Printer Friendly

Effect of nitrogen fertilization on oxalate content in Rhodesgrass, Guineagrass and Sudangrass.

ABSTRACT : An experiment was conducted to evaluate the effects of nitrogen (N) level on the dry matter (DM) yield, N concentration and oxalate content of some tropical grasses, namely Rhodesgrass (Chloris gayana), Guineagrass (Panicum maximum) and Sudangrass (Sorghum vulgare). Three levels of N as urea were applied (Standard- 260, Standardx2- 540 and Standardx4- 1,060 kg N/ha for Rhodesgrass; Standard- 380, Standardx2- 770 and Standardx4- 1,570 kg N/ha for Guineagrass and Sudangrass) in a completely randomized design and grasses were harvested twice at approximately two-month intervals. Dry matter yield tended to be higher with increased rate of N fertilizer in all species, while further additional N (Standardx2 or Standardx4) did not significantly (p>0.05) further increase DM yield, when compared with the Standard level of N fertilizer application. There was also a trend towards higher N concentration in plants as N fertilization increased in all species and it was increased significantly in Rhodesgrass and Sudangrass (p<0.05 or p<0.01, respectively). Further additional N (Standardx2 or Standardx4) application showed no significant (p>0.05) differences on oxalate content in plant tissue within species, when compared with the Standard level of N. The Rhodesgrass contained 0.11, 0.13 and 0.15% soluble oxalate and 0.23, 0.25 and 0.27% total oxalate with Standard, Standardx2 and Standardx4 level of N application, respectively. The Guineagrass contained 0.54, 0.50 and 0.42% soluble oxalate and 1.60, 1.56 and 1.45% total oxalate with Standard, Standardx2 and Standardx4 level of N application, respectively. The Sudangrass contained 0.06, 0.15 and 0.12% soluble oxalate and 0.22, 0.22 and 0.21% total oxalate with Standard, Standardx2 and Standardx4 level of N application, respectively The results from this study suggest that these grasses do not use further addition of N fertilizer (Standardx2 or Standardx4) to form high content of oxalate salts, when compared with the Standard level of N. In addition, the levels of oxalate present with these grasses are quite low as far as toxicity to animals is concerned. (Key Words : Nitrogen Fertilization, Oxalate Content, Dry Matter Yield, Nitrogen Concentration)

INTRODUCTION

The soluble oxalate content of forages is of great importance to ruminant animals if it is present in considerable amounts (2% or more) (McKenzie et al., 1988). Hegarty (1982) reported that forage grasses containing oxalate concentrations higher than 4% in the dry matter can be dangerous for ruminants. On the basis of the published literature, it is difficult to find any agreement regarding a safe level of oxalate content in plants for ruminants. However, if soluble oxalate is ingested rapidly by ruminants, the rumen microorganisms cannot detoxify soluble oxalate fast enough to prevent its absorption into the bloodstream, and the animal becomes intoxicated (James et al., 1967). Oxalate-producing tropical grasses, such as Setariagrass (Setaria sphacelata) and kikuyugrass (Pennisetum clandestinum), have been responsible for mortality (Jones et al., 1970; Dhillon et al., 1971; Sidhu et al., 1996), renal failure and incidences of hypocalcaemia in herbivores (Elphinstone, 1981; McKenzie, 1985; McKenzie et al., 1988). It was observed that oxalate content in Setariagrass increased from 3.3% to 5.6% with increasing levels of nitrogen (N) application from 0 to 200 kg/ha, and related to N concentration of 1.3 and 2.9%, respectively (Jones and Ford, 1972).

The use of excessive amounts of nitrogen fertilizer to stimulate dry matter yield from grassland is often justified, but it is important to ensure that in the quest for increased yields, forage toxin concentrations do not become dangerously high. However, there is very limited information on the rate of oxalate accumulation in tropical forages in response to heavy nitrogen fertilizer application. Therefore, the present study was conducted to investigate the effect of nitrogen fertilization on oxalate content in some tropical grasses.

