Pheng Sengxua 1 and Bruce Linquist 2. Abstract

Transcription

1 The effect of long-term application of the basally applied compound fertilizers and on lowland irrigated rice productivity in the Lao PDR Pheng Sengxua 1 and Bruce Linquist 2 1 Soil Survey and Land Classification Center, NAFRI. P.O. Box 811, Vientiane, Lao PDR, psengxua@laotel.com 2 Lao-IRRI Project, P.O. Box 600, Luang Prabang, Lao PDR, b.linquist@cgiar.org Abstract Most Lao farmers use either or as a basal fertilizer. Demonstrations were conducted to determine the long-term effects of using either or as starter fertilizers in different soil textures on rice production. The research was initiated at 17 sites during the 1998/99 dry season. In the 2001 dry season, they were continued at only nine sites. There were three treatments with only one replication per site. The treatments were: control (no fertilizer) and or (NPK) as basal fertilizer treatments. In the two treatments that received fertilizer, N was applied at a rate of 90 kg/ha. In the fifth season, almost all sandy loam and loamy sand sites (five sites) had a better response to the K containing fertilizer ( ), and only one clay and loam soil sites showed a positive of yield responses to application. Therefore, farmers should apply fertilizers containing K on sandy soil or incorporate rice straw combined with an application of and top dressing with urea (46-0-0). For the loam and clay soil, rice straw should be incorporated with an application of and top dressing application with urea (46-0-0). Key words: Laos; soil texture; basal fertilizers; dry season; wet season; loam; clay loam; sandy soil; top dressing; urea. 57

2 öì 1 2-êö - º - 3 4Ì -à É-± ÈÌ- ø 16Œ-20Œ-0 Áì1 2 15Œ-15Œ-15 ÃÌÄì ªÒ- öì 1 2-ìò À í3 4Ì3 4ÃÌÀ - ö -Ìì ê3 4ÌÃÌ - - ì3 4 ö - ñ -¹ Ó 3 4 Ì3 4-µøÈÃÌ 1 2-Àê -À»ö3 4 È Ìù ÈÁ ÈÌÌ -à É-± ÈÌÀ - ó- ø 16Œ-20Œ-0 (NPK) Áì1 2 ø 15Œ-15Œ-15 À ñì± ÈÌ»º -²œ -Ì ÈºÌ ¹ìõ- ²Éº - ñ Ì 3 4-êò Ì-š-Á ÈÌ-À²ô- -Ìö - öì- 1 2-êö ÃÌ 3 4ÌÌ -à É-± È -Ì º - ø - - È3 4 À ñì ± È -Ì»º -²œÌÃÌÄì µøè-ãì-áªè-ì À² ÀÌœº- òì-ªò- 1 2-ìò -ª1 2-²3 4 -À í Ì 3 4-êò Ì-š-Ä É-Àìš -À»ñ -µøè- 17 ÃÌ-ì1 2- ø-ì3 4-Á - ó 1998/1999, À - ó-²1 4 -ÁªÈ-Á -ê -à È-± È -Ì ø 16Œ-20Œ-0; ø 15Œ-15Œ-15»º -²œÌ Áì1 2 Á -ê - Ò-à È-± ÈÌ Áì1 2- ó-²1 4 -ÁªÈ- Õ- 1 4, º -Á -ê -à È-± È -ÌÀ - ó-ä É-à È-± ÈÌ-Ä-̪-ë-À Ì-ùÉ- ö -Ã-̺ñ -ª ì N/»-ª. Ã-Ìì1 2- ø-ê -ºò - ó-²1 4 -ÁªÈ 13% º êò -ê -À¹ñ -Ì È3 4-Á -ê -à È-± ÈÌ- ø 15Œ-15Œ-15»º -²œÌÄ É- 1 2-ìò -ª1 2- ²3 4 - ø È3 4Á -ê -à È-± È -Ì ø 16Œ-20Œ-0. ²3 4 -¹ìñ -à È-Ä É- -ì1 2- ø-à¹ñ -Ì È3 4- -Ì Ì- -ê -Á -à È-± È-Ì ø 15Œ-15Œ-15»º -²œÌÌ- Ì-Ä É- 1 2-ìò -ª1 2-²3 4 -¹ì3 4 È3 4Á -ê -à È-± È -Ì ø 16Œ-20Œ-0- À² - Ì-À«ò 40% Áì1 2 ÃÌ-Ì Ì 67% Á È-Ì -ê -À ñì-à윺- ò -Ì 3 4. Ã-Ìì1 2- ø-ê -ºò -ê -Á -à È-± È -Ì ø 16Œ-20Œ-0 Ä É- 1 2-ìò -ª1 2-²3 4 - ø È3 4-Á -à È- ± ÈÌ ø 15Œ-15Œ-15»º -²œÌÌ- Ì-Á È-̹ì3 4 È3 4, ÁªÈ- È3 4-²3 4 -¹ìñ -ê -à È-± È -ÌÄ É- -ì1 2- ø-à¹ñ -Ì È3 4 -ê -Á -à È-± È -Ì ø 16Œ-20Œ-0 Ä É- 1 2-ìò -ª1 2-²3 4 -À í3 4 ø È3 4-Á -à È-± È -Ì ø 15Œ-15Œ-15»º -²œ --ÌÁ ÈÌì -ìö - Áì1 2- ñ -ÁªÈ 20% º êò Áì1 2 Ã-ÌÌ Ì 67% Á È-Ì -ê -À ñì-à윺- òì-ªö Áì1 2 Î1 4. -Ì -Ì 3 4 Ì Ìà È-± ÈÌ-ê - ó-ê3 4 K 1 2- ö -µøè-ì -à È-ÃÌÌ-3 4-ê -À ñ -Ì ò -Ì 3 4 ¹ìõ- È3 4 à È-± È -Ì ø 16Œ-20Œ ö - ñ -à È-À³õº ¹ìõ Ä«- ö -À³õº -à È-ê Å- ó Áì1 2 Àì - É -± ÈÌ- ø 46Œ-0Œ-0, È Ì-ÃÌÌ3 4- ò -̪ö Áì1 2 Î1 4 - Ìà È-± È -Ì ø 16Œ-20Œ ö - ñ -à È-À³õº ¹ìõ Ä«- ö -À³õº -à È-ê Å- ó Áì1 2 Àì - É -± È -Ì ø 46Œ-0Œ-0. Introduction The or (NPK) are the most commonly used by farmers as a basal fertilizer in the rice cropping system. Of these is the most popular and it is available at the Agricultural Promotion Bank and the markets. However, does not contain potassium (K) which is required by rice. Therefore, in the longer term, with the application of , K could be become a limiting nutrient for rice and a main problem in lowland rice soils. Currently, in many lowland rice areas, K is still available and there is no response to K additions of inorganic, especially in clay soil. However, after continuous cultivation of high yielding rice varieties and increase double cropping, soil K will be lost from the soil rapidly. In order to sustainably manage the soil, K needs to be returned into the soil in term of straw or inorganic K fertilizers. Our demonstrations were conducted to compare the long-term effects of using either or as starter fertilizers in different soil textures on rice productivity. 58

