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ABSTRACT

Major crops in upland fields of Thailand are cassava, maize, and sugarcane which occupy a production area of about 1.327, 1.105, and 0.964 million hectares, resulting in total production about 30.088, 4.616, and 66.816 million tons, respectively. Nitrogen (N) fertilizer is applied to cassava, maize, and sugarcane fields approximately 50, 20, and 70 kg N ha-1, respectively, providing a total amount of nitrogen inputs of about 66,337 22,097 and 67,455 tons N, respectively. Nutrient loss is mainly caused by removal of crop yield and other plant parts such as stems (cassava), cobs (maize), and leaves (sugarcane). Therefore, nitrogen losses in cassava, maize, and sugarcane fields by removal of yield and other plant parts are about 41.96 57.82, and 53.80 kg N ha-1, respectively. Nitrous oxide emissions from unfertilized and fertilized maize field are 0.11 and 0.31 mg N2O-N m-2d-1, respectively. Nitrous oxide emitted from the fertilized field is approximately 0.31% of applied N. Nitrogen loss by ammonia volatilization in alkali soil occurred about 7-22% of applied N. Nitrogen in plant residues of cassava and maize are about 30.76, and 18.6 kg ha-1, respectively. This is usually returned into the fields with the exception for sugarcane fields, the residues of which are commonly burnt at harvesting. Therefore, only few amounts of plant residues are returned to the field.

Keywords:  Nitrogen balance, upland field, cassava, sugarcane, maize, Thailand

INTRODUCTION

Thailand is located in a tropical region. Mean annual rainfall is about 1,600 mm (Fig. 1). Minimum and maximum temperatures are about 23oC and 33oC, respectively (Fig. 2 and Fig. 3) (Thai Meteorological Department). This kind of climate enhances great soil degradation and decomposition. Therefore, most soils are rather highly affected by weather conditions of which Ultisols occupies the largest area of 21.6 million hectares followed by Inceptisols, Alfisols, and Entisols, respectively (Table 1).

Upland crops occupy a total production area of 4.372 million ha of which major crops are cassava, maize, and sugarcane (Office of Agricultural Economics, 2009). Most upland soils have low fertility, yet fertilizer is generally applied at a low rate. It has been reported that fertilizer consumption of the whole country for agricultural production in 2004 was about 3,919,766 tons. In addition, fertilizer application of farmers is still rather unfitting to soil fertility and crop's requirement. This is caused by many factors such as high cost of fertilizer while production yield is of low value. Farmers try to reduce application of chemical fertilizer and perform less soil improvement. Compost or manure is generally applied at a low rate of 200-600 kg ha-1. Moreover, plant residues are sometimes burnt especially in sugarcane cultivated areas. These can cause imbalance of soil nutrients and consequently, soil degradation. Nutrient balance is the flow of nutrients in and out of the whole farming system. The nutrient balance has been used as an indicator for sustainability of land use system (Dechert et al., 2004). Nutrient inputs to the farmland are regularly derived from chemical fertilizers, organic fertilizers, plant residues incorporation, and nitrogen fixation, whereas, nutrient losses usually are caused by harvesting yield, burning of crop residues, leaching and volatilization.

Matsumoto et al. (2002) presented a model for estimation of nitrogen cycles under agricultural production in Khon Kaen Province of Thailand from 1990 to 1992 (Fig. 4). Nitrogen fertilizer application was rather low at 18 kg N ha-1yr-1. Nitrogen fixation was estimated about 18 kg N ha-1yr-1. The nitrogen in crop residues was about 52 kg ha-1 yr-1, in which 12 kg ha-1 yr-1 was used for animal feeding, 29 kg ha-1 yr-1 emitted to the environment by burning, and 11 kg ha-1 yr-1 returned to farmland. Nitrogen balance in soil was estimated to be of negative value of 40 kg ha-1 yr-1.

When farming practices changed from extensive farming system with low inputs and self-sufficient methods to that of intensive farming system with high nutrient inputs, the nitrogen balance in the farmland increases to a positive value of 5.7 kg N ha-1 year-1 (Matsumoto et al., 2010).

The nitrogen balance in farmland varies in each farming system. This paper aims to summarize a rough estimation of nitrogen balance in each of the identified farmland fields planted to cassava, maize, and sugarcane in Thailand.

