Channel: SOIL & FERTILIZER·WATER-SAVING IRRIGATION·AGROECOLOGY & ENVIRONMENT https://www.chinaagrisci.com EN-US https://www.chinaagrisci.com/EN/0578-1752/current.shtml https://www.chinaagrisci.com 0578-1752 https://www.chinaagrisci.com/EN/10.3864/j.issn.0578-1752.2023.12.007 【Objective】The aim of this study was to investigate the effects of dextran modified phosphate fertilizer prepared by the reaction between dextran and phosphate fertilizer with different polymerization degrees on the growth and soil phosphorus effectiveness of wheat, so as to provide the scientific support and theoretical basis for the application of dextran in phosphate fertilizer. 【Method】By using the reaction method, glucose (monomer), maltose (2-polymer), oligomaltose (≈5-polymer) and polydextrose (≈20-polymer) were added to a mixture of phosphoric acid and potassium hydroxide at 1% addition to prepare glucose-modified phosphate fertilizer (GP), maltose-modified phosphate fertilizer (MP), oligomaltose-modified phosphate fertilizer (OP) and polydextrose-modified phosphate fertilizer (PP), and the normal phosphate fertilizer (P) was prepared without the addition of dextran. The structural characteristics of the reaction between dextran and phosphate fertilizer were investigated by Fourier infrared transform spectroscopy (FTIR) and ³¹P nuclear magnetic resonance spectroscopy (³¹P NMR). Five treatments, including P, GP, MP, OP, and PP, were set up according to the principle of equal phosphorus amount, and the control (CK) was applied with only nitrogen and potassium fertilizers. The effect of different polymeric dextran modified phosphate fertilizers on wheat yield and fertilizer utilization was investigated by soil column cultivation. 【Result】(1) Compared with P, the FTIR spectra of dextran modified phosphate fertilizer showed a new vibration peak at 975 cm^-1, and the ³¹P NMR spectra showed a new displacement peak at 3.09-4.51 ppm, which might be due to the reaction between the hydroxyl group of dextran and phosphoric acid to form orthophosphate monoester. (2) Wheat yields were increased by 5.1%, 9.3%, 11.2% and 1.4% for the treatments with different polymerization degrees of dextran modified phosphate fertilizers (GP, MP, OP and PP) compared with P, respectively, mainly through the number of spikes, followed by the number of grains. (3) Compared with P, the total phosphorus uptake of wheat was significantly higher by 8.2%-21.4% under different polymerization degrees of dextran modified phosphate fertilizer treatments, among which, OP treatment was significantly higher than the other treatments. (4) The apparent phosphate fertilizer utilization rate of dextran modified phosphate fertilizer treatment was increased by 4.4-11.5 percentage points compared with P. The phosphate fertilizer bias productivity and phosphorus fertilizer agronomic efficiency were increased by 1.4%-11.2% and 1.6%-13.1%, respectively. The phosphate fertilizer utilization rate of both MP and OP treatments were significantly higher than P. (5) Compared with P, the soil fast-acting phosphorus content of dextran modified phosphate fertilizer treatment was significantly higher 10.2%-29.9%, and the OP treatment was significantly higher than the other dextran modified phosphorus fertilizer treatments. 【Conclusion】 Compared with common phosphate fertilizer, all dextran modified phosphate fertilizers with different polymerization degrees could improve wheat yield, promote the uptake and utilization of phosphorus in wheat, increase soil fast-acting phosphorus content, and reduce phosphorus fertilizer fixation. With the increase of dextran polymerization degree, wheat yield and apparent phosphorus fertilizer utilization increased first and then decreased. The best effect of dextran polymerization on the modification and efficiency of phosphate fertilizer was achieved when the polymerization degree of dextran was 4-6.

