All-year round assessment of improved forages and impact on soil health in Mai Son district, Son La province, Vietnam Do, Trong Hieu1 ; Nguyen, Tien Sinh1; Dao, Thi Thu Hang2; Tran, Thi Bich Ngoc3; Peters, Michael4 and Atieno, Mary2 1Northern Mountainous Agriculture & Forestry Science Institute (NOMAFSI) 2Tropical Forages Program, International Center for Tropical Agriculture (CIAT), Hanoi, Vietnam 3National Institute of Animal Science (NIAS), Hanoi Vietnam 4Tropical Forages Program, International Center for Tropical Agriculture (CIAT), Nairobi, Kenya FINAL REPORT Photo credit: Hieu, Do Trong (NOMAFSI) December 2024 © 2024 This publication is copyrighted by the International Center for Tropical Agriculture (CIAT). It is licensed for use under the Creative Commons Attribution 4.0 International Licence. To view this licence, visit https://creativecommons.org/licenses/by/4.0. Unless otherwise noted, you are free to share (copy and redistribute the material in any medium or format), adapt (remix, transform, and build upon the material) for any purpose, even commercially, under the following condition: ATTRIBUTION. The work must be attributed, but not in any way that suggests endorsement by CIAT or the author(s). NOTICE: For any reuse or distribution, the licence terms of this work must be made clear to others. Any of the above conditions can be waived if permission is obtained from the copyright holder. Nothing in this licence impairs or restricts the author’s moral rights. Fair dealing and other rights are in no way affected by the above. The parts used must not misrepresent the meaning of the publication. ILRI would appreciate being sent a copy of any materials in which text, photos etc. have been used. Cover photo credit: Do Trang Hieu /NOMAFSI Citation: Do, T.H.; Nguyen, T.S.; Dao, T.T.H.; Tran, T.B.N.; Peters, M.; Atieno, M. (2023). All-year round assessment of improved forages and impact on soil health in Mai Son district, Son La province, Vietnam. Hanoi (Vietnam): International Center for Tropical Agriculture. CGIAR Initiative on Sustainable Animal Productivity; CGIAR Initiative on Nature-Positive Solutions. 28p. About SAPLING The CGIAR Research Initiative on Sustainable Animal Productivity for Livelihoods, Nutrition and Gender inclusion (SAPLING) is working in seven countries focusing on livestock value chains to package and scale out tried-and-tested, as well as new, innovations in livestock health, genetics, feed and market systems. SAPLING aims to demonstrate that improvements in livestock productivity can offer a triple win: generating improved livelihoods and nutritional outcomes; contributing to women’s empowerment; and, reducing impacts on climate and the environment. Its seven focus countries are Ethiopia, Kenya, Mali, Nepal, Tanzania, Uganda and Vietnam. https://www.cgiar.org/initiative/sustainable-animal-productivity/ About Nature+ The CGIAR Research Initiative on Nature-Positive Solutions (Nature+) aims to re-imagine, co-create, and implement nature-positive solutions-based agrifood systems that equitably support local food and livelihoods, while simultaneously ensuring that agriculture is a net positive contributor to nature. This Initiative prioritizes the following countries: Burkina Faso, Colombia, India, Kenya and Vietnam. https://www.cgiar.org/initiative/nature-positive-solutions/ https://creativecommons.org/licenses/by/4.0 https://www.cgiar.org/initiative/sustainable-animal-productivity/ https://www.cgiar.org/initiative/nature-positive-solutions/ Acknowledgments This study was conducted as part of the CGIAR Initiatives on Sustainable Animal Productivity for Livelihoods, Nutrition and Gender inclusion (SAPLING) and Nature-Positive Solutions (Nature+). CGIAR research is supported by contributions to the CGIAR Trust Fund. CGIAR is a global research partnership for a food-secure future dedicated to transforming food, land, and water systems in a climate crisis. We warmly thank the local authorities of Son La province, Mai Son District People’s Committee, Sub- Department of Animal Health, Animal Husbandry & Aquaculture (Sub-DAH) for their substantial support. Special thanks to the farmers in Hat Lot, Chieng Luong, Chieng Chung and Muong Bon communes for their contributions on the forage demonstration activities. https://www.cgiar.org/funders/ Contents Contents ........................................................................................................................................................ 4 List Of Table And Figure ................................................................................................................................. 5 1. Introduction ..................................................................................................................................... 6 2. Methodology .................................................................................................................................... 7 3. Results And Discussion ................................................................................................................... 10 3.1. PERFORMANCE OF FORAGE CROPS .................................................................................................................. 10 3.2. IMPACTS OF THE FORAGES ON SOIL HEALTH ..................................................................................................... 