FOR ETTER FARMER LIVELIHOODS, FOOD SECURITY AND ENVIRONMENTAL SUSTAINABILITY
* This country report has not been formally edited and the designations and terminology used are those of the author.
Pham Quang Ha1, Mike McLaughlin2, Ingrid Oborn3
Summary Viet Nam with a population 83.0 million, has reached its security in food on a national scale. Food production in Viet Nam, which has reached 36 million tonnes annually, was obtained from the full cultivation of about 11 million ha of agricultural lands. The great achievement in food security is largely obtained from liberal increases in fertilizers across the country. Viet Nam farmers used an average of 234 fertilizer unit per ha in 2004 a significant increase compared with 134 unit in 1998 and only 18 unit in 1976. However, it is fully recognized that supporting a large population on a small base of cultivable land has tremendous consequence on the environment. Researchers indicated and warned very strongly that under the current fertilization regime, potassium is being depleted from improper nutrient balance in applied fertilizers and which is exacerbated by recent increases in rice yield. This situation is especially true since only about 30 percent of soil resources in Viet Nam are of good quality and the rest have several soil fertility constraints and measure to mitigate their limitations vary and perhaps expensive. The widening prevalence of soil erosion, land degradation and decline of soil fertility in Viet Nam are generally attributed to land overuse. Aside from judicious use of chemical fertilizers, nutrient recycling is one important key in agricultural management to keep the balance in plant nutrient and soil fertility. In this paper, the authors described the integrated approached for fertilizer uses and nutrient recycling as support for some representative sustainable cropping systems in Viet Nam. |
1. Introduction of Viet Nam agriculture soils
The total territory of Viet Nam is 32 924 000 ha but only 35 percent of it is used for agriculture. Total cultivated soil is 11 569 591 ha, of which more than 50 percent are problem soils such as arenosol, thionic fluvisol and acrisols.
1.1 Soil fertility status
Beside two alluvial soils of Viet Nam (Red river fluvial soil and Mekong river fluvial soil), soil fertility in Viet Nam is not very high. The widespread soil in Viet Nam has low pH, low C, low N and very low CEC. It is especially true for soil with light texture as sandy soil or acrisol. The dominant feature of a degraded soil (Acrisol) is shown in Table 2. Results of routine soil testing conducted recently reveal that almost all of Vietnamese soil are low in N content, 80 percent of soil
Table 1. Main cultivated soils of Viet Nam
No. |
Soil group name |
FAO-Unesco |
Area (ha) |
Percent |
1 |
Sandy soil |
Arenosol |
533 434 |
4.61 |
2 | Saline soil | Salic fluvisol |
971 356 |
8.39 |
3 |
Acid sulfate soil |
Thionic Fluvisols |
1 863 128 |
16.10 |
4 | Alluvial soil | Fluvisols |
3 400 058 |
29.38 |
5 | Red soil | Ferralsols |
3 010 594 |
26.02 |
6 |
Grey Degraded soil |
Haplic Acrisol |
1 791 021 |
15.48 |
Total of cultivated soil |
11 569 591 |
100 |
||
Total of cultivated soil |
11 569 591 |
35 |
||
Total of Viet Nam soil |
32 924 000 |
100 |
||
Source: Viet Nam soil Assoc. 1996. |
Table 2. Selected physico-chemistry of Haplic-acrisols in Viet Nam
No. |
Item |
Unit |
Mean |
Std. |
N |
1 |
pHH2O |
4.69 | 0.49 | 52 | |
2 | pH KCl | 4.05 | 0.43 | 52 | |
3 | Bulk density |
g/cm3 |
1.47 | 0.23 | 16 |
4 | Density |
g/cm3 |
2.60 | 0.11 | 16 |
5 | Porosity | % | 43.29 | 9.08 | 16 |
6 | Texture | ||||
2-0.2 mm |
% | 24.72 | 9.96 | 16 | |
0.2-0.02 mm |
% | 32.44 | 14.65 | 16 | |
0.02-0.002 mm |
% | 14.05 | 8.15 | 16 | |
<0.002 mm |
% | 28.79 | 10.83 | 16 | |
7 | OC | % | 1.19 | 0.74 | 50 |
8 | CEC |
cmolc/kg |
6.93 | 3.88 | 53 |
9 |
Ca++ |
cmolc/kg |
1.75 | 1.62 | 53 |
10 |
Mg++ |
cmolc/kg |
0.42 | 0.36 | 50 |
11 |
K+ |
cmolc/kg |
0.15 | 0.08 | 49 |
12 |
Na+ |
cmolc/kg |
0.11 | 0.11 | 53 |
13 |
Al3+ |
cmolc/kg |
0.76 | 0.63 | 44 |
14 |
H+ |
cmolc/kg |
0.06 | 0.03 | 53 |
15 | N | % | 0.106 | 0.06 | 53 |
16 |
P2O5 |
% | 0.062 | 0.05 | 53 |
17 |
K2O |
% | 0.19 | 0.22 | 52 |
18 | P (bray II) | mgP/kg | 29.22 | 29.13 | 52 |
samples are deficient in K, 87 percent in P, 72 percent in Ca and 48 percent in Mg (Nguyen van Bo et al., 2003).