MATERIALS AND METHODS

Experimental design

This experiment was carried out at the experimental field station of the Faculty of Agriculture, University of Miyazaki, Japan from 10 May to 1 September 2004. The seeds of Rhodesgrass (Chloris gayana cv. Katambora), Guineagrass (Panicum maximum cv. Natsukaze) and Sudangrass (Sorghum sudanense cv. Haysudan) were sown in a burned soil of 1/2,000 in Wagner pots at a seeding rate of 25, 70 and 55 kg/ha, respectively. Three levels of nitrogen (N) fertilizer (standard level, standard levelx2 times, standard levelx4 times) were applied by dividing 4 times. The rate of fertilization is shown in Table 1. Standard level of fertilizer in all species was designed as recommended by Inosaka (1989). The fertilizer used was urea for N, super phosphate for [P.sub.2][O.sub.5] and potassium chloride for [K.sub.2]O. Each treatment of N fertilizer was replicated four times using a completely randomized design. The plants were cut twice at approximately two-month intervals. The cutting height was 5 cm above the ground.

Analysis

The harvested samples were chopped and then dried at 70[degrees]C for 48 h in a forced-air oven for determination of dry matter (DM) yield. The dried samples were ground in a Wiley mill through a 1-mm screen. Nitrogen content was measured by the Kjeldahl method (AOAC, 1990). Soluble oxalate and total oxalate in plant tissues were determined with high-performance liquid chromatography (Shimadzu Co. Ltd., Japan) by the method of Rahman et al. (2006) and Rahman et al. (2007), respectively. The amount of insoluble oxalate was evaluated as the difference between the total and the soluble.

Statistical analysis

All data were analyzed statistically by analysis of variance and statistically significant differences between the oxalate content of harvest 1 and harvest 2 were determined by the Student's t-test. The difference between mean values and among variants was calculated using the LSD method with a 5% level of significance (Steel and Torrie, 1984).

[FIGURE 1 OMITTED]

RESULTS AND DISCUSSION

Dry matter yield

Dry matter yield (t/ha) as affected by forage species, N fertilization and harvesting frequency is shown in Table 2. It was found that the overall effect of N fertilization on DM yield varied significantly (p<0.01) among the treatment groups when averaged across all species, and an increasing trend was observed with an increase of N fertilizer. The highest DM yield was found in standardx4 level of fertilizer (10.03 ton/ha/cutting) and the lowest in standard level of fertilizer (7.23 ton/ha/cutting). However, N fertilization had no significant (p>0.05) effect on average DM yield (harvest 1 and harvest 2) within species, while an increasing trend was observed with an increase of N fertilizer in all species. The results indicated that DM yield had peaked at standard levels of fertilizer in all species. The present findings follow the pattern reported by Lee et al. (1996) and Johnson et al. (2001).

Nitrogen concentration in plant tissues

Nitrogen concentration (% DM) as affected by forage species, N fertilization and harvesting frequency is presented in Table 3. Total N concentration increased (p<0.01) as N fertilization increased when overall effects of N fertilization across both harvest dates and all species were observed. Similar results were found within species except Guineagrass for the average of both harvest dates. However, an increasing trend of N concentration was found with increased rate of N fertilizer in all species. The present results follow the same pattern reported by earlier researchers (Penney et al., 1990; Khan et al., 1999; Sarwar and Mahr-un-Nisa, 1999; Johnson et al., 2001).

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

Oxalate content in plant tissues

The effects of nitrogen fertilization on oxalate content in Rhodesgrass, Guineagrass and Sudangrass are illustrated in Figure 1, 2 and 3, respectively. Oxalate content of Rhodesgrass was not increased significantly (p>0.05) with increased rate of N fertilizer at both harvests, except for soluble oxalate content at harvest 1 which increased significantly (p<0.05) with the increased rate of N fertilizer (Figure 1). Total oxalate content tended to be higher as N fertilization increased at harvest 1, whereas no such trend was found at harvest 2 and the causes of this dissimilar trend were unknown. In addition, oxalate levels in plants between harvest 1 and harvest 2 were not significantly (p>0.05) different for any treatment, except for the standardx4 treatment for total oxalate. Irrespective of N fertilizer levels, the mean total oxalate content (harvest 1 and harvest 2) of Rhodesgrass was 0.25%, and consisted of 48 and 65% soluble oxalate for harvest 1 and harvest 2, respectively.

