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Journal of Environmental Management 88 (2008) 547–555

www.elsevier.com/locate/jenvman

Developing a sustainable agro-system for central Nepal usingreduced tillage and straw mulching

Kishor Atreyaa,�, Subodh Sharmab, Roshan M. Bajracharyab, Neeranjan P. Rajbhandaric

aAlternative Development and Research Center (ADRC – Nepal), GPO Box 20078, Kathmandu, NepalbDepartment of Environmental Science and Engineering, Kathmandu University, Nepal

cSustainable Soil Management Program, Helvetas, Kathmandu, Nepal

Received 19 March 2006; received in revised form 24 February 2007; accepted 16 March 2007

Available online 3 May 2007

Abstract

In Nepal, soil erosion under maize (Zea mays) agro-ecosystems is most critical during the pre-monsoon season. Very few field

experiments have been conducted on reduced tillage and rice straw (Oryza sativa) mulching, although these conservation approaches

have been recommended. Thus, a five replicate field experiment was established in 2001 at Kathmandu University (1500m above sea

level) on land with18% slope to evaluate the efficiency of reduced tillage and mulching on soil and nutrient losses and maize yield. The

results showed non-significant differences among conservation approaches on runoff and maize yield. Mulching and reduced tillage

significantly lowered annual and pre-monsoon soil and nutrient losses compared to conventional tillage. Soil organic matter (SOM) and

nitrogen losses associated with eroded sediment were significantly higher in conventional tillage. However, due to limited availability and

high opportunity cost of rice straw, reduced tillage would be a better option for soil and nutrient conservation without sacrificing

economic yield in upland maize agro-ecosystems.

r 2007 Elsevier Ltd. All rights reserved.

Keywords: Himalayan region; Mulching; Reduced tillage; Residue; Runoff; Soil erosion

1. Introduction

Accelerated soil erosion has been a chronic problem eversince the dawn of settled agriculture and has adverseeconomic and environmental impacts (Lal, 1998). Forrainfed agro-ecosystems in Nepal, soil erosion is mostsevere during the pre-monsoon season (Ries, 1995; Schreierand Shah, 1995; Sherr and Yadav, 1996; Tripathi et al.,2000a; Schreier et al., 2001; Atreya, 2002; Gardner andGerrard, 2003; Atreya et al., 2006). During the pre-monsoon season, rainfall events tend to be of high intensityaccompanied by strong winds and occasionally hail.Further, before the onset of pre-monsoon, the agriculturallands are tilled several times, which makes soil dry, bareand devoid of vegetative cover. Thus, soil and nutrientlosses from the upland terraces are usually high even beforethe onset of actual monsoon. Gardner and Gerrard (2003)

e front matter r 2007 Elsevier Ltd. All rights reserved.

nvman.2007.03.017

ing author. Tel.: +977 1 6211252.

ess: k.atreya@gmail.com (K. Atreya).

clearly state that ‘‘in the case of middle hills, [soil andnutrient] losses will be seriously underestimated if the smallnumber of high magnitude storms in late April and Mayafter plowing but before development of weed cover, arenot measured’’. The rate of soil loss gradually diminishes asthe soil cover from maize (Zea mays) crop and othervegetation increases following the onset of the monsoonseason.There is a growing literature that indicates conventional

tillage to be the dominant practice leading to acceleratingsoil erosion especially in slopping farms of the Himalaya.In the Indian Himalaya, Sharma et al. (2001) and Jain et al.(2000) found very high rates of overland flow, soil andnutrient losses from bare agricultural fields followingtraditional practices compared to other land uses. InNepal, the tillage intensity is a major factor that enhancessoil erosion during pre-monsoon in upland agro-ecosys-tems. Thapa (1996) argues that farmlands have beenundergoing unsustainable rates of soil erosion and soilnutrients depletion due to frequent hoeing and plowing.

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Fig. 1. Location of the study area.

K. Atreya et al. / Journal of Environmental Management 88 (2008) 547–555548

Farmers believe that the exposure of land to the sun, rainand air for a long period helps to improve soil fertility(Thapa and Poudel, 2002). Therefore, they plow landsimmediately after the harvest of crops and leave themexposed without any vegetative cover. Atreya et al. (2006)pointed out that Nepalese farmers in central hills till landthree times before maize sowing viz. (i) before the onsetof pre-monsoon season (nearly 2 months earlier, February/March), (ii) after 20–25 days (March/April) of firsttillage, and (iii) at the time of maize sowing, which isafter 2 to 3 pre-monsoon rainfall events (April/May). Dueto this tillage operation, soils become extremely dry anddusty, without any vegetative cover allowing the highintensity pre-monsoon rain wash away a significant portionof top soil.

