, was highly susceptible to leaching. For acid soils containing adsorbed SO4, the extractability of SO4 in NaCl and CaCl2 solutions was dependent on both the ionic strength and cation species. Addition of small amounts (<∼ 10−2M) of either NaCl or CaCl2 actually decreased the amount of SO4 extracted, but SO4 extractability increased sharply with concentrations of NaCl or CaCl2 higher than about 0.1 M. At a similar ionic strength, more SO4 was extracted by NaCl than CaCl2. Sequential extraction with 1 M NaCl removed essentially all of the absorbed SO4. The release characteristics of SO4 were very different to those of phosphate and this difference in behaviour is not easily reconciled with the view that SO4 is chemisorbed, as is phosphate. Except for a few acid soils with high oxide contents, the capacity of the soils to adsorb added SO4 was quite small. None of the soils with pH values higher than 6 adsorbed a significant amount SO4. The results raise questions regarding the efficiency of SO4-containing fertilizers in correcting and preventing S deficiency in situations where leaching is important.
The effects of rate and pattern of fertilizer S application on herbage production from Perennial ryegrass-dominant swards at six potentially S-deficient sites in south-west Scotland were measured under a silage cutting regime (3 cuts year-1) with high fertilizer N application (300 kg ha−1 year-1). Fertilizer S (as gypsum) was applied at annual rates from 0 to 48 kg ha−1 as single spring applications before the first cut or split before each of the three cuts. The residual effect of S in the year following its application was assessed at one site.
Applied S increased total DM production at four of the six sites. These increases were restricted to the second and/or third cuts and were generally in the range 10-30% greater than where no S was applied. Timing of S application was not important in influencing annual DM yield. The residual effect of gypsum in the year following application was small.
The supply of available soil S is limiting herbage production in certain areas and soil types of south-west Scotland. Areas of S deficiency are likely to increase in the future and need to be identified more precisely than they are at present.
The effect of sulphur and sodium fertilizers on the response of a perennial ryegrass (Lolium perenne) sward was examined over 2 years. Sulphur fertilizer was applied as ammonium sulphate at 0 or 97·5 kg S ha−1 year−1 and sodium fertilizer as sodium nitrate at 0 (nil), 31 (low), 62 (medium) or 94 (high) kg Na ha−1 year−1, with nitrogen input balanced across all treatments. Both sulphur and sodium increased herbage yield. Sodium fertilizer increased herbage sulphur concentration and sulphur fertilizer slightly increased herbage sodium concentration, but there were no major interactions between the two fertilizers on herbage yield or composition in the season of application. Sodium fertilizer increased dry-matter digestibility, water-soluble carbohydrate concentration and the live proportion of the herbage. Herbage sodium and magnesium concentrations were increased and potassium concentration decreased by sodium fertilizer. Sulphur fertilizer increased herbage dry-matter digestibility and water-soluble carbohydrate concentration. Sulphur and potassium concentrations were also increased and non-protein nitrogen, magnesium and phosphorus concentrations decreased in response to sulphur fertilizer. It is concluded that, although there was evidence of facilitation of sodium uptake by sulphur fertilizer and vice versa, this was not sufficient to produce synergistic effects on herbage growth in the season of application.
An automated, rapid and much simplified XRF procedure for assessing total sulphur in graminaceous plant materials is described. Sample preparation has been refined and microprocessor control incorporated to provide considerable savings in analytical time.
The procedure has been tested using samples from two grass-silage cuts, taken from an ADAS (Agricultural Development and Advisory Service) trial studying responses, under intensive grassland management, to sulphur and nitrogen applications. Good correlation between XRF and wet chemical analysis was achieved, and sample turnround was markedly increased. The method produced accurate results for both cuts with high precision and reproducibility where careful attention was paid to sample homogeneity and disc preparation. The potential for wider application of XRF techniques to elemental analysis of agricultural materials is discussed.
The15N isotope was used to study the mode of action of individual nitrogen sources in a 30% urea:30% ammonium nitrate: 10% ammonium sulphate:30% filler (w/w) granular fertilizer for perennial ryegrass in a greenhouse pot experiment. The fertilizer consisted of two types of granules, one containing 80% urea and 20% filler and the second containing 48% ammonium nitrate (AN), 16% ammonium sulphate (AS) and 36% filler. In addition the effect of dolomite compared with silica as the filler was investigated on nitrogen recovery from the 30:30:10:30 formulation.
