Multiple Advantages of Pigeon Pea (Cajanas Cajan) in Maize Based Cropping Systems: Used as Live Stake for Climbing Bean with Phosphorus Rates and Maize Productivity Enhancement in Mono Cropping Areas

Continuous maize based monoculture is one of the major bottlenecks limiting land and crop productivity in western Ethiopia. Pigeon pea plays vital role in rehabilitating degraded land and depleted soils due to its high N-fixation capacity, high biomass production and high litter fall. It can also support climbing bean as live stake. Two sets of the experiment were conducted for five consecutive years at Bako Agricultural Research Center. In 2009 and 2010 cropping seasons, pigeon pea was established and two crops (tef and finger millet) which were considered as one factor were under sown as tangua systems until the pigeon pea reaches its maximum growth. In 2010 and 2011, climbing bean was planted in established pigeon pea under different pruning options ( 25%,50% and 75% branch remaining) and with P2O5 rates (0,15,30 and 46 kg/ha). Thus treatments were arranged in factorial combinations and replicated three times. In 2011 and 2012, maize was planted on the permanent plots that two crops sown during pigeon pea establishment and received pigeon pea biomass under different pruning options and with N application rates (0, 36, 72 and 110 kg/ha) and designed in RCBD factorial arrangement. The result revealed that better biomass and grain yield of finger millet under sown during the establishment of pigeon pea was obtained compared to tef. Significant yield increase of climbing bean was recorded when percentage of pigeon pea branch removal was increased. Application of phosphorus increased grain yield of climbing bean, but there was no significant difference on yield of pigeon pea. Seasonal variability highly affected maize yield performance and the yield was highly reduced during 2012 compared to 2011 due to the lowest annual rainfall amount received in this season against the last ten years. There was strong and positive correlation of maize yield and annual rainfall of cropping season. Maize yield was not significantly different due to the residual effects of pigeon pea biomass retained under different pruning levels. But, highly significant yield increase was observed due to residual effects of retained biomass as compared to farmers’ practices and even under maize-climbing bean intercropping. Application of N to maize planted on previous plots that received pigeon pea biomass showed no significant variations though the better yield was recorded when 33 kg/ha N and 72 kg/ha N were applied in 2012 and 2011 cropping seasons, respectively. However, significant yield increases were obtained when the crop was planted on previous plots that were retained by pigeon pea biomass, regardless of N application rates, compared to the sole maize monoculture and in intercropping system. The result also clarifies the performance of maize without N application gave similar grain yield compared to current farmers’ practices. Generally, significant yield increment by 6-17% and 5-30% over farmers’ practices were recorded in 2011 and 2012, respectively. In short rainy season, maize yield planted on previous plots retained by pigeon pea biomass or as litter fall and with no N performed significantly better than farmers’ practices. Retention of pigeon pea biomass or released as litter fall on the following year for maize production can also significantly reduce 66-100% of the total recommended N while significantly increase maize yield. In 2013, the maize was planted on the permanent plots that had pigeon biomass or litter fall and with no chemical fertilizers revealed more than 100% and 75% yield increments as compared to yield of maize under intercrops and farmers’ practices. Indeed, pigeon pea can be used as live stake for climbing bean production or pigeon pea-climbing bean intercropping at appropriate pruning level (up to 50% to 75% branch removals). Moreover, the buildup of soil fertility through establishing pigeon pea and its biomass retention evidently boost the productivity of the soil and even 100% reduction of chemical N fertilizer cost. Hence farmers are advised not to apply any N fertilizer sources in the following years since its left over effects significantly enhance maize yield. However, further investigation is needed to specify the frequency of organic matter buildup using this pigeon pea plant and its impact on availability of naturally fixed nutrients, likes phosphorus. Keywords: Pigeon pea, Climbing bean, Pruning levels, Nitrogen, Phosphoru