As alternatives to the conventional tillage system,various studies (Acharya, 1999; Rajbhandari, 2000; Bajra-charya, 2001; Ransom and Rajbhandari, 2001; Gardnerand Gerrard, 2003) reported minimum tillage and mulch-ing to be potential practices for mitigating soil erosionduring pre-monsoon. Tripathi et al. (2000b) also recom-mended developing options such as mulching and reducedtillage in order to enhance sustainability of agriculture inthe Himalaya. Use of crop residue mulch has profoundbeneficial effects on soil properties, microclimates, andagronomic productivity. Mulching conserves soil andwater, improves soil structure, improves soil organic mattercontent, adds cations to the soil, regulates soil temperature,and restore the productivity of degraded lands (Srivastavaet al., 1993). Mulching dissipates raindrop energy andthereby decreases soil detachment. It also encouragesinfiltration rates by minimizing surface sealing, and thusreduces runoff and soil loss (Adekalu et al., 2007). Edwardset al. (2000) reported that mulching of barley (Hordeum

vulgare) straw at 4 t/ha reduced soil loss by almost 50%compared to control. Tolk et al. (1999) also noted thatmulching at 6.7 t/ha increased grain and stover yields ofmaize by 17% and 19%, respectively, compared to baretreatment. Similarly, Smolikowski et al. (2001) and Bartonet al. (2004) also reported reduced runoff and soil loss bymulching, but no effects on crop yields. Reduced tillagealso decreases runoff through reducing surface crustingand increasing infiltration (Cassel et al., 1995; Acharya,1999; FAO, 2000). The practice of crop residue retentionand minimum tillage, in association with basal fertilizerapplication, increases the supply of carbon, nitrogen andenhances the degree of synchronization between cropdemand and nitrogen supply. Kushwaha and Singh(2005) pointed that retention of a small fraction ofabove-ground biomass and its incorporation in the soilthrough minimum tillage enhances crop productivity andsoil fertility in a cereal based tropical dry land agro-ecosystem.

The practice of covering the plowed land by cropresidues for soil and nutrient conservation has beendocumented in hills of Nepal (Paudel and Thapa, 2001;Khanal and Watanabe, 2006). However, only farmers with

a relatively large household size and small land holdingsused this method as availability of residue was a constraintfor others (Paudel and Thapa, 2001). Applications ofmulching and reduced tillage for soil and nutrientconservation during the pre-monsoon season have beenrecommended as potential researchable options in Nepal.However, to date very few field experiments have beenconducted on reduced tillage and rice-straw (Oryza sativa)mulching. Further, crop yield in sloping upland has been indecline in most areas, at the same time farmers continue tocultivate despite negative benefit–cost ratios as there arefew other alternatives for livelihood. There is an urgentneed to increase/stabilize crop yields and reverse this trend.Therefore, this study evaluated the effect of the twoconservation practices, namely reduced tillage and mulch-ing on soil and nutrient losses and maize yield in maize –mustard (Brassica juncea) and maize+soybean (Glycine

max) – mustard agro-ecosystems.

2. Materials and methods

2.1. Runoff plots and experimental design

Twelve runoff plots (two replicates), each of 6m� 3mwith an average slope of 18% and northeast aspect, wereestablished within the Kathmandu University premises(1500m above sea level) to measure soil and nutrient lossesand crop yield during 2001. Another 18 productivity plots(three replications) were also setup in nearby farmers’ field,each of dimensions 3m� 3m, for crop yield only. This wasdone basically to increase the replication and thus, tominimize the experimental errors for crop yield. It shouldbe noted that the university is situated in a rural area, inKavreplanchowk district of Nepal (Fig. 1) and theexperimental site was farmed by locals in a traditionalmanner. The runoff plots were bordered by galvanized ironsheets, 20 cm into the soil to prevent horizontal movementof soil water and 25 cm above the ground to check soilparticle splash between plots. The collection system ofrunoff plots consisted of two drums at the low end of eachplot connected with a five-slot splitter that drains one-fifthof the runoff into the second drum (see Fig. 2). Thesediment mixture of the collection drums were stirredvigorously before sampling after each storm generating soilloss. Each sample was filtered using Whatman No. 42 filter

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paper, oven dried at 105 1C for 24 h, for calculation ofsoil loss. These oven dried samples were used for soilnutrient analysis.

