Adverse climatic effects can influence farming output at any stage of development from cultivation to harvest. International Panel for Climate Change (IPCC, 2007) predicted that the average global surface temperature would increase by 2.8°C ranging from 1.8 to 4.0°C during 2050, assuming no emission control policies.  The agro-climate change includes increased drought affected  areas, reduced precipitation at lower altitudes, decreased water availability in mid-latitude and semi-arid low altitudes. Dry spell causes poor seedling emergence, drying of seedlings after germination, stunted growth of crops and poor or no yield (Ghini et al., 2008). Thus, any change in rainfall pattern, soil moisture, soil  temperature, soil fertility has direct  impact  on  the productivity and production of crops in general and common bean in particular. In semi-arid agro-ecologies, where food security is a priority concern, climate variability and uncertainty tend to be higher (Garette et al., 2006; IPCC, 2007; Niggli et al., 2009; Valipour, 2014a, b, c.), which will dispose subsistent farmers in the sub-Saharan region to high risks.

 

The strategies that a particular agro-ecological region will cope with climate variability depend largely on the societies` ability to create and use available knowledge (both indigenous and technology). Enhancing resilience to the effects of climate variability is important, and functional diversity is one of the most effective targets for improved sustainability (Newton et al., 2011). Nowadays, the debate on climate change is not on its occurrence and effects, but rather on how to mitigate the ever-happening effects of climate change to ensure food security of the ever-increasing human population and the proper functioning of the natural ecosystem. This needs to set alternative resilience strategies that mitigate the existing and ever happening impacts of climate change. Climatic condition contains a wide range of weather parameters  such  as  temperature,  relative  humidity,  wind  speed,  solar  radiation  and  the  like (Valipour, 2014a), which could be similar or different in different agroecological zones.

 

The most important and feasible climate change adaptation strategies for crop production and productivity are increased diversification with the use of species and cultivar mixtures through intercropping (Fininsa, 2003; Tana et al., 2007). Soil water conservation with furrow planting (Wang et al., 2008; Zhao et al., 2012), increasing nutrient use efficiency, improving  water-holding  capacity of a soil, crop rotation and use of irrigation (Katungi et al., 2009; Niggli et al., 2009: Valipour, 2014c). Intercropping refers to the spatial and temporal arrangement of different crops to exploit natural resources efficiently and enhance productivity per unit area and time by increasing the effective utilization of land, soil moisture, nutrients and solar radiation (Rahimi et al., 2014:Valipour, 2015). It is known to make a more efficient use of growth factors as it captures and makes a better use of radiant energy (Matusso et al., 2012: Valipour, 2015), available water and nutrients (Sullivan, 2003), maintains and improves soil fertility (Sanginga and Woomer, 2009; Seran and Brintha, 2010).

 

Furrow planting (FP) collects rainwater from ridges and it is especially useful in arid and semi arid regions, where irrigation water is not available or is costly (Wang et al., 2008; Valipour, 2015). Furrow planting system can improve soil moisture storage, prolong the period of crop water availability, and enhance crop growth (Qin et al., 2014). Furrowing has been played vital role in the improvement of grain yield and water use efficiency per unit area of crops (Zhao et al., 2012: Rahimi et al., 2014; Valipour, 2014a,b). Furrowing has been shown to reduce topsoil temperature, especially at the seedling stage, decrease soil evaporation, increase topsoil moisture (Zhou et al., 2012), and enhance plant maturity and grain yield (Li et al., 2012; Zhou et al., 2012: Valipour, 2014b).  Furrowing  controls  water  evaporation  from  the  surface  soil  and  improves  soil  water retention (Grose, 2012; Rahimi et al., 2014; Valipour, 2015).