15 3.3. FEEDBACK FROM FARMERS AND LOCAL STAKEHOLDERS ....................................................................................... 23 4. Conclusion ...................................................................................................................................... 24 5. References ..................................................................................................................................... 25 ANNEX 1: PLANT HEIGHT OF THE VARIETIES THROUGHOUT THE CUTS IN 2023 AND 2024. ............................................. 27 List of Table and Figure Table 1. Location of the demo farms in Mai Son district, Son La province...................................... 7 Table 2. The arrangement of the forages in the demo farms .......................................................... 8 Table 3. Date of data collection conducted in 2023 and 2024 ........................................................ 8 Table 4. Plant height of the forage in the demo farms in 2023 and 2024 ..................................... 10 Table 5. Comparison of the number of tillers in the wet and dry seasons .................................... 12 Table 6. Fresh and dry yield of selected forages ........................................................................... 13 Table 7. Soil physical characteristics at experimental sites ........................................................... 15 Table 8. Soil chemical properties at experimental sites ................................................................ 16 Table 9. Soil pH level in the demo plots after two years .............................................................. 16 Table 10. Soil organic carbon in the demo plots after two years ................................................. 17 Table 11. Total nitrogen (%) in the demo plots after two years ................................................... 18 Table 12. Levels of available phosphorus (mg/100 g) ................................................................... 19 Table 13. Levels of available potassium (mg/100g) ...................................................................... 21 Table 14. Cation exchange capacity in the demo plots after the experiment ............................... 22 Figure 1. Experimental sites in Mai Son district ............................................................................... 7 Figure 2. Growth of forages in the experimental sites .................................................................. 11 Figure 3. Rainfall and temperature changes during the wet and dry seasons in 2023 and 2024 . 11 Figure 4. Fresh and dry matter yield of selected forages .............................................................. 14 Figure 5. Soil pH (H2O) in the demo plots after Year 1 and Year 2 ... Error! Bookmark not defined. Figure 6. Soil organic carbon in the demo plots after Year 1 and Year 2 ...................................... 18 Figure 7. Total N (%) in the demo plots after Year 1 and Year 2 ................................................... 19 Figure 8. Available phosphorus in the demo plots after Year 1 and Year 2 .................................. 20 Figure 9. Available K in the demo plots after Year 1 and Year 2 .................................................... 21 Figure 10. Soil CEC in the demo plots after Year 1 and Year 2 ...................................................... 22 Figure 11. Feedback from ToF participants on the forages in August 2023 .................................. 23 Figure 12. Feedback from the demo farm owners in August 2023 ............................................... 23 Figure 13. Feedback from ToT participants from Mai Son district, Son La province in August 202323 Figure 14. Feedback from ToT participants from Mai Son and Phu Yen districts in May 2024 ..... 23 1. Introduction Son La province, with a significant number of buffalo and cattle, has seen significant transformation in the livestock sector. The expansion of perennial crops and increased mechanization has led to a reduction in grazing areas and a decline in buffalo herds (SLSO, 2022). Conversely, cattle numbers are rising due to local government support (SLSO, 2022). However, feed shortages, particularly during the dry season, remain a critical threat to the sustainability of the livestock industry . In addition, a survey using the Gendered Feed Assessment Tool (G-FEAST) Atieno et al. (2021)1 and (Ngoc et al., 2023)2 in Mai Son district underscored the roles of livestock as a primary income source but highlighted insufficient feed as a major challenge. This issue is particularly acute in the dry season, emphasizing the need for introducing high-yielding forage crops resilient to local conditions. To address these challenges, the CGIAR initiative on Sustainable Animal Productivity for Improved Livelihoods, Nutrition, and Gender Inclusion (SAPLING) evaluated eight improved, high-quality forage varieties in Mai Son district (Do et al., 2023). This study aimed to diversify livestock forage varieties, crucial for resolving feed source issues and aligning with the project's goals. The study's purpose of evaluating and comparing the growth and development of these forage varieties across wet and rainy seasons was vital. It aims to identify optimal forage types for different seasons, ensuring a reliable and nutritious feed supply year-round. Additonally, the impact of growing these forages on soil health, supported by the Nature+ initiative, was assessed to provide a comprehensive evaluation and benefits of these varieties in the region. By addressing seasonal feed shortages and enhancing livestock productivity, while simultaneously improving soil health, these efforts are essential for ensuring the long-term sustainability and prosperity of Son La's livestock sector. 