Sedi Reconnaissance Survey

sedi study area

A Reconnaissance Survey of the Agricultural Practices and Resource Management of the Sedi Gau Area of Pokhara, Nepal.

Objectives

The primary purpose of this report was to provide the author with a starting point from which to build a more comprehensive overview of the practices and resources available to agriculturalists in Nepal.

Duration: The survey was undertaken during the month of December 2017

Disclaimer

This report has been produced by and for the benefit of the author. It has not been commissioned, sponsored or endorsed by any agency within or outside of Nepal. It is the authors personal view and observations and any actions undertaken by any third party on the basis of this report are done so at that parties own risk and without liability or recourse to the author.

1.0 Background

1.1 Nepal: The Federal Democratic Republic of Nepal is a secular South Asia state. Divided into seven regional districts it has a total population of 28.17 million[1] (Nepal Population Report 2016). Tourism (46%) and Agriculture (38%) are responsible for generating the majority of the countries GDP with the remainder being contributed by Industry (15%) [2] (Nepal investment guide 2016).

1.1.1 Geography: A mountainous landlocked country Nepal lies at a latitude of 26.3 and 30.5 degrees North and a longitude of 80 and 88.2 degrees East. Approximately 800 kilometres long and 200 kilometres wide Nepal is roughly trapezoidal in shape. Covering an area of 147,181 km2 Nepal has a south facing aspect as the land rises from 59m in the south to over 8800m (mt Everest) in the north.[3] (Wikipedia).

1.1.2 Climate: Nepal experiences three distinct climatic zones differentiated by altitude: a lower Terai region (below 700m) that has a sub-tropical climate, the main central Hilly region (700m to 3000m) which experiences a moderate temperate climate and the high Mountain region to the north (above 3000m) which is alpine [2] (Nepal investment guide 2016)

1.1.3 Resources: Land, Water, Soil, Mineral, Ecological [To Be Researched]

Pokhara
Pokhara utilitarian area

1.2 Pokhara: Lying in the northwestern corner of the Pokhara Valley the city of Pokhara is the largest city by area (464.24 km2) and second largest by population (320,000) [table:1]. ‘The provincial capital of district number 4 and the headquarter of Gandaki Zone and Kaski District.’ [Wikipedia]

Extending along the banks of the Seti Gandaki river and along the eastern and northern shores of the Phewa lake. The city lies in the foothills of the Hilly region (800m to 1700m) where it experiences mild temperatures with high annual precipitation (3900mm) [table:1].

Table 1

1.2.1 Tourism: As the starting point for the Annapurna circuit and mountain conservation area hiking Pokhara is popular with tourists who come for the lakes, the scenic beauty, trekking and outdoor activities.

1.2.2 Agriculture: Agriculture in Pokhara takes place on the lower flooded plains of the lakes and upon the south facing terraces rising up the steep mountain slopes. On the flood plains standing water limits the agricultural use to paddy rice and rough grazing. On the mountain terraces the sub tropical climate and range of altitudes permit all year round cultivation of tropical and temperate crops. The lakes also support aquaculture (fish farming) and apiculture is also practised by small holders.

1.2.3 Environment: The lakes, the mountains that feed the lakes, the forests that clad the mountains and the wildlife that inhabits the forests are what attracts tourists to Pokhara and Nepal in general. This natural environment however competes with agriculture for access to resources (i.e. land and water), whilst crop choices and management techniques (i.e. herbicides and pesticides) can have adverse impacts on flora and fauna diversity. Poor use of manures and fertilisers coupled with poor soil husbandry can further lead to erosion and run off that degrades the donor land and pollutes any receiving rivers and lakes.

Sedi Gau Study Area

2.0 The Sedi Gau Study Area: Bound to the West by the Trug Khola, an ephemeral monsoon river that feeds the Phewa lake, to the East by a natural tree covered ridge and to the North by a dirt road the study area compromised of a mix of used and abandoned terraces above the flood plain of Sedi Bagar.

2.1 Soil Resources : Within the study area three agricultural sites were chosen for analysis of soil texture, pH and WHC.

Note: All field and analytical methods used in survey from D.L. Rowell, Soil Methods and Applications, Longman (1994) ISBN O 582 087848

2.1.1 Site A : Consisted of seven terraces (A-G) below Gorgeous Village Guest house. Rising 11m and 100m in length the 7 terraces covered a surface area of approx. 1500m2. Cultivated by draft animal and rain fed, a typical cropping cycle involved winter mustard (90 days), spring maize (60 day) and summer paddy rice (100-120 days). Three transects at approximately ¼, ½ and ¾ along and down the terraces were sampled. From each terrace a sample was taken for moisture content, texture and pH analysis. [table.2]. The width, height and a crude % veg cover of the supporting wall of each terrace was also recorded.