In Guineagrass, compared to Standard level of N, further addition (Standardx2 or Standardx4) of N fertilization did not significantly increase (p>0.05) the oxalate content, apart from soluble oxalate content at harvest 1 which tended to decrease with increased rate of N fertilizer but differences between Standard and Standardx2 level of N were not significant (p>0.05) (Figure 2). Oxalate content of Guineagrass tended to be lower as N fertilization increased at harvest 1, whereas no trend was found at harvest 2 and the causes of this dissimilar trend were unknown. In all treatments, plants at harvest 1 had significantly (p<0.05) higher insoluble and total oxalate content in plant tissue than at harvest 2, whereas there was no significant (p>0.05) difference in soluble oxalate content except for Standardx4 treatment which produced a significantly (p<0.05) lower soluble oxalate content at harvest 1 (0.35%) than harvest 2 (0.50%). Irrespective of N fertilizer level, the mean total oxalate content (harvest 1 and harvest 2) of Guineagrass was 1.53%, and most of the oxalate content seemed to be in an insoluble form (78% of total oxalate) at harvest 1, while the content of insoluble oxalate was 48% of total oxalate at harvest 2.

Regarding Sudangrass, compared to Standard level of N, further addition of N fertilizer (Standardx2 or Standardx4) application did not affect (p>0.05) the content of soluble, insoluble or total oxalate in the plants either at harvest 1 or harvest 2 (Figure 3). However, soluble oxalate content at harvest 1 tended to increase with increased N fertilization, while no such trend was found at harvest 2 and the causes of this dissimilar trend were unknown. In all treatments, plants at harvest 1 had significantly (p<0.05) higher insoluble oxalate content than at harvest 2, apart from Standardx4 treatment. There was no significant (p>0.05) difference in total oxalate content between harvest 1 and harvest 2 within the same level of N fertilizer application, except for the Standard treatment which produced a significantly (p<0.05) higher total oxalate content at harvest 1 (0.35%) than harvest 2 (0.09%). The mean total oxalate content (harvest 1 and harvest 2) of Sudangrass was 0.22% across all N fertilizer levels and most of the oxalate content seemed to be in an insoluble form (70% of total oxalate) at harvest 1, while insoluble oxalate content was very negligible at harvest 2.

The data from the present study indicates that further addition of N fertilizer (Standardx2 or Standardx4) does not affect either the content of soluble, insoluble or total oxalate in plant tissue, when compared with the Standard level of N fertilizer application. This is partially supported by the work of Williams et al. (1991) who found that a high level of N did not significantly increase soluble oxalate content in kikuyugrass. Our results are also in agreement with earlier reports on the effects of total N on oxalate content in Tetragonia tetragonioides (Ahmed and Johnson, 2000). The results of the present study may be explained by ammonium activity in plants, which may have served as a negative signal to inhibit oxalate accumulation (Ji, 2004; Palaniswamy et al., 2004; Xu et al., 2006). Xu et al. (2006) observed that glyoxalate accumulated in ammonium-fed rice leaves and was negatively correlated with oxalate, which suggested that downstream glyoxalate metabolism, including oxidation to oxalate, could be interrupted under ammonium treatment. Plants can absorb N both as N[O.sub.3.sup.-] and N[H.sub.4.sup.+] forms. In the present study, plants absorbed N as urea and it is commonly accepted that urea converts quickly to ammonium nitrogen. Ammonium nitrogen can be directly used by plants in the synthesis of amides and amino acids, whereas N[O.sup.-.sub.3]-N has to be reduced in the shoots (nitrate reduction by nitrate reductase) before absorption of N by plant. Ammonium nitrogen as a sole source of N acidifies the rhizosphere due to the excretion of [H.sup.+] from plant roots, and can be deleterious to plant growth (Weir et al., 1972). Schubert and Yan (1997) also suggested that the low oxalate found in plants grown with ammonium was due to ammonium assimilation favoring a slight acidification of the cytoplasm. In the present study, the absence of significant differences in the oxalate content of experimental plant species with different levels of N fertilizer as urea may be due to slight acidification of the rhizosphere or the cytoplasm by ammonium assimilation. In another study, Xu et al. (2006) reported that nitrate fertilizer stimulated oxalate accumulation in rice leaves, while ammonium fertilizer reduced its level. However, this observation contradicts the results of Jones and Ford (1972) who reported that the oxalate content in Setariagrass increased (p<0.01) significantly from 3.3% to 5.6% as N fertilizer (as urea) level increased from 0 to 200 kg/ha, respectively. This suggests that accumulation of oxalate in plant species by N forms is likely to be genetically controlled.

High levels of soluble oxalate (0.5% or more) cause severe calcium deficiencies by binding calcium in nonruminants (McKenzie, 1985). However, ruminants can adapt to diets containing soluble oxalate (Allison et al., 1977). While soluble oxalate is utilized by rumen microbes of adapted animals, insoluble oxalate seems to pass through the digestive tract and is eliminated in the faeces (Ward et al., 1979). According to McKenzie et al. (1988), levels of 2% or more soluble oxalate can lead to acute toxicosis in ruminants. Cymbaluk et al. (1986) pointed out that certain prairie forages with moderate amounts of oxalate (13-18 g/kg DM) could cause sub-clinical bone diseases. In the present study, the soluble oxalate content of the experimental grasses in all treatments was far lower than the critical levels cited in the literature.

