Agric. Chem. Biotechnol. 46(3), 114-117 (2003)
Article
Soil Chemical and Biological Characteristic of the Continuous Cropping Area of Garlic or Onions
Hee-Gwon Kim*, Bong-gi Yun, Hyoung-Koog Choi, In-Jin Park and Sang-chul Kim Jellanam-Do Agricultural Research and Extension Services, Sanje-Ri, Sanpo-Myeon, Naju 520-715, Korea
Received July 3, 2003; Accepted September 15, 2003
This study researched the soil chemical properties and microflora in upland fields that had been cultivated with either garlic or onion crops for a long period of time. The soil samples were collected from 60 spots in 5 experimental sites at the final (20 May to 10 June) garlic and onion harvests in 2000.
Then the soil chemical and biological properties were determined. The soil pH and organic matter content significantly decreased when the garlic and/or onion crops were continuously grown in the same area, while EC and phosphate increased. The number of bacteria and actinomycetes in the soil that continuously grew with garlic was lower when compared to the soil from onion crops. For the fungal population, however, no significant difference was found between the soils from the different garlic and onion crops. These results indicate that the continuous cropping of garlic and onions produced a nutrient imbalance in the soil.
Key words: garlic, onion, continuous cropping, soil chemical property, microflora.
In Korea, garlic and onions are very important spicy vegetables, which are impossible to remove from cooked food. The cultivating area of the garlic and onions was 37, 337, and 14, 806 ha in 1998, respectively. With the production of 393, 903 and 872, 143 M/T, The amount of consumption tended to increase every year. Even though the price of garlic and onions greatly fluctuates, depending on both the supply and demand, they are major over wintering crops that lead to high economical profit1). However, it has been suggested that if these crops are grown continuously in an area, then there will be a serious negative effect in the soil, which will limit bulb growth and eventually reduce the yield and quality of the crops. This is usually referred to as injury by continuous cropping, mainly caused by the aggravation of soil texture, accumulation of phytotoxin, and an increase in the nematode population. There are several methods to cope with the injuries of continuous cropping, such as soil disease control, fertilization management, flooding to eliminate salt, application of missing nutritions, and crop rotation2). Despite many studies that have been undertaken to overcome the injury that is accompanied by continuous cropping, the soil chemical properties of the fields that are continuously grown in garlic and onions has not been extensively investigated.
Also, the effect of continuous cropping with garlic and onions on the succeeding crops remains unclear. In this study, we investigated the soil chemical properties and microbial population in the continuous cropping area with garlic and
onions, in order to determine the soil factors on the succeeding crops and to provide the farmers a choice for the proper succeeding crop.
Materials and Methods
In 2000, soil samples were collected from a farmer’s upland field that continuously grew garlic or onions as a continuous crop in the same area for a long time. Soil was sampled from 60 spots of 5 experiment sites (i.e. Goheung, Mooan, Sinan, Hampyeong, and Haenam) at the final harvest of the garlic or onion crops. These crops were harvested from 20 May to 10 June, depending on weather conditions and crop maturity.
According to the methods that are recommended by RDA8) the soil chemical properties were determined as follows: i.e. soil pH (1 : 5 water extraction), OM contents (Turin method), available phosphate (Lancaster method), exchangeable cations (1 N ammonium acetate, pH 7.0), cation exchange capacity (CEC 1 N ammonium acetate, pH 7.0), and electrical conductivity (EC, 1 : 5 water extraction). For the soil microbial population determination, the methods that are recommended by RASM (Research Association of soil microorganism)7) were employed as follows: egg-albumin agar media was used for the count, both the bacterial and actinomycetal flora and rose-bengal agar media were used for the population.
Results and Discussion
Soil chemical properties of the continuous-cropping area of garlic and onions: Table 1 shows the soil chemical properties of garlic and onions from a continuous-cropping area. The soil
*Corresponding author
Phone: 82-61-330-2682; Fax: 82-61-336-4076 E-mail: [email protected]
Abbreviations: RDA, Rural Development Administration
Soil Chemical and Biological Characteristic of the Continuous Cropping Area of Garlic or Onions 115
chemical properties of the continuous-cropping area with garlic and onions were as follows: (garlic vs. onions) pH 6.03 vs. 5.88, EC 0.749 vs. 0.716 dS⋅ m−1, organic matter 19.7 vs.