NITROGEN BALANCE IN CASSAVA FIELDS

Thailand is the world's major producer and exporter of cassava roots and its by-products. The office of Agricultural Economics (2009) reported that cassava production area of Thailand in 2009 was 1.327 million ha which produces cassava yield of 30.088 million tons. About 70% of total cassava production is exported, mainly as chips, pellets and starch. The major cultivated area of cassava is in the Northeast region, about 1.327 million ha followed by Central Plain, and North regions (Office of Agricultural Economics, 2009). Most soils in Northeast region of Thailand are coarse-textured such as sandy clay loam and sandy loam which are low fertility and easily eroded. Most farmers grow cassava continuously on the same fields without soil erosion control and adequate fertilizer applications to specific location. This causes the soil's productivity to steadily decline over the past several decades leading to an imbalance of plant nutrients in the soil, and resulting in a decrease in cassava growth and yield as well as environmental damage in the future.

General practices for cassava production of Thai farmers are those chemical fertilizers applied at approximate rate of 50 _ 25 -25 kg N-P2O5-K2O ha-1. Organic fertilizer is rarely used withapplication rate of about 200 - 600 kg ha-1. After harvesting, cassava roots and stems are removed whereas stocks and leaves are returned into the soil. Total fresh root production is approximately 8.515 million tons which means a production yield of 22.674 t ha-1 (Table 2). This produces dry matters of roots, stems, stocks, and leaves about 6,418, 1,623, 559, and 568 kg ha-1, respectively. Cassava roots are totally removed from the field resulting in N loss 17.33 kg N ha-1 (Table 3). Stems are cut and their stakes are used for the next cropping season. After planting, the unused stakes will be burnt. Thus, nitrogen in cassava stems is considered to be removed from the field approximately 24.64 kg N ha-1. Cassava leaves contain high nitrogen content. Putthacharoen et al. (1992) reported that cassava leaves produced low dry matter of 11.823 t ha-1 but contained high nitrogen of 329 kg N ha-1. Therefore, if cassava stocks and leaves are left in the field which are later incorporated into the soil, the nitrogen returns into the soil 6.25 and 24.51 kg N ha-1, respectively (Table 3). This can be roughly estimated for nitrogen balance at positive value of 38.76 kg N ha-1 (Table 4).

Paisancharoen et al. (2002) evaluated nutrient balances in cassava fields of Khon Kaen and Maha Sarakam Provinces of Thailand and found that cassava produced low yield under the farmer practices but small amount of nitrogen losses, whereas, higher input of fertilizer resulted in greater yield but also larger nutrient losses (Table 5).

Nitrogen loss by harvested roots depends on cassava variety and soil potential to release nitrogen for plant growth. Paisancharoen et al. (2004) reported that nitrogen absorbed root yield of cassava grown in 3 soils of Thailand, i.e. Loei clayey soils (very fine, kaolinitic, isohyperthermic, Typic Kandiustoxs), Mae Rim sandy loam soils (fine-loamy, siliceous, subactive, isohyperthermic, Typic Paleustults) and Satuk sandy loam soils (loamy-skeletal, mixed, isohyperthermic, Typic Paleustults), varied from 33.75 _ 51.88 kg N ha-1 and the Rayong-72 cassava absorbed higher level of nitrogen than the Rayong-5 variety. Cassava stems are another part which was removed out of the cultivated field. Some cassava stems are used as stakes for planting in the next cropping season and the remaining stakes are burnt. Nitrogen removals by stems of cassava grown on Loei, Mae Rim and Satuk soils were 61.88, 53.75, and 68.75 kg N ha-1, respectively (Table 6). As noticed the cassava grown on coarse-texture Satuk soil the nitrogen of which was removed from the farmland soil had higher fine-texture in Mae Rim and Loei soils.

Since most cassava in Thailand are planted on coarse-textured soils which have poor aggregate stability and are located in undulating and rolling topography, there is greater soil loss due to erosion by heavy rains especially in the early growth stages when the canopy does not fully cover the soil (Tongglum et al., 1990). Paisancharoen et al. (2004) found that nitrogen removal by soil loss in cassava field of Loei soils varied from 16.438- 24.384 kg N ha-1, and in Mae Rim soils varied from 5.625-8.625 kg N ha-1 (Table 7).

The nitrogen removed by run-off in Loei soils and Mae Rim soils under cassava production varied from 1.875-2.750 and 1.188-1.563 kg N ha-1 (Table 8). Puttacharoen et al. (1992) reported that soil loss by erosion from cassava field at 7% slope in Sriracha, Chonburi, Thailand was approximately 71.39 t ha-1 (dry weight) which caused nitrogen loss about 37.1 kg ha-1. Moreover, nitrogen loss by leaching is another considerable factor in the case of sandy soil. Suriyapan (1999) found that nitrogen loss by leaching in cassava field of Huai Pong sandy loam soil was about 28% of applied fertilizer.

