Published in Agron J 100:447-453 (2008)
DOI: 10.2134/agrojnl2007.0159
© 2008 American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA
PULSE CROPS
Tie-Ridge Tillage for High Altitude Pulse Production in Northern Ethiopia
Gebreyesus Brhane Tesfahunegna and
Charles S. Wortmannb,*
a Mekelle Agricultural Research Center, P.O. Box 492, Mekelle, Ethiopia. Present address: Axum Univ., Faculty of Agriculture and Rural Development, P.O. Box 287, Axum, Ethiopia
b Dep. of Agronomy and Horticulture, Univ. of Nebraska-Lincoln, Lincoln, NE 68583–0915. Partial support was provided by the U.S. Agency for International Development under the terms of Grant No. LAG-G-00-96-900009-00
* Corresponding author (cwortmann2{at}unl.edu).
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ABSTRACT
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Pulses including faba bean (Vicia faba L.), lentil (Lens culinaris Medic.), and field pea (Pisum sativum L.) are important components of the cropping systems of semiarid high-altitude northern Ethiopia. Yield potential is often constrained by severe water deficits during grain fill which might be alleviated by reducing runoff throughout the season using microbasin or tie-ridge tillage. Research was conducted to determine the effects of time of tie-ridge tillage and planting method on soil water availability and on the performance of these three pulse crops. The site was at 2740 m altitude on Torriorthent sandy loam or loamy sand soils. Eight treatments, including a 3 x 2 factorial of tillage x planting method, were evaluated in separate trials for each crop species in 2005 and 2006 with a randomized block design with three replications. Tie-ridge tillage improved soil water availability compared with the traditional practice of planting without ridges, and soil water was least depleted during the growing season with tie-ridge formation at 4 wk after planting (TR4WAP) when the first weeding was done. Grain yield and nodulation were also highest with TR4WAP, with mean grain yield increases of 79, 31, and 96% for faba bean, lentil, and field pea, respectively, compared with flat planting. Tie-ridging at other times typically resulted in increased grain yield compared with traditional flat planting if planted on the ridge, but decreased yield with in-furrow planting. Mean grain yield was 48, 23, and 35% with planting on the ridge compared with in-furrow if tie-ridging was done before planting for faba bean, lentil, and field pea, respectively. Soil water availability, however, was higher with in-furrow planting. Tie-ridging, or possibly reshaping earlier-formed tie-ridges, at the time of the first weeding after planting was most effective in improving pulse yield.
Abbreviations: HI, harvest index • IF, in-furrow planting • OR, on-ridge planting • PWP, permanent wilting point • TR4MBP and TR4MBPR, tie-ridging 4 mo before planting with and without reshaping of tie-ridges at planting time, respectively • TR0WAP and TR4WAP, tie-ridging at and 4 wk after planting, respectively • WAP, weeks after planting
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NOTES
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All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher.
Received for publication May 14, 2007.
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INTRODUCTION
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PULSE CROPS are important components of high altitude farming systems in semiarid Ethiopia, both as food crops and marketable commodities (Amede, 1998). Faba bean, lentils, and field pea are produced under low-input, water-deficit conditions, commonly in rotation with wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.). In Ethiopia, the land base with pulses includes more than 470,000 ha cropped with faba bean (mean yield = 1.04 Mg ha–1), about 70,000 ha in lentil production (mean yield = 0.64 Mg ha–1) and about 235,000 ha with field pea (mean yield = 0.76 Mg ha–1) (FAOSTAT, 2007). Crop performance is much affected by the quantity and distribution of rainfall during the growing season.
Intense rainfall events before and after planting often result in considerable water loss from the field. Runoff can be reduced to store water in the soil for crop use later in the season by creating microcatchments or microbasins, such as with tie-ridging. Tie-ridges typically consist of furrows of 0.20- to 0.30-m depth that are blocked with earthen ties spaced according to the slope of the land, water infiltration rate, and expected intensity of rainfall (Lal, 1977; Gebrekidan, 2003; Brhane et al., 2006). Tie-ridging effectively reduced runoff and increased soil water in Tanzania (Macarthey et al., 1971), the United States (Jones and Clark, 1987; Krishna, 1989; McFarland et al., 1991; Howell et al., 2002), Burkina Faso (Hulugalle et al., 1990), and Zimbabwe (Piha, 1993; Vogel, 1993). In northern Ethiopia, Brhane et al. (2006) found sorghum (Sorghum bicolor L. Moench) yield to be increased by 62% with tie-ridging compared with flat planting. Adoption of tie-ridging for small-scale sorghum production in Africa was found to increase farm income by 12% (Sanders et al., 1996). Tie-ridging is expected to be most effective in increasing productivity in cases of continuous annual cropping with common occurrence of large early-season runoff events and soil water deficits during the growing season (Jones and Clark, 1987).