17.9 g⋅ kg−1, available phosphate 808 vs. 788 mg⋅ kg−1. Also, K, Ca, and Mg of exchangeable cations (garlic vs. onions) were 1.30 vs. 1.58, 5.03 vs. 5.16, and 2.38 vs. 2.25 cmol+⋅ kg−1. As mentioned previously, the organic matter (OM) contents in both the garlic and onion continuous-cropping soil were lower than the recommended level by RDA. Available phosphate and potassium contents were as much as 3 or 4 fold higher than those recommended by RDA. Calcium and magnesium contents were kept at an optimum level. However, even if the calcium and magnesium contents in the soil were at the same level, they would still be difficult to be taken up by the crop because of the imbalance of the base saturation degree. The accumulation of potassium and phosphate was observed in a lot of soil that was cultivated with vegetables9). The heavy application of chemical fertilizers, consecutive cultivations, and vinyl mulch result in the deterioration of soil properties3).
The soil pH, where rice and watermelons were grown following garlic crops, was over 6.0. This was less than 6.0 in soil with soybeans and pumpkins (Table 2). Sesame following garlic crops led to strong acidic soil with a pH of 4.67. Rice crops following garlic resulted in a lower soil EC (0.046 dS⋅ m−1) when compared to succeeding crops. In contrast, sesame crops had a positive effect on soil EC with an average of 3.610 dS⋅ m−1. This was greater than the RDA recommendation levels, and probably due to vinyl-mulching treatment. However, the OM content of the soil with sesame was lowest (8.3 g⋅ kg−1) when compared to soil from succeeding crops (19.3-21.9 g⋅ kg−1). The OM content of soil, where the crop was grown following garlic, was lower than recommended by RDA. This was the case for all of the succeeding crops that were tested.
The soil pH from various succeeding crops following onions ranged from 5.38 (sesame) to 6.13 (watermelon)
(Table 3). Interestingly, sesame crops, when they were employed as the succeeding crop following both garlic and onion crops, led to the lowest soil pH. EC of soils from various crops following onions ranged from 0.411 (pumpkin) to 1.161 (soybean) dS⋅ m−1. Except for the soil from soybeans and watermelons, all of the soils had an EC of less than 1.0 dS⋅ m−1. The OM contents of soil from various crops following onions ranged from 18.1 to 21.7 g⋅ kg−1. This was less than the optimum level of 307 g⋅ kg−1. Soil phosphate ranged from 722 (watermelon) to 1061 (sesame) g⋅ kg−1, when various succeeding crops were grown following onion crops. The phosphate levels were 4-5 times greater than recommended (200 g⋅ kg−1) by RDA. The potassium, Ca, and Mg of soils ranged from 1.13 to 4.72, 2.29 to 5.62, and 2.06 to 2.66 cmol+⋅ kg−1, respectively, depending on the succeeding crops. Of these, in particular, the potassium of soils with sesame crops following onions was about 9-fold greater than the optimum level of 0.5 cmol+⋅ kg−1, while Ca was less than the optimum (Table 3). From these result, the cropping system with either soybean or pumpkin crops, following garlic and onion crops, was likely to be acceptable for keeping desirable soil chemical properties. However, the cropping system with sesame could easily result in a nutritional soil imbalance.
Some farmers empirically say, “Although it looks good to grow rice crops following garlic or onion, the yield of all crops, including rice, are decreased if the cropping system is continued more than 2 years.” This suggests that rice is not a suitable crop for the succeeding crops (garlic and onion), which supports our findings (see below for further discussion).
Chemical properties (i.e. pH, OM, and exchangeable cation) of soil with either garlic or onion crops decreased by increasing the continuous-cropping year, while EC and phosphate tended to increase (Tables 4 and 5). The magnitude of the effect of the continuous cropping on EC and phosphate was greater in soil with onion when compared to soil with Table 1. Averaged chemical properties of the continuous-cropping soil of garlic and onion before plant cultivation
Crop No of
sample
pH (1 : 5)
EC (dS ⋅ m-1)
OM (g ⋅ kg−1)
P2O5 (mg ⋅ kg−1)
Ex. cat. (cmol+⋅ kg−1) CEC (cmol+⋅ kg-1)
K Ca Mg
Garlic 60 6.03 0.749 19.7 808 1.30 5.03 2.38 9.04
Onion 60 5.88 0.716 17.9 788 1.58 5.16 2.25 9.35
Optimum 6.50 2.0 30.0 200 0.55 6.50 2.50 16.0
Data given is the average values across all soil samples from the 5 experimental sites.