 

Composting is one of the few green house gases emission reduction methodologies related to agriculture. Compost is a valuable resource offering significant agricultural and environmental benefits  to  farmers  and  the  community  because  of  its  unique  characteristics,  which  can  offer significant returns in the form of increased crop yields and improved quality of produce. Compost contains macro and trace elements essential for healthy plant growth (Stutz et al., 2003; Shehata et al., 2011), which reduces the need to use synthetic fertilizers by returning valuable nutrients to the soil. Compost improves soil structure resulting in increased water holding capacity and nutrient retention of the soil.  It also reduces the potential ground water contamination from synthetic fertilizers that are toxic to plants and beneficial organisms. Therefore, it is important to apply nitrogen via composts at environmentally and agronomically responsible levels, which requires understanding of soil factors regulating the release of nitrogen compounds in soil systems, such as moisture content, pH, soil organic matter content and quality, soil texture, buffering capacity and nitrification rate (Sullivan, 2003; Bryan et al., 2009).

 

Integrating field based climate change resilience strategies for understanding the effects of climate change on crop  production  that  leads  to appropriate adaptation measures in action has to be investigated. Research in climate change related issues could result in improved understanding and management of crop production in the face of current and future climate extremes (Garette et al., 2006; Niggli et al., 2009). However, little is known about the effect of different climate change resilience strategies on productivity of crops especially common bean. Therefore, the influence of integrated field based climate change resilience strategies on crop productivity need to be assessed since such data of crop production under climate change resilience strategies would be useful in climate prediction and modelling (Valipour, 2004a). The objective of this study, therefore, was to assess the effects of integrated climate change resilience strategies on the productivity of common bean.

Experimental sites

 

Field experiments were conducted at Haramaya University experimental field stations at Babile in 2012 and 2013 and Haramaya in 2012, eastern Ethiopia, during main cropping seasons (June to November). Haramaya is located at 09° 26´ N and 42° 3´ E. The altitude of the area is 1980 m above sea level with average annual rainfall of 786.8 mm, with mean minimum temperature of 10.4°C and means maximum temperature of 23.4°C. The location has varied soil types (from luvisol to vertisol) with pH range of 5.0 to 8.0. Babile is situated at 09?13´ N and 42?19´ E, with altitude of 1655 m above sea level with annual total rainfall of 719.2 mm. The mean minimum and maximum temperatures are 15.4 and  28.3°C, respectively. The soil of Babile has sandy loam texture with pH of 7.6.

 

Both locations represent important common bean and sorghum growing areas in eastern Ethiopia. Babile  is  a  representative  of  semi-arid  agro  ecology  whereas  Haramaya  is  a  representative  of midland agro ecology, and both locations are highly  affected  by  climate  change   events   such   as   increased temperature and variable rainfall pattern. The weather variables (mean maximum and minimum monthly temperature, mean monthly total rainfall) for 2012 and 2013 of both locations during growing seasons are presented in Figure 1.

 

 

Treatments and experimental design

 

Three field based climate change resilience strategies and a control were used as treatments. The strategies consisted of crop diversification (row intercropping), moisture conservation (furrow planting) and soil nutrient management (composting). The treatments were common bean-sorghum row intercropping, furrow planting, compost application, and sole planting. The treatments were applied separately and in integration (minimum of two) using two common bean varieties Gofta (G-2816) and Mexican 142 (G-11239). The varieties were obtained from Melkasa Agricultural Research Center, Ethiopia. Sorghum variety, Teshale (3442-2 OP) developed for the semi-arid environment as moisture stress and striga weed tolerant was used (Table 1). A sole planted sorghum was also included as control. Seventeen treatment combinations were arranged in randomized complete block design in a factorial arrangement and replicated three times per treatment.

 

 

 

order to harvest the rainwater. Sorghum seeds were sown on 21 June 2012 and 28 June 2013 at Babile, 20 June 2012 at Haramaya by hand drilling seeds at the rate of 5 kg ha^-1 and after emergence, the plants were thinned to one plant per hill of 25 cm intra-row spacing. Common bean seeds were sown on 11 July 2012 and 05 July 2013 at Babile, 07 July 2012 at Haramaya manually by planting two seeds per hill. After emergence and establishment of seedlings, the rows were thinned to one plant per hill. The plots were hand weeded three times at Haramaya and two times at Babile and cultivated once during the growth periods at both locations.

