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In situ rain water harvesting techniques increase maize growth and grain yield in a semi-arid agro-ecology of Nyagatare Rwanda.

Byline: Ferdinand Mudatenguha Jennifer Anena Clement K. Kiptum and Arnold B. Mashingaidze

Abstract

Droughts short growing seasons and poorly distributed rainfall are major constraints to maize production in eastern semi-arid region of Rwanda. In situ rain water harvesting offers an alternative option to reduce rainwater runoff increase infiltration and storage of water in soil and reduce the effects of drought stress on maize grain yield. The objective of the study was to assess the effects of in situ water harvesting techniques on soil moisture content maize growth and grain yield in Nyagatare Rwanda in the 2011-2012 seasons. The study comprised of four treatments: pot holing tied-ridging and mulching compared to control treatment of planting on the flat. The experimental design was randomized complete block with three replicates. Soil moisture content and maize plant dry weight were measured at 8 11 and 14 weeks after emergence (WAE). There was a significant increase (Pless than 0.001) in soil moisture content and maize plant dry weight from planting on the flat (control) pot hole tied ridges to mulching at 8 11 and 14 WAE. Yield components (ear mass number of grains per ear and 100 grain weight) and grain yield significantly increased (Pless than 0.001) from planting on the flat pot holes tied ridges and were highest in the mulched treatment. Maize grain yield increased(Pless than 0.001) by 49.6 103 and 136% of the maize grain yield harvested from the flat planting(1593.36 kg ha-1) in the pot-holing tied ridging and mulching treatments respectively. The results of this study indicate that mulching tied ridges and pot holes in decreasing order of effectiveness have potential to increase soil moisture content and reduce the damage caused by drought stress to maize growth and grain yield and therefore recommended for farmers in Nyagatare and other drought prone regions. Copyright 2014 Friends Science Publishers

Keywords: Water harvesting; Percent soil water; Growth; Grain yield

Introduction

Moisture stress is a major limiting factor to maize grain production in semi-arid parts of the world (Bruce et al.2002). Water deficits are triggered when the soil is drying from field capacity and evaporative loss of water exceeds passive water movement into plant roots. The evaporative demand of the atmosphere depends on its relative humidityand temperature. Hot dry conditions accompanied by drying soil are associated with water deficits that cause stress anddamage to plant processes and growth. Recurrent droughtsmid-season droughts and delayed start and premature end of the season are the major cause of water stress to plants and are responsible of widespread food shortages in semi-arid areas in sub-Saharan Africa (SSA).Climate change scenarios generally indicate higher temperatures for most of Africa although projections for precipitation vary from slight increases in West Africa and slight decreases in Southern Africa (Washington et al.2004; Stige et al. 2006). However there is greater consensus about a higher climate variability which will leadto an increase in both intra- and inter-seasonal drought and flood events and greater uncertainty about the onset and end of the rainy season. Climate change is posing the greatest threat to agriculture and food security in the 21st century particularly in many of the poor agriculture-based countries of SSA with their low capacity to effectively cope (Shah et al. 2008; Nellemann et al. 2009).Irrigation is poorly developed in SSA compared to other regions of the world. African countries only irrigate 6percent of their total cropland compared to a world averageof 18 per cent mainly due to low investments in irrigation infrastructure (Svendsen et al. 2009). Water harvesting using in situ techniques constitutes a simpler more affordable and adoptable technology for resource poor smallholder farmers in SSA compared to irrigation with its large investments in water impoundments and delivery systems. In situ water harvesting techniques increase the amount of water stored in the soil profile by trapping or holding rainwater where it falls it involves small movements of rainwater as surface runoff in order to concentrate the water where it is required in the root zone ofthe crop (UNEP 1997). In situ water harvesting techniques such as pot-holing ridging tied ridging pit planting and mulch ripping reduce runoff and hold water long enough to allow most of it infiltrate into the soil. The benefits of in situ water harvesting are reduction in runoff and erosion and increased infiltration and storage of water in the soil profile which delay the onset and occurrence of severe water stress thereby buffering the crop against damage caused by water deficits during dry periods (Nyamadzawo et al. 2013).In situ water harvesting improved crop yields food security and livelihoods in SSA. Mmbaga and Lyamchai (2001) reported maize grain yield increased from 0.8 t ha-1 on flat planting to 2.3t ha-1 with tied ridges in northern Tanzania in a season with less than 500 mm rainfall. However with higher rainfall of 800 mm there was no maize grain yield advantage recorded with tied ridges ridges and pit planting when compared to flat planting (Mmbaga and Lyamchai 2001). Other studies have shown that the effectiveness of in situ water harvesting techniques was dependent on soil textural class because of its influence on water holding capacity and drainage characteristics of the soil. Dagg and McCartney (1968) showed that tied ridges produced significantly more grain yield than flat planting only on vertisols but not on alfisols and andisols. Belay et al. (1998) recorded higher maize grain yield in Ethiopia on tied ridges than flat planting in two soil types (entisols and vertisols) with the effect of the tied ridges generally better in drier seasons and when the ends of the ridges were tied.Maize (Zea mays L.) is one of the most important food crops grown in Rwanda. It ranks second to sorghum among cereals and third to all crops covering 10% of the total cultivated land after beans (25%) and banana (22%). Maize production is rapidly expanding from the highlands (greater than 1700 m altitude) where it was mainly grown before 1996 to the moist mid-altitude (1450-1700 m altitude) and the semi-arid low altitude zone (900-1450 m altitude) (ISAR 2009) where temperatures are higher and more suitable for maize. Most of the maize in Rwanda is now grown in the semi-arid low altitude agro-ecologies of the Eastern Province which contributed 45% of the total maize grain harvest (79 500 t) produced in the 2008 season in Rwanda compared to 33% from highlands (National Institute of Statistics of Rwanda2010). The shift in maize production from the highlands and moist middle altitude to the semi-arid low altitude agro- ecologies has greatly increased the risk of crop failure due to droughts. Maize production decreased by 60.3% from a peak production of 508000 t in 2011 to 200000 t in 2012 (www.indexmundi.com) due to widespread crop failures caused by low and erratic rainfall in 2012 season in the low altitude semi-arid agro-ecology of the Eastern province where maize is now mainly grown. There is no information on the potential benefits from the use of in situ water harvesting techniques to trap rainfall increase infiltration and soil water content on maize growth and yield in the semi-arid low altitude agro-ecologies of Rwanda. The objective of this study was determine the effect of in situ rain waterharvesting techniques (pot-holes tied ridges and mulching) on soil moisture content maize growth and grain yield at Nyagatare Rwanda.