Table 2. Soil chemical properties with succeeding crops following garlic
Crop pH
(1 : 5)
EC (dS ⋅ m−1)
OM (g ⋅ kg−1)
P2O5
(mg ⋅ kg−1)
Ex.cat. (cmol+ ⋅ kg−1) CEC (cmol+ ⋅ kg−1)
K Ca Mg
Rice 6.13 0.046 21.9 727 1.17 5.57 2.42 9.12
Soybean 5.88 0.678 19.3 817 1.13 4.79 2.47 8.62
Pumpkin 5.99 0.411 21.7 1034 1.44 4.90 2.08 8.42
Watermelon 6.69 0.373 20.4 821 1.68 5.11 2.18 9.41
Sesame 4.67 3.610 8.3 895 1.21 4.84 2.58 12.9
116 Hee-Gwon Kim et al.
garlic. When garlic or onion crops were continuously grown in the same area for a long period of time, a decrease in the exchangeable cation and increase in phosphate of the soils most likely caused an imbalance in soil nutrition. The decreased OM and exchangeable cation led to a subsequent decrease in cation exchangeable capacity (CEC) (Tables 4 and 5).
Microorganism in the soil samples collected from the continuous-cropping soils of garlic and onions: Table 6 showed a soil microbial population of the continuous- cropping area with either garlic or onion crops. Microbial populations were greater in the soil with onions than in the soil with garlic crops. For example, the populations (onion- soil vs. garlic-soil) were 29.45×105 vs. 15.0×105cfu⋅ g−1 for bacteria, 5.0×102 vs. 4.4×102 cfu⋅ g−1 for fungi. Overall, the microbial population in this experiment was lower when compared to those observed in other studies with cucumbers in a plastic house4). Kwon et al.5) reported that bacterial (i.e.
fluorescent Pseudomonas and Bacillus) numbers and microbial biomass carbon contents increased with the increasing soil OM under a plastic house.
Shu et al.10) reported that thermophilic Bacillus, fluorescent Pseudomonas, and algae numbers increased when the cropping years of a plastic film house was increased.
However, soil microbial diversity decreased as the cropping years increased.
Onion crops had a greater bacterial density in the soil with
their succeeding crops than the garlic crops did (Table 7). A similar result was found for the bacterial to fungi ratio (B/F).
This was also the case for actinomycetes, except when pumpkins and watermelons were the succeeding crop.
However, the response of soil fungi population to continuous crops varied with succeeding crops. In this survey, we grew 5 different crops (i.e. rice soybean, pumpkin, watermelon, and sesame) for the succeeding crops, following the continuous cropping of garlic and onion crops. Of these, the sesame crops particularly led to lower bacterial density in the soil when compared to other succeeding crops, resulting in a lower B/F (see Table 7). Pumpkin crops had the adverse case when they were grown following the onion crops.
As with soil chemical properties, soil biological properties (in terms of bacterial, actinomycetes and fungi population) also decreased with increasing the continuous-cropping year (Table 8). This decline was more significant with onion crops than with garlic crops. Our results suggest that continuous- cropping systems with garlic and onion crops could cause a Table 3. Soil chemical properties with succeeding crops following onions.
Crop pH
(1 : 5)
EC (dS ⋅ m−1)
OM (g ⋅ kg−1)
P2O5
(mg ⋅ kg−1)
Ex. cat. (cmol+ ⋅ kg−1) CEC (cmol+ ⋅ kg−1)
K Ca Mg
Rice 5.79 0.637 20.7 812 1.13 4.38 2.06 8.60
Soybean 6.07 1.161 19.0 825 1.32 5.62 2.48 9.63
Pumpkin 5.99 0.411 21.7 1034 1.44 4.90 2.08 8.42
Watermelon 6.13 1.091 18.1 722 1.36 5.16 2.66 10.15
Sesame 5.38 0.485 20.8 1061 4.72 2.29 2.41 9.11
Table 4. The effect of the continuous-cropping (garlic) period on soil chemical properties Cultivation
Years
No. of samples
pH (1 : 5)
EC (dS ⋅ m−1)
OM (g ⋅ kg−1)
P2O5
(mg ⋅ kg−1)
Ex.cat. (cmol+ ⋅ kg−1) CEC (cmol+ ⋅ kg−1)
K Ca Mg
1- yrs 15 6.52 0.352 22.1 874 1.60 5.40 2.31 9.67
6-10yrs 15 5.80 0.372 21.5 1198 1.72 4.44 1.82 7.98
11-5 yrs 15 6.07 0.387 20.4 944 1.32 4.90 2.02 8.24
16-20yrs 15 5.91 0.390 20.3 1122 1.59 4.63 1.74 7.96
Table 5. The effect of the continuous-cropping (onion) period on soil chemical properties Cultivation
years
No. of samples
pH (1 : 5)
EC (dS ⋅ m−1)
OM (g ⋅ kg−1)
P2O5 (mg ⋅ kg−1)
Ex. cat. (cmol+ ⋅ kg−1) CEC (cmol+ ⋅ kg−1)
K Ca Mg
1-5 yrs 15 5.82 0.943 16.6 638 1.85 4.09 3.01 8.51
6-10yrs 15 5.86 0.966 22.2 896 1.29 4.98 2.28 8.69
11-15yrs 15 5.45 0.954 19.8 1031 0.72 2.26 1.51 8.15
16-20yrs 15 4.60 0.971 15.7 1189 0.97 2.80 0.99 7.76
Table 6. Effect of continuous cropping with either garlic or onion crops on soil microflora densities (unit: cfu ⋅ g−1dry soil)
crop Bacteria (x105)
Actinomycet es (x102)
Fungi
(x103) B/F
Garlic 15.0 4.4 6.4 235
Onion 29.4 5.0 8.5 345
Soil Chemical and Biological Characteristic of the Continuous Cropping Area of Garlic or Onions 117
significant deterioration in the soil chemical and biological properties, possibly leading to yield loss as well as quality deterioration of the products. In conclusion, although it is inevitable that crops will be grown continuously in the same area to ensure a stable income, it is also necessary to rotate the crops properly. This proper rotation will reduce the soil deterioration potential, and preserve an agricultural ecosystem having higher productivity.