1 G-FEAST Vietnam 2020 Final Report (CGIAR) 2 Assessment of feed resources availability and use for cattle and pigs in Mai Son District, Son La Province, Vietnam. https://hdl.handle.net/10568/134570 https://cgspace.cgiar.org/bitstream/handle/10568/111524/G-FEAST%20Vietnam_2020%20final%20report.pdf?sequence=3&isAllowed=y https://hdl.handle.net/10568/134570 2. Methodology The experiment was set up in four different sites with the details below: Figure 1. Experimental sites in Mai Son district Table 1. Location of the demo farms in Mai Son district, Son La province Site Commune Village Longitude Latitude 1 Muong Bon Doan Ket 21.25274° 104.0575° 2 Chieng Chung Khoa 21.21501° 103.9061° 3 Chieng Luong Mon 1 21.09511° 104.1099° 4 Hat Lot Na Sang 21.167687° 104.09958° Eight forage varieties were used in the experiment consisting of: 1. Mun River Guinea - Megathyrus maximus cv. Mun River (MR) 2. Mombasa Guinea - Megathyrus maximus cv. Mombasa (MG) 3. Mulato II - Urochloa hybrid cv. Mulato II (MII) 4. Taiwanese Green Elephant Grass - (Cenchrus purpureus)- (GE) 5. VA06 - Cenchrus purpureus cv. VA06 (Napier grass) 6. Biomass maize variety NK7328s - Zea mays (NK7328/ NK7328s) 7. Stylosanthes guianensis var. guianensis cv. Ubon stylo (US) 8. Rice bean - Vigna umbellata – RB Trial arrangement: In each experimental site, the trial was arranged as follows: Table 2. The arrangement of the forages in the demo farms Block 1 MII MR RB US NK732 8 GE Napier MG Block 2 RB MII Napier NK7328 MR MG GE US Block 3 NK7328 MR MII Napier RB MG US GE Details on date and time of planting and data collection: Table 3. Date of data collection conducted in 2023 and 2024 Commun e Plantin g date Date of data collection Rainy season Dry season Rainy season Dry seas on 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th Muong Bon May 19, 2023 Jul 19, 202 3 Sep 4, 202 3 Oct 22, 202 3 Dec 1st, 202 3 Jan 15th, 202 4 Mar 1st, 202 4 Apr 10th, 202 4 Aug 4th 2024 Sep 6th 202 4 Nov 3th 202 4 Chieng Chung May 20, 2023 Jul 29, 202 3 Sep 4, 202 3 Oct 22, 202 3 Dec 1st, 202 3 Jan 15th, 202 4 Mar 1st, 202 4 Apr 10th, 202 4 Aug 4th 2024 Sep 6th 202 4 Nov 3th 202 4 Chieng Luong May 18, 2023 Jul 20, 202 3 Sep 5, 202 3 Oct 23, 202 3 Dec 1st, 202 3 Jan 15th, 202 4 Mar 1st, 202 4 Apr 10th, 202 4 Aug 4th 2024 Sep 6th 202 4 Nov 3th 202 4 Hat Lot May 19, 2023 Jul 21, 202 3 Sep 5, 202 3 Oct 23, 202 3 Dec 1st, 202 3 Jan 15th, 202 4 Mar 1st, 202 4 Apr 10th, 202 4 Aug 4th 2024 Sep 6th 202 4 Nov 3th 202 4 Fertilizer application: NPK (basal fertilizer) was applied at a rate of 200 kg/ha (5-10-3) at the time of planting. Top dressing - 12-5-10 NPK - was applied 30 days after planting and immediately after harvesting, at a rate of 50 kg/ha applied each time. Soil sampling and analysis: Soil sampling was conducted three times over the two years of the experiment (2023 and 2024), one before planting and two at the end of each year after legumes started flowering. During the first soil sampling, samples were taken from random points in each plot, at soil depths of 0-20 cm and 20-40 cm. In the second and the third sampling, soil samples were taken from five different points in each plot. The parameters analyzed included soil pH, total nitrogen, available phosphorus, potassium, organic carbon, cation exchange capacity (CEC), and texture. Data collected included: - Rainfall and weather data: Monthly rainfall, temperature (mean maximum and minimum), and relative humidity data were collected from the nearest meteorological station for the period from May 2023 to April 2024. - Number of tillers: The number of tillers per plant was counted from 4 plants within a 1 x 1 m frame every 4 weeks during the establishment stage and after every 8 weeks (at harvest) during the production stage. - Plant height: A ruler was used to measure the height from the ground to the top of 2/3 of the longest and tallest group of leaves. - Fresh and dry matter yield: Fresh biomass samples were taken and weighed every 45 days in the wet season and every 60 days in the dry season, from a 2 x 2 m2 spot per plot and weighted. The dry matter yield was done twice, one in the wet season and another in the dry season. 