Dolomite adversely affected the recovery of nitrate N from the system and evidence suggested that MgCO3 was the active component. Granules containing dolomite resulted in a lower dry-matter yield than those containing silica, however the difference was not significant as nitrate contributed only 20% of the N in the formulation. AN gave the greatest DM yield and urea the lowest with AS being intermediate. The15N budget in shoots, roots and soil indicated that only 65% of the N from urea was recovered at the end of the experiment compared with 86% for AN and 91% for AS. The dry-matter yield of the 30:30:10:30 formulation using silica as the filler was intermediate between urea and AN; however, the apparent N recovery was significantly higher than expected from the sum of the individual components. The use of15N labelling indicated that using separate granules for ammonium N and urea the recovery of urea was improved by 11% in the triple N mixture when both AN and AS were present in the second granule compared to the recovery on its own. The enhanced recovery of urea appeared to be a function of AN and AS acting together as neither source in double combination with urea had any effect on urea N recovery.
Urea enhanced the recovery of nitrate N by 10% but decreased the recovery of AS by 6% (in the 30:30:10:30 formulation) in comparison with the single sources on their own. The results indicate that interactions can occur between N sources even when they are physically separated by being in different granules.
Quantifying spatial variability in forage grass yield within individual fields is hampered by the lack of accurate yield monitoring equipment. Here, it is shown how dry matter (DM) yield of silage swards can be predicted on the basis of their mineral composition. This empirical method of predicting yield enables diagnoses of sward nutrient status to be made simultaneously from the tissue test information, and provides a unique opportunity for identifying the nutritional and non-nutritional factors responsible for variability in sward productivity at sub-field scales. Maps of sward DM yield at first, second and third cut silage stages in 1999, and at first cut silage stage in 2000, on a large (7.9 ha) grassland field were produced using two different yield models: one model for first cut and a separate model for second and third cuts. The maps indicated that DM production varied considerably across the field, particularly at first cut, but that the pattern of yield variability at this cut was consistent from 1999 to 2000. The results of the plant tissue tests suggested that N deficiency had been responsible for limiting DM production on the lower yielding parts of the field.
A DRIS model for perennial ryegrass, based on data collected from a glasshouse experiment, was used to diagnose the nutrient sufficiency status of perennial ryegrass swards growing in field situations. Initially, DRIS overestimated the N and P status of these swards and underestimated their S status. However, by calibrating the model outputs on the basis of actual sward dry matter yield responses to specific fertiliser inputs, correction factors were evaluated, and the nutrient indices modified to reflect the nutritional status of swards in field situations.
Modified DRIS diagnoses of the N, P, K and S status of swards were compared with those made using the critical value approach. DRIS proved to be as reliable as the critical value approach at diagnosing N deficiency (both approaches having reliability scorings of 90%), but was superior to the latter at diagnosing P, K and S deficiencies, having reliability scorings of 100% (P), 90% (K) and 70% (S), compared with scorings of only 0% (P), 80% (K) and 30% (S), for the critical value approach.
Herbage analysis offers a definitive means of determining the N, P, K and S status of perennial ryegrass swards. Unfortunately, the results of such analyses can be difficult to interpret, simply because the minimum or ''critical'' concentration of a nutrient in plant tissue for optimum growth, varies both with crop age and with changes in the concentrations of other nutrients. The Diagnosis and Recommendation Integrated System (DRIS) could help to improve the reliability of such interpretations. Diagnoses made using DRIS are based on relative rather than on absolute concentrations of nutrients in plant tissue, and as such should be comparatively independent of crop age.The aim of this study was to establish and test DRIS methodology for high-yielding perennial ryegrass swards. Because of prohibitive costs, setting up a whole new series of field experiments to evaluate DRIS model parameters for perennial ryegrass was out of the question. Instead, the diagnostic norms and associated coefficients of variation for the model were evaluated using data from a single (large) multi-factorial glasshouse experiment.Of the nutrient ratios selected to form the diagnostic norms, K/N and S/N had the clearest physiological rationale, whereas those involving Ca and Mg in combination with N, P, K and S appeared to have little physiological basis. It was reasoned, though, that because Ca and Mg uptake by plants are largely passive processes (ultimately governed by plant growth), the DRIS indices for these nutrients, together reflected the degree to which growth may be limited by non-nutritional (environmental) factors relative to nutritional ones. Both indices were combined to form a single reference (Ri) index. Without such an internal reference, plant growth could be limited by multiple nutrient deficiencies, and yet N, P, K and S indices might all be close to, or equal to zero (i.e. the optimum), simply because the absolute concentrations of each nutrient (while low) had been in the correct state of balance. Moreover, by effectively using Ca and Mg as internal reference parameters in DRIS, ''nutrient concentrations'' which previously formed the basis of the critical value approach, were essentially incorporated into the DRIS model, thus combining the strengths of the two diagnostic approaches; the only difference being that Ca and Mg, and not dry matter, were the internal references against which the levels of the major nutrients were compared.