The experiment was conducted as a factorial randomizedcomplete block design. The three main factors wereconventional tillage (CT), CT with rice-straw mulching(5 t/ha), and reduced tillage (RT). Main plots were split onthe basis of cropping pattern, i.e., maize mono-croppedand maize and soybean mix-cropped, i.e., grown simulta-neously. Thus, there were altogether six treatments viz.(1) conventional till, sole maize, (2) conventional till,maize+soybean, (3) conventional till and mulching, solemaize, (4) conventional till and mulching, maize+soybean,(5) reduced till, sole maize, and (6) reduced till, maize+soybean.

2.2. Benchmark soil properties of the runoff and productivity

plots

A baseline of soil physical properties of the runoff plotswere established at the inception of the experiment forfuture comparison during monitoring of soil and nutrientlosses. Slope and aspect, soil pH, and soil chemicalparameters like organic matter (OM), total nitrogen (N),and exchangeable potassium (K2O) were similar at bothsites, with the exception of available phosphorus (P2O5),which was significantly higher in the productivity plots(Table 1). Based on USDA Soil Taxonomy (SMSS, 1985),soils of the runoff plots were classified as mixed mesic lithic

Fig. 2. Layout of an erosion block and runoff collection systems.

Table 1

Comparison of soil properties of the runoff and productivity plots

No. of plots Aspect Slope (%)

Runoff plots 12 Northeast 16–21

Productivity plots 18 Northeast 12–17

t-test

Note: ns ¼ not significant.

** ¼ significant at probability level of 0.01.

Dystocrept. Soils of the runoff plots were sandy loamhaving dark yellowish brown (10 YR 4/4) surface layer.Soil depth of top layer was 15 cm and that of entire profilewas only 50 cm.The initial gravimetric soil water content,and infiltration rate, determined before the onset of pre-monsoon in the year 2001 were 5.3% and 4.31 cm/h,respectively. Double ring infiltrometer (Gupta, 2000) wasused to determine infiltration due to simplicity and wideadoption even in small areas (Rao and Sharma, 1997).Slopes of erosion plots ranged from 16% to 21%. Bulkdensity was 1.38 g/cm3.

2.3. Soil chemical analyses

The study was concerned with the loss of primarynutrients namely: N, P2O5, K2O and OM. N is the mostimportant limiting nutrient to plant growth and develop-ment in Nepal (NARC, 2000). Due to high solubility andtransport, some researchers (Shah, 1996; Gardner et al.,2000) observed a decreasing trend of K in soils. Brown andSchreier (2000) also found significant deficits in N and P,especially in maize agro-ecosystems. For this study, soil pH(1:1), soil OM (Walkey and Black), total N (ModifiedKjeldahl digestion), available P (Modified Olsen) andexchangeable K (Flame Photometer) of the eroded sedi-ments were analyzed (Farm Resources and SystemsResearch Division, 1980).

2.4. Agronomic practices

Plots under conventional tillage, as generally done bylocal farmers, were tilled thrice (1) before the onset of pre-monsoon season (February/March); (2) after 20–25 days offirst tillage (March/April), and (3) at the time of maizesowing, which is after 2 to 3 pre-monsoon rainfall events(April/May). Plots under mulching were also tilled thrice,and after sowing maize, rice straw at 5 t/ha was surfaceapplied along the slope and straw was incorporated intosoil after first weeding (30 days after planting, DAP). Plotsunder reduced tillage were tilled only once at the beginningby opening narrow furrows across slope using a hand-hoei.e., during maize sowing. First and second weeding(60 DAP) was done in all plots, even in reduced till plots,because here the objective of the reduced tillage was tocheck soil erosion during pre-monsoon rain, which is

pH SOM (%) N (%) P2O5 (kg/ha) K2O (kg/ha)

3.23 0.6142 0.0461 66 330

3.08 0.7889 0.0471 127 421

ns ns ns ** ns

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believed to be most serious in terms of soil and nutrientloss. Farmers in hills of Nepal cultivate land by hand-hoeor ox-drawn wooden plough. Due to the small size of plotsused in this study, a small pointed hand-hoe was employedto till the land. Hand-hoe technique is commonly used onterraces narrower than about 1.5m, or used by thosefarmers who possesses only small parcels of land and donot own oxen (Bajracharya, 2001). Most importantly, thistechnique is used intensively in and around the Kathmanduvalley area including the study site due to religious belief,which does not permit use of oxen for land plow.