Intercropping system between cassava and some kinds of legumes is used to retain nitrogen in the farmland soil. Paisancharoen et al. (2011) found that nitrogen returns to the soil through the incorporation of cowpea residues averaging 17.917 kg N ha-1 year-1. Therefore, the intercropping of cassava and cowpea resulted in nitrogen balance with a positive value of 22.375 kg ha-1 whereas the nitrogen balance in the sole cassava system had an average value of 11.250 kg N ha-1 (Table 9).

NITROGEN BALANCE IN MAIZE FIELDS

Maize production area in Thailand is 1.105 million ha which produces total grains with 14% moisture of the 4.616 million tons or 4.177 t ha-1 (Office of Agricultural Economics, 2009) (Table 10). Thailand's production yield of maize is rather low as compared to the average of world production yield which is at 5.113 t ha-1. This is caused by many factors such as drought and low fertilizer input. Chemical fertilizer is generally applied to maize field at 20-25-0 kg N-P2O5-K2O ha-1. Organic fertilizer is less applied at 300 kg ha-1. In maize fields, nitrogen loss by yield is higher than that of cassava and sugarcane. As total production yield is at 4.177 t ha-1, this produces dry matter of grains, cobs, hulls, stems, and leave at 3.551 0.624 0.624 1.225, and 1.313 t ha-1, respectively (Table 11). Thus, nitrogen losses in maize fields by yield components which includes grains and cobs is approximately 57.82 kg N ha-1 and nitrogen returns to the farmland by residues of stems, leaves, and hulls is about 18.6 kg N ha-1. As a result, estimated nitrogen balance in maize field of Thailand is at negative value of 19.21 kg N ha-1 (Table 12).

Luanmanee et al. (2011) reported that there is a negative nitrogen balance of 68.125kg N ha-1 on the maize field without chemical fertilizer application and without crop residues incorporation. If the crop residues were incorporated into the field, the nitrogen balance rose to 3.125 kg N ha-1. Though chemical fertilizer was applied at 93.75 kg N ha-1, the nitrogen balance still got negative value of 31.250 if the crop residues were removed from the farmland field (Table 13).

Nitrogen is also removed from soil by volatization or emission in gaseous form like nitrous oxide and ammonia. Luanmanee et al. (2011) found that estimated ammonia volatization of alkali upland soils, Samo Thod soil, occured about 7-22% of nitrogen content in fertilizer. Minami et al., (1998); Chairoj (2000); Watanabe et al. (2000); Wongwiwatchai and Chairoj (2000) had detected nitrous oxide emission in maize fields of Takli soils (Loamy-skeletal, carbonatic, isohyperthermic Entic Haplustolls) at Nakorn Sawan Field Crop Research Center (FCRC), Pak Chong soils (very fine, kaolinitic, isohyperthermic Rhodic Kandiustoxs) at Phra Phutthabat Field Crop Experimental Station, Yasothon soils (fine-loamy, siliceous, semiactive, isohyperthermic, Typic Paleustults) at Khon Kaen FCRC and San Sai soils (coarse-loamy, siliceous, subactive, isohyperthermic Aeric Endoaqualfs) at Chiang Mai FCRC from 1997 to 1998. The average N2O flux is shown in Table 14. The N2O flux from nitrogen fertilized plots was significantly larger than those from unfertilized plots in all experimental sites. The average N2O flux from N fertilized plot was detected at 12.71 µg N2O-N m-2h-1 whereas the unfertilizer plot emitted N2O at rate of 1.32 µg N2O-N m-2h-1. Clayey and loamy clay soil of Takli and Pak Chong soils, respectively, emitted N2O at higher rates than loamy sand soils of Yasothon and San Sai soils. The amount of N2O emission from soils during maize growing period was averaged 30.76 mg N2O-N m-2 in fertilized plots and 11.02 mg N2O-N m-2. The N2O emission is averaged 0.31% of applied N fertilizer.

Application of nitrogen fertilizer and organic material significantly affects N2O emission. Wongwiwatchai et al. (2000) estimated N2O emission in Yasothon soils under maize cultivation with different chemical fertilizer and organic material applications and found that the incorporation of bagasse altogether with nitrogen fertilizer application enhances N2O emission significantly higher compared with other treatments as shown in Table 15.