An ‘AutoAnalyzer’ method is described for determination of sulphate in 0.01M calcium phosphate extracts of agricultural soils. The method is turbidimetric, based on precipitation as barium sulphate, and can measure as little as 0.5 ppm sulphate sulphur in soil. Extracts are treated with charcoal before analysis to remove organic matter which otherwise seriously suppresses barium sulphate precipitation. Analysis of extracts of 22 soils showed good agreement between the proposed ‘AutoAnalyzer’ method and the well-established reduction/distillation method. On results ranging from 1.6 ppm to 175 ppm sulphate sulphur, the coefficient of variation calculated from duplicate ‘AutoAnalyzer ’ analyses was 1.7%.
A rapid and precise method of determining total sulfur in soils is described. The soil sample is heated with alkaline sodium hypobromite solution to oxidize soil sulfur compounds to sulfate, and the sulfate thus formed is reduced to hydrogen sulfide by a modified Johnson‐Nishita procedure and determined colorimetrically as methylene blue. The method gives quantitative results with pure organic and inorganic sulfur compounds, including amino acids, sulfonic acids, organic sulfates, sulfoxides, thioureas, sulfates, sulfites, sulfides, and elemental sulfur. It gives quantitative recovery of organic and inorganic sulfur added to soils and soil extracts, and its results with soils agree closely with those obtained by other methods proposed for total sulfur analysis of soils.
Surface and subsurface samples of 17 of the most agriculturally important soils of the eastern Canadian prairies were analyzed for total S, sulphate S, total N and organic C. The soils varied in texture from sandy loam to clay loam. Fifteen of the soils were of the Chernozemic order, one was Brunisolic and the other Luvisolic. The subgroups included were Orthic Blacks, Gleyed Rego Blacks, Orthic Dark Greys, Eluviated Eutric Brunisol and Orthic Luvisol. The total S of the soils decreased with depth and was significantly correlated with total N and with organic C. The sulphate sulphur extracted with 0.1 M CaCl 2 accounted for an average of 2.6% of the total S in each of the three soil depths analyzed. The calculated N:S and C:N ratios averaged 8.3 and 1.25 (0–15 cm), 7.2 and 14.1 (15–30 cm), and 6.5 and 11.0 (30–60 cm), respectively. The N:S ratios, and to limited extent the C:N ratios, were used to describe the sulphur status of the soils. Soil with N:S and C:N ratios 6.0 and 12.5 (0–15 cm), 5.2 and 13.5 (15–30 cm), 4.7 and 11.4 (30–60 cm), respectively, could have a high potential to supply sulphate S to plants and may not be deficient in plant-available S. Soils with N:S and C:N ratios of 8.7 and 13.5 (0–15 cm), 7.2 and 14.7 (15–30), 6.3 and 11.2 cm (30–60 cm), respectively, may be deficient in sulphur for some crops. However, they may have a high potential to convert total S to sulphate S. Soils with N:S and C:N ratio of 12.4 and 11.2 (0–15 cm), 11.1 and 13.0 (15–30), 10.2 and 9.9 (30–60 cm), respectively, may be deficient in plant-available S and could have a low potential for conversion of total S to sulphate S. Key words: Sulphur status of soils; potential available sulphur
Seventy-five grass samples for first-cut silage and 131 samples for second-cut silage were collected in 1983 from intensively managed farms with coarse-textured soils. Samples with total sulphur less than 2·0 g/kg or Kjeldahl nitrogen greater than 28 g/kg, together with nitrogen to sulphur ratio greater than 14, and adequate phosphorus and potassium, were selected as suboptimal in sulphur. The extent of sulphur deficiency was assessed using water-soluble sulphate values of 300–500 and 200–300 mg S/kg to indicate yield depressions of less than 5 and 10% respectively. In the first cut, 20 and 8% of sites were likely to have suffered yield depressions of less than 5 and 10% respectively. Soil-extractable sulphate values less than 10 mg S/kg indicated marginal sulphur reserves for second-cut silage at 49% of the sites. Grass analyses of the second-cut samples showed that 11 and 3% of the sites were likely to have suffered yield depressions of less than 5 and 10% respectively. Incidental sulphur inputs from deposition, organic manures and mineralization may have obviated much of the potential sulphur deficiency for second-cut grass.(Received May 07 1985)
The sulphur balance in eight lysimeters containing four different soils under grass was examined over a 4-year period during which the annual mean concentration of sulphur dioxide (SO2) in the air at the site decreased from 30 to 14 μg/m3. The amounts of sulphur harvested in the grass and lost in drainage were set against additions in fertilizer, rainfall and from dry deposition. A decline in annual dry-matter yield was accompanied by a decrease in the concentration of sulphur in the herbage and an increase in the ratio of nitrogen to sulphur. It was concluded that atmospheric sources and soil reserves may become insufficient to meet the sulphur requirement of grassland.