Test crops were maize cultivar ‘Arun 2’ and soybeancultivar ‘Ransom’. Maize was planted with 75 cm� 25 cmspacing across slope for all treatments. For the maize+soybean mixed-cropped, soybean was planted in betweenrows of maize, spacing 25 cm, under reduced till and mulchplots. However, in conventional plots, the farmer practiceof planting at random spacing in plots across slope wasfollowed. Test crops were planted on 31 April andharvested on 25 August in 2001, whereas, because ofsufficient soil moisture due to early rain in 2002, crops wereplanted on 10 April and harvested on 9 August. Foradditional details refer to Atreya et al. (2006).

2.5. Data analysis

Statistical analyses were performed using Statistix forWindows, version 2.2 (Analytical Software, 2000). Soil andnutrient losses were monitored only from two replications;therefore, two sample t-test was performed to assess thedifferences between conservation approaches. However,analysis of variance (ANOVA) was also used to describe

0

100

200

300

400

500

600

700

Rain

fall (

mm

)

Jan Feb Mar Apr May June

Mo

Fig. 3. Monthly rainfalls at exp

the differences of treatment means in terms of annualrunoff, soil and nutrient loss and crop yield. Seasonaldynamics of soil and nutrient losses were also describedwith the help of t-test and ANOVA at 0.05 probabilities.

3. Results and discussion

3.1. Precipitation at experimental site

The amount of rainfall received in different months ispresented in Fig. 3. Total rainfall received were 1445 and2143mm in 2001 and 2002, respectively, indicating a dryyear in first and wet year in the latter. During pre-monsoonseason (March–May), 15% of annual rainfall occurred in2001 and 16% of annual rainfall in 2002. Total numbers ofrain events that eroded soil from the runoff plots were 30 in2001 and 24 in 2002. Of these, only seven (in 2001) and 11(in 2002) events occurred during pre-monsoon season.

3.2. Runoff

The unusual conditions created by runoff plot construc-tion during the establishment year 2001 should be noted.Soils along plot boundaries were substantially disturbedand there was very little cover (upland weeds), even inreduced till plots due to trampling during plot esta-blishment. This likely affected the system outputs; espe-cially increased soil and nutrient losses from reduced tillplots in 2001.With this caution, statistical analysis showed that the

conservation approaches were non-significant for annual

July Aug Sep Oct Nov Dec

nths

Year 01 Year 02

erimental site (2001–2002).

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Table 2

Treatment and seasonal dynamics on runoff, soil and nutrient losses in hills of central Nepal (2001–2002)

Treatment Annual

runoff

(mm)

Soil loss (t/ha) SOM loss (kg/ha) Annual nutrient losses (kg/ha)

Pre-

monsoon

Monsoon Annual Pre-

monsoon

Monsoon Annual Total N P2O5 K2O

Conventional till,

sole maize

129 12.4 3.4 15.8 262.7 74.1 336.9 18.8 1.9 4.0

Conventional till,

maize+soybean

117 14.9 2.3 17.3 269.6 41.7 311.4 18.8 1.9 4.4

Mulching, sole

maize

123 5.7 3.5 9.3 108.7 61.9 170.6 9.6 1.0 2.3

Mulching,

maize+soybean

110 5.6 2.7 8.3 102.6 49.5 152.1 9.1 0.8 2.2

Reduced till, sole

maize

128 7.2 3.5 10.8 167.7 59.2 226.8 11.9 0.9 2.6

Reduced till,

maize+soybean

134 7.9 3.4 11.4 146.8 60.4 207.2 11.7 1.1 2.7

F-test

Replication ns ns * ns ns ns ns ns ns *

Treatment (T) ns ** ns ** ** ns ** ** ** **

Year (Y) ns ns ** ** ns ** ns ns ** **

T�Y ns ns ns ns * ns ns ns * *

LSD for T (0.05) – 2.1 – 3.1 55.0 – 64.7 3.9 0.3 0.7

*Significant at probability level of 0.05.