2.1.2 Sites B and C :Both sites B and C were part of a single horticultural enterprise.

Site B: Approximately 10m below Site A consisted of a long mechanically cultivated and irrigated terrace of 600m2 (10m x 60m). Divided into two by a low wall it was used for mixed cropping of horticultural crops (currently onion and garlic). Both sections were sampled for moisture content, texture and pH using a standard ‘W’ sampling strategy. [table 3]

Site C: consisted of four tunnels approximately 2m and 4m below Site B and covering an area of 750m2. Each tunnel contained five drip irrigated beds approximately 1m wide. Typical cropping cycle: all year round tomato, climbing beans, lettuce, basil. Three samples from beds 2 and 4 in the top east and bottom west tunnel were taken for moisture, texture and pH [table 3]

Table 2
table 3

2.1.3 Soil Texture: The dominant soil texture was silty loam with Site B having a slightly higher clay content. A sample from site A terraces was air dried and sieved through 2mm, 0.2mm and 0.06mm to yield a dry sieve PSD . The course and fine sands were then washed, dried and reweighed.

FRACTION DRY SIEVED WASHED

2.1.4 Soil Water: An estimation of the soils transmission and storage porosity was made using a sample of field soil that had been flooded. Three 100g samples were taken 1 hour after all surface water had drained and again 24 hours later. The samples were then air dried for 5 days, re-weighed and then passed through a 2mm sieve to remove any stones. Note: residual porosity was not measured (lack of a suitable oven) and so a value of 17.5% (typical for a silt) was assumed. [table. 4]

table 4

A silty clay would typically have 10-15% transmission, 20-25% storage and 15-20% residual pores with a total porosity of 45-55%. At field capacity the volumetric water content in an unstructured silty clay soil would typically be 44% (0.44cm3 cm-3) by volume with just 16% (0.16cm3 cm-3) easily available to plants (Rowell 1994). It is likely that 24 hours was insufficient time for the soil to drain to field capacity, hence the distribution of 7% transmission, 28% storage in the results.

2.1.5 Soil pH: A well balanced mineral soil should have a pH of between 6.5 and 6.7. Soils with a pH below 6.0 are likely deficient in basic cations and this should be addressed with mineral additions to raise the pH to the target level. Soils are though buffered against changes with heavy (clay) textured soils having buffer capacities as high as 8t CaCO3 ha-1 pH-1 and light textured (sandy) soils as low as 2t CaCO3 ha-1 pH-1. As the buffer capacity of the terraces silty soils was unknown a buffer curve was derived using the method described in Rowell (1994)

2.1.6 Buffer Capacity: The air dried and 2mm sieved transect samples were combined, with the lowest (T1A, T2A, T3A, T3E) and highest (T1C, T2G, T3G) excluded to create a sample with uniform texture (ZL)and pH (pH5.4). Once mixed 5 plastic bags were filled with 110g of soil. 10g was then removed from each bag and the pH measured before 0.2, 0.4, 0.6, 0.8 or 1g Ca(OH)2 was added and thoroughly incorporated in each bag. The bags were then moistened to 40% WHC with 25ml of distilled water and then allowed to equilibrate for 10 days [table 5]

table 5

The buffer capacity for the terrace soils was estimated to be higher than it was and ideally the procedure should be repeated using 0.1g increments . The results suggest a buffer capacity of

2.0g Ca(OH)2 kg-1 pH-1 ( 2.7g CaCO3 kg-1 pH-1)

2.1.7Soil Organic Matter: Soil Organic Matter content was not measured but approximated from the addition of fresh buffalo manure and crop residues during the survey. Manure was applied and incorporated at a rate of 3.5kg m2 immediately prior to the sowing of mustard. Practised three times a year (prior to each sowing) then 10kg fresh manure m2 is applied each year (100t ha-1 an-1) . However as the manure is fresh (under 4 months old), 80% or more of it’s mass is likely water . The SOM value is therefore closer to 2kg m2 (20t ha-1 an-1). Assuming residual crop material and roots double this input then annual SOM additions is below 50t ha-1 an-1 (1.5%).