The effect of soil water deficits on yield of grain legumes may be alleviated by reducing runoff throughout the season using tie-ridge tillage. The objective of this research was to determine the benefit of tie-ridging, with planting on the ridge and in furrow, on faba bean, lentil, and field pea yield and soil water availability in a semiarid high-altitude area of northern Ethiopia.
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MATERIALS AND METHODS
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The study site was at Atsbi-Womberta in Tigray in northern Ethiopia (13°55' N, 39°45' E, about 2740 m altitude). Historical weather data was lacking for this site but annual rainfall was represented by the monthly means of two nearby locations which had a uni-modal pattern with estimated total precipitation of 550 to 600 mm with peaks in July and August (Fig. 1
). Mean monthly temperatures during the growing season range from 16 to 19°C. The Torriorthent soil at the experimental site for the faba bean and lentil trial sites was a sandy loam and a loamy sand for the field pea site (Table 1
). The slope gradients ranged from 0.03 to 0.04 m m–1.
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Table 1. Selected soil properties (0–0.20 m) at the faba bean, lentil, and field pea trial sites near Atsbi-Womberta in northern Ethiopia.
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The field trials were conducted in 2005 and 2006 with treatments applied to the same experimental units each year in a randomized complete block design with three replications. The plot size was 2.4 by 6 m and the row spacing was 40 cm. The 2004 crop was wheat. The entire experimental area was tilled once using the traditional oxen-drawn maresha plow before imposing any treatments.
The eight tillage and planting treatments included the control and traditional practice which was planting into a flat soil surface (flat planting), tie-ridging at 4 wk after flat planting (TR4WAP), and a factorial of three tillage and two planting levels. The factorial treatments were: tie-ridging 4 mo before planting with planting in-furrow (TR4MBPIF) or on-ridge (TR4MBPOR); tie-ridging 4 mo before planting and reshaping the ridges before planting with planting in-furrow (TR4MBPRIF) or on-ridge (TRMBPROR); and tie-ridging at planting with planting in-furrow (TR0WAPIF) or on-ridge (TR0WAPOR) (Table 2
). Tie-ridges were not reshaped at weeding time. The ridges were 20-cm high and constructed using hand hoes. The furrows were tied every 2 m using hand hoes.
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Table 2. Dates of tillage, planting, and harvest activities for faba bean, lentil, and field pea trials conducted at Atsbi-Womberta in northern Ethiopia.
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Faba bean cv. Alquai, lentil cv. Bursin, and field pea cv. Aine-Ater were planted by hand with a 10-cm seed spacing giving a sowing rate of 25 seed m–2. All plots were weeded with hand hoes twice during the cropping season. No fertilizer was applied. Olsen P indicated adequate soil P availability and the legumes are capable of biological N fixation. No major insect pest problems were seen and no chemical control measures were applied.
Volumetric soil water content was determined gravimetrically by collecting soil samples for the 0- to 0.30-m and 0.30- to 0.60-m depths every 3 wk from the date of planting until after harvest of lentil and faba bean, and after physiological maturity but before harvest of field pea. The soil samples were composed of three subsamples collected from within plant rows from the two soil depths. The samples were wet-weighed, dried in a forced-air oven at 105°C until constant weight, and weighed again. Volumetric soil water content was calculated as:
where 
v = volumetric soil water content (m3 m–3), SWi = initial weight of the soil (g), SWd = oven-dry weight of the soil (g), 
b = dry soil bulk density (Mg m–3); and v = density of water (Mg m–3) (Hillel, 1980).