3. Results and discussion 3.1. Performance of Forage Crops The demo farms were established between May 18 and 20, 2023. Preliminary results from the wet season in 2023 can be found in this report (https://hdl.handle.net/10568/137318). So far, the forage varieties at the demonstration farms have gone through both wet and dry seasons of 2023 and 2024. The forage varieties demonstrated varying performances across the wet and dry seasons. During the wet season, Green Elephant Grass, VA06, Mun River Guinea, and Mombasa Guinea exhibited the highest growth rates, with Green Elephant Grass achieving the greatest biomass production. Mulato II emerged as a notable performer in the dry season, maintaining relatively high dry matter yields despite the challenging conditions (Table 4). Table 4. Plant height of the forage in the demo farms in 2023 and 2024 Forage varieties Plant height (cm) Growth speed (cm/day) Wet Season (May-Oct 2023) Dry season (Dec 2023- Apr 2024) Wet season (Aug-Sep 2024) Dry season (Nov 2024) Wet season Dry season Mun River Guinea 96.4 24.9 119.3 59.4 1.8 0.7 Mombasa Guinea 106.1 25.3 123.8 66.7 2.0 0.7 Mulato II 63.7 16.7 70.8 42.8 1.1 0.4 GE grass 128.8 29.6 145.4 108.7 2.4 0.8 Maize NK7328 139.5 23.7 164.7 0.0 2.0 0.7 Ubon Stylo 97.8 14.1 75.6 82.4 0.8 0.2 Rice bean 136.5 - 102.3 169.8 1.7 - VA06 120.2 28.2 129.2 99.1 2.7 0.8 Figure 2. Growth of forages in the experimental sites Figure 3. Rainfall and temperature changes during the wet and dry seasons in 2023 and 2024 Three additional data collections were conducted in August, September, and November of 2024 to validate the growth and development of the varieties in the demo farms. In general, the data on plant height was consistent in both 2023 and 2024. The forages grew better in the wet season and poorer in the dry season. Details on the data collection time and data for each cutting can be found in Table 5. The growth and development of the forage varieties showed a clear correlation with weather changes, particularly rainfall. Their performance showed a decline in growth during the dry season. While the number of tillers increased, the plant height of the forage varieties decreased sharply towards the end of the dry season. Green Elephant Grass, VA06, Mun River Guinea, and Mombasa Guinea demonstrated better growth than the other varieties during the dry season. Table 5. Comparison of the number of tillers in the wet and dry seasons in 2023 and 2024 Note: The first biomass yield was recorded 60 days after planting, followed by subsequent cuts and yield measurements every 45 days in the wet and 60 days in the dry seasons. The forage varieties' performance differences were partly reflected in yield indices. Green Elephant Grass, VA06, Mun River Guinea, and Mombasa Guinea had significantly higher yields than the other varieties (p=0.05) in the wet season. Fresh biomass yield ranged from 106.85 tons/ha to 143.13 tons/ha, and dry matter yield ranged from 21.64 tons/ha to 25.36 tons/ha. However, when it came to the dry season, Mulato II and Mun River Guinea showed better performance in dry matter yield. Table 6. Fresh and dry yield of selected forages Forage varieties Fresh biomass yield (tons/ha) Dry matter (tons/ha) Wet season Dry season Wet season Dry season Mun River Guinea 108.83b 9.51ab 25.36a 3.48ab Mombasa Guinea 106.85b 7.25bc 24.09a 2.66b Mulato II 66.58c 11.08a 12.86b 3.74a Green elephant grass 143.13a 12.15a 22.79a 2.51b Maize NK7328 44.58c 5.59c 11.35bc - Ubon Stylo 57.50c 1.64d 9.53bc 0.57c Rice bean 53.08c - 7.24c - VA06 124.03ab 9.29ab 21.64a 2.04b Note: a, b, and c indicate the similarities and/or differences at p=0.05. Data was collected from May 2023 to April 2024. The productivity of these forage varieties decreased significantly in the dry season. The best- performing varieties were Mulato II and Mun River Guinea, with 3.74 tons/ha and 3.48 tons/ha DM, respectively, followed by Mombasa Guinea, Green Elephant, and VA06. The remaining varieties did not grow well in the dry season (like rice bean) or had very low yields (such as Ubon stylo and Maize NK7328).These results underscore the importance of selecting resilient forage varieties to address seasonal feed shortages. While high rainfall supported the growth of Green Elephant Grass and VA06 during the wet season, Mulato II's drought resistance ensured its suitability for dry conditions, making it an invaluable option for year-round cultivation. Figure 4. Fresh and dry matter yield of selected forages 3.2. Impacts of the forages on Soil Health The introduction of forage crops showed varying effects on soil health over the two-year period. Before trial setup, soil analysis of the samples from the experimental sites showed minimal variation in the 20 to 40-cm soil layer (Tables 7-9). In contrast, the 0-20 cm layer exhibited more distinct chemical property differences across the sites. All sites had slightly acidic soil, with pH levels ranging from 4.84 to 5.15. Chieng Luong stood out for its higher total organic matter content than other locations. Regarding the total nitrogen, the soil at these sites fell in the medium range, with nitrogen content varying from 0.08 to 0.15%. Additionally, high levels of available phosphorus content were observed, exceeding 15 mg P2O5 per 100g in the topsoil. The available potassium (K) content was categorized as medium, falling within the range of 10-20 mg K2O per 100 g soil (Tien, 2019). Furthermore, with a cation exchange capacity (CEC) between 1.48 and 1.81, these soils are classified as having low CEC. Table 7. Soil physical characteristics at experimental sites Location Soil layer 0 - 20 cm Coarse sand (2.0-2.0 mm) Fine sand (0.2-0.02 mm) Limon (0.02-0.002 mm) Clay (<0.002 mm) Chieng Luong 2.63 27.10 34.53 35.73 Muong Bon 2.31 35.12 21.57 41.00 Chieng Chung 8.68 40.12 26.40 24.80 Hat Lot 5.48 30.52 27.07 36.93 Soil layer 20 - 40 cm Chieng Luong 4.00 35,33 35,20 25.47 Muong Bon 3.77 20.76 44.93 30.53 Chieng Chung 5.35 