 

Data collection

 

Crop data

 

The plant heights (cm), number of pods per plant, number of seeds per pod were recorded from 10 randomly taken plants and the averages were calculated. Hundred seed weight (g) of common bean, 1000-kernel weight of sorghum and yield of both crops (kg) were recorded at 12.5% seed moisture content for sorghum and 10% for common bean. The grain yields (kg) of both crops were converted to ton per hectare (t ha^-1). Yield data of common bean was recorded for each plot from the middle seven rows of sole and four rows of intercropped plots excluding two border rows on both sides to avoid border effects. In addition, yield of both crops from sole and from the intercropped plots were evaluated by using land equivalent ratio (LER) as described by Mead and Wiley (1980):

 

 

Where Yab is seed yield of common bean in intercrop with sorghum; Yaa  seed yield/ha of sole common bean; Yba is grain yield/ha of sorghum in intercrop with common bean Ybb is grain yield/ha of sole sorghum.

 

Meteorological data

 

Weather data of each location were collected from the nearby meteorological station (as means of five years) for both experimental stations. Weather variables of minimum temperature at 09:00 h and maximum daily air temperature at 18:00 h (°C), relative humidity (%) at 06:00 h, 09:00 h, 12:00 h, 15:00 h and 18:00 h, and daily rainfall (mm) were collected and the averages were calculated. In addition, the data of soil moisture (%) and soil temperature (°C), minimum temperature at 09:00 h and maximum temperature at 15:00 h from sole planting or control and most integrated (row intercropping + compost application + furrow planting)  plots  of  both  experimental  sites  were  monitored    and  recorded  with  soil  thermometer  during 2013  cropping  season  every week  from August to October. The data of soil moisture was also recorded using soil sample collector (Auger) from the depth of 20 to 40 cm at 09:00 h from the most integrated and sole planted plots of both sites during of 2013 cropping season every week. The monthly averages for each variable were calculated. The water content of soil was calculated based on wet weight of soil sample obtained immediately after sample collection and dry sample recorded after drying the soil in the oven at 105°C for 24 h. The percentage of water content was calculated based on gravimetric method.

 

Percentage moisture= (Wet wt-dry wt.)/dry wt. x100.

 

Data analysis

 

Data of plant height, number of pods per plant, seeds per pod, 100-seed weight and yield were subjected to analysis of variance using PROC GLM procedure of SAS version 9.1, (SAS Institute. 2003) to determine treatment effects. Homogeneity of variances was tested using the procedure described by Gomez and Gomez (1984) and as the test showed heterogeneity of variances, separate analysis of the two-year and two location data was performed. Differences among treatment means were compared using the Fisher's least significant difference test at 5% level of significance.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Plant height, number of pods per plant, number of seeds per pod, 100-seed weight and grain yield were significantly affected by climate change resilience strategies. The highest plant height was obtained from the row intercropping + compost application of Mexican 142 variety at Haramaya in 2012 might be due to the indeterminate growth and climbing nature of Mexican 142 to component crop, the sorghum and the availability of nutrients from the compost. There was a decreasing trend in yield and yield components from the most integrated climate change resilience strategies to the less integrated and sole planting.

