▣ Cultural practices

 

(Table 9) Some of standard soybean cultural practices in Korea.

Cropping	Planting time	Planting density 1)				Fertilizer 2) N-P2O5-K2O
		RW(cm)	BH(cm)	P/H	P/㎡
Summer	Early-mid. April	40	15	2	33	30-30-34
Full-season	Early-late May	60	15	2	22	30-30-34
Late-season (After barley)	Mid.-late June	June	10	2	33	30-30-34

*1) RW : Row width, BH : Distance between hills
      P/H : Number of plants per hill; P/m² : Number of plants per m²
*2) Composition rate of compound fertilizer applied : 8-14-12, 500 kg/ha
 

(1) Crop rotation
the crop preceding soybeans has an influence on yield potential. If soybeans are planted after soybeans, diseases and other pest problems may be intensified in the second and later years of production. difficult to control weed problems will become worse. In addition, research evidence suggests that growth inhibiting substaNICS (allelopathic chemicals) are released from soybean residue as it decomposes in the soil. These substaNICS have a negative effect on growth and production of soybeans. To avoid this problem, sufficient time must elapse between one soybean crop and next to allow decomposition of the soybean crop residue. Planting soybeans after soybeans will not provide a sufficient interval. Higher yields tend to result from soybeans grown in rotation, compared to those from soybeans after soybeans.

(2) Planting date
Soybean planing time in Korea varies with three different cropping : summer cropping, Full-season cropping, and late-season (after barley) cropping of which planting times are early to middle April, early to late May, and mid.-to late June, respectively. For full-season cropping, an attempt to make its planting earlier, which will bring longer growth period of higher seed yield, is being made on an experimental farms. The planting of the late-season cropping which accounts for the largest area planted to soybean (about 43% of the total area) is often delayed and take place in early July due to labour competition for barley harvest and rice transplanting.

(3) Land preparation and planting
For land preparation, power tillers (37%) and tractors (56%) are generally used. Soybean fields are thoroughly plowed and harrowed except in the lowlands where two or four plowed ridge hill plantings are more common. Due to the labour competition for barley harvest and rice transplanting in late-season soybean planting and lower income from soybeans compared to other competing summer crops, less input of labours or labour saving planting methods are required. There are several labour saving planting methods.

(a) Scattering on barley stubble
Scattering on barley stubble planting method is commonly practiced in the late-season cropping area where most of soybeans are planted as the second crops after barley harvest. Soybean seeds are scattered on the barley stubbles without tillage. Fertilizers are also top or side dressed before hilling-up of inter-row soils to cover the soybean seeds as sown in Fig. 2. Covered soils by plow are softened by breaking up the lumps with a hoe or solid wood rake.

 

 

(b) Minimum tillage planting after barley harvest
More labour can be saved for soybean planting with minimum tillage by use of drill seeder and rotavator attached to tractor or power tiller. This planting method can be successfully practiced only with well organized herbicide application. The mixture application of non-selective and pre-emergence herbicides after machine planting can control the weeds above and in the soils. Minimum tillage planting bring better standing and a great deal of labour saving as shown in Table 10.

 

(Table 10) Labour saving by minimum tillage planting in soybean. [Unit : hour/ha]

Planting method	Herbicide application	Ploughing & harrowing	Fertilizer application	Planting	Total
Minimum tillage	2.1	-	0.9	4.6	7.6(4.7) *
Conventional	-	40.00	87.0	2	163.0 (100.0)

 * The numbers within parenthesis are labour input index.

(Table 11) Percent of full-yield potential for timely planted soybeans, as influenced by plats per meter of row and percent stand reduction.

Stand reduction	Plants per meter of row*
	27	20	13
Conventional	Percent of full-yield potential
Percent of full-yield potential	100	97	95
10 percent	98	96	93
20 percent	96	93	91
30 percent	93	90	88
40 percent	89	86	83
50 percent	84	81	78
60 percent	78	75	73

 

(b) Weed control
Inter-tillage and hilling up are performed twice or three times before flowering for weeding and preventing of lodging. A power tiller, or tractor, is used of that purpose. Controlling weeds is a vital step in the production of any crop but is especially important in successful soybean production. Weeds generally should be controlled within the first four weeks after soybean emergence to avoid yield loss. In many instance, the best weed control program includes a combination of cultural, mechanical and chemical practices. Herbicides are commonly applied at the pre-emergence stage of soybean to control weeds in Korea as to be shown in Table 12.

 

(Table 12) Kinds and application methods of herbicides for weeds control of soybean fields.

Application	Herbicides	Per hectare		Treatment time	Weed spectrum
		Application rate	Amount of spray
Pre- emerqence	Alachlor Ec	2,000~3,000 cc	1,000L	Within 3 to 4 days after planting	Annual weeds
	Alachlor G	30~50 kg	-	"	"
	Linuron Wp	1.0 kg	1,000L	"	"
	Alachlor Ec+	2,000 cc+	1,000L	"	"
	Linuron Wp	1.0 kg
Post- emergence	Haloxyfop Lq	750 cc	1,000L	3 to 5 leaf stage of weeds	Grasses

(Table 13) Chemical control of major diseases and insect pests in soybean.

Times	Control time	Diseases and insect pests	Diseases and insect pests Kinds and application methods of fungicides and pesticides
1st	Late July~Early Aug.	Purple seed stain Pod and stem blight Anthracnose Downy mildewPlusia agnata	Mancozeb 600 times of Benomyl 1,500 times plus Fenitrothion (Smithion) 1,000 times. Amount of spraying perhectare : 1,000~1,200L
2nd	Late Aug.~Early Sept.	Same diseases above, and soybean pod borer and bean bugs	"

(6) Harvesting and drying
Harvesting time of soybeans differs with the type of cropping mentioned before. Summer-type soybean is harvested in early August while full-season (monoculture) soybean is harvested from late September to early October. Soybeans in the farms are harvested commonly by uprooting the whole plant or cutting the stalks with a sickle except some great unit area of soybean culture by bush cutter (attached gasoline engine) and binder. Recently, combine harvesters are used at large scale farm household. Harvested soybeans are generally tied up in bundles and dried in the sun.