46.91 28.00 19.73 Hat Lot 3.43 30.17 35.87 30.53 Table 8. Soil chemical properties at experimental sites Location Soil layer from 0 - 20 cm pH (H20) OC (%) Total N (%) Available P (mg/100g) Available K (mg/100g) CEC (meq/100g) Chieng Luong 5.15 3.01 0.10 38.80 10.83 1.50 Muong Bon 4.84 2.16 0.14 20.00 7.07 1.48 Chieng Chung 5.00 1.76 0.10 35.00 15.24 1.60 Hat Lot 5.16 1.72 0.13 19,30 11.27 1.81 Layer 20 - 40 cm Chieng Luong 5.33 2.23 0.14 20.53 7.73 1.36 Muong Bon 5.06 1.74 0.14 15.03 3.54 1.58 Chieng Chung 5.26 1.75 0.14 19,17 8.40 1.68 Hat Lot 5.45 1.59 0.15 7.80 8.84 1.58 The results of soil pH analysis showed that, after two years of the experiment, the forage crops did not cause any significant changes in soil pH compared to before the experiment (Table 9). Soil pH ranged from approximately 5 to 6, which is consistent with the conclusions of studies done by Pokhrel et al. (2021) and Liebig et al. (2015). These studies indicated that cover crops did not cause any changes in soil pH after three years. Table 9. Soil pH level in the demo plots after two years Forage varieties pH (H2O) – Topsoil (0-20 cm) Hat Lot Chieng Luong Chieng Chung Muong Bon Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 GE grass 5.58 5.76 5.57 5.78 5.27 5.90 4.87 5.26 Stylo 5.79 5.39 5.56 5.74 5.07 6.09 4.94 5.48 Rice bean 5.72 5.55 5.59 5.70 5.24 5.90 4.97 5.28 Mombasa Guinea 5.69 5.36 5.60 5.71 5.27 5.89 4.91 5.33 Mun Rive Guinea 5.70 5.32 5.61 5.60 5.19 6.20 4.78 5.73 Mulato II 5.61 5.75 5.71 5.87 5.16 5.92 4.80 5.52 VA06 5.58 5.30 5.63 5.78 5.20 6.18 4.75 5.24 Maize (NK7328) 5.53 5.61 5.50 5.88 5.26 5.93 4.80 5.26 Regarding soil organic carbon (OC), the comparison between the two years showed that the demo farm in Chieng Luong still had a higher OC level than the other sites (Table 10, Fig. 5). An improvement in OC was recorded for all experimental treatments across all four demo farms. Diversifying (Sarkar et al., 2020, McLauchlan et al., 2006) and maintaining (Nascente et al., 2013) grazing species and cover crops could help accumulate organic matter, increasing OC levels. However, in the context of this experiment, the forage varieties were planted in monoculture and harvested periodically, therefore, the improvement could be attributed to the root systems of the forage crops used in the experiment, as highlighted by studies from Allen Jr et al. (2006) and Sundaram et al. (2012). However, this OC level remains comparable to the levels before the experiment. Table 10. Soil organic carbon in the demo plots after two years Forage varieties OC % (0-20 cm) Hat Lot Chieng Luong Chieng Chung Muong Bon Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 GE grass 1.61 1.52 1.67 2.33 1.43 1.75 1.47 1.16 Stylo 1.39 1.75 1.72 2.37 1.67 2.09 1.22 1.43 Rice bean 0.95 2.16 1.94 2.11 1.34 1.91 1.46 1.33 Mombasa Guinea 0.94 2.17 1.62 1.97 1.50 2.07 1.15 1.33 Mun River Guinea 1.23 1.11 1.79 1.92 0.99 1.59 1.18 1.48 Mulato II 1.57 1.53 2.06 2.38 1.35 2.01 1.17 2.01 VA06 1.66 1.04 1.78 2.15 1.04 1.68 1.60 2.13 Maize (NK7328) 0.96 1.04 1.83 2.20 0.91 1.49 1.13 1.16 Figure 5. Soil organic carbon in the demo plots after Year 1 and Year 2 In all the demo plots, the total nitrogen levels in most treatments remained equal or increased compared to the first year (Table 11, Fig. 6). Top-dressing fertilizer application contributed to this stability since most of these forages are herbaceous species without the ability to fix nitrogen, and all the biomass was harvested for feeding animals. In addition, this stability suggested that the top-dressing level of 50 kg of 12-5-10 NPK per hectare after each cut would be enough to maintain the nitrogen level in the topsoil. Table 11. Total nitrogen (%) in the demo plots after two years Forage varieties Total N (%) (0-20 cm) Hat Lot Chieng Luong Chieng Chung Muong Bon Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 GE grass 0.15 0.26 0.11 0.12 0.16 0.18 0.16 0.21 Stylo 0.19 0.22 0.14 0.18 0.14 0.11 0.15 0.11 Rice bean 0.16 0.24 0.16 0.16 0.11 0.17 0.17 0.13 Mombasa Guinea 0.15 0.23 0.13 0.16 0.11 0.15 0.17 0.13 Mun River Guinea 0.12 0.23 0.13 0.19 0.13 0.17 0.21 0.13 Mulato II 0.13 0.22 0.11 0.18 0.11 0.15 0.16 0.17 VA06 0.15 0.17 0.14 0.20 0.13 0.18 0.20 0.16 0 0.5 1 1.5 2 2.5 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Hat Lot Chieng Luong Chieng Chung Muong Bon OC % (0-20 cm) Organic Carbon (%) GE grass Stylo Rice bean Mombasa Guinea Mun River Guinea Mulato II VA06 Maize (NK7328) Maize (NK7328) 0.15 0.20 0.14 0.12 0.13 0.20 0.14 0.15 Figure 6. Total N (%) in the demo plots after Year 1 and Year 2 The available phosphorus content declined at all sites compared to the pre-experiment and the first year of the experiment (Table 12; Fig.7). This result confirmed the conclusion that forage crops, especially the herbaceous species, are known to deplete available phosphorus in the topsoil due to their high uptake rate (Welsh et al., 2009). This finding suggested that an additional application of phosphorus for top-dressing should be considered to maintain the biomass yield of the forages. Table 12. Levels of available phosphorus (mg/100 g) Forage varieties Available P (mg/100g) (0-20 cm) Hat Lot Chieng Luong Chieng Chung Muong Bon Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 GE grass 13.48 5.42 16.01 5.22 25.83 5.53 8.50 5.17 Stylo 1.65 5.20 