2.1.8 Redox Potential: It was not possible to measure the Redox potential as the necessary equipment ( Platinum and Calomel electrodes) were not possessed. However with the high summer rainfall and cultivation of paddy rice the soils experience prolonged anerobic conditions. Whilst beneficial for rice production the practice of flooding and puddling the terraces destroys soil structure and porosity to the detriment of following crops. Whilst it slows down oxidation of organic carbon and the evolution of CO2 the mechanisms by which the anerobic bacteria obtain energy under flooded conditions results in the evolution of methane, a greenhouse gas 200 times more potent than CO2.

2.2 Water Resources

2.2.1 Precipitation: Pokhara has a high annual rainfall of 3900mm. The highest precipitation (600-900mm per month) occurs during the monsoon period from June to September. November through to January are typically dry with less than 25mm per month [table 1].

2.2.2 Surface Water: There was no natural surface water on any of the terraces with all of them designed to drain in the broad direction of the ephemeral Trug Khola. Only on site B and C was there storage facilities: a 50,000ltr (6m x 6m) concrete storage tank immediately west of the covered crops and used to irrigate Site B; and two 1000ltr storage tanks used to drip irrigate the covered crops.

2.2.3 Ground Water: A recent bore hole sunk to supply the toilets of a new cable car being constructed approximately 20m below site C (but on the opposite side of the Turg Khola, so outside the study area) and 60m above the lake reached a depth of 230m before finding an aquifer capable of delivering the 11000ltrs of water required. Given the high annual rainfall and mountainous terrain one would expect water to be present at much shallower depths and certainly not 150m below the level of the Phewa lake.

2.2.4Irrigation: With less than 25mm of precipitation for the months of November – January irrigation is essential if crops are to avoid drought stress. Communal water is supplied via a pipe that leads from the foot of a waterfall at the start of the Trug Khola river some 100m or so above Site A (no measurements were taken). The pipe supplies numerous properties down the hill and whilst used for irrigation has limited use without separate storage facilities.

Site A had no storage facilities and irrigated directly from a hose pipe with a restricted flow. Site B with storage facilities irrigated using both a sprinkler and with a hose pipe. On Site A irregular irrigation led to over and under watering simultaneously on the same terrace. On site B the storage facility simple encouraged over watering and flooding on a grander scale.

The the pH of the irrigation water was measured on both site A and Site B and directly from the source at the foot of the falls. The measurements ranged from pH7.8 – pH8.0. The cause of the alkalinity was not known.

2.3 Land: Land in this report includes the whole surface area, the vertical walls as well as horizontal surfaces of terraces. It includes land covered by water as well as drainage channels, banks and any outcrops of rock.

Site A covered a surface area of approximately 1500m2. The supporting walls covered an area of approximately 1000m2. Thus on site A there was a total of 2500m2 of land, of which 60% was covered by soil and cultivated and 40% by drystone wall, 50% of which had been naturally colonised by herbs and grasses. These herbs and grasses were now being cut and used as animal fodder. So whilst not counted as a resource the dry stone walls represented 1000m2 of land used as rough grazing.

Site B’s supporting terrace wall (approximately 2m high) and representing an area of 100m2 had not been colonized by vegetation and was obscured by the placement of the covered tunnels to which it offered protection.

Site C’s terrace walls were not assessed.

2.4 Livestock: Nearly all the small holders keep some livestock for both dairy and manure production. All kinds of fowl including chickens, ducks and geese are similarly kept as are bees.

2.4.1 Dairy: Within the whole study area 6 Buffalo, 4 cows and half a dozen goats were kept for dairy production. The animals were housed and fed with forage gathered from the terrace walls, banks and forests and their manure applied directly to the land. Withing the study area but not on the field sites animals were seen to freely roam and browse the terrace walls on the fallow rice terraces below Site C.

2.4.2 Apiary: Eight honey bees hives were maintained on and around the terraces of site A. The main source of forage for the bees being the forested area above and the flowers and shrubs on the walls of the terraces below.

2.4.3 Other: Poultry: A few chickens were kept on site B

Dogs: 2 dogs were kept on site A

2.5 Environment: During the period of the study an assessment of species diversity of the small fauna was undertaken. The assessment involved the recording (photographing) of the insects, mainly butterflies, and birds that frequented the field sites. The diversity of both these animals relies on a varied and rich ecosystem and thus they serve as good ‘indicators’ of the relative diversity and general health of the environment.

Over the study period approximately 20 different bird species, including waders, raptures, nectar, seed and insectivores and over 50 species of Butterflies and moths were recorded. There were as many if not more birds and butterflies spotted but because of their habit of not resting long enough to be photographed they were only observed. In addition bark lice were found grazing on the algae of rocks in the Trug Khola, two species of lizard, frogs, fish, a bat and several beetles and crickets were also captured on camera.