2. Food production in Viet Nam
Rice dominates Vietnamese agriculture (Table 3). Viet Nam’s agriculture sub-sector, particularly rice, has seen a dramatic production increase since 1986. Rice production was 11.6 millions tonnes in 1980, more than 31 million tonnes in 2000 and 38 millions tonnes in 2004. Viet Nam is now in safe situation in terms of food and each year exports about 3 millions tonnes of rice.
Table 3. | Area and production figures for the major crops in Viet Nam (Statistical Data of Viet Nam agriculture, forestry and fishery 2003, statistical publishing house) |
Crop |
Sown area |
Average yield |
Rice | 7 499.3 |
4.63 |
Maize | 909.8 |
3.22 |
Sweet potato | 219.9 |
7.24 |
Vegetables | 200.0 |
20-100 |
Sugarcane | 306.4 |
53.91 |
Cassava | 371.9 |
14.7 |
Soybean | 166.5 |
1.35 |
Groundnut | 242.8 |
1.67 |
Fruit crops | 719.8 |
6.38 |
Coffee | 513.7 |
1.50 |
Tea | 116.2 |
0.22 |
Rubber | 436.5 |
0.18 |
Increased production, particularly in rice, has been achieved through greater cropping intensity including fertilizer use rather than any other factor in cropping area.
3. Fertilizer use
Contributing to the increased yield were the widespread adoption and use of improved, high yielding varieties, better irrigation, plant protection, together with inputs of fertilizer. According to research from NISF (1998-2000), one unit of N-P-K gives in average of 7.5-8.5 kg of paddy. Each year, Viet Nam spends almost $600 millions US for importing almost 100 percent, 80 percent and 10 percent of the country’ requirement in K, N, and P respectively, for food production. Details of fertilizer sources and uses are shown in Tables 4 and 5. Viet Nam farmers used an average of 234 fertilizer unit per ha in 2004 comparison with 134 unit in 1998 and only 18 unit in 1976.
Table 4. Chemical fertilizer sources (1 000 tonnes) in Viet Nam
Items |
Source |
1996 |
1997 |
1998 |
1999 |
2000 |
2001 |
2002 |
2003 |
2004 |
|
Urea | Total | 1 597 | 1 610 | 2 011 | 1 940 | 2 279 | 1 699 | 1 907 | 2 149 |
1 941.5 |
|
Imported | 1 467 | 1 480 | 1 944 | 1 890 | 2 159 | 1 600 | 1 800 | 1 889 |
1 708 |
||
NPK | Total | 530 | 678 | 913 | 913 | 1 200 | 1 385 | 1 035 | 2 000 |
1 871.2 |
|
Imported | 350 | 318 | 411 | 133 | 200 | 155 | 0 | 0 |
306 |
||
DAP | Imported | 298 | 268 | 364 | 545 | 591 | 510 | 616 | 923 |
593 |
|
Ssp + FMP | Produced | 950 | 890 | 934 | 1 061 | 1 220 | 974 | 1 058 | 1 276 |
1 282.1 |
|
MOP | Imported | 108 | 296 | 344 | 711 | 350 | 835 | 900 | 1 050 |
807 |
|
SA | Imported | 311 | 128 | 343 | 501 | 436 | 524 | 125 |
665 |
||
SUM | Total | 3 794 | 3 870 | 4 909 | 5 671 | 6 076 | 5 400 | 6 040 | 6 900 |
7 159.8 |
|
Imported | 3 484 | 3 380 | 4 340 | 4 841 | 4 956 | 3 100 | 3 840 | 3 987 |
4 079 |
||
Source: Gen. Statistic. Dept. 2004. |
Table 5. Mineral fertilizer use kg/ha/year
Items |
1996 |
1997 |
1998 |
1999 |
2000 |
2001 |
2002 |
2003 |
2004 |
N |
77.0 |
87.2 |
86.3 |
95.5 |
108.2 |
133.2 |
122.0 |
136.0 |
120.2 |
P2O5 |
28.6 |
32.7 |
29.8 |
31.3 |
40.4 |
50.8 |
60.4 |
89.7 |
63.3 |
K2O |
5.3 |
13.7 |
17.9 |
22.0 |
33.4 |
41.7 |
60.9 |
73.4 |
50.3 |
Total |
110.9 |
133.6 |
134.0 |
148.8 |
182.0 |
225.7 |
243.3 |
299.1 |
233.8 |
Efficient fertilize use in Viet Nam is still very low. According to research results (NISF, 1998-2000) efficient fertilizer use depends not only on the crop variety, cropping systems, soil and seasons but also on the use in combination with other fertilizrs. On average, efficient use of fertilizer for rice is 34-50 percent, 13-20 percent and 31-40 percent respectively for N, P and K in the Red River Delta soil (fluvisol). Results showed that the efficiency of N fertilizer use for rice is closely relative with that of P fertilizer. For rice, the recommendation for fertilization is often in relation (ratio) with other element/s, N:P or N:P:K, such as (1:0.5:0.4).