14.05 5.26 21.56 5.18 16.27 5.24 Rice bean 5.65 5.22 16.50 5.57 22.35 6.01 16.10 5.77 0 0.05 0.1 0.15 0.2 0.25 0.3 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Hat Lot Chieng Luong Chieng Chung Muong Bon Total N (%) (0-20 cm) Total N (%) GE grass Stylo Rice bean Mombasa Guinea Mun River Guinea Mulato II VA06 Maize (NK7328) Mombasa Guinea 2.94 5.58 12.19 5.22 15.56 6.08 14.14 5.40 Mun River Guinea 3.41 4.93 13.49 5.38 17.68 5.45 13.73 5.47 Mulato II 4.74 5.20 10.98 5.44 25.23 5.98 13.57 5.72 VA06 10.93 5.01 15.30 5.52 17.83 5.46 16.88 5.36 Maize (NK7328) 13.22 5.14 19.33 6.03 13.75 5.70 18.12 5.63 Figure 7. Available phosphorus in the demo plots after Year 1 and Year 2 Except for Chieng Luong, the available potassium content in all demo plots was lower than in the initial pre-planting and first year of the experiment, with the lowest levels observed at the demo plot in Muong Bon (Table 13, Fig 8). This suggested that these forage crops significantly impact the depletion of potassium in topsoil through a high uptake rate. Similar findings were also reported for maize and wheat (Correndo et al., 2021), Napier grass (which is in the same family as Green elephant grass and VA06) (Dokbua et al., 2021), and Guinea grass (Galindo et al., 2018). Hence, studies should be conducted on the appropriate top- dressing levels of potassium to maintain the fertility of the soil growing the forage crops. 0 5 10 15 20 25 30 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Hat Lot Chieng Luong Chieng Chung Muong Bon Available P (mg/100g) (0-20 cm) Available P (mg/100g) GE grass Stylo Rice bean Mombasa Guinea Mun River Guinea Mulato II VA06 Maize (NK7328) Table 13. Levels of available potassium (mg/100g) Forage varieties Available K (mg/100g) (0-20 cm) Hat Lot Chieng Luong Chieng Chung Muong Bon Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 GE grass 4.68 4.05 1.07 3.99 3.70 1.40 0.58 0.79 Stylo 5.07 5.97 2.14 3.97 3.60 2.16 0.68 0.38 Rice bean 3.21 3.93 3.21 6.92 2.92 2.58 0.58 1.70 Mombasa Guinea 3.02 2.69 0.97 5.87 2.53 1.38 0.39 1.28 Mun Rive Guinea 4.09 3.71 1.36 4.06 1.95 1.72 0.49 1.46 Mulato II 2.24 2.52 1.46 5.49 2.82 2.13 0.20 1.29 VA06 4.19 3.96 1.56 5.48 1.56 3.26 0.29 0.55 Maize (NK7328) 4.77 3.50 2.34 8.10 6.43 2.53 0.39 0.81 Figure 8. Available K in the demo plots after Year 1 and Year 2 0 1 2 3 4 5 6 7 8 9 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Hat Lot Chieng Luong Chieng Chung Muong Bon Available K (mg/100g) (0-20 cm) Availabe K (mg/100 g) GE grass Stylo Rice bean Mombasa Guinea Mun River Guinea Mulato II VA06 Maize (NK7328) All four experimental sites observed a consistent trend of improvement in the soil CEC index (Table 14, Fig. 9). This indicated that these forage crops do not negatively affect the soil CEC. However, since soil CEC is influenced by several factors, including the amount of clay, organic matter content, and pH levels (Purnamasari et al., 2021), cropping system (Galindo et al., 2020) and crop residue management (Koulibaly et al., 2017), further studies are needed to gain a deeper understanding of the effects of different forage crops on the soil CEC. Table 14. Cation exchange capacity in the demo plots after the experiment Forage varieties CEC (meq/100g) (0-20 cm) Hat Lot Chieng Luong Chieng Chung Muong Bon Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 GE grass 3.59 3.21 2.16 3.05 1.45 1.25 1.53 2.23 Stylo 4.05 6.37 1.96 1.17 1.81 2.31 2.39 2.93 Rice bean 4.45 3.37 2.06 1.97 1.91 2.43 2.03 1.49 Mombasa Guinea 4.07 4.31 2.56 2.25 1.87 1.36 1.89 2.36 Mun River Guinea 3.92 3.00 3.35 4.12 1.24 3.47 1.69 3.89 Mulato II 4.39 4.95 2.16 3.31 1.08 2.07 1.45 4.29 VA06 4.29 3.39 1.80 2.28 1.11 1.01 1.92 1.43 Maize (NK7328) 3.85 3.52 1.73 2.12 1.13 1.67 1.28 2.17 Figure 5. Soil CEC in the demo plots after Year 1 and Year 2 0 1 2 3 4 5 6 7 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Year 1 Year 2 Hat Lot Chieng Luong Chieng Chung Muong Bon CEC (meq/100g) (0-20 cm) CEC (meq/100g) GE grass Stylo Rice bean Mombasa Guinea Mun River Guinea Mulato II VA06 Maize (NK7328) 3.3. Feedback from Farmers and Local Stakeholders During the Training of Trainers (ToT) and Training of Farmers (ToF) co-organized with National Institute of Animal Science (NIAS)3, we conducted six assessments to get feedback from farmers and local partners on the performance of the forages in the demo farms. The scores indicated that Green Elephant grass was the most favored variety, followed by Mun River guinea and Mombasa guinea. While leguminous forages like Ubon Stylo were less favored due to lower yields, their ability to fix nitrogen and contribute to soil fertility should not be overlooked. These attributes make them an essential component of sustainable forage systems, particularly when integrated with high-yield grasses. The study underscores the importance of promoting awareness among farmers about the long-term benefits of leguminous forages to enhance both soil health and livestock productivity. The positive reception of the tested forages, combined with ongoing capacity-building efforts, ensures the potential for these varieties to address feed shortages and contribute to the sustainability of livestock farming in Son La province. Figure 6. Feedback from ToF participants on the forages in August 2023 Figure 7. Feedback from the demo farm