No assessment of the native/wild flora was carried out but Brugmansia ‘angels trumpets’, a South American ornamental shrub was noted as prevalent and potentially invasive.

2.6 Summary

2.6.1 Soil texture: The terrace soils are poorly structured acid silts, prone to water logging and weakly buffered against changes in pH. They have the physical disadvantages of clay and the buffer capacity of sand.

2.6.2 Soil pH: The mean soil pH was: pH 5.4 Site A, pH6.0 Site B and pH 5.5 Site C. The slight rise in pH of site B was not determined but possible causes include: higher redox potential (a consequence of being maintained in a more flooded state than either the upper terraces of Site A or the covered crops of site C), a slightly higher clay content (giving rise to a stronger buffer capacity), or the historical addition of basic minerals. Furthermore the soils may not have all arisen in situ but may have been created using silts transported up from the lake and lower flood plain. Signs of Calcium and/or Magnesium deficiency were present in basil growing on site C. The leaf of the tomato on Site C appeared small, as did the heads of lettuce and cauliflower curds growing on site B. This may have been varietal traits but as all the crops observed appeared retarded it is as likely an expression of calcium deficiency, the soils low porosity, lack of structure or a combination of all three.

2.6.3Soil Organic Matter (SOM): Whilst not directly measured the organic inputs observed during the study suggested SOM levels to be low (1- 3%).

2.6.4 Soil Water: The cultivation of paddy rice and the practice of flooding following horticultural crops has negative impacts on the soil structure and hence the availability of water and oxygen to crop roots.

2.7 Recommendations

2.7.1 Adjust pH:With both Site A and Site C having acid conditions (pH 5.4) addition of lime as Calcium Carbonate (CaCO3) or (as would be more beneficial) Dolomite Lime (CaMg(CO3)2) is recommended.

The low buffer capacity on the terrace soils of Site A (2.7g CaCO3 kg-1 pH-1) is likely duplicated on site C and or slightly higher on site B. A ll three can be treated as having the same buffer capacity.

Site A and Site C require the pH to be increased by one point (pH 5.5 – pH 6.5). For Site B that aim is to raise it half a point, (pH 6.0 to pH 6.5) . Assuming a dry bulk density of 1.5g cm3 a square meter to a depth of 20 cm would have a dry mass of 30kg . To achieve an increase of 1.0pH point on site A and Site C and half a pH point on site B to a raise pH to a target pH 6.5 would require the application CaCO3 or as recommended Dolomite Lime at rates of:

Site A and Site C (to raise pH one point) : 80g (CaMg(CO3)2) m2 (2.5kg Aana)

Site B (to raise pH half a point) : 40g (CaMg(CO3)2) m2 (25kg 600m2)

Six months following application the pH should be retest to ensure the target pH has been reached.

The rate of the neutralising effect will though depend on the particle size of the liming material used. However given the low buffer capacity of the soil an application of relatively course grade material will still produce results in a reasonable response time (under 6 months).

2.7.2 Improve Soil Structure: SOM values for most agricultural mineral soils are typically below 3% with the optimum or target value being 5% (200t ha-1 an-1). Approximately 20t ha-1 an-1 of OM was provided by buffalo manure and another 20t ha-1 an-1 was potentially contributed from crop residues and roots providing a net annual input of 1.5% OM. With such low inputs alternative sources of OM need to be sourced. Options include:

.2.7.2.1 Bulky Organic Manures:

Green manuring: The growing of a crop to cut and incorporate into the soil. The crop may be grown in-situ where it’s roots as well as it’s aerial parts will contribute to the soils organic matter content, or as with Russian Comfrey (2.7.3) in a permanent stand where it is cut and the leaves transported to the field site.

Composting: The controlled process by which the breakdown of organic matter is accelerate to produce a more uniform, weed and pathogen free manure in which the nutrients have been made more available.

For more information visit the compost science pages on the main phasm site

Marling: Whilst the soils have some of the physical properties of a clay the actual clay content is likely low. If calcareous clays deposits exist in Nepal then Marling (adding ‘Marls’ calcareous clays) would improve soil structure and raising both the cation exchange and buffer capacities. The potential for marling though depends on sufficient and accessible deposits of Marls being relatively localized (i.e. in Nepal).

Gypsum (Calcium and Magnesium Sulphate CaSO4, MgSO4 ): Whilst generally of benefit on clay ‘blocky’ lands, where Gypsum aids flocculation and colloid formation, it’s addition, particularly to soils with a texture of silty clay loam, may also help to breakdown soil clods and improve soil structure. The benefits of gypsum to a Silty Loam is though unknown.