4. Farmyard manure resources and use
Data collected from on-farm trials conducted between 1991 and 2000 (Nguyen van Bo et al., 2003) showed the response of plants to fertilizer and farmyard manure (FYM). In North Viet Nam, farmers generally use about 7-12 tonnes of FYM for each rice crop. These rates vary according to season and to the availability of farm organic sources. If the manure from all Viet Nam’s domestic animal production were collected and used, it is estimated that more than 200 unit of fertilizer were supplied from organic sources (Table 6). In principle, it is understood that organic fertilizer support soil fertility maintenance by supplying nutrient and enhancing soil physical condition. Crop yield generally increased when organic nutrients are applied in addition to mineral fertilizers (Table 7). Response to organic fertilizer in selected cropping system is very much higher in low fertility soil such as degraded soil (Acrisol).
Table 6. Potential nutrient from organic sources kg/ha/year
Items |
1996 |
1997 |
1998 |
1999 |
2000 |
2001 |
2002 |
2003 |
2004 |
N | 43.2 | 43.4 | 42.9 | 40.8 | 39.2 | 39.7 | 41.4 | 43.7 |
39.7 |
P2O5 |
48.9 | 49.5 | 49.2 | 47.1 | 46.1 | 48.1 | 50.6 | 53.8 |
49.3 |
K2O |
105.3 | 105.4 | 104.2 | 98.7 | 94.0 | 93.4 | 96.9 | 102.5 |
94.9 |
Total |
197.4 |
198.3 |
196.2 |
186.6 |
179.3 |
181.2 |
188.9 |
200.0 |
183.9 |
* Organic source (pig, cattle, cow, goat, sheep, chicken)
Table 7. Crop yield on Acrisol and in Fluvisol as affected by FYM
Treat |
Crops |
Soil |
Yield (tonne/ha) |
Difference (%) |
NPK | Rice | Acrisol | 3.32 |
100 |
NPK + FYM | Rice | Acrisol | 4.02 |
121 |
NPK | Tea | Acrisol | 0.68 |
100 |
NPK + FYM | Tea | Acrisol | 0.83 |
122 |
NPK | Maize | Fluvisol | 3.45 |
100 |
NPK + FYM | Maize | Fluvisol | 4.33 |
126 |
5. Balance fertilization in relation to organic fertilizer
Integrated nutrient management is the efficient use of all types and forms of nutrients, both those originating from the field or farm and those from outside the field or farm. Balanced fertilization is achieved when the cropping system is supplied with the correct proportions of N, P, K, Mg and other nutrients.