CONCLUSIONS

Forage DM yield tended to increase with increased rate of N fertilizer application in all forage species, but the differences were not statistically significant within species. Increasing N application rate produced higher N content in all forage species and the differences were statistically significant in Rhodesgrass and Sudangrass. However, high N application rates did not significantly increase the oxalate content in plant tissue. The levels of oxalate present in the experimental grasses were quite low in terms of toxicity to animals.

Received June 22, 2007; Accepted September 14, 2007

REFERENCES

Ahmed, A. K. and K. A. Johnson. 2000. The effect of the ammonium: nitrate nitrogen ratio, total nitrogen, salinity (NaCl) and calcium on the oxalate levels of Tetragonia tetragonioides Pallas. Kunz. J. Horti. Sci. Biotech. 75:533-538.

Allison, M. J., E. T. Littledike and L. F. James. 1977. Changes in ruminal oxalate degradation rates associated with adaptation of oxalate ingestion. J. Anim. Sci. 45:1173-1179.

AOAC. 1990. Official Method of Analysis. pp. 66-88. 15th ed. Washington, DC. USA.

Cymbaluk, N. F., J. D. Millar and D. A. Christensen. 1986. Oxalate concentration in feeds and its metabolism by ponies. Canadian J. Anim. Sci. 66:1107-1116.

Dhillon, K. S., B. S. Paul, R. S. Bajwa and J. Singh. 1971. A preliminary report on a peculiar type of napiergrass (Pennisetum purpureum) (Pusa giant) poisoning in buffalo calves. Indian J. Anim. Sci. 41:1034-1036.

Elphinstone, G. D. 1981. Pastures and fodder crops for horses in southern coastal Queensland. Queensland Agric. J. 107:122126.

Hegarty, M. P. 1982. Nutritional limits to animal production from pastures (Ed. J. B. Hacker). Commonwealth Agricultural Bureaux CSIRO. pp. 133-150.

Inosaka, M. 1989. "Tropical Grasses" in Nogyo Gijutsu Taikei. Chikusan Hen, Shiryo Sakumotsu, Nobunkyo Co. Ltd., Tokyo, pp. 638-645 (In Japanese).

James, L. F., C. S. Joseph and E. B. John. 1967. In vitro degradation of oxalate and of cellulose by rumen ingesta from sheep fed Halogeton glomeratus. J. Anim. Sci. 26:1438.

Ji, X. M. 2004. The physiological and biochemical basis of oxalate metabolism as regulated by different nitrogen forms in rice. PhD Thesis, South China Agricultural University Guangzhou, China (in Chinese with an English abstract).

Johnson, C. R., B. A. Reiling, P. Mislevy and M. B. Hall. 2001. Effects of nitrogen fertilization and harvest date on yield, digestibility, fiber and protein fractions of tropical grasses. J. Anim. Sci. 79:2439-2448.

Jones, R. J., A. A. Seawright and D. A. Little. 1970. Oxalate poisoning in animals grazing the tropical grass Setaria sphacelata. J. Aust. Inst. Agric. Sci. 36:41.

Jones, R. J. and C. W. Ford. 1972. Some factors affecting the oxalate content of the tropical grass (Setaria sphacelata). Aust. J. Experi. Agric. Anim. Husb. 12:400-406.

Khan, R. I., M. R. Alam and M. R. Amin. 1999. Effect of season and fertilizer on species composition and nutritive value of native grasses. Asian-Aust. J. Anim. Sci. 12:1222-1227.

Lee, J. S., J. H. Ahn, I. H. Jo and D. A. Kim. 1996. Effects of cutting frequency and nitrogen fertilization on dry matter yield of Reed Canarygrass (Phalaris arundinacea L.) in uncultivated rice paddy. Asian-Aust. J. Anim. Sci. 9:737-741.

McKenzie, R. A. 1985. Poisoning of horses by oxalate in grasses. In: Plant Toxicology, Proceedings of the Australian-USA Poisonous Plant Symposium, Brisbane, Australia, quoted by Nutr. Abstr. 56:3446.

