Management and utilization of mulberry for forage in Japan. 1. Productivity of the mulberry-pasture association system and nutritive value of mulberry

N. Kitahara, S. Shibata and T. Nishida
Department of Grassland Management
National Grassland Research Institute, Japan.

INTRODUCTION

Pastures in Japan are mainly composed of temperate species such as orchard grass, tall fescue, timothy and white clover, which are native to Asia (now Anatolia) and Southern Europe region. The climatic conditions of Japan, unlike Europe, are not always suited to the growth of these temperate grasses and pastures based on them create some problems. One of the most serious concerns is seasonal forage production, which is remarkably uneven compared with Europe. Summer forage production in particular decreases to an extreme low because of high summer temperatures. Consequently, there is insufficient forage for grazing animals from summer to autumn.

Mulberry (Morus sp.) was once widely planted for sericulture purposes in Japan. However, since the industry has been on the decline for the last few decades, there are many abandoned mulberry farms all over the country. There is an opportunity to utilize these farms for other purposes, especially for mixed pastures.

In view of the above situation, the authors started research on the use of mulberry in temperate grass pastures in order to reduce the summer-autumn forage shortage and to find alternative uses for the abandoned sericulture farms.

The productivity of mulberry-pasture mixtures and the nutritive value of mulberry leaves and shoots are presented in this paper.

MATERIALS AND METHODS

This trial was carried out from 1997 to 1999 on a volcanic ash soil at the National Grassland Research Institute (Nishinasuno, Tochigi) located at 36^o 55' latitude north, 139^o 55' longitude east and at 320 m above sea level.

The mulberry varieties were Shinkenmochi (M. bombycis) and Aobanezumi (M. alba). Mulberry-pasture association was established as follows: Mulberry was planted at a spacing of 3 m - between rows and 0.7 m between plants (4 762 plants/ha) in the spring of 1996. A mixture of five temperate species - orchard grass, tall fescue, perennial ryegrass, red top and white clover - was sown among mulberry rows the following autumn. The association was compared with a sward of those species and with mulberry in a pure stand. The design was a randomized complete block with three replications. In all three treatments plot size was 84 m² (7 m x 12 m). Four mulberry rows, two of each mulberry variety, were used in both the association and the pure stand. Harvest times were for 1997: 30 April, 10 June, 11 August, 3 October and 10 November; for 1998: 30 April, 9 June, 10 August, 5 October and 5 November; and for 1999: 30 April, 11 June, 9 August, 6 October and 2 November. As mulberry began sprouting at the end of April and stopped shooting about the middle of October, it was harvested three times from June to October. Mulberry plants were trimmed at 1 m high when they were planted and the new shoots harvested by cutting approximately 1 cm above the old shoots. Swards were cut at 5 cm above ground. Fertilizer was applied at the rate of 68 kg/ha/year of N, P and K.

Forage production and nutritive value were determined in the three treatments. Forage samples from September were used to determine CP, ADF, NDF, ash, organic cellular content (OCC), organic cell wall (OCW), high digestible fibre fraction (Oa), low digestible fibre fraction (Ob), Ca, P, Mg, and K. The K/(Ca+Mg) ratio was calculated.

RESULTS AND DISCUSSION

Productivity of mulberry-pasture association

Table 1 shows the results of the DM production of three treatments from 1997 to 1999.

Since, mulberry is very palatable for cattle (Kitahara, 1999) and both new shoots and leaves are well consumed, mulberry production data shown also include shoots.

Excellent yearly DM production of mulberry-pasture association was obtained in all three years. DM production of the mulberry-pasture mix was 13 percent, 32 percent and 57 percent above the grass alone in 1997, 1998 and 1999, respectively, resulting from the contribution of mulberry. In general, grassland productivity in Japan decreases with time. This was the case in this experiment for the temperate sward where the yield decreased from 1997 to 1999. On the contrary, the productivity of the mulberry-pasture association did not drop. This interesting result seems to result from the protective shading effect of mulberry on the grass sward. Seasonal forage production in the mulberry-pasture association was well distributed compared with other treatments. Consequently, a mulberry-pasture association can be a way of solving the problem of the summer-autumn forage deficit in Japan.

None of the mulberry plants was killed by defoliation three times a year during the experiment.

Nutritive value of mulberry leaves and shoots

Table 2 shows the nutritive value of mulberry leaves and shoots compared with a temperate sward and Table 3 shows the comparative mineral content.