owners in August 2023 Figure 8. Feedback from ToT participants from Mai Son district, Son La province in August 2023 Figure 9. Feedback from ToT participants from Mai Son and Phu Yen districts in May 2024 3 Training of local stakeholders on animal nutrition in Son La Province, Vietnam (https://hdl.handle.net/10568/158400) https://cgspace.cgiar.org/items/b7d15256-c88c-4145-b13b-80d58cdada2f https://hdl.handle.net/10568/158400 4. Conclusion The forage varieties' growth and development throughout both the wet and dry seasons revealed significant potential to address feed shortages in Son La Province. Green Elephant grass and VA06 excelled during the wet season, offering high biomass yields. The Guinea grass varieties, including Mun River Guinea and Mombasa Guinea, demonstrated strong adaptability across both seasons, providing consistent yields and highlighting their suitability for year-round cultivation. While the growth and development of all forage varieties decreased sharply during the dry season, Mulato II showed better drought resistance than the other varieties, achieving the highest dry matter yield of 3.74 tons per hectare. While leguminous forages such as Stylo bean did not perform in terms of biomass yield, their ability to survive the dry season and contribute to soil cover and nitrogen fixation makes them an essential component of sustainable forage systems. This diversification of forage varieties is crucial for achieving long-term sustainability and improving livestock productivity. After two years of experimentation, soil analysis results revealed no significant changes in the pH and organic carbon (OC) levels of the topsoil in the demonstration plots. Regarding soil nutrients, total nitrogen (N) levels remained stable or slightly increased. However, there was a noticeable decline in available phosphorus (P) and potassium (K) across all demonstration farms, suggesting high uptake rates of these nutrients by the forages. This underscores the need for higher levels of top-dressing to replenish P and K. In terms of cation exchange capacity (CEC), a marginal increase was observed, indicating potential improvements in the soil's nutrient retention capacity. Nevertheless, since CEC is influenced by multiple factors, further studies are required to fully understand the impact of the forages on this indicator. The positive feedback from farmers and stakeholders further validates the potential of these forage varieties to improve livestock productivity and resilience in the region. By incorporating both high-yield grasses and legumes, farmers can achieve a balanced and sustainable feed system. Training and capacity-building programs will be instrumental in ensuring the successful adoption and management of these improved forages. In summary, the study highlights that the strategic selection of forage varieties, combined with proper soil management and ongoing farmer engagement, can significantly enhance the sustainability and profitability of livestock farming in Son La Province. Future research should continue to explore integrated forage systems that optimize both productivity and soil health, contributing to the long-term resilience of local agricultural practices. 5. References ALLEN JR, L. H., ALBRECHT, S. L., BOOTE, K. J., THOMAS, J. M., NEWMAN, Y. C. & SKIRVIN, K. W. 2006. Soil organic carbon and nitrogen accumulation in plots of rhizoma perennial peanut and bahiagrass grown in elevated carbon dioxide and temperature. Journal of environmental quality, 35, 1405-1412. https://doi.org/10.2134/jeq2005.0156 CORRENDO, A. A., RUBIO, G., GARCIA, F. O. & CIAMPITTI, I. A. 2021. Subsoil-potassium depletion accounts for the nutrient budget in high-potassium agricultural soils. Scientific reports, 11, 11597. https://doi.org/10.1038/s41598-021-90297-1 DOKBUA, B., WARAMIT, N., CHAUGOOL, J. & THONGJOO, C. 2021. Biomass productivity, developmental morphology, and nutrient removal rate of hybrid napier grass (Pennisetum purpureum x Pennisetum americanum) in response to potassium and nitrogen fertilization in a multiple-harvest system. Bioenergy Research, 14, 1106-1117. https://doi.org/10.1007/s12155-020-10212-w GALINDO, F. S., BUZETTI, S., TEIXEIRA FILHO, M. C. M., DUPAS, E. & LUDKIEWICZ, M. G. Z. 2018. Dry matter and nutrients accumulation in mombasa guineagrass in function of nitrogen fertilization management. DOI: 10.32404/rean.v5i3.2132 GALINDO, F. S., DELATE, K., HEINS, B., PHILLIPS, H., SMITH, A. & PAGLIARI, P. H. 2020. Cropping system and rotational grazing effects on soil fertility and enzymatic activity in an integrated organic crop-livestock system. Agronomy, 10, 803. https://doi.org/10.3390/agronomy10060803 KOULIBALY, B., DAKUO, D., TRAORÉ, O., OUATTARA, K. & LOMPO, F. 2017. Long-term effects of crops residues management on soil chemical properties and yields in cotton-maize- Sorghum rotation system in Burkina Faso. Journal of Agriculture and Ecology Research International, 10, 1-11. https://doi.org/10.9734/JAERI/2017/31178 LIEBIG, M., HENDRICKSON, J., ARCHER, D., SCHMER, M., NICHOLS, K. & TANAKA, D. 2015. Short‐term soil responses to late‐seeded cover crops in a semi‐arid environment. Agronomy journal, 107, 2011-2019. https://doi.org/10.2134/agronj15.0146 MCLAUCHLAN, K. K., HOBBIE, S. E. & POST, W. M. 2006. Conversion from agriculture to grassland builds