Winter wheat is the main winter cereal crop. Winter barley accounts for only a very small proportion of the total area under winter crops. While the expected yield potential on farms for winter wheat under normal weather conditions is around 3 t/ha, the annual average yields during the last two years have ranged between 1.02 and 1.85 t/ha.
Spring barley is the main spring cereal crop. Spring wheat accounts for only a very small proportion of the total area under spring crops. While the yield potential for spring barley is at least 3 t/ha, the annual average yields have ranged between 0.59 and 1.63 t/ha during the past two years.
The main summer crops are rice and maize. Whereas the average yields of rice and maize could easily be raised to the level of 6.5 t/ha with the support of adequate agricultural inputs, at present the average yields are of the order of only 3.2 t/ha and 2.1 t/ha for rice and maize respectively (FAO/WFP Crop Assessment Mission, 2000).
These substantial yield gaps are due partly to abnormal weather conditions but also to the inadequate use of inputs.
Rice nurseries are heavily fertilized. Nursery fertilizer recommendations by the Ministry of Agriculture (MOA) for a unit nursery are as follows:
Western area
Humus soil: 7.5 to 9 tonnes
Urea: 46 to 55 kg
Single
superphosphate: 150 to 180 kg
Potassium chloride: 15 to 18 kg
Eastern area
Humus soil: 8.4 to 9.6 tonnes
Urea: 51 to 59 kg
Single
superphosphate: 168 to 192 kg
Potassium chloride: 16.8 to 19.2 kg
(In the eastern area a unit nursery has an area of 100, in the west 70 to 80 pyong. 100 pyong = 0.033 ha).
After a period of 40 to 55 days in the nursery, the seedlings are transplanted into the main paddy fields. In the southern states about 40 to 45 days in the nursery suffices, but in the northern states such as South Hamgyong and Kangwon, with lower temperatures, a longer stay of 50 to 55 days is required.
A cover of plastic sheeting is used to protect the seedlings from low temperatures, especially during the night, and from strong winds. Windbreaks using rice straw are erected around the nursery area. The highest wind speeds, ranging from 3.1 to 3.4 m/sec, occur between March and May.
Maize transplanting, a method probably unique to DPR Korea, is adopted in most areas. The advantages of transplanting are a reduced mortality compared with direct seeding, scope for the selection of strong and healthy seedlings to ensure a better plant stand and economies in the seed rate. Hand transplanting is evidently labour intensive.
A unit nursery of 70 pyong provides a number of seedlings sufficient for the transplantation of one hectare. The seed requirement is of the order of 45 to 55 kg for a unit nursery. About 1 200 seedlings are supported per pyong of nursery area. The total availability of seedlings from a unit nursery is of the order of 84 000 plants, providing scope for selection, the plant density per hectare being 66 000. Fertilized humus briquettes are used for the nursery raising of seedlings. MOA recommendations for nursery fertilizer application per unit nursery area are as follows:
Western area
Humus soil: 10 to 12 tonnes
Urea: 13 to 15 kg
Single
superphosphate: 210 to 240 kg
Potassium chloride: 4 to 5 kg
Eastern area
Humus soil: 15 tonnes
Urea: 18 kg
Single superphosphate:
300 kg
Potassium chloride: 6 kg
Maize seedlings are usually grown for up to 25 days in the nursery before being transplanted to the main field. Seedlings along with their root-balls are transplanted by hand in furrows drawn by bullock-drawn ploughs.
The double cropped spring crop should typically be harvested by 20 June and the planting of the following crop, rice or maize, should be completed by 25 to 30 June on the same fields. This provides very little time for harvest operations plus land preparation and the planting of the following crop, emphasizing the need for varieties with a short length of growing period (LGP) both winter/spring crops and for summer crops. If the planting of the succeeding crop is delayed, the yield is reduced.
In place of the varieties with long LGP used for mono-culture rice i.e. the Pyongyang series (variety Pyongyang 21: yield potential 8.3 t/ha; LGP 170 days), varieties with medium LGP (Olbyo 4 and 5: yield potential 7.3 to 7.5 t/ha, LGP 146 days and Hamju 3 yield potential 6 to 7 t/ha, LGP 135 to 140 days) are now commonly planted for double crop rice. The expansion of the area under recently developed varieties with a shorter LGP such as Olbyo 8 (yield potential 6.8 t/ha, LGP 127 days) needs to be speeded up in the double-cropped areas.
