Document(s) 29 of 41

Most of the 0.5 million ha of croplands in Jiangxi Province are pit fields, ridged fields, alluvial fields, and low grounds near the lakeside. These areas make up about 20% of the total ricefields in Jiangxi, but they are mostly cold, waterlogged, middle- or low-yield plots. The high water table is mainly responsible for the poor drainage of accumulated water. Constant water saturation has turned the soil to gley, which is cold, infertile, acidic, poisonous and lacks oxygen. Under these conditions, water, nutrients, air, and temperature are unfavourable to the growth and development of rice. Most regions yield one crop of rice a year, i.e., middle–late rice, but yield is low. To transform these low-yielding lands and increase crop production, a semiarid rice production initiated by Professor Hou Guangjiong was introduced in 1986 into the mountainous area of Gannan Prefecture, Jiangxi Province. This method of semisubmerged cropping in rice–fish culture has been improved to suit local conditions and has increased crop yields.

Main Principles

This method makes drastic changes to the system of rice cropping: planting on mounds instead of in furrows, putting ridges and ditches side by side to change the conditions in the field and add an active layer, planting rice on dikes, and culturing azolla and fish in the ditches. The physical changes raise the temperature of the soil and water, speed the catabolism of organic matter and the release of nutrients, and decrease the effect of toxic substances. As a result, seedlings revive sooner after transplanting, grow quickly, and have more white roots.

This method of rice–fish culture can turn single-crop agriculture into a double or multiple-harvest system and the slack winter season into a busy time. It is an excellent model of ecological agriculture that is applicable in all districts.

Continuous Nontillage

After the topsoil is ploughed for the first time, ridges and ditches are constructed side by side in the fields. Rice is planted on the ridges and fish are cultured in the ditches. Thereafter, the topsoil is not ploughed or harrowed to ensure that the active top layer is not destroyed. The soil does not become a caked mass; it grows softer with time. If the topsoil is ploughed, pockets of air and water capillaries in the soil are blocked. This decreases the percolation ratio, destroys the soil structure and the balance of water, nutrients, air, and temperature, and, as a result, reduces crop yields.

Continuous Ridge Tillage

Ridge tillage raises both the temperature of the water and soil and the oxidation–reduction potential of the soil. It activates soil nutrients and reduces toxic substances. This stabilizes the water, nutrients, air, and temperature and makes conditions more suitable for the growth and development of rice.

Continuous Infiltration

Capillary water in the soil is the only form of water that contains available nutrients and can flow freely, aerate the soil, and conduct heat. The key to semisubmerged cropping is improving the hydrological system of the soil. The continuous infiltration of capillary water aerates the soil, conveys nutrients, and prevents the soil from becoming a caked mass. The water level must be controlled according to the growth of the rice and the needs of the fish.

Demonstration and ApplicationNo Tillage, Rice on the Ridge, Fish in the Ditch

Experiment were carried out for the first time in 1986 in Longhui Village, Nankang County, Ganzhou Prefecture, in cold, waterlogged mountain fields with an area of 0.3 ha. In 1987, the area was increased to 2 ha. Experiments were also carried out in lateritic low-yield plots at Luoding Village, Xingjiang County, and in a waterlogged lowland area near the lakeside at the Dongfeng Branch Farm of the Hongxing State Reclamation Farm. The total experimental area in these two areas was about 1.3 ha. In 1988, the method was popularized in over 1330 ha in several counties (Ruijing, Nankang, Shicheng, Xingfeng, and Shangyou). In Ruijing County alone, there were 667 ha. Rice and fish were equally emphasized. In a few of the experimental plots, azolla was also cultured. The method was extended by the Agriculture, Animal Husbandry and Fish Department to an area of 200 ha in the counties of Fuzhou Prefecture.

Rice on the Bed, Fish in the Ditch

In 1987, this method was demonstrated on 2.8 ha in Shangyon County, Ganzhou Prefecture. The method features a wide ridge (0.8–1.2 m) that is constructed after the topsoil is ploughed. Rice is planted 13–17 cm apart on beds in rows that are 20 cm apart; fish and azolla are cultured in the ditch.

Rice on the Bed, Fish in the Ditch

In 1987, this method was demonstrated on 2.8 ha in Shangyon County, Ganzhou Prefecture. The method features a wide ridge (0.8–1.2 m) that is constructed after the topsoil is ploughed. Rice is planted 13–17 cm apart on beds in rows that are 20 cm apart; fish and azolla are cultured in the ditch.