McKenzie, R. A., A. M. Bell, G. J. Storie, F. J. Keenman, K. M. Cornack and S. G. Grant. 1988. Acute oxalate poisoning of sheep by buffel grass (Cenchrus ciliaris). Aust. Vet. J. 65:26.

Palaniswamy, U. R., B. B. Bible and R. J. McAvoy. 2004. Oxalic acid concentrations in Purslane (Portulaca oleraceae L.) is altered by the stage of harvest and the nitrate to ammonium ratios in hydroponics. Scientia Horticulturae 102:267-275.

Penney, D. C., S. S. Malhi and L. Kryzanowski. 1990. Effect of rate and source of N fertilizer on yield, quality and N recovery of bromegrass grown for hay. Fertilizer Research 25:159-166.

Rahman, M. M., M. Niimi, Y. Ishii and O. Kawamura. 2006. Effects of season, variety and botanical fractions on oxalate content of napiergrass (Pennisetum purpureum Schumach). Grassl. Sci. 52:161-166.

Rahman, M. M., M. Niimi and O. Kawamura. 2007. Simple method for determination of oxalic acid in forages using high-performance liquid chromatography. Grassl. Sci. 53:201-204.

Sarwar, M. and Mahr-un-Nisa. 1999. Effect of nitrogen fertilization and stage of maturity of Mottgrass (Pennisetum purpureum) on its chemical composition, dry matter intake, ruminal characteristics and digestibility in Buffalo bulls. Asian-Aust. J. Anim. Sci. 12:1035-1039.

Schubert, S. and F. Yan. 1997. Nitrate and ammonium nutrition of plants: effects on acid/base balance and adaptation of root cell plasmalemma H+ ATPhase. Z. Pflanzenernahr. Bodenk. 160: 275-281.

Sidhu, P. K., D. V. Joshi and A. K. Srivastava. 1996. Oxalate toxicity in ruminants fed overgrown napiergrass (Pennisetum purpureum). Indian J. Anim. Nutr. 13:181-183.

Steel, R. G. D. and J. H. Torrie. 1984. Principles and procedures of Statistics: A Biometrical Approach. 2nd Ed. McGraw-Hill International Book Company, New York.

Ward, G., L. H. Harbers and J. J. Blaha. 1979. Calcium containing crystals in alfalfa: their fate in cattle. J. Dairy Sci. 62:715-722.

Weir, B. L., K. N. Paulson and O. A. Lorenz. 1972. The effect of ammoniacal nitrogen on lettuce (Lactuca sativa) and radish (Raphanus sativus) plants. Soil Sci. Soc. Am. Proc. 36:462465.

Williams, M. C., B. J. Smith and R. V. Lopez. 1991. Effect of nitrogen, sodium and potassium on nitrate and oxalate concentration in kikuyugrass. Weed Tech. 5:553-556.

Xu, H. W., X. M. Ji, Z. H. He, W. P. Shi, G. H. Zhu and J. K. Niu. 2006. Oxalate accumulation and regulation is independent of glycolate oxidase in rice leaves. J. Exp. Bot. 57:1899-1908.

M. M. (1), M. Yamamoto (2), M. Niimi and O. Kawamura * Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan

* Corresponding Author: Osamu Kawamura. Tel: +81-985-587259, Fax: +81-985-58-7259, E-mail: kawamura@cc.miyazakiu. ac.jp

(1) The United Graduate School of Agricultural Sciences (University of Miyazaki), Kagoshima University, Kagoshima, Japan.

(2) Boston Scientific Japan K.K., Miyazaki Techno Research Park, 16079-48 Higashi Kaminaka, Sadowara, Miyazaki-shi, Miyazaki 880-0303, Japan.
Table 1. Rate of fertilizer application (kg/ha)

 Amount of fertilizer

 Phosphorus
 ([P.sub.2] Potassium
Species Treatment Nitrogen (N) [O.sub.5]) ([K.sub.2]O)

Rhodesgrass Standard 260 300 290
 Standard x 2 540 300 290
 Standard x 4 1,060 300 290
Guineagrass Standard 380 260 430
 Standard x 2 770 260 430
 Standard x 4 1570 260 430
Sudangrass Standard 380 150 380
 Standard x 2 770 150 380
 Standard x 4 1,570 150 380

Table 2. Dry matter yield (t/ha) as affected by forage species, N
fertilization and harvesting frequency

 N fertilization rates (X)
Species Harvesting
 frequency Standard Standard x 2 Standard x 4