Daily rainfall was measured with a rain gauge. Days when 50% of the plants were flowering were determined based on counts of all plants in the harvest area. Days to 95% maturity were determined as when the plants had yellowed and the lower pods started to blacken for faba bean and lentil, or to whiten for field pea. Nodules per six plants were counted at flowering, first pod set, and maturity in 2005 by loosening the soil and carefully uprooting the plants. Plant height was determined by measuring 12 randomly selected plants. Harvested plants were counted. Pods plant–1 was determined by counting the pods with at least one seed of 12 randomly selected plants. Seeds of these 12 plants were counted and divided by pods plant–1 to determine seeds pod–1. After air-drying, 100-seed wt. was determined. Aboveground biomass yield was determined by harvesting the two middle rows and weighing after air-drying. The dried biomass was threshed and the grain was weighed and tested for water content to determine grain yield at 125 mg g–1. Harvest index was obtained by dividing air-dried grain yield by total biomass yield.
Analyses of variance combined across years was conducted after testing for equality of variances; the only variable where the variance in 1 yr was more than twice the variance in the other year was for lentil seeds pod–1. Data were analyzed using Statistix 8 (Analytical Software, Tallahassee, FL). Treatment x season interaction effects were not significant and the means across the 2 yr are presented. The tillage x planting interaction was determined for the subset of treatments comprising a complete factorial. Contrasts were conducted to compare flat planting with on-ridge plant and in-furrow planting, and to compare on-ridge with in-furrow planting. Treatment effects were considered significant at P < 0.05.
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RESULTS
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Total seasonal rainfall was considered typical in 2005 and 2006 but July rainfall was less than normal in 2006 (Fig. 1). Treatment x year interaction effects were not significant at P < 0.05, unless indicated otherwise, and treatment means over the 2 yr are presented (Tables 3, 4, and 5 and Fig. 2
, 3
, and 4
).
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Fig. 2. Soil water as affected by tie-ridging treatments in faba bean trials conducted at Atsbi-Womberta in northern Ethiopia. The results are the means for 2005 and 2006. The Y-bars are the LSD values at 0.05 level for soil water volume.
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Fig. 3. Soil water as affected by tie-ridging treatments in lentil trials conducted at Atsbi-Womberta in northern Ethiopia. The results are the means for 2005 and 2006. The Y-bars are the LSD values at 0.05 level for soil water volume.
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Fig. 4. Soil water as affected by tie-ridging treatments in field pea trials conducted at Atsbi-Womberta in northern Ethiopia. The results are the means for 2005 and 2006. The Y-bars are the LSD values at 0.05 level for soil water volume.
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Faba Bean
Faba bean yield of TR4WAP was the highest among the treatments and 91% higher than the national average (Table 3
) (FAOSTAT, 2007). In comparing the means with on-ridge compared to in-furrow planting, flowering, and maturity were 3 d earlier, plant density at harvest was 34% more, plants were 20% taller, seeds pod–1 were 29% more, 100-seed wt. was 19% more, biomass and grain yield were nearly twice as much, but lower HI was 11% less. The tillage x planting method interaction was significant for all traits except days to flowering and to maturity and HI. The interaction was due to more planting effect with TR4MBPR and TR0WAP than with TR4MBP.
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Table 3. Crop phenology, nodule number and volume, yield and yield components of faba bean as affected by tie-ridging treatments at Atsbi-Womberta in northern Ethiopia. The results are the means for 2005 and 2006.
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Flowering and maturity were about 6 d earlier with flat planting than with tie-ridging (Table 3). Compared with flat planting, mean grain yield was 51% more with on-ridge planting and 36% less with in-furrow planting for TR4MBPR and TR0WAP. Biomass yield and grain yield components were similarly affected by planting method. The effect of tie-ridging time or method before or at planting was significant for days to maturity, pods plant–1, biomass yield, but was not significant for days to flowering, grain yield, and HI. Biomass yield and pods plant–1 were higher with TR4MBPR and less with TR4MBP compared with TR0WAP. Grain and biomass yield, and yield components were highest with TR4WAP. Faba bean had a HI < 0.35 for most treatments, possibly due to stress with some treatments during grain fill which was reflected in seed size differences. The seed size was 27% higher with TR4WAP than with some in-furrow planting treatments.
Nodule number was 20% more with on-ridge compared with in-furrow planting and was higher for TR4MBPR and TR0WAP than for TR4MBP. Nodule number was highest with TR4WAP and higher at flowering time than later in the season (data not shown).
Soil water was least available in the 0- to 60-cm depth with flat planting, and most available or equal to other treatments with TR4WAP (Fig. 2). The tillage x planting interaction was not significant for all sample times. Soil water was more with planting in-furrow compared with on-ridge, and less with flat planting than with tie-ridging, throughout the season. Soil water was near the estimated permanent wilting point (PWP) for flat planting at 12 wk after planting (WAP) but the crop had reached maturity by this date. Soil water availability was more at planting with TR4MBPR compared with TR0WAP, but generally soil water availability was similar for these tillage treatments later in the season.