Benefit Analysis

Because management of agricultural production is presently carried out by individual households, the experiments, demonstrations, and applications were arranged at the household level. During the entire production period, technicians were sent to the areas to provide technical advice, conduct quality inspections, and observe and record results. The results are analyzed and compared in Tables 36-38.

Table 36. Output (kg/ha) of rice–fish culture (rice-on-ridge ROR; rice-on-bed ROB) compared with output (kg/ha) of conventional flat cropping (CONV). Values of output expressed as CNY.
	ROR	CONV	Increase		ROB	CONV	Increase
			kg/ha	%			kg/ha	%
Rice yield	10 896	8673	2223	25.6	7504	6825	680	10.0
Value of rice	3886	3456	430	27.5	2979	2554	425	15.4
Value of fish	2012	0	2012	—	1539	0	1539	—
Total value	5898	3456	2442	86.3	4518	2554	1964	75.7

Table 37. Fish output (kg/ha) and economic benefits of two new methods (CNY/ha).
	Number of households	Fish output	Breeding cost	Net income
Rice-on-ridge, fish-in-trench	8	3333.0	885.0	2448.0
Rice-on-bed, fish-in-trench	6	1288.5	109.5	1179.0
Difference	—	2044.5	775.5	1269.0

Table 38. Comparison of economic benefits of different combinations of fish species reared using the rice-on-ridge, fish-in-trench method.
Area (ha)	Cost (CNY/ha)	Output	Value (CNY/ha)	Net income (CNY/ha)
Grass carp	0.21	199.2	698.4	499.2
Common carp	0.31	38.2	651.0	612.8
Grass carp, common carp, and silver carp	0.14	889.4	2988.9	2099.5
Grass carp, common carp, and variegated carp	0.10	501.0	2299.9	1798.9
Grass carp, common carp, silver carp, and variegated carp	0.28	1258.4	4190.1	2931.7

Compared with conventional flat cropping, there were considerable increases in rice output and income from fish whether the rice-on-ridge or the rice-on-bed method was used. For example, 11 households used the rice-on-ridge method. Their average rice output increased by 2223 kg/ha (range 420–7140 kg/ha) and average net income from fish was CNY 2010/ha (range CNY 450–4935/ha). When the value of the fish and the increased amount of rice were both counted, the total rate of increase in value was 36.5–216.9% (average 86.3%). In another four households that used the rice-on-bed method, the increase in rice production was 680 kg/ha (range 530–990 kg/ha) and the net value of the fish was CNY 1540/ha (range CNY 531–3170/ha). The total net value of fish and rice increased by 76% (Tables 1 and 2).

The rice-on-ridge method is superior to the rice-on-bed method because it improves the ecological environment of the farmland (and enhances the growth of rice) and because it has a larger area of water, which is favourable for fish breeding. Higher economic benefits were obtained from the rice-on-ridge method when mixed species of fish, instead of a single species, were raised (Table 3).

Soil Improvement

Professor Hou Guangjiong has reported many improvements in the soil using the rice-on-ridge, fish-in-trench, no-tillage method of semiarid rice cultivation. Preliminary observations, suggest that unit weight of the soil decreases, temperature increases, and that the soil contains more organic matter, total nitrogen, available nitrogen, phosphorus, and potassium (in some cases, there was a tendency toward less total phosphorus compared with conventional flat cropping) (Tables 39–41).

Table 39. Reduction in soil unit weight (g/cm3) as a result of semiarid fish culture.
Household	Semiarid fish culture	Flat cropping	Reduction
Zhu Longpeng	1.11	1.21	0.10
Zhu Changrui	0.96	0.98	0.02
Zhu Qiusheng	0.84	1.14	0.30
Zhu Xiaoping	0.85	0.93	0.08
Zhu Changfa	0.74	1.01	0.27
Lin Yuanxiao	0.84	0.95	0.11
Lin Chuanrong	0.98	1.00	0.02
Lin Yuanrong	0.97	0.99	0.02
Mean	0.91	1.03	0.12