2.7.3 Managing Terrace Wall for fodder, honey and compost production

More than 50% of the 1000m2 of terrace walls on site A had been colonised by perineal species which were now harvested as forage crops for dairy animals (buffalo). The banks also serve as a source of flower forage for the apiary operation. Consideration should be given to managing and enhancing the flora on the terrace walls in order to provide improved forage for buffalo and bees and or organic material for composting and green manuring.

Potential species include:

Lolium perenne(Perennial Rye Grass)

A commercial high forage value grass that can also be used as a compost additive or green manure/mulch.

Trifolium repens (White Clover)

A high protein legume valued for its bovine forage benefits, it’s white flowers which are favoured by honey bees and it’s nitrogen fixing abilities. Can also be cut and used as a compost ingredient.

Symphytum Uplandicum (Russian Comfrey bocking 14)

A fast growing perennial popular with organic farms where it is used as an ingredient in compost manufacture, green manure and to produce liquid feed for tomato’s. Can also be used as fodder. It’s white flowers are similarly attractive to bees. The bocking 14 strain is also sterile and can only be propagated by root cutting so posses no risk of escaping into the environment.

The above plants are examples only. They have been chosen for their known benefits and the likelihood that they are native or naturalized and commonly used in grassland management in Nepal or, as with Russian Comfrey bocking 14, sterile and so pose no risk to native flora or environments. Further research into the forage and compost benefits and potential impacts (i.e. wall damage from roots) of any plants should be undertaken before any seeding program commences.

2.7.4 Improve irrigation practices: Poor and irregular irrigation on the upper terraces (site A) and excessive irrigation on Site B were two good examples of bad practices. Irrigation systems should be designed that operate within the boundaries of the soils hydrological properties (permeability, Water holding capacity, drainage characteristics). Consideration should be given to creating Soil Moisture Deficit charts so as to determine the quantity of irrigation water needed to raise the soil moisture to field capacity. The aim should be to deliver not too little, not too much, not too fast.

2.7.5 Adopt appropriate technology: Whilst the terraces on site B were accessed and cultivated mechanically the terraces of site A were too narrow for even small machinery to cultivate, and were instead cultivated using oxen and yoke: itself a struggle. The terraces could perhaps be better and more easily cultivated using a spade or a fork. Likewise manures would be better and more easily spread and incorporated with a fork or muck spreader than with bare hands. The use of the appropriate tools (hoes and hand forks) would similarly improve the efficiency and quality of weeding.

2.7.6 Develop Market Gardening: The mild climate and southern aspect of the terraces make them ideal for adopting intensive market gardening and nursery practices. Through the use of module raised seedlings, nursery beds, cold frames and inter-cropping techniques all year round production of horticultural crops could be maintained. With complimentary and good soil husbandry, irrigation and weeding practices yield responses could be increased considerably.

However the production of paddy rice, which requires flooded soils to thrive, conflicts with the soil requirements of horticultural crops which require free draining and well aerated soils. Consideration should be given to switching to dry rice, which does not require flooding, or abandoning rice as a crop on the higher terraces and concentrate on building good soil structure for horticultural crops. With the mild climate and the adoption of new and old methods of soil and crop husbandry one hectare of land could be made to yield three times or more the yields under current management practices.

3.0 Conclusions: Improved soil husbandry, better resource management, improved crop/varietal choices and the adoption of appropriate technology will all lead to more sustainable and productive terraces. Raising the pH through basic mineral additions [2.7.1] and developing composting system [2.7.2] in particular will lead to early and noticeable soil improvements that will be realized through subsequent crop quantity and quality. Irrigation done at a rate and duration that does not exceed the permeability and water holding capacity of the soil will also aid root development instead of starving roots of essential oxygen and stunting their growth. The use of hand tools for both soil maintenance (forks, spades and muck spreaders) and crop management (hoes, hand forks) would easy and improve the execution and efficiency of both tasks resulting in bigger and higher quality crops for less physical effort.

4.0 Future Work:

Extend research to whole catchment area East of and feeding the Trug Khola and asses texture and pH on all terraces

Measure redox, CEC and % base saturation. Measure SOM

Measure soil hydrological properties (soil tension/release curve/pore distribution) and create Soil Moisture Deficit charts for catchment

Research hydrology & map/audit hydrological resources (surface water, rivers, springs, wells) for whole catchment area

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