Rhodesgrass 1st 6.79 9.12 8.82
 2nd 6.04 6.86 9.48
 Average 6.42 7.99 9.15
Guineagrass 1st 12.62 (B) 12.95 (B) 14.15 (B)
 2nd 4.73 (Aa) 5.82 (Aa) 9.20 (bA)
 Average 8.67 9.39 11.67
Sudangrass 1st 8.47 (B) 8.28 9.4
 2nd 4.70 (aA) 5.76 (a) 9.16 (b)
 Average 6.59 7.03 9.28

Overall effect of N 7.23 (a) 8.13 (a) 10.03 (b)
 fertilization (Z)

Species Harvesting Harvest
 frequency SEM mean (Y)

Rhodesgrass 1st 0.71 8.24
 2nd 0.65 7.46
 Average 0.48 7.85
Guineagrass 1st 0.44 13.24 (B)
 2nd 0.70 6.58 (A)
 Average 0.80 9.91
Sudangrass 1st 0.66 8.72 (B)
 2nd 0.70 6.54 (A)
 Average 0.52 7.63

Overall effect of N 0.37
 fertilization (Z)

(X) Standard, 380 kg N/ha for each grass except Rhodesgrass (260 kg
N/ha); Standard x 2, two times the Standard; Standard x 4, four times
the Standard.

(Y) Contrasts testing the effect of harvesting frequency across all
species and fertilization rates (p<0.01).

(Z) Contrasts testing the effect of fertilization across all species
and harvesting frequency (p<0.01).

(a, b) Within a row, means without a common superscript differ
(p<0.05).

(A, B) Within a column for each species, means without a common
superscript differ (p<0.05). SEM = Standard error of the mean.

Table 3. Nitrogen concentration (% DM) as affected by forage species,
N fertilization and harvesting frequency

 N fertilization rates (X)
 Harvesting
Species frequency Standard Standard x 2 Standard x 4

Rhodesgrass 1st 0.95 (aA) 1.18 (aA) 1.67 (bA)
 2nd 1.78 (B) 1.84 (B) 2.25 (B)
 Average 1.36 (a) 1.51 (ab) 1.96 (b)
Guineagrass 1st 1.30 (aA) 1.57 (aA) 2.05 (bA)
 2nd 2.41 (aB) 2.78 (abB) 3.10 (bB)
 Average 1.86 2.17 2.57
Sudangrass 1st 1.47 (a) 1.83 (b) 2.24 (c)
 2nd 1.78 1.96 2.26
 Average 1.62 (a) 1.90 (b) 2.25 (c)
Overall effect of N 1.61 (a) 1.86 (a) 2.26 (b)
 fertilization (Z)

 Harvesting Harvest
Species frequency SEM mean (Y)

Rhodesgrass 1st 0.11 1.27 (A)
 2nd 0.10 1.96 (B)
 Average 0.10 1.61
Guineagrass 1st 0.11 1.64 (A)
 2nd 0.12 2.76 (B)
 Average 0.14 2.20
Sudangrass 1st 0.11 1.85
 2nd 0.09 1.99
 Average 0.07 1.92
Overall effect of N 0.07
 fertilization (Z)

(X) Standard, 380 kg N/ha for each grass except Rhodesgrass (260 kg
N/ha); Standard x 2, two times the Standard; Standard x 4, four times
the Standard.

(Y) Contrasts testing the effect of harvesting frequency across all
species and fertilization rates (p<0.01).

(Z) Contrasts testing the effect of fertilization across all species
and harvesting frequency (p<0.01).

(a, b, c) Within a row, means without a common superscript differ
(p<0.05).

(A, B) Within a column for each species, means without a common
superscript differ (p<0.05). SEM = Standard error of the mean.
COPYRIGHT 2008 Asian - Australasian Association of Animal Production Societies
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2008 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Rahman, M.M.; Yamamoto, M.; Niimi, M; Kawamura, O.
Publication:Asian - Australasian Journal of Animal Sciences
Article Type:Report
Geographic Code:9JAPA
Date:Feb 1, 2008
Words:4070
Previous Article:Effects of feeding extruded soybean, ground canola seed and whole cottonseed on ruminal fermentation, performance and milk fatty acid profile in...
Next Article:Increasing dietary phosphorus level for finishing yearling Holstein steers *.
Topics:


Related Articles
Effect of salinity stress on dry matter yield and oxalate content in napiergrass (Pennisetum purpureum Schumach).

Terms of use | Copyright © 2018 Farlex, Inc. | Feedback | For webmasters