**Significant at probability level of 0.01.

ns ¼ not significant.

K. Atreya et al. / Journal of Environmental Management 88 (2008) 547–555 551

runoff; however, reduced tillage produced slightly higherrunoff than conventional tillage and mulching (Table 2).Highest runoff was observed in reduced till maize+soybean (134mm) followed by conventional till sole maize(129mm). Previous studies claimed that reduced tillagesignificantly decreases runoff through reducing surfacecrusting and increasing infiltration (Cassel et al., 1995;Acharya, 1999; FAO, 2000). However, in the present study,slightly higher runoff from reduced tillage plots could bedue to compaction from trampling and less porous soilconditions due to lack of complete tillage. A study inNigeria (Adekalu et al., 2006) under rainfall simulatorshowed that as the compaction level increases runoffincreased and soil loss decreased significantly. In conven-tional tillage, the plots were freshly plowed having highersurface roughness and porosity than reduced till plots;therefore, retained and absorbed more water. Atreya et al.(2006) and Basic et al. (2001) have also made similararguments. Moreover, farmer practice of maize sowingautomatically tends to create small ridges on the soilsurface across slope (Atreya, 2002; Atreya et al., 2006),which may have increased time for infiltration, thus,decreased total runoff.

On the other hand, the reductions in runoff with mulchwas small (5–18%), but consistent. For example, conven-tional till sole maize was nearly 5% lower with mulch thanwithout (123mm vs. 129mm) and the conventional tillmaize+soybean with mulch was 18% lower than reducedtill maize+soybean without mulch (110mm vs. 134mm).However, as shown in previous studies, the anticipated

reduction in runoff due to mulching was not observed. Lal(1976a,b) showed negligible runoff by mulching comparedto bare-fallow. Kukal et al. (1993) also documented 58%reduction in runoff by the application of 4 t/ha of mulch.Bhatt and Khera (2006) also showed that compared withun-mulched, mulch spread over whole plot reduced runoffby 33%. In this study straw mulching produced compar-able runoff with other treatments which was presumablydue to the length and placement of straw mulch. About50 cm long rice straw was surface applied along the slope,which may have facilitated rainfall to drain out of the plotsinto the collection systems.

3.3. Soil loss

Annual soil loss was significantly affected by treatmentsand by years. Soil loss during pre-monsoon seasonwas only affected by treatments, whereas, monsoon losswas affected by replication and by years (Table 2).Conventional till maize+soybean produced the highestannual (17.3 t/ha) as well as pre-monsoon soil loss(14.9 t/ha), followed by conventional till sole maize (15.8and 12.4 t/ha, respectively). A significant difference byyears was observed for annual and monsoon soil loss, butnot for pre-monsoon loss because of yearly variation inrainfall amount. As compared to conventional tillagepractice, annual and pre-monsoon soil losses were sig-nificantly lowered by mulching and reduced tillage (Fig. 4and Table 3). Reduced tillage minimized 33% of annualand nearly 50% of pre-monsoon soil loss. Similarly,

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16.56

13.62

2.86

11.10

7.51

3.47

8.81

5.62

3.13

0

2

4

6

8

10

12

14

16

18

So

il lo

ss (

t/h

a/y

r)

Conventional tillage Reduced tillage Mulching

Annual Pre-monsoon Monsoon

Fig. 4. Effects of conservation approaches on soil loss in central Nepal.

Table 3

Two-sample t-test resultsa

Soil and nutrient loss t-test values

CT versus RT CT versus mulching

Annual runoff �0.74b 0.652b

Annual soil 3.27** 9.02**

Pre-monsoonc 5.90** 10.81**

Monsoon �0.67b �0.36b

Soil organic matter 3.91** 8.01**

Total N 5.53** 9.04**

Available P2O5 2.42* 2.61*

Exchangeable K2O 3.45** 7.53**

*Significant at probability level of 0.05.

**Significant at probability level of 0.01.aDegree of freedom ¼ 14.bNot significant.cSoil loss during March–May was considered as pre-monsoon and that

of June–October as Monsoon.

K. Atreya et al. / Journal of Environmental Management 88 (2008) 547–555552

mulching also reduced annual soil loss by nearly 53% andpre-monsoon soil loss by 59%. Annual runoff wassimilar for all treatments, but soil loss was significantlydifferent. This was reflected in differences in sedimentconcentration among the treatments. Sediment concentra-tions per thousand ml of runoff were observed to be thehighest for conventional till followed by reduced till andmulching.