The characteristics of the nutritive component of mulberry were as follows. The contents of crude protein and OCC in the leaves were high, but those of ADF and NDF were low compared with the sward. Mulberry leaves were more digestible than the sward. On the other hand, the contents of ADF, NDF and OCW in the mulberry shoots were relatively high. This shows that mulberry shoots might have low digestibility. As the ratio of DM production of mulberry leaves to the shoots is 3:1, whole nutritional quality of the mulberry foliage, likely to be consumed by cattle, seems to be high.

With regard to mineral content, Ca, P and Mg in mulberry leaves were higher than in the sward. K content and K/(Ca+Mg) in mulberry leaves were markedly lower than in grass.

Grass tetany is a significant disease during the grazing season, and has generally been related to low Mg, high K, and high K/(Ca+Mg) equivalent ratios in the forage (Karlen et al., 1978). Gross (1973) reported that generally accepted values of less than 0.2 percent Mg, more than 2.5 percent K, and K/(Ca+Mg) equivalent ratios greater than 2.2 could cause forage to be tetany prone. It is apparent that mulberry has good mineral components that prevent grass tetany.

TABLE 1

The productivity of mulberry and temperate sward in the three treatments (kg of DM/10a)

Year/ treatment	Fraction	Date					Total
1997		30/04	10/06	11/08	03/10	10/11
Association	Sward	531	394	223	162	69	1 380
	Mulberry leaves		83	86	71		239
	Mulberry shoots		26	38	23		86
	Subtotal		109	124	94		325
	Total	531	503a	347a	256a	69	1 706a
Sward	Sward	588	434a	232b	203a	57	1 514a
Mulberry pure stand	Mulberry leaves		111	152	86		349
	Mulberry shoots		48	84	24		156
	Total		160b	236b	110b		505b
1998		30/04	09/06	10/08	05/10	05/11	Total
Association	Sward	228	213	192	172	36	841
	Mulberry leaves		43	72	58		173
	Mulberry shoots		14	21	16		51
	Subtotal		57	93	74		224
	Total	228	271Aa	285Aa	246Aa	36	1 065a
Sward	Sward	181	203Bab	196Bab	183Ba	44	807b
Mulberry pure stand	Mulberry leaves		90	126	51		267
	Mulberry shoots		32	50	15		97
	Total		122Cb	177Bb	66Cb		364c
1999		30/04	11/06	09/08	06/10	02/11	Total
Association	Sward	128	286	183	85	39	722
	Mulberry leaves		31	84	101		216
	Mulberry shoots		7	34	35		75
	Subtotal		38	118	136		291
	Total	128	324Aa	301A	221Aa	39	1 013a
Sward	Sward	121	194Bab	206B	93Bb	32	647b
Mulberry pure stand	Mulberry leaves		63	111	94		268
	Mulberry shoots		18	39	24		82
	Total		82Cb	150B	118Bab		350c

Statistical comparisons were among treatments within same year. Values with the same letter do not differ (A <0.05, a <0.01).

The nutritive value of mulberry leaves and shoots compared with temperate species

Fraction	CP	ADF	NDF	Ash	OCC	OCW	Oa	Ob
Mulberry
Leaves	25.8	21.0	31.6	11.8	51.8	36.5	10.0	26.5
Shoots	12.1	45.6	60.5	8.8	32.8	58.5	9.4	49.1
Sward	20.4	27.9	53.5	11.6	34.0	54.4	12.3	42.1

Harvesting month: September 1997. The mulberry variety was Shinkenmochi.

Mineral content of mulberry leaves and shoots compared with the temperate sward

Fraction	Ca	P	Mg	K	K/(Ca+Mg)
Mulberry
Leaves	2.98	0.44	0.43	2.84	0.41
Shoots	1.01	0.37	0.36	3.78	1.21
Sward	0.28	0.37	0.30	4.99	3.29

Harvesting month: September 1997. The mulberry variety was Shinkenmochi.

This study has demonstrated that the productivity of mulberry-pasture association is very high and has even seasonal distribution compared with a sward of temperate species. The nutritive value of the mulberry leaves was also high and mineral content was excellent. A mulberry-pasture system seems to be a promising grazing method. However, that further studies on this system need to be conducted to solve further practical problems.

BIBLIOGRAPHY

Gross, C.F. 1973. Managing magnesium-deficient soils to prevent grass tetany. Proc. 28th Annu. Meeting Soil Conserv. Soc. Am., Hot Springs, Ark., p88-92.

Karlen, D.L., Ellis, R. Jr., Whitney, D.A. & Grunes, D. L. 1978. Influence of soil moisture and plant cultivar on cation uptake by wheat with respect to grass tetany. Agronomy J. 70: 919-921.

Kitahara, N. 1999. Some cases of available roughage in the riverbank and abandoned arable land. Dairy J. 4: 22-24.