Influence of Varietal Selection and Treatments on Nutritive Value of Some Pulse Residue
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Crop residue (CR) is a multi-purpose resource in the mixed crop-livestock systems of Ethiopian highlands. They serve mainly as livestock feed and inputs for soil and water conservation. They are generated predominantly from cereals and pulses. However, in view of the allocation of CR, soil conservation and livestock are two competing enterprises. Identifying determinants of the intensity of use of cereal and pulse residue may help in designing strategies for more efficient CR utilization. Data on CR was generated and its utilization was collected in two highland regions in Ethiopia from 160 households using a structured questionnaire. The data was analyzed using a multivariate Tobit model. Results of the study showed that farmers prefer using CR from pulses over CR from cereals for livestock feeding purposes. The proportion of CR from pulses that was used as feed was positively affected by education level of the farmer, livestock extension service, number of small ruminants and CR production from the previous season. Distance of farm plots from residences of the farm households negatively affected the proportions of cereal and pulse residue used for feed. The use of pulse residue increased significantly when the women participated in decision making on CR utilization. The proportion of cereal and pulse residue used for soil mulch was positively affected by the education level of the farmer, the distance between the homestead and the cultivated land, extension service, awareness about soil mulch, the slope of cultivated land, participation in farmer-to-farmer extension and CR generated in the preceding season. In view that pulse CR have better nutritive value compared to cereal CR, better utilization of CR could be achieved by maximizing the use of pulse residue as livestock feed and optimizing the use of cereal residue as soil mulch. More livestock extension on the nutritive value of pulse residue should be provided to the farmers who cultivate sloppy plots. Encouraging the culture of labor exchange among the farmers could result in an increased labor availability in the farms that would facilitate the transport and storage of pulse residue and increase its use as livestock feed. Increasing the awareness among farmers about the superiority of the pulse residue over cereal residue as feed and encouraging use of cereal residue as soil mulch could optimize the utilization of CR in the household. Increasing the biomass of CR will help optimizing the utilization of this resource for both livestock feeding and soil mulching. According to the previous results, improving the yield and the nutritive value of chickpea, faba bean and lentil can improve the utilization of CR and enhance livestock productivity in the farming unit. Varietal selection based on straw traits requires sufficient genotypic variation in straw parameters. Furthermore, the expected improvement in the nutritive value of CR during multi-trait improvement has to be considerable compared to that could be achieved by practical treatments. Thus, urea treatment, widely used to improve the nutritive value of CR and ash treatment, a practical and cost-effective treatment to improve CR quality, were used as a baseline to evaluate the variation in straw quality. Besides, integrating straw quality into improvement programs of pulses requires a reliable method to phenotype straw samples for nutritive quality traits. Final evaluation of superior straws should be done in situ trial; such trials need an evaluation of IVOMD and ME before commencement. Thus, predicting IVOMD and ME using chemical analysis facilitates conducting such trials. An evaluation of the relationship between straw and grain traits is important to explore the existence of any tradeoff between grain yield and straw traits. Accordingly, to determine the existence of varietal variation in straw quality, twenty three cultivars, one local variety and one improved and released variety of lentil released for high grain yield were replicated four times in a randomized complete block trial. Fourteen cultivars, one local variety and two improved and released varieties of chickpea released for high grain yield were replicated four times in a randomized complete block trial. Both trails were carried out in Ethiopia, Debre Ziet Agricultural Research Centre. Five varieties of faba bean, four improved and released variety and one local variety, were investigated for varietal variation in straw yield, grain yield and nutritive value of straw morphological fractions. Samples of the whole faba bean biomass were collected and separated into grain and straw. The straw was further divided into leaves, stems and pods. Straw from plots of the local varieties of the trials was used to determine the effect of 4% urea treatment, the effect of dung ash treatment (control, 0g ash/L, 100 g ash/L, 200 g ash/L 300 g ash/L) and wood ash treatment (control, 0 g ash/L, 150 g ash/L, 200 g ash/L) on the nutritional value. All straw samples were evaluated for proximate analysis, in vitro organic matter digestibility (IVOMD) and metabolizable energy (ME) using Near Infra-red Spectroscopy. Varietal variation (P<0.001) in grain yield and straw yield and nutritive value was found in chickpea and lentil. Significant varietal variations (P<0.001) were detected in dry matter (DM), ash, IVOMD, ME and potential ME intake (MEI) but not in CP, neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL), potential DM intake (DMI) and potential CP intake (CPI) of whole faba bean straw. Urea treatment significantly (P<0.001) improved CP, ME, IVOMD, DMI, CPI and MEI of chickpea straw, faba bean and lentil straw. Least significant difference (LSD) among chickpea genotypes was higher than the increase resulted from urea treatment for IVOMD, ME, DMI, and MEI (1.15, 1.17, 1.45 and 1.24 folds respectively). The increase in CP and CPI in chickpea straw due to urea treatment was higher than the corresponding genotypic LSD (1.53 times and 1.66 time respectively). The increase caused by urea treatment of faba bean straw was higher than corresponding genotypic LSD (66.2 times for CP, 12.5 times for IVOMD, 2.1 times for ME, 5.5 times for CPI and 1.4 times for MEI). Genotypic LSD of DMI of faba bean straw was 1.3 times higher than that resulted from urea treatment. Urea treatment significantly (P<0.001) improved CP, ME, IVOMD, DMI, CPI and MEI of lentil straw. In lentil, the increment in CP and CPI of straw resulted from urea treatment was 2.61 times and 0.47 times higher than the corresponding genotypic based LSD respectively while that increment in IVOMD, ME, DMI was 1.1 times, 2.5 times and 0.92 times higher than the corresponding genotypic LSD. Dung and wood ash treatment failed to improve the nutritive value of faba bean, chickpea and lentil straws. Leaves of faba bean straw showed the highest IVOMD and content of CP, while pods were highest in ME. Varietal variations in straw quality traits within fractions were significant (P<0.001). Canonical correlation analysis showed significant correlations between the nutritive value of the whole faba bean straw and the nutritive value and proportions of its botanical fractions. (P<0.001). Furthermore, canonical correlation between nutritive value of whole faba bean straw and relative proportion of fractions was significant and moderate (P<0.001). Therefore, botanical structure can be used as reliable method for screening faba bean genotypes for straw quality. The results of the current study showed that ADF, correlating very strongly (r>0.8) to other nutritional quality parameters in chickpea, faba bean and lentil straws, can present solely straw nutritive value. Straw yield of chickpea correlated weakly with grain yield (r=0.367, P= 0.002) while no relation between grain yield and straw quality traits was found (CP: r=0.087, P=0.526; IVOMD: r=,-0.49 P= 696; ME: r=-0.049, P= 0.668). Grain and straw yields were positively, strongly and significantly (P<0.001) correlated in faba bean. Grain yield of faba bean weakly correlate to CP (r= 0.162, P= 0.42), IVOMD (r= 0.027, P= 0.741) and ME content of straw (r=0.164, P= 0.05). In lentil, straw yield correlated weakly with grain yield (r=0.39, P<0.001) while no relation between grain yield and straw quality traits was found (CP: r=-0.23, P= 0.06; IVOMD: r= -0.104, P= 0.397; ME: r= -0.11, P= 0.37). Accordingly, straw yield and quality traits can be integrated into multi-trait improvement programs of chickpea, faba bean and lentil without compromising grain yield leading to varieties with superior grain and straw traits. These varieties are expected to have a multi-dimensional benefit in the farm including securing more food for humans and feed for livestock and contributing positively to soil conservation.