Productivity and chemical composition of green biomass from Sudan grass, grown as a second crop, with optimal and insufficient water supply

The aim of the present study is to determine the impact of the disturbed irrigation regime on the yield and the chemical composition of Sudan grass, grown as a second crop. To accomplish this goal, a trial was conducted in the experimental field of the Agricultural Institute - Stara Zagora with Sudan grass on meadow-cinnamon soil under irrigated conditions. The following variants have been studied: 1 - without irrigation (control variant); variant 2 - optimal irrigation, 75-80% of field capacity (FC); variant 3 - irrigation as in variant 2, but with the removal of the first watering; variant 4 - irrigation as variant 2, but with the removal of the second irrigation; variant 5 - irrigation as variant 2, but with the removal of the third watering. It was found that when growing Sudan grass as a second crop with optimal irrigation and disturbed irrigation regime done by canceling successive watering, the highest yield of dry biomass is obtained with optimal irrigation including three irrigations. Its yield increased by 24.2% compared to the control treatment. Irrigation of Sudan grass with only the second and the third irrigation in a row, without the first irrigation provided, leads to the lowest yield of dry biomass - 11290 kg / ha. Among the chemical composition indicators, the most significant change is observed in the content of the crude fat, followed by that of the crude fiber and crude protein, depending on the method of growing Sudan grass (with or without irrigation).

Research on the Influence of Typical Soil Parameters on Critical Breakdown Field Strength and Residual Resistivity Based on Discharge Topography

Partial discharge of soil occurs when a lightning current enters the ground, and the strength of partial discharge is closely related to the magnitude of its critical breakdown field strength. Therefore, how to accurately obtain the variation law of the typical soil critical breakdown field strength and residual resistivity is the key to realizing the safe operation of the grounding devices and cables in the ground. This paper first selects a variety of typical soils to study the influence of various factors on the morphology of the discharge channel, and then studies the calculation methods of the soil critical breakdown field strength and residual resistivity under the introduction of different discharge channel morphologies and structures, and further discusses the reason why typical soil media factors have a small impact on the critical breakdown field. The experimental results show that under the same conditions, the critical breakdown field strengths of different soils from small to large are sand soil, loam soil and Yellow cinnamon soil. The largest ratio of residual resistivity to initial resistivity of the three soils is sand soil.

Effect of irrigation rate on Sudan grass yield, grown as a second crop

The aim of the present study was to establish the effect of irrigation rate on the yield of Sudan grass variety Engje-1, grown as a second crop for silage on meadow-cinnamon soil for the region of Southern Bulgaria. For this purpose, an experiment with Sudan grass variety Endje-1 on the experimental field of the Agricultural Institute – Stara Zagora, after its predecessor barley, was conducted. The Sudan grass was harvested in the brooming stage. Five variants were explored: Variant 1 – without irrigation (control); Variant 2 – with optimal irrigation, 75-80% of field capacity (FC); Variant 3 – irrigation as Var.2 but with removal of the first watering; Variant 4 – irrigation as Var.2 but with removal of the second watering; Variant 5 – irrigation as Var.2, but with removal of the third watering. It was found that the efficiency of 1m3 of irrigation water was the highest at the optimum variant (Var.2), where 5.36 kg of dry mass (DM) were produced by 1 m3 of water. With the removal of the second irrigation (Var.4), the yield on the dry mass decreased by 6.4% compared to the optimal variant (Var.2), and with the removal of the first irrigation (Var.3) the losses on the dry mass reached, 12.3%, respectively. The highest values of this indicator were obtained by varying the second irigation (Vаr.4) – 7.53 kgDM/m3 water. The coefficient of efficiency of the irrigation rate, representing the ratio between the increase of the yield (in comparison with the version without irrigation – Vаr.1), and the size of the realized irrigation norm had the highest value in the version without second irrigation (Vаr.4) and the lowest values for the version without first irrigation (Vаr.3).