In Central Nepal, Maskey et al. (1992) also found a 77%reduction in soil loss by minimum tillage as compared tothe farmers’ practice. Soil loss during pre-monsoon seasonwas significantly higher in terms of amount and intensity.During this season, only seven (out of 30) and 11 (out of24) rainfall events occurred in 2001 and 2002, respectively.Significant soil loss during pre-monsoon period from

conventional tillage was due mainly to freshly plowedconditions with minimal vegetation cover. Freshly plowedfield is susceptible to erosion and 40–50 days is requiredbefore maize crop cover can provide enough coverprotection to reduce soil loss. In hills of central Nepal,farmers plant the land only after the first few pre-monsoonrain events. The mid-hills also experience local ascendingwinds (March–May) that lead to violent thunderstormsaccompanied by hail before the arrival of actual monsoonfront (Shah and Friend, 1992). This leads to significantlyhigher soil losses during pre-monsoon season compared tomonsoon. It is not possible to establish early live vegetativecover in upland areas due to insufficient moisture and lackof irrigation; therefore, it is necessary to modify the currenttillage practices for upland agriculture in the hills of Nepalin order to conserve soil resources.

3.4. Soil organic matter (SOM) and nutrient losses

Treatments were significantly different in annual andpre-monsoon SOM loss (Table 2). SOM loss was thehighest in conventional till sole maize (337 kg/ha) followedby conventional tillage maize+soybean (311 kg/ha) andreduced till sole maize (227 kg/ha). The interaction betweentreatments by year was also significant, especially in pre-monsoon, indicating inconsistent treatment responses toSOM losses in the two years. This was likely due to thedifferences in soil surface conditions and vegetative(weed) cover during the two years. In 2002 significantreduction in soil and SOM loss was observed in reduced tillplots because of presence of weeds during pre-monsoon,which were destroyed in the first year due to plotconstruction (Atreya et al., 2006). As compared toconventional tillage, conservation approaches reduced

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18.8

1.9

4.2

11.8

1.0

2.6

9.3

0.9

2.3

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

Nu

trie

nt

loss (

kg

/ha/y

r)

Total N Available P2O5 Exch. K2O

Conventional tillage Reduced tillage Mulching

Fig. 5. Effects of conservation approaches on soil nutrient losses in central Nepal.

Table 4

Mean treatment effects on maize height, grain and stover yield

Treatments Cob

height

(cm)

Plant

height

(cm)

Grain

yield

(t/ha)

Stover

yield

(t/ha)

Conventional till,

sole maize

107 215 3.82 4.10

Conventional till,

maize+soybean

122 224 3.98 3.89

Mulching, sole

maize

101 208 4.10 3.16

Mulching,

maize+soybean

102 200 4.00 3.20

Reduced till, sole

maize

80 169 3.49 2.74

Reduced till,

maize+soybean

86 187 3.94 2.72

F-Test * * ns ns

LSD 0.05 24 44 – –

*Significant at probability level of 0.05.

ns ¼ not significant.

K. Atreya et al. / Journal of Environmental Management 88 (2008) 547–555 553

SOM from maize agro-ecosystems, which was alsostatistically significant (Table 3).

Although there were treatments effects on nutrient lossesby water erosion (Table 2), nutrient losses in erodedsediment, for this study, appeared to be minor with theexception of nitrogen (Fig. 5). Sediment bound nitrogenloss was highest in conventional till plots, and lowest inmulched plots. Maskey et al. (1992), Pilbeam et al. (2000),and Brown et al. (1999) also argue that SOM and nitrogenlosses through water erosion during the rainy season areserious problems in Nepal.

This study showed that mulching and reduced tillage waseffective in controlling soil and nutrient losses from uplandhills of Nepal. However, it should be noted that naturaldeposition under traditional cultivation practices was notmonitored in the plot experiment (Gardner and Gerrard,2003) and re-deposition of sediments may occur in lowerterraces (Schreier et al., 2001), which was also notaccounted in plots. Thus, it is important to understandthe dynamics of soil and nutrient transports within as wellas among the terraces. Therefore, quantification of soil andnutrient losses from multiple terraces is recommended.However, the seasonal interactions on the intensity andmagnitude of soil and nutrient losses at plot scale is notonly important for the timing of conservation planning,but also important for understanding and selecting types ofconservation measures, especially in the fragile hillsides ofNepal.