Materials and Methods

The study was carried out at Agricultural Processing Industry(API) farm owned by the Rwandan army at Gabiro (1 18'0.00"S 30 19' 30.00"E altitude 1400 m) in Nyagatare district in the Eastern Province of Rwanda. The district of Nyagatare is located in the north-east of Rwanda and shares a border with Uganda to the north and Tanzania to the east (Fig. 1). Soils are fersiallitic oxisols loams with 30% clay pH of 5.8 and 3.2% organic matter (Table 1) and have been under continuous cultivation for less than twenty years as Nyagatare district was only settled after the 1994 war in Rwanda. Rainfall ranges between 800-1000 mm with a bimodal distribution consisting of season A (September to January) and season B (February to May) with approximately half the rainfall (400-500 mm) received in each season.Three in situ water harvesting treatments (pot-holes tied ridges and mulching) were compared to control treatment with planting on the flat. The experiment was laid out as randomized complete block design of treatments replicated three times. The experiment was planted in season A in 2011/2012 season on 10th October 2011. The land was disc ploughed using a tractor to a depth of 25cm and plots were marked. Plots were 4.5 m A- 4.5m in size with 5m wide pathways around each plot within a block to avoid inter-plot treatments effects. A short season open pollinated variety ZM 607(R) (Crop Breeding Institute Zimbabwe) was planted at 75 cm A- 25 cm spacing for a target maize population of53333 plants ha-1. A basal compound fertilizer (N 17% P2O517% and K2O 17%) was applied into the planting station at200 kg ha-1 at planting before two maize seeds were placedto one side of the fertilizer and the planting station covered. The maize crop was thinned to one plant per station three weeks after emergence (WAE). At the same time all plots were hoe weeded and in situ water harvesting treatments were applied. Pot holes consisted of 30 cm long A- 20 cm wide A- 15 cm deep holes on alternate row centers spaced 50 cm apart. Tied ridges were produced by scooping soil towards the maize plants in the row forming a 15cm deep furrow between the rows and placing a cross-tie to hold water within the furrow every meter. The mulching treatment consisted of application of soybean crop residues to achieve100% soil cover. At five WAE the crop was hoe-weeded and top dressed with urea (46% N) nitrogen fertilizer at 200 kg ha-1 and a third hoe weeding was done at 9 WAE.Percent soil moisture content was measured using the gravimetric method at 8 11 and 14 WAE. Soil sampleswere collected to a depth of 25 cm using a soil auger at fiverandomly distributed points within each plot and immediately sealed in plastic bags. The soil samples were weighed using a precision balance oven dried for 48 h at105C and re-weighed. The difference in mass between the wet and the dry soil sample was expressed as percent soil moisture content. The mean percent moisture content fromfive samples is presented. Two maize plants were randomlyselected from the two border rows at 8 11 and 14 WAE cut at ground level and dried for 24 h at 85C to a constant massand then weighed. Maize grain yield was measured afterphysiological maturity from 3 m A- 4.5 m net plot consistingof four middle rows in each gross plot. A random sample of five ears were selected from each plot and ear mass numberof grains per ear and 100 grain weight determined. Grainmoisture content was measured using a moisture meter andgrain yield and 100 grain weight adjusted to 12.5% moisture content before statistical analysis.Data from the study was subjected to analysis of variance (ANOVA) using Genstat Discovery 12th Edition statistical package. Means were separated using standard error of the difference when F-test showed significant treatment effects at Pless than 0.05.ResultsSeason A in the 2011/2012 growing season at Gabiro Nyagatare was characterized by low monthly rainfall totals of below 100 mm per month and premature end of the season with little rain falling in January when the crop was at grain filling stages (Fig. 2). Total rainfall in season A was228.1 mm in comparison to 400-500 mm which is normally expected.Percent soil moisture significantly increased (Pless than 0.001) from flat planting pot-holing to tied ridging and was highest in the mulching treatment at 8 11 and 14 WAE. There was no difference in percent soil moisture content at 14 WAEbetween the pot-holing and tied ridging treatments (Fig. 3). The dry weight of maize plants significantly increased (Pless than 0.001) from flat planting pot-holing to tied ridging treatment and was highest in the mulching treatment at 8 11 and 14 WAE (Fig. 4). Maize grain yield followed the soil moisture and maize plant dry weight trends and significantly increased (Pless than 0.001) by 49.6 103 and 136 percent of the maize grain yield harvested from the flat planting control in the pot-holing tied ridging and mulching treatments respectively (Table 2). Maize yield components viz. ear mass number of grain per ear and 100 grain weight were similarly increased (Pless than 0.001) by the in situ water harvesting techniques with highest values obtained in the mulching treatment and the lowest in the flat planted control (Table 2).Correlation coefficients (Pearson r) between maize grain yield and percent soil water content (PWC) showed that maize grain yield was significantly correlated (Pless than 0.05) with percent soil water content with in situ water harvesting treatments at 8 and 11 WAE but not at 14 WAE (Pgreater than 0.05). Maize grain yield was significantly correlated (Pless than 0.05) to number of grains per ear but not to ear mass and100 grain weight. Ear mass was only significantly correlated

