Effect of Reseeding and Water Harvesting on Productivity Botanical Composition and Diet Selected by Grazing Transhumant Sheep in Sheikan Locality North Kordofan State Sudan

Abstract

This experiment was conducted at El Obeid Research Station Farm at Bannu area, Sheikan Locality, North Kordofan State, over the two seasons of 2009/10 and 2010/11.The area has a unimodal annual rainfall of 300-400 mm occurring during July-October. The main economic activities are crop and livestock production. Livestock are raised either under sedentary or migratory systems where natural grazing is practised. The dominant livestock species are sheep, cattle, goats and camels. A main determinant of livestock production is low forage production resulting from low soil moisture due to low total precipitation and also to poor water infiltration rate associated with the prevalent type of sandy clay soils locally known as “gardud”. The objective of this study was to investigate the effect of re- seeding and water harvesting on rangeland forage biomass production, plant botanical composition, plant density and vegetation cover percent, at two range sites reseeded and un-reseeded and at flowering and seed set stages of growth. Diet botanical composition, voluntary intake of dry matter by grazing sheep, digestibility, the nutritional value of rangeland and the effect of three water harvesting techniques namely contour ridges, runoff strips and flat (control); and two planting methods specifically reseeding and natural regeneration (un-reseeded) on forage biomass production, plant density and vegetation cover were all also investigated. The loop method was used to determine botanical composition of the rangelands, forage biomass production was estimated by use of cut and weigh method, diet botanical composition was estimated using the bite-count technique, voluntary intake was assessed using a relationship between total fecal collection and dry matter digestibility; and digestibility was measured by using acid insoluble ash method. The nutritional value of rangeland was evaluated by determination of the chemical composition to assess pasture quality. 13 On average, the total plant density at the reseeded range was 307 plant/m2 compared with the un-reseeded range where it was 224 plant/m2. The vegetation cover at the flowering stage at the reseeded site was 74.8% compared with 43.0% in the un-reseeded site, while at the seed set stage it was 70.6% and 41.8% at the reseeded and un-reseeded sites respectively. Forage biomass productivity at flowering stage was 2.13 (t/ha) and 1.82 (t/ha) at reseeded and un-reseeded sites respectively compared with seed set stage of 1.89 (t/ha) at the reseeded range and 1.68 (t/ha) at the un-reseeded range. These differences were highly significant (P<0.001). The differences in biomass productivity between the two sites was probably due to the management system, where broadcasting of seeds of some species increased plant density and led to a reduction in bare soil percent and consequently increased biomass productivity. The species that were established by reseeding practice namely Blepharis linarifolia, Crotalaria spp. and Dactyloctenium aegyptium formed 6.78%, 4.55% and 0.72% respectively in the botanical composition on rangeland. At the flowering stage acid insoluble ash digestibility was higher in the reseeded range (67.3%) than in the un-reseeded range (64.7%) and was also higher for the reseeded site (64.2%) compared with the un-reseeded site (59.9%) at seed set stage. These differences were highly significant (P<0.001). At the flowering stage, dry matter intake in this study was 52.80 g/kg w0.75 and 40.99 g/kg w0.75 at the reseeded and un-reseeded range sites respectively. At the seed set stage, intake was 37.51g/kg w0.75 and 29.08 g/kg w0.75 at the reseeded and un-reseeded range sites respectively. Some plant species were classified as preferred species such as Ipomoea blepharosepala, Crotalaria spp., Indigofera spp., Tephrosia spp., Dactyloctenium aegyptium and Sesbania sesban and others as undesirable species such as Echinocloa 14 colonum, Acanthus spp., Ipomoea sp., Solanum dubium, Acacia nubica and Tribulus terrestris because these plants lost their leaves at seed set stage. These results indicate that the more nutritious plants and plant parts might have already been selected and consumed by livestock leaving the ones with less nutritive value. There were highly significant differences between chemical analysis of the plants selected by sheep and of the herbage biomass in the crude protein and crude fiber content between the phenological stages of flowering and seed set in the reseeded site and also in the un-reseeded site. Depending on the results, crude protein (CP), crude fiber (CF), enzyme soluble organic matter (ESOM), enzyme in-soluble organic matter (EIOM), water soluble carbohydrate (WSC), acid detergent fiber (ADF), acid detergent lignin (ADL), crude cellulose (CC), neutral detergent fiber (NDF) and hemi-cellulose (HC) were predicted by NIRS with good degrees of accuracy, thus, it was concluded that the accuracy of utility of NIRS to predict these parameters was acceptable. Therefore, NIRS application could be adopted to estimate above parameters because the laboratory methods take a lot of time. Under runoff strips, contour ridges and flat plant densities were 291 plant/m2, 262 plant/m2 and 162 plant/m2 at reseeded range. In the un-reseeded range site these were 236 plant/m2, 223 plant/m2 and 124 plant/m2 respectively. Vegetation cover for the three water harvesting methods in the reseeded site were 86.9%, 85.9% and 38.9%. In the un-reseeded range site these were 76.8%, 80% and 26.1% respectively. Forage biomass production in the reseeded site was 3.65, 2.25 and 0.65 t/ha for the three treatments respectively. In the un-reseeded range site the values were 2.85, 1.75 and 0.55 t/ha respectively. These differences were highly significant (P<0.001). The study gave strong evidence that marginal and fragile environments provide enough feed for livestock. The results provided very useful indicators for use in 15 designing range management practices, such as selecting species required for reseeding deteriorated range and in identifying key species that will form a base for range management. Livestock diets’ botanical composition could be used as an indicator for range quality. The results were discussed in relation to effect of increasing soil moisture content and reseeding on improving forage biomass production and animal production and on livelihoods and mitigation of environmental degradation. It was concluded that water harvesting techniques and reseeding resulted in increased biomass production and plant cover from rangelands.