NITROGEN BALANCE IN SUGARCANE FIELDS

Sugarcane is another important field crop in Thailand which occupies a production area of 0.964 million ha. Total production of sugarcane in 2009 was 66.816 million tons. This resulted in average yield of 69.337 t ha-1 (Office of Agricultural Economics, 2009) (Table 16). Prasertsak (2005) noted that the main utilization of sugarcane biomass in Thailand is as following: 1) cane stalks are mainly utilized for sugar production except only for small amounts (4.2 %) which are used for planting material; 2) cane residues (mainly tops and leaves) are left in the field and are recommended not to be burnt, however, some farmers choose to burn the dry leaves for easy harvesting; 3) bagasse is mainly used for power cogeneration producing electricity and for paper and particle board production; 4) molasses are mainly used for ethyl alcohol (ethanol) production which can be further utilized for the distillation industry.

Fertilizer application for sugarcane production varies in each area. However, nitrogen fertilizer application at 70 kg N ha-1 is most common. As the total production figure mentioned above implies, dry matters of stems, dry leaves, and fresh leaves are estimated to be 22.465, 1.991, and 1.396 t ha-1, respectively (Table 17). Stems are the major part which are removed from the farmland field. Dry leaves are usually burnt whereas fresh leaves are left in the field. The nitrogen is therefore removed out of the field by stems and dry leaves about 42.01 and 4.04 kg N ha-1, respectively (Table 17). Thus, total nitrogen loss is approximately 53.80 kg N ha-1 and the nitrogen balance is consequently about 21.2 kg N ha-1 (Table 18).

Nitrogen input in sugarcane field can be derived from N2 fixation. Ando et al. (2000) investigated nitrogen fixation in sugarcane field in different varieties of sugarcane planted at the fields of Suphan Buri and Khon Kaen Field Crop Research Center and found that nitrogen derived from N2 fixation averaged at 21.9% and 34.4%, respectively (Table 19).

CONCLUSION

Nitrogen inputs to cassava, maize, and sugarcane farmland fields in Thailand principally came from chemical fertilizers followed by incorporation of crop residues. Organic fertilizers are currently getting more widely used but are still applied at a low rate so they are rather insufficient to improve the soils. Nitrogen fixation might be found in sugarcane cultivated soil. Contrarily, nitrogen losses in those field crops cultivated areas are mainly affected by yield and crop residues removal. Burning of crop residues is found in some sugarcane fields which causes partial nitrogen loss. Ammonia volatilization is a major source of nitrogen loss in alkali soils which covers a total area of approximately 0.15 million ha. Nitrous oxide emission is considered to be less about 0.31% of nitrogen applied. Nitrogen loss by erosion could be found in the slope areas which accounted for 10-20 kg N ha-1. The nitrogen balance in cassava and sugarcane farmland fields are generally at positive values whereas maize cultivated area causes negative balance value due to its low nitrogen inputs. Low input of nitrogen fertilizer may cause nitrogen imbalance in farmland fields but yields lesser N2O emission in the atmosphere.

REFERENCES

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  • Chairoj P. 2000. Nitrous oxide emission from upland soils. In: Full research report of Chairoj P. Department of Agriculture, Thailand. p. 26-41.
  • Chairoj P, Wongwiwatchai C, and Watanabe T. 2002. Effect of organic materials incorporation on nitrous oxide emission. In: Proceeding of Soil Science Division Annual Seminar, March 26-28, 2002, Department of Agriculture, Thailand. p.74-75.
  • Dechert G, Veldkamp E and Brumme R. 2004. Are partial nutrient balances suitable to evaluate sustainability of land use system? Results from a case study in central Sulawesi, Indonesia. Nutrient Cycling in Agro ecosystem 72: 201-212.
  • Jantawat S, Vichukit V, Putthacharoen S, and Howeler RH. 1991. Cultural practices for erosion control in cassava. In: Schnepf M. editor. Proceeding International Workshop on Conservation Farming on Hill Slopes. Taichung, Taiwan, March 20-29, 1989. p. 201-205
  • Luanmanee S, La-ied C, Tancharoen S, Petchraporn K, and Areerak S. 2011. Nutrients balance management for maize production on Samo Thod soils. Project research report 2011. Department of Agriculture, Thailand. 11p.
  • Matsumoto N, Paisancharoen K, Wongwiwatchai C, Chairoj P. 2002. Nitrogen cycles and nutrient balance in agro-ecosystems in northeast Thailand. In: Ito O and Matsumoto N. editors. Development of Sustainable Agricultural System in the Northeast Thailand through Local Resource Utilization and Technology Improvement. JIRCAS Working Report No. 30. Japan International Research Center for Agricultural Sciences. p. 49-54.
  • Matsumoto N, Paisancharoen K, and Ando S. 2010. Effects of changes in agricultural activities on the nitrogen cycle in Khon Kaen Province, Thailand between 1990-1992. 86: 79-103.
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  • Office of Agricultural Economics. 2009. Agricultural Statistics of Thailand 2009. 200 p.
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Index of Images