There are three main approaches to soil fertility and plan nutrition management:
Crop residue management is a subject to study and to practice in Viet Nam especially for the sloping area and degraded soil (Acrisols). Normally the soil in the area is very low in CEC (cation exchange capacity), low in organic matter, N, P and K (as reported above in the Table 3). Returning crop residue to soil significantly improves soil physico-chemical properties. However, inappropriate agricultural practices and continuous cropping without adequate nutrient are occurring in many places in Viet Nam fields. Recent research results emphasize that there is a large potassium imbalance. For example, each ton paddy exploits from soil about 20 kg K2O, which means a 200 kg K2O per ha for a rice annual yield of 10 tonnes. Nutrient depletion is indicated not only for major elements (N, P, K, S, Mg...) but also for micro-elements (Mo, Bo) as well. Further, imbalance (depletion or eutro-phication) in fertilization alters the chemical and physico-chemical characteristics of soil and destroys microorganisms’ lives. Management of the soils requires integrated practices that can increase fertility, nutrient and water holding capacity. Biological management of the soils can be an effective way to increase soil quality through management of biomass, i.e. farmyard manures, crop residues, green manures and alley cropping. In addition, theeffective management of the soils needs careful consideration of appropriate techniques not only to address the issue of low productivity but also to protect the environment.
5.1 A case study of nutrient recycling in 4 crops of season-based cropping systems
Crop rotation of four annual crops, spring rice, summer soybean, late summer rice and winter potato, respectively, was conducted on degraded soil in Bacgiang province (North Viet Nam). Results in Table 8 and in Figure 1 showed that crop residues returned to soil had immediate positive effect on yield. In case of no fertilizer input, the yield of all studied crops increased up to 70-100 percent and saving up to 20 percent fertilizers with completed fertilization (fertilizer with farmyard manure).
Use of crop residue or crop residue with suitable rate of chemical fertilizers seems to be more efficient compared to that of not using crop residues. Actually, a rotation of 4 crops in a year leave in the field at least 140 kg N ha-1 and 241 kg P2O5 ha-1 based on farmers’ practice. A saving of 20-30 percent for N and P fertilization was derived and crop yields were at an acceptable level not only for rice but also for soybean and potato.
Table 8. Crop yields (mean and std) as affected by crop residues returning to soil
Spring rice (quintal/ha) |
Soybean (quintal/ha) |
Summer rice (quintal/ha) |
Winter potato (quintal/ha) |
|
Control (T1) | 22.25 (0.49) | 5.40 (2.82) | 16.70 (1.69) |
26.90 (2.26) |
T1 + Residue (T2) |
29.90 (2.54) | 10.75 (0.49) | 27.30 (1.41) |
42.45 (7.14) |
Fertilizer + FYM (T3) |
59.20 (2.12) | 16.75 (0.49) | 39.90 (0.42) |
122.90 (16.22) |
80% T3 + Residue (T4) |
59.90 (2.44) | 17.75 (1.62) | 43.25 (1.19) |
129.60 (20.08) |
Figure 1. Crop yields as affected by different treatments on Acrisols
Table 9. Nitrogen fertilizer use efficiency for rice as affected by crop residues to soils
Spring rice 2003 |
Summer rice 2003 |
|||
Mean (%) |
Std |
Mean (%) |
Std |
|
Low input (T1) | 10.46 | 0.40 | 15.54 | 1.53 |
T1 + Residue (T2) |
19.96 | 1.39 | 25.16 | 0.48 |
High input (T3) |
44.09 | 14.08 | 39.72 | 2.95 |
T3 + Residue (T4) |
43.88 | 20.61 | 39.72 | 1.26 |
By N-15 technique (FAO/IAEA, 2001), the study showed that, at low mineral fertilizer input, crop residue positively affected the nitrogen fertilizer uptake. Crop residues had no effect on N uptake efficiency at high input level. It is supposed that most of N uptake comes from other sources such as soils, bio-fixation, irrigation or rain rather than from direct fertilization. If fertilization is low, the relative N-lost is higher.
5.2 Warning of overloading nutrient to soils
Nutrients sources can be of mineral or organic in origin. The principle of balance fertilization is to make full use of both of these sources in an integrated way that is economically and environmentally sound. Recently, organic farming has been promoted as an alternative to common agriculture in Viet Nam. The adverse effect is that some fertilizers and organic materials contain not only nutrients but also heavy metals (Table 10). This may be toxic in some level with high accumulation through time. In some areas of very intensive cropping systems with cash crop such as vegetable and flower, fertilizer use were especially high, both for inorganic and organic materials, soil was probably overloading of fertilization (Table 11).