Soil phosphorus composition, loss risk and contribution to the aquatic environment in a typical agricultural area

River eutrophication risk increased significantly in agricultural areas. In this paper, spatial variability of soil phosphorus (P) and loss risk in the Jialu River Basin, China, were analyzed using a geostatistical approach. The correlation between soil and river sediment P was analyzed to identify the main aquatic P source. The results showed that inorganic phosphorus (IP) was the main form of soil TP (82.13%), but the ratio of apatite phosphorus (AP) and non-apatite phosphorus (NAIP) varied between different soil types. AP was the primary form of IP in fluvo-aquic cinnamon soil, while NAIP dominated in meadow aeolian sandy soil. Calculated soil total dissolvable P (TDP, 94–622 mg/kg) exceeded the environmental threshold. High TDP (>400 mg/kg) in mixed soil and sandy soil indicated a high P loss risk. The spatial variability of soil P was moderate to weak, indicating a low heterogeneity. In sediment, IP and AP showed a significant correlation with total organic carbon (p < 0.05), indicating a P source of soil erosion. Sediment AP had a significant positive correlation with soil AP (p < 0.05), confirming soil as the main source of sediment P. Furthermore, an accumulation of sediment P along the Jialu River and its consistency with water TP was revealed.

Evapotranspiration in Sudan grass second culture grown under non – irrigated and optimal irrigated conditions

The aim of the present study was to establish the evapotranspiration of Sudan grass variety Engje-1, grown as a second crop for silage on meadow-cinnamon soil for the region of Southern Bulgaria under irrigation conditions and without irrigation. For this purpose, an experiment with Sudan variety Endje-1 was conducted in the experimental field of the Agricultural Institute – Stara Zagora on soil type meadow-cinnamon soil, after its predecessor barley. The Sudan grass is harvested in the brooming stage. Two variants were explored: Variant 1 – without irrigation (control) and Variant 2 – with optimal irrigation, 70-75% of field capacity (FC). Evapotranspiration of Sudan grass grown as a second crop under non-irrigated conditions, depending on the nature of the year, ranges from 168.7 mm to 183.7 mm. Under conditions of irrigation, the largest share in the formation of the water consumption is occupied by the irrigation norm – 87.1% on average (from 86.3 to 90.8%). Under irrigated conditions, the relative participation of the initial water reserve in the formation of evapotranspiration significantly decreases.

The Effect of a Fly Ash-Based Soil Conditioner on Corn and Wheat Yield and Risk Analysis of Heavy Metal Contamination

The utilization of coal fly ash (CFA) as a soil conditioner has been a research hotspot in recent years. In this paper, the continuity and stability of the yield-increasing effect of a fly ash-based soil conditioner were investigated through field trials for three consecutive years. The yield-increasing effect and applicability were also investigated by planting a variety of crops in different types of soil. Field test results revealed that the new fly ash-based soil conditioner had wide adaptability and stability under the condition of reducing the application of traditional fertilizers by 20%. For corns grown in castano-cinnamon soil and dark brown soil, the application of the new fly ash-based soil conditioner for three consecutive years has steadily increased the yield by more than 10%. The yield of wheat planted in castano-cinnamon soil also increased by 15%. Additionally, considering that heavy metals (HMs) contained in the fly ash-based soil conditioner may cause environmental contamination, this paper calculated and analyzed the bio-concentration factor (BCF) and the translocation factor (TF) of Cr, As, Cd, Hg and Pb in the corn experimental fields. The results showed that the five heavy metals were not significantly enriched in various parts of the corn stalk after application of the soil conditioner, and there was temporarily no environmental risk in terms of returning straws to the field or raising livestock.

Study on Water Absorption–Dehydration Characteristics for SAP Composite Soil for Rainwater Harvesting

As a water absorption material, superabsorbent polymer (SAP) has gained its popularity in agriculture and environmental remediations. This study conducted a comparative investigation on saturated water content of cinnamon soil mixed with SAP. Two SAPs, SAP1 and SAP2, with different behaviors were tested, where SAP1 is an organic superabsorbent polymer, and SAP2 is polyacrylic acid sodium salt polymer. The saturated water content of SAP composite cinnamon soil was investigated with the weighing method. The repeated water absorption capacity and dehydration behavior of SAP composite soil under different designed rainfall intensity were investigated with a soil column tester. The results showed that (1) cinnamon soil mixed with SAP increased the saturated soil water content, and SAP1 was more effective than SAP2; (2) SAP held strong water absorption ability and recycling efficiency with eight repeated absorption–dehydration tests; (3) the average dehydration time for SAP composite soil were 626 h and 1214 h under 5-year and 10-year design rainfall intensities.