Phosphorus is an essential macronutrient, both as a component of several important plant structural compounds and as a catalyst in the conversion of numerous important biochemical reactions in plants. The soil Olsen P (OP) level is an important factor affecting crop production and P-use efficiency (PUE). We tested the effect of six OP levels and P doses on maize yield, where the P doses were 0, 22, 44, 59, 73, and 117 kg P₂O₅ ha⁻¹, with three replications, from 2017 to 2019. The response of crop yield to the OP level can be divided into two parts, below 28 mg kg⁻¹ and above 28 mg kg⁻¹. The change point between the two parts was determined as the agronomic critical level for maize crops in the study area. The PUE (%) increased with soil OP levels and decreased with P fertilizer application rates. In addition, results for the low P application rate (P2), 22 kg P₂O₅ ha⁻¹, showed that PUE significantly increased with an increase in the soil OP level compared with PUE at a low OP level (OP1), 0 kg P₂O₅ ha⁻¹. The PUE value increased by 49.5%, 40.1%, and 32.4% at a high OP level (OP6) in 2017, 2018, and 2019, respectively, compared to that at a low OP level (OP1). At the same OP levels, in all three years, the PUE at a high P application rate (P6) decreased significantly, in the range of 62.8% to 78.7%, compared to that at a low P application rate (P2). Under an average deficit of 100 kg ha⁻¹ P, the OP level of the soil in all three years decreased by 3.9 mg kg⁻¹ in the treatment without P addition (P1) and increased by 2.4–3.5 mg kg⁻¹ in the P treatments for each 100 kg ha⁻¹ P surplus. A phosphorus application rate of 44 kg P₂O₅ ha⁻¹ and an OP level of 28 mg kg⁻¹ are sufficient to obtain an optimum yield, increase the PUE, and reduce environmental hazards in the study area in northeastern China.

This study was conducted in Um "Nabag" (15km north of "Bara"), "Dilling" (160km south of "Elobeid") and "Eldemiokya" (30km east of "Elobeid"). The main objective of this study is to assess the effect of grazing on growth performance of natural rangelands in Kordofan region. The specific objectives: To assess the effect of grazing level on vegetation frequency. The results showed different levels of grazing intensity at different sites as indicated by plants frequency and biomass. Intensive grazing levels were found at Bara in the north, early and late in the rainy season but in Dilling it was not found in the late in the rainy season for both seasons (2008 and 2009) which indicated longer stay of herders in "Bara" area as a rainy season residences. Frequency of the species between non- grazed and grazed areas showed a decrease for the two seasons especially for preferred species at the different sites as in the case of Eragrostis termula and Cenchrus biflorus in (2008 ),Similar results were observed in (2009) with Fimbirsty dichotomo and Cenchrus biflorus. The study recommended that grazing level can be used as practical mean to assess utilization level as expressed by growth performance indicators including frequency. Level (II) is expected to result in negative impact on rangeland plants growth performance.

Abstract: This study was conducted for two consecutive years (2008 and 2009) on the natural rangeland of greater Kordofan region at three sites:, the main objective was to investigate the variation in rangeland vegetation as indicated by different growth conditions. The field work was carried out at the start of rainy seasons and seed setting stages in the three locations.Results showed that the biomass production at Dilling showed highest values followed by Demokeya and then Bara. Plant composition in Dilling, showed highest values followed by Demokeya and then Bara. Litter % in Dilling showed lowest values. The variations investigated by the study justify differential management prescriptions that cater for activities such as seed broadcasting and enrichment of range with certain plant species. Vegetation cover% was lowest in Bara followed by Demokeya and then Dilling. Bare soil incidents were higher in Bara and Demokeya than in Dilling. The crude protein content of herbaceous biomass was higher in Bara and Demokeya (sandy soil) than in Dilling (clay soil). The crude fiber content (CF) decrease or increase according to the plant age in the three sites. The high ash content was in Dilling compared with Bara and Demokeya. However, in time of sampling, the differences were recorded in ash but their values decreased by the plant growth. The differences in dry matter between the seasons and among sites were minor. The grasses were the dominant plants in the three sites.The similarity index indicated that there was minor similarity recorded between Bara and Damokeya (45%), followed by Damokeya and Dilling (30%) and dissimilarity was between Bara and Dilling (3%).