soil organic matter on decadal timescales. Ecological applications, 16, 143-153. https://doi.org/10.1890/04-1650 NASCENTE, A. S., LI, Y. C. & CRUSCIOL, C. A. C. 2013. Cover crops and no-till effects on physical fractions of soil organic matter. Soil and Tillage Research, 130, 52-57. https://doi.org/10.1016/j.still.2013.02.008 NGOC, T. T. B., GIANG, N. T. T., THAO, H. X., HANG, D. T. T., PHUONG, N. T. M., TRIANA, N., PETERS, M., DUNCAN, A. & ATIENO, M. 2023. Assessment of feed resources availability and use for cattle and pigs in Mai Son District, Son La Province, Vietnam. https://hdl.handle.net/10568/134570 POKHREL, S., KINGERY, W. L., COX, M. S., SHANKLE, M. W. & SHANMUGAM, S. G. 2021. Impact of cover crops and poultry litter on selected soil properties and yield in dryland soybean production. Agronomy, 11, 119. https://doi.org/10.3390/agronomy11010119 PURNAMASARI, L., ROSTAMAN, T., WIDOWATI, L. & ANGGRIA, L. Comparison of appropriate cation exchange capacity (CEC) extraction methods for soils from several regions of Indonesia. IOP Conference Series: Earth and Environmental Science, 2021. IOP Publishing, 012209. DOI 10.1088/1755-1315/648/1/012209 SARKAR, R., CORRIHER-OLSON, V., LONG, C. & SOMENAHALLY, A. 2020. Challenges and potentials for soil organic carbon sequestration in forage and grazing systems. Rangeland Ecology & Management, 73, 786-795. https://doi.org/10.1016/j.rama.2020.04.002 https://doi.org/10.32404/rean.v5i3.2132 https://doi.org/10.3390/agronomy10060803 https://doi.org/10.9734/JAERI/2017/31178 https://hdl.handle.net/10568/134570 https://doi.org/10.3390/agronomy11010119 https://doi.org/10.1016/j.rama.2020.04.002 SLSO 2022. Socio-economic situation of Son La province in March and first quarter of 2022. Son La: Son La Statistical Office. https://fileportalcms.mpi.gov.vn/TinBai/DinhKem/53701/132BC-CTK.pdf SUNDARAM, M., SIVAKUMAR, T., SANKARAN, V., RAJKUMAR, J. & NISHANTH, B. 2012. Farming forage crops for improving soil organic carbon stocks in agricultural lands. Int. J. Res. Biol. Sci, 2, 116-119. https://www.semanticscholar.org/paper/ISSN-2249-9687-Original- Article-FARMING-FORAGE-FOR-Sundaram- Sivakumar/3360d256abfab8d0913196c5371f118718ef3e04?utm_source=direct_l ink TIEN, T. M. 2019. Bản đồ nông hóa vùng sản xuất nông nghiệp tỉnh Hải Dương. Viện Thổ nhưỡng Nông hóa (Soil and Fertilizer Research Institute). WELSH, C., TENUTA, M., FLATEN, D., THIESSEN‐MARTENS, J. & ENTZ, M. 2009. High yielding organic crop management decreases plant‐available but not recalcitrant soil phosphorus. Agronomy Journal, 101, 1027-1035. https://doi.org/10.2134/agronj2009.0043 https://fileportalcms.mpi.gov.vn/TinBai/DinhKem/53701/132BC-CTK.pdf Annex 1: Plant height of the varieties throughout the cuts in 2023 and 2024. Forage varieties Plant height (cm) Growth speed (cm/day) Wet season (May-Oct 2023) Dry season (Nov 2023 – Apr 2024) Wet season (Aug-Sep 2024) Dry season (Nov 2024) Wet season Dry season 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th Mun River Guinea 106.4 100.9 81.8 46.0 33.4 20.9 20.5 159.9 78.6 59.4 1.8 0.7 Mombasa Guinea 126.8 103.9 87.5 44.7 30.9 21.7 23.4 152.6 95.0 66.7 2.0 0.7 Mulato II 68.0 74.3 48.9 28.8 20.7 14.5 14.8 100.2 41.3 42.8 1.1 0.4 GE grass 135.9 137.6 112.8 53.1 34.2 26.4 28.3 199.3 91.4 108.7 2.4 0.8 Maize NK7328 152.1 199.4 67.1 56.1 71.0 0.0 0.0 164.7 164.7 0.0 2.0 0.7 Ubon Stylo 45.0 103.5 144.9 0.0 6.3 18.3 17.6 108.6 42.6 82.4 0.8 0.2 Rice bean 103.8 137.8 167.8 0.0 0.0 0.0 0.0 96.6 108.0 169.8 1.7 - VA06 163.5 97.3 99.7 53.2 37.9 22.2 24.6 183.7 74.7 99.1 2.7 0.8 Trong Hieu Do Tien Sinh Nguyen Thi Thu Hang Dao, h.dao@cgiar.org Thi Bich Ngoc Tran, Michael Peters, m.peters-ciat@cgiar.org Mary Atieno, mary.otieno@cgiar.org CGIAR is a global research partnership for a food-secure future. CGIAR science is dedicated to transforming food, land, and water systems in a climate crisis. Its research is carried out by 13 CGIAR Centers/Alliances in close collaboration with hundreds of partners, including national and regional research institutes, civil society organizations, academia, development organizations and the private sector. www.cgiar.org We would like to thank all funders who support this research through their contributions to the CGIAR Trust Fund: www.cgiar.org/funders. To learn more about this Initiative, please visit this webpage. To learn more about this and other Initiatives in the CGIAR Research Portfolio, please visit www.cgiar.org/cgiar-portfolio © 2024 Alliance of Bioversity International & CIAT. Some rights reserved. This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 International Licence (CC by 4.0). | | | http://www.cgiar.org/funders https://www.cgiar.org/initiative/sustainable-animal-productivity/ http://www.cgiar.org/cgiar-portfolio https://creativecommons.org/licenses/by/4.0/ https://twitter.com/CGIAR?ref_src=twsrc%5Egoogle%7Ctwcamp%5Eserp%7Ctwgr%5Eauthor https://www.facebook.com/onecgiar/ https://www.linkedin.com/company/cgiar https://www.youtube.com/channel/UCYuSEwWKAsoNwg6MJEI-qeA Contents List of Table and Figure 1. Introduction 2. Methodology 3. Results and discussion 3.1. Performance of Forage Crops 3.2. Impacts of the forages on Soil Health 3.3. Feedback from Farmers and Local Stakeholders 4. Conclusion 5. References Annex 1: Plant height of the varieties throughout the cuts in 2023 and 2024.