3 Materials and methods The experiment was initiated at 17 sites in the 1998/99 dry season (DS) and maintained for five seasons to examine the long-term effects of each fertilizer. In the 2001 DS, only nine sites were continued, because other sites were not representative sites and some of the collaborators who conducted the demonstration moved to other jobs or went to continue their graduate studies. The demonstrations consisted of three treatments with only one replication per site. The treatments were as follows: a control with no fertilizer and or as basal fertilizer treatments. In the two treatments that received fertilizer, N was applied at a rate of 90 kg/ha. The compound fertilizer was applied in the first application, while urea was the N source for the two top dressings at 30 and 50 DAT. The total P 2 O 5 and K 2 O for each were 38 and 0 kg/ha, respectively for the compound fertilizer; and 30 and 30 kg/ha respectively for the compound fertilizer. Plot size was 5 x 10 m for each treatment and large enough for tillage with small hand tractors or water buffalo. The variety used differed with each site but was always an improved variety. Transplanting was done at approximately 15 x 15 cm which is what farmers typically use for irrigated rice. The whole plot was harvested to determine grain yield and yields were adjusted to 14% moisture. The result was focused on the higher yield increase by the respective compound fertilizer and soil textures. Results and discussion In a continued application of and as a basal fertilizers for lowland rice in different soils texture for five seasons, the rice yields showed a better response to the application of fertilizer than to in some sandy loam and in all loamy sand sites. Yield increases were more than 0.4 t/ ha higher in the treatment than in the fertilizer treatment (Table 1). However, all clay sites and one loam site showed better yield responses to the application of fertilizer than to the application. These results are a continuation from last years results (ATR ) and indicate that K deficiencies would become more prevalent if farmers apply only N and P containing fertilizers on sandy soils, due to K loss if rice straw is continously removed from the fields and not returned. Table 1. Grain yields with and as basal compound fertilizers from the nine sites in the 2001 dry season (t/ha). A basal fertilizer was considered better than the others if yields were greater than 0.4 t/ha. Shared numbers are those which are at least 0.4 t/ha better than the other basal fertilizers. Province District Soil texture '99 '99 '00 '00 '01 '99 '99 '00 '00 '01 Houapanh Et CL Saravane Vapi CL Bolikhamxai Paksan L Champasak Sanasomboun SL Savannakhet Champhone SL Saravane Saravane SL Champasak Khong LS Vientiane Houeysone LS (Naxaithong) Km 35 LS Sites where either or is better (%)

4 Practical implications for extension Our data clearly indicate that in the long term, farmers should either apply fertilizers containing K compound fertilizers on sandy soils ( : ) or incorporate rice straw combined with an application of and a top dress of urea (46-0-0). For the loam and clay soils, rice straw should be incorporated with an application of and top dressed with urea (46-0-0). Acknowledgements We would like to thank the Swiss Agency for Development and Cooperation (SDC) through the Lao- IRRI Project and all of the government organizations, which supported this research activity and thanks also the collaborators, and farmers who carried out these experiments. In addition, we would like to thank Dr. Renate Braun and Philip Gibson, who helped us to write this paper. References Lao IRRI, Annual Technical Report of the National Rice Research Program and Lao-IRRI Project. 60

5 Table 1. Comparison of and as starter compound fertilizers from 1999 DS to the 2000 WS. The shaded cells are for comparing and and highlight those that were at least 0.4 t/ha different from the others. Soil Province District texture 98/ / /01 98/ / /01 Houaphan Et CL Saravan Vapi CL Borikhamxay Paksan L Khammouane Thakek L Khammouane Gnommolaht L Savannakhet Saybouli L Sekong Thateng L Vientiane Saythani L Vientiane Prov. Phonhong L Saravane Saravane SL Sayabouli Phiang SL Champasak Sanasomboun SL Champasak Soukouma SL Savannakhet Champhone SL Champasak Khong LS Vientiane Houay Sone LS Vientiane km35 LS Mean Sites where either or is better (%)