Table 10. Mineral fertilizers and farmyard manure using in different cropping in North Viet Nam (2003-2004)
Cropping system |
Location, Code |
NPK (kg/ha) |
FYM (tonne/ha) |
Rice-Rice-Soybean |
HaTay, PT01 |
729 |
22 |
Rice-Rice | ThaiBinh, KX04 |
621 |
19 |
Rice-Rice-Maize |
NamDinh,VB02 |
448 |
17 |
Rice-Rice-Maize |
NinhBinh, NB02 |
1 356 |
28 |
Maize-Soybean-Maize |
VinhPhuc, VT02 |
780 |
8 |
Mulberry | VinhPhuc, YL03 |
279 |
8 |
Vegetables | VinhPhuc, ML1 |
1 700 |
110 |
Flower | VinhPhuc, ML1 |
1 530 |
160 |
Source: Pham Quang Ha et al., 2002. Study on Fluvisol of Viet Nam. |
Table 11. Annual nutrient budget (mean, std) at the field levels
Cropping systems |
Input levels |
N (kg/ha) |
P(kg/ha) |
K (kg/ha) |
Cu (g/ha) |
Zn (kg/ha) |
Dry vegetable |
Fertilizer
+ |
390 (350) | 420 (161) | 291 (203) | 401 (326) | 3.96 (1.23) |
Water vegetable |
Waste
water |
489 (375) | 155 (32) | 137 (366) | -72 (103) | 2.43 (3.88) |
Source: NISF-Rurbifarm project report, 2004. |
Table 12. Heavy metals in some manure recycling for agriculture in North Viet Nam
Cu (mg/kg dry) |
Pb (mg/kg dry) |
Zn (mg/kg dry) |
Cd (mg/kg dry) |
|
Sludge | 45 | 27 | 154 |
0.39 |
std |
5.1 |
0.35 |
5.43 |
0.01 |
Pig manure | 250 | 14 | 556 |
0.65 |
std |
413 |
6.8 |
835 |
0.22 |
Goat manure | 19 | 7.5 | 75 |
0.21 |
std |
2.0 |
2.6 |
12 |
0.05 |
Chicken manure | 64 | 16 | 222 |
1.49 |
std |
54 |
8 |
106 |
1.78 |
Cow manure | 67 | 20 | 153 |
0.48 |
std |
71 |
8 |
70 |
0.07 |
TCVN7209-2002 Viet Nam standard for agri. soil |
50 | 70 | 200 |
2 |
Source: LWR/119/1198 (NISF-Viet Nam ACIAR project, 2002). |
6. Conclusion
At low level farming system input, nutrient recycling in Viet Nam was widely applied years ago. The main activity consists of using farmyard manure and crop residues. Today, nutrient recycling should involve a balance approach of environment-friendly fertilization. Results and experiences showed that recycled nutrient may save chemical input but it can not replace all chemical inputs. Biological and environmental farming should integrate harmoniously with intensive agriculture. This is probably a sustainable way that different stake-holders will accept and it will save not only agricultural productivity but also save the environment that we all need such as soil, water and other life forms.
Acknowledgment
The authors gratefully acknowledge the International Atomic Energy Agency (IAEA) for N-15 technique, the Rurbifarm/EU project ICA4-CT-CT-2003-10021 for nutrient and water recycling, the ACIAR/LWR/119/1998 projects for bio-solid recycling study both in technical and material support. Thanks are also due to FAO (Regional Office for Asia and the Pacific) for the invitation to the Regional Workshop on Improving Plant Nutrient Management for Better Farmer Livelihood, Food Security and Environment. Beijing, People’s Republic of China, 12-16 December 2005.
References
FAO/IAEA 2001. Use of isotope and radiation methods in soil and water management and crop nutrition. Training course series 14. FAO/IAEA, Vienna, 2001.
LWR/119/1998. NISF-Viet Nam ACIAR project report, 2002.
NISF (1998-2000). Annual Research Results. Proceeding of NISF, Hanoi, 1999.
Nguyen Van Bo, Ernst Mutert, Cong Doan Sat (2003). BALCROP: Balance Fertilization for Better crop in Viet Nam. Potash & Phosphate Institute.
Pham Quang Ha et al., 2002, 2003, 2004. Study on Fluvisol, Acrisols of Viet Nam.
Rurbifarm project. 2004. Second annual report. Sustainable farming at the rural-urban interface. NISF-Hanoi-Viet Nam
STAT, 2004. Gen. Statistic. Statistical yearbook 2003. Statistical publishing house. Hanoi, 2004.
1 Dept. of Soil Environment Research, National Institute for Soil and Fertilizers, Chem, Tu Liem, Hanoi, Viet Nam.
2 School of Earth and Environmental Sciences, The University of Adelaide, PMB1, Glen Osmond, SA 5064, Australia.
3 Dept. of Soil Science, Swedish University of Agricultural Sciences (SLU, Uppsala, Sweden).