  • Fig. 1 Mean annual rainfall in Thailand (Source: Thai Meteorological Department)

    Fig. 1 Mean annual rainfall in Thailand (Source: Thai Meteorological Department)

  • Fig. 2 Mean minimum temperature in Thailand. (Source: Thai Meteorological Department)

    Fig. 2 Mean minimum temperature in Thailand. (Source: Thai Meteorological Department)

  • Fig. 3 Mean maximum temperature in Thailand. (Source: Thai Meteorological Department)

    Fig. 3 Mean maximum temperature in Thailand. (Source: Thai Meteorological Department)

  • Fig. 4 Model for estimation of nitrogen cycle in agricultural activities in Khon Kaen Province from 1990 to 1992 (kg N ha-1 yr-1). Italics: indicate input - output. (Source: Matsumoto <I>et al.</I>, 2002)<BR>

    Fig. 4 Model for estimation of nitrogen cycle in agricultural activities in Khon Kaen Province from 1990 to 1992 (kg N ha-1 yr-1). Italics: indicate input - output. (Source: Matsumoto et al., 2002)

  • Table 1 Area of soil orders in Thailand's soil

    Table 1 Area of soil orders in Thailand's soil

  • Table 2 Production area and yield of cassava in Thailand.

    Table 2 Production area and yield of cassava in Thailand.

  • Table 3 Cassava dry matter and nitrogen content.

    Table 3 Cassava dry matter and nitrogen content.

  • Table 4 Nitrogen balance in general cassava field.

    Table 4 Nitrogen balance in general cassava field.

  • Table 5 Nitrogen balances in cassava fields in Khon Kaen, and Maha Sarakam Provinces in 1999.

    Table 5 Nitrogen balances in cassava fields in Khon Kaen, and Maha Sarakam Provinces in 1999.

  • Table 6 Nitrogen removals from cassava field by root yield and stem.

    Table 6 Nitrogen removals from cassava field by root yield and stem.

  • Table 7 Nitrogen removals from cassava field by soil loss.

    Table 7 Nitrogen removals from cassava field by soil loss.

  • Table 8 Nitrogen removals from cassava field by run-off.

    Table 8 Nitrogen removals from cassava field by run-off.

  • Table 9 Estimation of nitrogen balances in the intercropping system of cassava-Rayong 72 and cowpea and the sole cassava system at Khon Kaen Field Crop Research Center during 2007-2009.

    Table 9 Estimation of nitrogen balances in the intercropping system of cassava-Rayong 72 and cowpea and the sole cassava system at Khon Kaen Field Crop Research Center during 2007-2009.

  • Table 10 Production area and yield of maize in Thailand.

    Table 10 Production area and yield of maize in Thailand.

  • Table 11 Maize dry matter and nitrogen content.

    Table 11 Maize dry matter and nitrogen content.

  • Table 12 Nitrogen balance in maize field.

    Table 12 Nitrogen balance in maize field.

  • Table 13 Effect of nitrogen fertilizer application and crop residue incorporation on nitrogen balances in Samo Thod alkali soil under maize cultivation at Nakorn Sawan Field Crop Research Center.

    Table 13 Effect of nitrogen fertilizer application and crop residue incorporation on nitrogen balances in Samo Thod alkali soil under maize cultivation at Nakorn Sawan Field Crop Research Center.

  • Table 14 Nitrous oxide flux from upland fields of Thailand under maize cultivation.

    Table 14 Nitrous oxide flux from upland fields of Thailand under maize cultivation.

  • Table 15 Amount of N2O emission and nitrogen loss from nitrogen fertilizer application under maize cultivation.

    Table 15 Amount of N2O emission and nitrogen loss from nitrogen fertilizer application under maize cultivation.

  • Table 16 Production area and yield of sugarcane in Thailand.

    Table 16 Production area and yield of sugarcane in Thailand.

  • Table 17 Nitrogen in sugarcane.

    Table 17 Nitrogen in sugarcane.

  • Table 18 Nitrogen balance in sugarcane field.

    Table 18 Nitrogen balance in sugarcane field.

  • Table 19 Estimation of N2 fixation of sugarcane in the field of Suphan Buri and Khon Kaen Field Crops Research Center by 15N natural abundance method.

    Table 19 Estimation of N2 fixation of sugarcane in the field of Suphan Buri and Khon Kaen Field Crops Research Center by 15N natural abundance method.

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