Lentil
Lentil grain yield was 110% of the national average with TR4WAP (Table 4
) (FAOSTAT, 2007). Lentil flowering and maturity were latest for TR4WAP and earliest with flat planting. Yield performance was generally best with TR4WAP, followed by on-ridge planting with TR4MBPR and TR0WAP.
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Table 4. Crop phenology, nodule number and volume, yield and yield components of lentil as affected by tie-ridging treatments at Atsbi-Womberta in northern Ethiopia. The results are the means for 2005 and 2006.
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In comparing the means with on-ridge compared to in-furrow planting, flowering, and maturity were 2 d earlier, plant density at harvest was 13% more, plants were 19% taller, seeds pod–1 were 17% more, 100-seed wt. was 13% more, biomass and grain yield were 30 and 40% more, respectively, and HI was 9% more (Table 4). The tillage x planting method interaction was significant for most traits due to more planting effect with TR4MBPR and TR0WAP than with TR4MBP. Exceptions were with days to flowering and maturity where planting effects were higher with TR4MBP than with other tie-rdige treatments. Lentil biomass and grain yield, and yield components, were more and less, respectively, for on-ridge and in-furrow planting for TR4MBPR and TR0WAP as compared with flat planting. Grain and biomass yield, and yield components, were highest with TR4WAP compared with other treatments. Lentil had a higher HI compared with the other pulse crops and was >0.50 for most treatments.
Nodule number was 20% higher with on-ridge compared with in-furrow planting (Table 4). Mean nodule number was also 7% higher with TR4MBPR and TR0WAP than for TR4MBP. Nodulation was highest for TR4WAP and higher at flowering time than later in the season (data not shown).
Soil water was generally most and least available with TR4WAP and flat planting, respectively (Fig. 3). The tillage x planting interaction was not significant for all sampling dates. Soil water availability was more with in-furrow compared with on-ridge planting, and less with flat planting than with tie-ridging, throughout the season. Soil water availability was generally similar with TR4MBP, TR4MBPR, and TR0WAP. Soil water levels in the 0- to 60-cm depth were less than estimated permanent wilting point at 12 WAP for flat planting and on-ridge planting.
Field Pea
Field pea flowering and maturity were latest for TR4WAP and earliest with flat planting (Table 5
). Yield performance was best with TR4WAP, followed by on-ridge planting with TR4MBPR and TR0WAP. The yield with TR4WAP was 109% higher than the national mean field pea yield of 0.76 Mg ha–1 (FAOSTAT, 2007). In comparing the means with on-ridge compared to in-furrow planting, flowering, and maturity were 3 d earlier, plant density at harvest was 13% more, plants were 30% taller, seeds pod–1 were 17% more, 100-seed wt. was 10% more, biomass and grain yield were 41 and 61% more, respectively, and HI was 15% more. The tillage x planting method interaction was significant for yield and yield components due to a greater planting method effect with TR4MBPR and TR0WAP than with TR4MBP. Field pea biomass, grain yield, and yield components were more and less with on-ridge and in-furrow planting, respectively, for TR4MBPR and TR0WAP as compared with flat planting. Crop performance with flat planting was similar and better compared with on-ridge and in-furrow planting, respectively, for TR4MBP.
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Table 5. Crop phenology, nodule number and volume, yield and yield components of field pea as affected by tie-ridging treatments at Atsbi-Womberta in northern Ethiopia. The results are the means for 2005 and 2006.
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Nodule number was 29% higher with on-ridge compared with in-furrow on-ridge planting (Table 4). Nodule number was highest for TR4WAP and higher at flowering time than later in the season (data not shown).
Soil water was generally most available with TR4WAP and least available with flat planting (Fig. 4). The tillage x planting interaction was significant for the 12 wk after planting sampling only due to relatively less planting effect with TR4MBPR than with the other tie-ridging practices. Soil water was more with planting in-furrow compared with on-ridge, and less with flat planting than with tie-ridging, throughout the season. Soil water availability was generally similar with TR4MBPR and TR0WAP, but occasionally less with TR4MBP. Available soil water in the 0- to 60-cm depth was depleted at 12 WAP for flat planting and below the estimated PWP for all treatments at 15 WAP.