Table 1: Mineral composition of soil at Gabiro site Nyagatare Rwanda before planting the experiment in October 2011

Soil###Value Soil###Value Soil###Value Soil###Value

property###property###property###property

pH (1.1)###5.8 OM (%) 3.2###Mg###1.8 Zn###1.6

###(meq 100 g-1)###(mg kg-1)

E.C.(1.1) 0.50 P###15###Na###0.14 Mn###323.1

(nmhos/cm)###(mg kg-1)###(meq 100 g-1)###(mg kg-1)

NH4-N###16.0 K###349###S###43###Cu###3.0

(mg kg-1)###(mg kg-1)###(mg kg-1)###(mg kg-1)

NO3-N###13.6 Ca (meq 4.6###B###0.61 Fe###133

(mg kg-1)###100 g-1)###(mg kg-1)###(mg kg-1)

(Pless than 0.05) to late season percent water content of soil at 14WAE and not mid-season at 8 and 11 WAE. In contrast number of grains per ear was significantly correlated to mid- season soil moisture content at 8 WAE (Pless than 0.05) and 11WAE (Pless than 0.01) and not (Pgreater than 0.05) in the late season at 14WAE. The 100 grain weight was not significantly correlated(Pgreater than 0.05) to percent soil moisture mid-season at 8 and 11WAE but had a highly significant relationship (Pless than 0.01) to late season percent soil moisture content at 14 WAE. The100 grain weight was highly related (Pless than 0.001) to ear mass but did not have a significant relationship with number of grains per ear (Table 3).

Discussion

This study demonstrated the beneficial effects of in situ water harvesting techniques on percent soil water maize growth and grain yield in a below-normal rainfall season that ended early in a semi-arid low altitude agro-ecological zone in Rwanda.Maize grain yield was increased by 50 103 and 136 percent compared to flat planting in the pot-holing tied ridging and mulching treatments in this study. Further the differences in effectiveness in the capture and storage of rainfall within the soil recorded in these in situ water

Table 2: Effect of in-situ water harvesting treatments on grain yield and its yield components at Gabiro Nyagatare district Rwanda in season A in the 2011-2012 growing season

Treatment###Grain yield Ear mass###No. of grains###100 grain

###(kg per ha) (kg per ear)###per ear###weight (g)