]]> https://www.chinaagrisci.com/EN/10.3864/j.issn.0578-1752.2023.12.008 【Objective】The aim of this study was to clarify the effects of long-term no-tillage and mulching measures on soil aggregate structure and organic carbon content in Weibei dry plateau farmland, and to explore suitable tillage measures to improve the local soil.【Method】On the basis of continuous 16-year field positioning experiments, a total of 5 field management measures were selected as experiment treatments, including traditional tillage (CT), no-tillage and no mulch (NT), no-tillage + straw mulch (NS), no-tillage + plastic film mulching (NP), and no-tillage + straw + plastic film mulching (NSP). The 0-40 cm ring knife and profile soil samples were collected during the spring maize harvest in October 2019, and the bulk density, aggregate particle size distribution and organic carbon content were determined.【Result】(1) No-tillage and mulching measures (NT, NP, NS and NSP) affected the bulk density and aggregate size distribution of Heilu soil. No-tillage and mulching measures both increased the soil bulk density of the plough layer (0-20 cm), of which 0-10 cm increased significantly (6.8%-17.8%). The changes of bulk density and porosity of the plough layer were opposite to those of the plough layer. The proportion of micro-aggregates was significantly reduced, which promoted the transformation of micro-aggregates into macro-aggregates. The weight percentage of aggregates of each particle size in the plough layer (0-20 cm) was distributed as follows: larger aggregates (0.25-2 mm)>large aggregates (>2 mm)>micro aggregates (0.053-0.25 mm)>powder. The clay fraction (<0.053 mm), the larger aggregates and silty clay fractions in the plow bottom layer (20-40 cm) were significantly higher than the macroaggregates and microaggregates. (2) Under no-tillage and mulching measures, the organic carbon content increased with the increase of aggregate particle size. In the 0-40 cm soil layer, the organic carbon content of the aggregates of each particle size under NT treatment was significantly lower than that under CT treatment, while the NS and NSP treatments were significantly higher than those under CT treatment. (3) The particle size distribution of aggregates was the dominant factor causing the change of the nutrient contribution rate of aggregates. The total organic carbon accumulation in the plough layer was dominated by aggregates>0.25 mm, and the plough layer was mainly composed of silty clay components and organic carbon in larger aggregates. 【Conclusion】Long-term no-tillage and mulching measures promoted the transformation of micro-aggregates into macro-aggregates in the plough layer. Compared with traditional tillage, no-tillage and plastic film mulching decreased the organic carbon content of aggregates of various particle sizes in Heilong soil and in the plough layer, respectively. However, no-tillage mulching (NS, NP and NSP) increased the organic carbon content of aggregates of each particle size compared with no mulching. Straw mulching alone had the best effect, and significantly improved the bulk density and the organic carbon content of each particle size aggregate increased the most, which was the best treatment in this study.

]]> https://www.chinaagrisci.com/EN/10.3864/j.issn.0578-1752.2023.12.009 【Objective】This study was conducted to explore the responses of saline-alkali soil respiration to straw interlayer and irrigation regime, and to clarify the relationships between soil respiration rate and soil temperature/water content in Hetao Irrigation District. 【Method】A randomized block design was set up in 2015 with three treatments: autumn and spring irrigation (I_SA), spring irrigation without autumn irrigation (I_S), and spring irrigation plus straw interlayer without autumn irrigation (SI_S). Soil respiration, soil temperature and moisture content were measured in 2017 and 2018, and the temperature sensitivity of soil respiration rate was also estimated. 【Result】(1) Soil temperature and soil moisture content in the 0-20 cm soil layer fluctuated obviously, while it was relatively stable in the 20-40 cm soil layer. SI_S increased the soil temperature in 0-40 cm soil depth and moisture content in 20-40 cm soil depth. (2) The soil respiration rate in 2017 was higher than that in 2018. It was the highest in the flowering stage, followed by budding stage, before spring irrigation, before sowing, and harvest stage. (3) The soil respiration rates of I_S and SI_S were significantly higher than I_SA at the flowering stage (P<0.05). Compared with I_SA, I_S and SI_S increased soil respiration rate by 0.12-0.44 and 0.06-0.42 μmol·m^-2·s^-1, respectively. Compared with the I_S, the soil respiration rate of SI_S decreased by 0.01-0.49 μmol·m^-2·s^-1. These results indicated that the soil respiration rate was increased without autumn irrigation, while it was decreased with straw interlayer. (4) The soil respiration rate positively correlated with soil temperature (P<0.01), while it had no significant correlation with soil moisture content. Soil temperature at the 0-20 and 20-40 cm soil layer explained 40.74%-53.84% and 39.27%-53.46% variation of soil respiration rate, respectively. (5) The temperature sensitivity of soil respiration (Q₁₀) varied within 1.68-1.98 for different treatments, and the Q₁₀ of the 20-40 cm soil depth was higher than that of the 0-20 cm soil depth. Compared with I_SA, I_S and SI_S reduced Q₁₀. However, SI_S increased Q₁₀ compared with I_S. 【Conclusion】Overall, the straw interlayer increased the soil temperature in 0-40 cm soil depth and moisture content in 20-40 cm soil depth, reduced soil respiration rate, and increased the temperature sensitivity of soil respiration, which was used as an effective practice for water saving and emission reduction in the Hetao Irrigation District.

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