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DISCUSSION
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The value of tie-ridge tillage to water conservation and crop performance is best illustrated by the comparison of flat planting and no tie-ridging with flat planting and tie-ridging 4 wk later. Available soil water in the 0- to 60-cm depth was depleted at 12 WAP with flat planting but 0.045 m3 m–3 remained with TR4WAP. The value of this higher soil water availability during grain fill with TR4WAP is reflected in grain size that was 10% to 16% higher with TR4WAP than with flat planting. More available soil water for most of the season with TR4WAP than with flat planting resulted in more plants ha–1, more pods plant–1, and more kernels pod–1. Mean grain yield was 31, 79, 96% higher for lentil, faba bean, and field pea, respectively, with TR4WAP compared with flat planting.
The trial results confirm the criteria for tie-ridging of Jones and Clark (1987) that yield response can be expected with tie-ridging if (i) the crop is an annual, (ii) heavy rains occur early in the growing season, and (iii) there is limited growing season precipitation. During the first 2 mo after planting, 60% of the rainfall was in events of 
25 mm with significant potential for runoff. Only about 100 and 30 mm of rain fell after 50% flowering in 2005 and 2006, respectively, with the crop largely dependent on stored soil water during the grain-fill period.
The results confirm the effectiveness of tie-ridge tillage conducted at or after planting in maintaining soil water levels and delaying water depletion compared with flat tillage for these coarse texture soils. There was more soil water at the first sampling time with early tie-ridging compared with tie-ridging at planting or at first weeding, but this did not result in increased yield, even when the tie-ridges were renewed at planting time. Crop yield and soil water availability were generally highest with planting into a flat soil surface and tie-ridging 4 wk later. Grain yield was 79, 31, and 96% higher for faba bean, lentil, and field pea, respectively, with TR4WAP compared with flat planting. Brhane et al. (2006) also found a 62% sorghum yield advantage with tie-ridging, but with higher benefit in tie-ridging before planting rather than after planting. In the pulse trials, there was little precipitation during the months before planting and much of the extra water retained before planting with earlier tie-ridging was probably lost to evaporation.
Tie-ridges were not regularly rebuilt during the season, for example at weeding time, and the earlier constructed tie-ridges lost height and capacity to hold water from heavy rainfall during the season. Most of the large rainfall events were in August, indicating that creation or reshaping of tie-ridges in mid to late July is important for maximum effectiveness in preventing runoff.
Soil water was higher with in-furrow compared with on-ridge planting, but crop performance was better with on-ridge planting. Crop yield was 49, 29, and 38% higher with on-ridge compared with in-furrow planting for faba bean, lentil, and field pea, respectively. Reduced plant density and poorer crop performance with in-furrow planting may have been due to periodic exposure to standing water although water-logged conditions probably did not persist long on these sandy soils. Adjei-Twum (1987) and Brhane et al. (2006) also obtained better crop yield with on-ridge compared with in-furrow planting, although those studies were on vertic clay soils where internal drainage was likely to be slower than for sandy loam or loamy sand soils. The higher soil water availability with in-furrow may have been due to less evapotranspiration as plant density and growth were less with in-furrow planting. Estimates of soil water availability may have been affected by the sampling procedure as the sampling depth was measured from the base of plants whether planted on-ridge or in-furrow.
The results demonstrate the potential of tie-ridging for water conservation and increased yield. The practice of TR4WAP was most effective. If labor or draft animal availability is expected to be too limiting at this time, creating or reforming earlier made tie-ridges at planting may be more appropriate provided planting is on the ridge rather than in-furrow.
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CONCLUSIONS
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Choosing the appropriate time for tie-ridging application is important to pulse crop performance in semiarid high-altitude areas of northern Ethiopia. Tie-ridging at 4 WAP or at first weeding and planting on-ridge with tie-ridging at planting are appropriate practices for improving soil water availability and increasing yield. Reshaping of earlier-formed tie-ridges at first weeding may improve tie-ridge effectiveness and increase pulse yield. An added advantage of planting flat and tie-ridging at first weeding is that the work load at planting is reduced allowing for timely planting. In these studies, tie-ridging was done using manual implements but the labor requirement could be reduced using available oxen (Ovibos spp.)-drawn implements.
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher.
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ABSTRACT
INTRODUCTION