Sulphur deficiency reduced the yield and sulphur content of ryegrass at the fourth cut, while increasing the nitrogen content and N:S ratio. The distribution of the forms of nitrogen was also altered, with a decrease in the proportion of nitrogen recovered as amino acids and an increase in the concentration of asparagine. Amino acid analysis showed that the concentrations of the sulphur-containing amino acids cyst(e)ine and methionine were depressed by sulphur deficiency as well as those of arginine, histidine, lysine, glycine, leucine, serine and threonine. Sulphur deficiency, therefore, decreases the quality of crude protein found in grass, as well as reducing the yield.
The relationships of the amounts of sulphate extracted by different extractants with the yield, response to added sulphate, and the sulphur uptake of oats in pot cultures have been studied for ten acid soils. The L-value, representing the quantity of isotopically exchangeable sulphur sampled by the plants, was estimated using radioactive sulphur. The best relationships with the crop variables were given by sulphate extracted with calcium chloride, potassium dihydrogen phosphate and sodium bicarbonate. Critical values, below which a response to added sulphate is likely to be obtained under the pot conditions, are given for the phosphate and bicarbonate extractants.
The effect of sulphur fertilisation on yield and herbage composition was investigated in two successive years at two grassland sites, one with ryegrass and one with ryegrass/ clover, where the available sulphur in the soil was less than 10 mg kg−1. When supplies of N, P and K were not limiting, herbage yields increased with added sulphur at both sites, particularly at the second and third cuts and in the second year. Sulphur additions also increased the concentrations of total S and SO4−2−S in the crop, and reduced the N:S ratio. The figures for these parameters in herbage from control plots confirmed that low yields in the presence of normal nitrogen fertilisation were probably caused by sulphur deficiency.
From a review of published data on S- and N-fractions it has been shown that on a gram atom basis these elements occur in organic forms in a ratio ranging from 0.025 (legumes) to 0.032 (gramineous plants) and that this is the same as the S : N ratio in the proteins which constitute about 80 per cent of the organic S and N present.
In plants deficient in sulphur, the ratio organic-S : organic-N becomes less than normal due to an increase in the proportion of non-protein organic-N compounds low in sulphur. With sulphur deficiency the cytoplasmic proteins decrease out of proportion to the chloroplast proteins of a higher S content so that the ratio of protein-S to protein-N tends to increase. A similar change may occur during the fall in tissue protein content with increasing plant age.
Sulphur-deficient plants show a subnormal ratio of organic-S to organic-N in the absence of sulphate in the tissues. Plants in which the protein content is decreased by proteolysis may have subnormal organic-S : organic-S ratios in the presence of sulphate in the tissues,i.e. without S shortage. This may occur during dark starvation or in seedlings drawing upon reserve proteins in the seeds.
The S-requirements for growth are reflected in the normal ratio of organic-S to organic-N.
In most species investigated, organic-S occurs mainly as cystine and methionine and is directly related to protein metabolism. Because of the presence of other forms of organic-S, the organic-S : organic-N ratio in the Brassica species is higher.
Several authors are advocating the use of the SO4−S/total S ratio in the plant as the best index of S status. We have traced the arguments put forward in support of this index, and we show that they are based either on unfair comparisons with other indices, such as SO4−S or total S alone, or inappropriate statistical treatment.
The SO4−S/total S index has two fundamental disadvantages compared with SO4−S or total S alone: (1) the numerator (SO4−S) is the major variable in the denominator, so the ratio is likely to be less sensitive than either of the measurements alone; (2) its determination involves twice as much analytical work as either measurement alone.
Examination of some of the source references indicates that SO4−S by itself is the most satisfactory S index. Whenever whole plants are analysed, any index which includes organic S is subject to variation due to tissue age.
Sulphur and amino acid fractions in perennial ryegrass as influenced by soil andatmospherio supplies of sulphur
- D W Cowling
- L H P Jones
Responses to sulphur on grassland
- M D Murphy
- J C Brogan
- D Kelly
Much Irish grassland is deficient in sulphur
- Murphy