 

The result of this study revealed that there is the synergic effect of the climate change resilience strategies, in increasing yield and yield components. It is important to note that the benefits of climate change resilience strategies discussed above are location specific that is why compost application + furrow planting and furrow planting increased plant height by 16 and 14%, respectively, compared to sole planting on variety Gofta at Babile in 2012. Although the water holding capacity of soil at Babile is very low due to its light texture (sandy loam), integration  of  compost  with furrow planting improved the productivity of common bean. In the shortage of rainfall especially in 2012 cropping season, intercropping common bean with sorghum, did not significantly increase yield and yield components of common bean. It might be because of the competition for limited water available between the two crops, such that the canopy of common bean in the intercropping system was very low since sorghum had higher water absorption capacity. In 2013, row intercropping + compost application + furrow planting and row intercropping + compost application, significantly increased yield and yield components at Babile. The intercropped climate change resilience strategies, significantly increased plant height, number of pods per plant, number of seeds per pod and 100-seed weight and grain yield of both crops than sole planting at Babile in 2013, which might be due to relatively higher rainfall and lower mean temperature during 2013 compared to 2012 at Babile.

 

The climate change resilience strategies were more effective when they were integrated and when the risk factors are minimized. At Haramaya, there was heavy frost on 14 October 2012, when the crop was at physiological maturity, which might be the cause for reduction in yield and yield components, especially 100 seed weight of variety Mexican 142, the late maturing variety.   It is highly observed that relatively lower yield obtained from intercropping was compensated by the yield of the component crop (sorghum) when evaluated using land equivalent ratio (LER) and all of the intercropping plots had additional yield advantage over sole crop of common bean.

 

The present study revealed that the integrated climate change resilience strategies (row intercropping + compost application + furrow planting, row intercropping + compost application) tested at Babile and Haramaya are feasible  in  conserving  soil  moisture,  increasing productivity of common bean, averting crop failure risks, hence increasing climate change resilience. This result was in agreement with the reports of Niggli et al. (2009) that described sustainable land management practices such as compost   application,   crop   diversification   and   water   harvesting   can   improve   soil   carbon sequestration, crop yields and enhances resilience to climate change and increasing crop productivity (Bryan et al., 2011). Compost application had increased yield and yield components of both crops might be due to the availability of major elements of plant nutrients. In addition to its long-term effect of maintaining soil chemical property and physical structure, reduces emissions of greenhouse gases by compensating utilization of inorganic fertilizers harmful to the atmosphere (Niggli et al., 2009). The chemical analysis of compost used in this study had higher organic content; higher nitrogen content and higher available phosphorus, hence might have improved soil fertility, which agreed with the reports of Bryan et al. (2011), where the application of compost to fields provides benefits in terms of crop yields, increases climate change resilience. Furrowing could be one of the factors that increased yield and yield components, reduced soil temperature and increased soil moisture when integrated with intercropping and compost application based on the soil type and rainfall amount. This result is also agreed to report of Qin et al. (2014) where furrowing increased yield and soil moisture and to the report of Grose et al. (2012) where furrowing can reduce yield variability and heat stress in dry areas.

 

Overall, the results of present study showed that the most integrated and row intercropping + compost application can be applied to increase the climate change resilience at higher extent, although the optimal integration of strategies depends on a number of factors including crop variety, soil type and agroecological zone. Generally integrating climate change resilience strategies reduced climate  variability  and  significantly  increased  yield  and  yield  components  of  common  bean: However, the application rate of compost and furrow preparation needs further investigation for common bean production.

 

The soil moisture and temperature data showed that the most integrated climate change resilience strategy gave promising result in reduction of soil temperature and retention of water in the soil, hence, might be responsible for mitigating climate change. The results obtained from this study suggested the importance of climate change resilience strategies alone and in combination for increasing of yield and yield components of common bean in eastern Ethiopia and in areas with similar agro-ecological conditions. The compost application rate and furrow preparation need to be further investigated for common bean and other crops in the study area. The importance of solar radiation, temperature, relative humidity, and wind speed for calculation of reference evapotranspiration need to be investigated for proper utilization of furrow planting.

The authors have not declared any conflict of interest.

Authors would like to thank Masresha Lebie, Woinishet Feleke, Birhanu Asfaw, Azeb Tegenu and the late Cholamu Faltamo, field assistants in the School of Plant Sciences of Haramaya University, for their assistance in data collection and fieldwork. The project was financed by Haramaya University.