Pot holes###2384.51 b###0.12 b###350.10 b###26.10 b

Tied ridges###3233.35 c###0.15 c###423.50 c###27.05 c

Mulch###3770.80 d###0.22 d###450.90 c###30.33 d

Flat###1593.36 a###0.09 a###237.70 a###24.58 a

P value###less than .001###less than .001###less than .001###less than .001

S.e.d###195.323###0.0123###27.71###0.650

CV (%)###8.4###1.7###2.9###1.3

Table 3: Correlation coefficients (Pearson r) among maize grain yield percent soil water content (PWC) at 8 11 and

###Grain PWC at PWC at###PWC at Ear###No of###100

###yield 8 WAE 11###14###mass###grains###grains

###WAE###WAE###per ear###weight

Grain###X###X###X###X###X###X###X

yield

PWC at 8###0.98 X###X###X###X###X###X

WAE

PWC at###0.98###0.98###X###X###X###X###X

11 WAE

PWC at###0.87###0.87 ns 0.78 ns X###X###X###X

14 WAE###ns

Ear mass###0.94 0.92 ns 0.86 ns 0.94###X###X###X

###ns

No of###0.98 0.98###0.99 0.98 ns 0.98 ns X###X

grains

per ear

100 grain 0.94 0.92 ns 0.86 ns 0.93 0.92 0.87 ns X

weight ns

14 WAE and yield components of maizeharvesting treatments at 8 and 11 WAE was significantly correlated to the maize grain yield. In situ water harvesting techniques therefore increased crop growth and economic yield by increasing soil available water. Tied ridges (Belay et al. 1998; Mmbaga and Lyamchai 2001; Araya and Stroosnijder 2010) and mulching (Lal 1974; Ramakrishna et al. 2006) were beneficial in increasing crop yields in seasons with below-normal rainfall in semi-arid environments. Pot-holes were relatively less effective than tied ridges in increasing maize grain yield compared to the control most probably because they were placed on every alternate row while tied ridges were placed on every row and potholes captured and stored less water in the soil. Mulching was the most effective treatment in capturing and storing moisture in the soil and concomitantly had the highest maize dry weights and grain yield among the three in situ water harvesting treatments. The maize crop residues not only reduced runoff and allowed the rain water to infiltrate into the soil but reduced soil temperatures and loss of water from the soil caused byevaporation as reported by Lal (1974) and Ramakrishna et al. (2006). Pot-holes and tied ridges only reduced runoff and enhanced infiltration of water into the soil and did not reduce evaporation of water from the soil hence the lower percent soil moisture plant dry weights and grain yield recorded in these treatments compared to mulching in this study.Maize grain yield was significantly correlated to soil moisture content mid-season at 8 and 11 WAE but not late season at 14 WAE. No meaningful rainfall was received after 11 WAE and by 14 WAE low soil moisture levels most likely reduced grain filling equally across all in situ water harvesting treatments explaining the lack of correlation between maize grain yield and percent soil moisture recorded at 14 WAE in this study. Number of grains per ear was the only yield component that was significantly correlated to maize grain yield in this study. Tollenaar (1977) and Fischer and Palmer (1984) also reported that kernel number per unit area was the most important determinant of maize grain yield. Number of grains per ear was significantly correlated to percent soil moisture content at 8 and 11 WAE but not at 14 WAE similar to grain yield. Number of grains per ear is strongly correlated to crop growth rate during the critical period bracketing silking (Aluko and Fischer 1987; Cirilo and Andrade 1994) which occurred at 10 WAE. Our results not only confirmed the strong relationship between number of grains per ear and grain yield but indicate that positive effects of in situ water harvesting techniques on maize grain yield were expressed through increases in number of grains per ear. Ear mass and 100 grain weight were significantly correlated with percent moisture content late season at 14WAE but not at 8 and 11 WAE because ear formation and grain filling (100 grain weight) occur late in the season after pollination at 10 WAE. Pollination was followed by ear growth and grain filling which were affected by percent soil water content at 14 WAE. The highly significant correlation between number of grains per ear and ear mass show that number of grains was a more important determinant of ear mass than 100 grain weight in this study.The results of this study suggest that pot holing can increase maize grain yield by 50 percent and tied ridging and mulching can potentially double it in the semi-arid agro- ecology where maize is increasingly being grown in Rwanda. These in situ water harvesting techniques are recommended for incorporation into the production practices of smallholder farmers in semi-arid areas to increase the resilience of crop production systems against droughts that are predicted to increase in frequency and severity because of climate change in SSA.

Acknowledgements

The management and staff of Agricultural Processing Industry and the Rwandan Army who provided land labor and inputs for this study are thankfully acknowledged.

References

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Author:Mudatenguha, Ferdinand; Anena, Jennifer; Kiptum, Clement K.; Mashingaidze, Arnold B.
Publication:International Journal of Agriculture and Biology
Article Type:Report
Geographic Code:6RWAN
Date:Oct 31, 2014
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