References
1. Cho, W. K. (2000) Farm management Diagnosis of Garlic and Onion: With an Emphasis on Bench-marking Analysis with a Standardize Management Diagnosis Method, MS Thesis, Chonnam National University, Kwang-Ju, Korea 2. Jung, J. H. (1990) Studies on microflora and Phytotoxin in
the Continuous-cropping soil of Red-pepper, Sesame, and Peanut, Ph.D Thesis, Wonkang University, Iksan, Korea 3. Kim, C. B., Kim, C. Y., Park, M., Lee, D. H. and Choi, J.
(2000) Effect of Chemical Properties of Cultivation Soils on The plant Growth and the Quality of Garlic, J. of Korean Society of Soil Science and Fertilizer, 33, 333-339.
4. Kim, H. K., Park, I. J., Kim, J. K., Kim, S. C. (2000) Soil Environmental Investigation of Plastic House in Chonnam Area, J. of Korean Society of Soil Science and Fertilizer, 33, 40-46.
5. Kwon, J. S., Shu, J. S., Weon, H. Y. and Shin, J. S. (1998) Evaluation of 6. Soil Microflora in salt Accumulated Soil Plastic House, J. of Korean Society of Soil Science and Fer- tilizer, 31, 204-210.
7. Research Association of Soil Microorganism (1975), The Method of Soil Microorganism, 431-445.
8. Rural Development Administration (1988) Soil Chemical Analysis Method.
9. Shon, B. K., Cho, J. S., Kang, J. G., Cho, J. Y., Kim, K. Y., Kim, H. Y. and Kim, H. L. (1999) Physico-chemical prop- erties of soils at red pepper, garlic and onion cultivation areas in Korea, J. of Korean Society of Soil Science and Fertilizer, 32, 123-131.
10. Shu, J. S., B. G.., Jung, and J. S., Kwon (1998) Soil Micro- bial Density of the Plastic Film House Fields in Korea, J.
of Korean Society of Soil Science and Fertilizer, 31, 197- 203.
Table 7. Microflora densities in soils with various succeeding crops following garlic and onion crops (unit: cfu ⋅ g-1 dry soil) Crop Bacteria (×105)
Garlic Onion
Actinomycetes (×102) Garlic Onion
Fungi (×103) Garlic Onion
B/F Garlic Onion
Rice 13.3 21.0 4.6 7.5 7.9 3.3 169 636
Soybean 11.6 28.1 3.4 4.7 4.3 6.5 270 432
Pumpkin 15.4 63.8 6.0 3.0 3.9 8.7 395 733
Watermelon 18.9 23.9 8.0 4.7 11.9 6.5 159 368
Sesame 6.3 10.2 3.0 5.3 5.0 10.0 126 102
Table 8. The change of soil microflora with the cropping year of garlic and onion crops (unit: cfu ⋅ g−1 dry soil) Cultivation
years
Bacteria (×105) Actinomycetes (×102) Fungi (×103) B/F
Garlic Onion Garlic Onion Garlic Onion Garlic Onion
1-5yrs 187 249 74 84 70 73 267 341
6-10yrs 83 159 45 63 33 70 252 227
11-15yrs 79 53 48 59 40 54 198 98
1-20yrs 53 20 20 16 30 30 177 66