Table 40. Soil temperatures (°C) at different depths with different cropping systems.
Households	Time	Semiarid rice and fish culture		Flat cropping		Differences in temperature
		0–10 cm	10–20 cm	0–10 cm	10–20 cm	0–10 cm	10–20 cm
Zhu Longpeng
May 11	11:00	24.5	24.2	24.1	23.7	0.4	0.5
May 14	10:00	23.7	23.6	23.4	23.2	0.3	0.4
May 17	10:00	25.0	24.8	24.6	24.5	0.4	0.3
Mean	—	24.4	24.2	24.0	23.8	0.4	0.4
Zhu Changgui
May 11	12:00	24.5	24.3	24.0	23.8	0.5	0.5
May 14	11:00	23.9	23.7	23.5	23.2	0.4	0.5
May 17	11:00	25.1	24.9	24.5	24.3	0.6	0.6
May 19	11:00	21.0	20.8	20.5	20.3	0.5	0.5
Mean	—	23.6	23.4	23.1	22.9	0.5	0.5
Zhu Changfa
May 11	11:00	25.0	24.8	24.6	24.4	0.4	0.5
May 14	11:00	24.0	23.7	23.5	23.3	0.5	0.4
May 17	11:00	25.1	24.9	24.5	24.3	0.6	0.6
May 19	14:00	21.4	21.3	21.0	20.7	0.4	0.6
Mean	—	23.9	23.7	23.4	23.2	0.5	0.5

Table 41. Analysis of soil nutrients (semiarid SA; conventional C).
	Organic matter		Total N		Total P		Available N		Available P		Available K
	SA	C	SA	C	SA	C	SA	C	SA	C	SA	C
(1)*	4.30	3.49	0.146	0.102	0.019	0.012	76.5	64.9	6.69	3.11	28.3	29.8
(2)	4.91	3.34	0.111	0.115	0.007	0.003	51.0	56.9	4.48	3.12	48.3	39.8
(3)	4.62	2.60	0.116	0.094	0.014	0.020	42.2	40.7	5.22	3.37	46.1	41.0
(4)	4.46	3.46	0.165	0.113	0.007	0.016	178.3	92.0	7.70	6.45	54.4	35.4
(5)	3.42	2.79	0.114	0.100	0.013	0.022	87.4	71.7	4.53	3.84	99.1	43.6
(6)	4.30	3.66	0.149	0.138	0.012	0.007	69.5	67.2	4.52	7.44	87.5	49.5
Avg	4.34	3.21	0.134	0.110	0.012	0.013	84.2	65.6	5.52	4.56	60.6	39.8
* Households were (1) Zhu Longbin, (2) Zhu Changrui, (3) Zhu Longze, (4) Zhu Xiaoping, (5) Zhu Xidi, and (6) Lin Yuan Xiao.

Remaining Problems

In experiments and demonstrations, the semiarid rice-on-ridge, fish-in-trench method has remarkably increased production and income and improved soil conditions. In 1989, the Prefectural Department of Ganzhou planned to apply the new method on 33 330 ha. Farmers who had become aware of the benefits of the method were happy. But, to extensively disseminate any new technique, potential problems should be examined and addressed.

Farmers do not believe that rice can be grown without ploughing the field. For thousands of years, rice has been planted in water using the flat basin irrigation cropping method. Ricefields with ridges are new. Most farmers doubt that the rice plants can absorb water and nutrients when they are planted on the ridges. Some farmers also complain that the ridges make it difficult for them to put their threshing tubs and machines in the fields at harvest time. More demonstration and extension efforts are needed to overcome these problems.

Many places have no previous experience with raising fish in ricefields. There are also some social problems. Fish in the fields are often stolen, especially in cold, waterlogged fields that are usually located in remote mountain areas. Farmers worry about this. Local governments must strictly enforce the law to protect farm production from theft. The villagers could also develop some protective measures.

The farming activities in the new method (e.g., digging trenches, forming ridges, clearing mud from the trenches, and applying fertilizer) require much labour. In Longhui Township, Nankang County, a small iron spade that was light and handy for clearing mud from trenches was popularized. Such labour-saving tools or devices for trench digging, ridge forming, and row fertilization need to be developed.

When a new technique is applied in a large area, farmers, because of their different levels of understanding, sometimes fail to follow the technical requirements for certain farming activities. Because of this, not only should extension and guidance be stressed, but input supplies, such as chemical fertilizers and pesticides, must also be made available.

Document(s) 29 of 41