Although rice straw was observed to be effective incontrolling soil and nutrient loss, farmers tend not toaccept this practice. Most farmers, especially in the mid-hills, use rice-straw as fodder for livestock; some farmersuse it as thatch material for roof, and if available insurplus, they sell it to neighbors and industries, such aspaper factories. The value of soil protection and improved

crop yields would need to exceed the cost of residue to befeasible. Due to limited availability and high cost of ricestraw, further research is needed to quantify the economicbenefits of soil and nutrient conservation provided by ricestraw mulch and/or evaluate alternative mulch materials.

3.5. Maize parameters

All treatments produced statistically similar grain andstover yields (Table 4). Grain yield was highest in mulchingplots. Even under reduced-till condition, there was nosignificant sacrifice of grain yield as compared to conven-tional till. However, in previous studies conducted inNepal, minimum/no tillage was found unsuitable for crop

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yield and thus, farmers did not accept minimum tillage dueto low crop yield (Maskey et al., 1992). In some instancesthe crop even failed completely (Khadka and Shah, 1987).But a recent review paper in China (Wang et al., 2007) haveshowed increased crop yields, however, farmers’ adoptionof such tillage practices is still limited. For this study,reduced tillage significantly lowered cob and plant heightsand as a result, dry stover yield was also lower in reducedtill plots. The shorter plant height and lower stover yield inreduced till plots could be due to restriction in rootsdevelopment at early stages of growth.

The present study revealed good crop yields even inreduced till plots, which was attributed to a specificcombination of soil type (sandy loam), crop rotationsand agronomic practices. Conservational tillage systemsare specific to soil characteristics. Soils at the experimentalsites were sandy loam, which is favorable for cropestablishment. During winter season, mustard was sownin each plot, and residue was taken out completely. Inpreparing land for mustard, maize stubbles were removed(generally these are used as fuel materials by farmers) androots were incorporated into the soil. The cultivation ofmustard in winter season further facilitates tillage opera-tions for maize crop, even under reduced till plots.Furthermore, the reduced tillage here is different fromthat in other studies. Firstly, tillage intensity was sig-nificantly minimized (only during the pre-monsoon peri-od), soil was less disturbed by opening small furrows at75 cm spacing during maize planting (only once againstthrice in conventional tillage), which could restrict rootdevelopment at early stages. Secondly, reduced till plotswere also tilled during first and second weeding. Weedingoperations after 30 and 60 days of planting and applicationof chemical fertilizers (top dressing) at the first weeding inreduced till plots helped plant roots development andmaintained yield. Although such weeding operations andfertilizer application were done in all treatments, betterresponse was found in reduced tilled plots. Thus, a slightmodification in tillage intensity and fine tuning agronomicpractices may be required to conserve plant availableresources in cultivating upland maize agro-environment inhills of Nepal.

4. Conclusion and recommendations

Mulching and reduced tillage significantly lowered soiland nutrient losses compared to conventional tillage. Soilnitrogen and organic matter losses, as particulate organicmatter associated with eroded sediment, was quite high inconventional tillage. Thus, there is an urgent need tomodify conventional tillage practices to protect plantavailable nutrients in agricultural land, especially in hillsof central Nepal, which has 42% of the total farmland and44% of the population of the nation. Most of the soil lossoccurred during high intensity pre-monsoon rain underconventional tillage because of freshly tilled fields withminimal vegetation cover. Future research thrusts on

conserving soil should focus on this critical period. Ricestraw mulch was found effective in conserving soil andnutrients, however, due to its limited availability andhigher opportunity cost, farmers may not adopt thistechnology. Alternative mulch materials need to beexplored. This research showed that reduced tillage couldbe an option for management of soil resources in theHimalayan agro-ecosystem without sacrificing crop yields.It was further observed that a mulch residue was beneficialfor runoff and soil loss control in the hill region of Nepal.Further work is needed to determine the long-termcost–benefit ratios for these practices in order to developa sustainable agro-ecosystem for this region.

Acknowledgments

Authors are thankful to International Maize and WheatImprovement Centre (CIMMYT), South Asia RegionalOffice, Kathmandu, Nepal for the financial support. Weare also grateful to J.K. Ransom, B.P. Tripathi, and P.B.Shah for their support during the study period.

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