The spring barley variety 'Red Sun 3' brought in from China fulfils the need for varieties with a shorter LGP for this crop since it matures by 15 to 20 June and gives yields higher by about 200 kg per hectare compared with local varieties such as 'Pungsan 1', Pungsan 8', Taechong Dan 21', 'Unpa 18', 'Olbory 4', and 'Haeju 4. However, in the northern provinces of South Hamgyong and Kangwon, with colder and longer winters, traditional varieties such as 'Haeju 4' have been found to be more suitable. 'Red Sun 3' has been found to be a suitable variety for most of the areas but it has poor germinating capacity.
A new wheat variety i.e. 'Kangnam 43' with a shorter LGP enabling a greater photo-duration for the following crop may be released soon. The likely date of maturity of the variety is 10 June instead of 20 June for the 'Jin Dong 8' variety. It is suitable for planting in the areas below 40-degree latitude (Pyongyang, South Pyongan, parts of the North Pyogan below the Jongju City, South and North Hwanghae, Kangwon, South Hamgyong, Kaesong and Nampo).
Inadequacy of the seed multiplication infrastructure presents problems of availability of new varieties of seeds.
Potato cultivation, although a recent introduction in DPR Korea, has substantial potential for increasing the food supply. The Government has encouraged the potato crop both in the context of a double crop programme and as a main crop. At present an area of about 188 700 ha is cropped with potatoes, up from about 40 000 ha in recent past. The average productivity of about 10.5 t/ha in a normal year results in production of about 1 981 350 tonnes annually.
The production of two or more crops per year is possible in the country. The first crop is planted in March and April in the warmer southern parts of the country and harvested in July. The main crop is planted in May in the cooler and higher areas in the south and in the north of the country and harvested in September.
For the year 2002, the target for potato cultivation was set at 188 700 ha, 90 000 ha of main crop and 98 700 ha of double crop (spring crop). About 50 per cent of this area is located in the northern provinces of Ryanggang and North and South Hamgyong and the remainder in the southern provinces of North and South Hwanghae and North and South Pyongan.
The Ministry of Agriculture and the Agricultural Academy of Sciences provided overall supervision of the crops.
With the recent introduction of double cropping, spring potatoes can now be seen in many fields. There is considerable potential for increasing the per hectare yields, given an optimum use of inputs. With good quality potato seed, free from virus and other diseases, spring potato yields could attain 15 t/ha, and the double-cropped main potato grown in southern parts could easily give average yields up to 20 t/ha.
Crop rotations involving legume crops are being developed. The Swiss Agency for Development and Cooperation (SDC) is giving assistance to explore crop diversification opportunities through field trials and demonstrations. Cropping patterns with green manure crops such as spring oats (Chinese variety: Jin Yan Za), common vetch (Chinese variety: Jian She Wandu) and red clover are being developed as a component of the Project for Sustainable Agriculture, in Miru Hills, North Hwanghae.
Alternating a cereal-cereal rotation with a cereal-legume rotation at regular intervals could be beneficial from the viewpoint of soil fertility maintenance and breaking regular cycles of pests and diseases. Inter-cropping with leguminous crops might usefully be promoted.
The development of an Integrated Plant Nutrition System (IPNS) approach is indicated. This approach takes a holistic view of the management of soil fertility and plant nutrition for a targeted yield, based not only on cropping and farming systems but also on systems adapted to distinct geographical areas. Appropriate combinations of various types of plant nutrients in different situations are designed to ensure balanced plant nutrition, high yields, sustainable soil fertility and reduced nutrient losses.
In view of the poor nutrient status of the soils of DPR Korea and the scarcity of fertilizers and other nutrient resources, it is important that the available fertilizers should be used as efficiently as possible. Rates of fertilizer application based on soil tests represent one of the most appropriate tools for ensuring higher levels of fertilizer use efficiency.
Soil test based fertilizer recommendations have long been used in DPR Korea. Soil samples used to be taken and analyzed every three years on a large scale. However, since the mid-1990s, soil analyses have been carried out on a six-year cycle. Due to lack of resources, the soil-testing programme suffers from outdated equipment, shortage of chemicals, glassware and technical staff acquainted with latest techniques, prevalence of old methodology and an inadequate research base. This has affected the efficiency of the soil test programme and even sometimes the validity of the soil test results. Micronutrient analysis facilities in general are not available.
The Government has submitted a proposal for an FAO funded project for the establishment of a model soil test laboratory in an agricultural area of good potential (South Pyongan). In addition, another five soil testing laboratories at the provincial levels are needed, one in each of the provinces of South Pyongan, North Hwanghae, South Hwanghae, South Hamgyong and Kangwon.
