基于FDR原理的自动灌溉系统设计

利用土壤的介电特性测量土壤含水量是一种快速、简便、可靠的方法。根据频域反射(FDR)法测量原理,电磁波在土壤中的传播频率可用来测试土壤的介电常数,从而得到土壤容积含水率,设计出了一种基于FDR原理的自动灌溉系统,介绍了FDR测量原理,阐述了自动灌溉系统的软硬件构成,土壤水分传感器测得的土壤水分含量信息,经信号处理,输出为0~5V电压信号,经A/D转换送至AT89S52单片机进行判断处理,根据输出数值的大小控制电磁阀的通断时间,从而实现自动灌溉和节水灌溉的目的。试验表明:该系统工作稳定,控制准确,反应灵敏,满足自动灌溉要求。     

含温度补偿的便携式土壤水分测定仪研制

针对现有土壤水分测定仪的不足,研制了一种新型的便携式土壤水分测定仪。传感器快速测量出土壤温、湿度数据,GPS自动获取时间、经纬度信息,数据既可临时保存在仪器的存储芯片中,又可通过GPRS/GSM将数据及时发送到后台数据库和手机用户。通过温度补偿和野外验证实验得出,温度补偿项为Δy=0.0002 t3-0.011 t2+0.444 1 t-6.423 2,仪器所有功能运行正常,测量绝对误差为-3.64%~3.82%,平均绝对误差为2.24%,精度较高,适合在地方农技和水利部门推广应用,有助于农业水利信息化水平的提高。     

电容式土壤水分传感器的电导变异性试验研究

为评估电容式土壤水分传感器受土壤电导率的影响及其对农田土壤电导率变化范围的适用性,配制了一系列土壤等效含水率为40.6%、电导率为0~1.91dS/m的土壤等效介电溶液,分别对激励信号频率为40,50,60,70,80,90,100MHz的7种传感器进行了电导变异性试验,并且配制了相同含水率但电导率分别为0,0.31,0.46和0.61dS/m的4种土样进行了验证试验。试验结果表明:1)土样中的测试结果基本上与介电溶液吻合,可采用等效介电溶液评估传感器的电导变异性;2)传感器的电导变异率随待测介质电导率的升高而近似线性增大,相同电导率下,传感器激励信号频率越高其电导变异率越小;3)在农田土壤电导率基本变化区域0.239~0.650 dS/m内,当传感器激励信号频率从不低于80MHz时,其最大电导变异率为9.2%,能满足工程上的实际应用要求。     

Summary of research on soil testing for rock phosphate fertilizers in Western Australia

The relationship between plant yield and values of soils tests for phosphorus (P) was studied in long-term field experiments in south-western Australia for soil previously fertilized with rock phosphate and superphosphate. The rock phosphates studied were: Queensland (Duchess) apatite rock phosphate; reactive apatite rock phosphate from North Carolina; and rock phosphate from Christmas Island (as either C-grade ore or Calciphos). The P fertilizers were applied once only at the start of each experiment, and in subsequent years, soil samples were collected in January-March to measure soil test values. These were compared with plant yields measured later on in that year. The Colwell alkaline bicarbonate soil test was used in all years in all experiments. Olsen, Bray, lactate and Troug tests were used in some years in some experiments. For all soil tests the relationships between yield and soil test values was generally different for rock phosphate and superphosphate. For a given source of P, none of the different soil test reagents was significantly superior for predicting plant yields. The relationship between yield and soil test value was also generally different for different plant species. At one site cultivation was included as a treatment and the relationship varied depending on the cultivation treatment of the topsoil before sowing oats (Avena sativa). The relationship between yield and soil test also differed between years.     

不同频率激励信号下土壤水分传感器性能试验

激励信号频率是影响高频电容式土壤水分传感器性能的重要因素。利用去离子水和2—异丙氧基乙醇(2—isoproxyethanol)或二氧六环(dioxane)2种溶液混合,配制了一系列等效土壤体积含水率为0.9%~51.8%的待测介电溶液来替代土样。从与土壤含水率的函数关系、温度变异性2个方面,分别对激励信号频率为40,50,60,70,80,90,100 MHz的7种土壤水分传感器进行了性能测试与分析。结果表明:7种频率的传感器的输出电压均与土壤体积含水率呈线性负相关,其相关系数R2均大于0.94;激励信号频率不影响传感器输出电压的温度变异性,温差是影响温度变异性的主要因素,其最大变异率均小于4%。试验结果可为设计高频电容式土壤水分传感器时选择激励信号频率提供依据。     

Ammonium transformation in paddy soils affected by the presence of nitrate

Coupled nitrification and denitrification is considered as one of the main pathways of nitrogen losses in paddy soils. The effect of NO₃ ^– on NH₄ ⁺ transformation was investigated by using the ¹⁵N technique. The paddy soils were collected from Wuxi (soil pH 5.84) and Yingtan (soil pH 5.02), China. The soils were added with either urea (18.57 mol urea-N enriched with 60 atom% ¹⁵N excess) plus 2.14 mol KNO₃-N (natural abundance) per gram soil (U+NO₃) or urea alone (U). The KNO₃ was added 6 days after urea addition. The incubation was carried out under flooded condition in either air or N₂ gas headspace at 25°C. The results showed that in air headspace, ¹⁵NH₄ ⁺ oxidization was so fast that about 10% and 8% of added ¹⁵N in the treatment U could be oxidized during the incubation period of 73 hours after KNO₃ addition in Wuxi and Yingtan soil, respectively. The addition of KNO₃ significantly inhibited ¹⁵NH₄ ⁺ oxidation (p<0.01) in air headspace, while it stimulated ¹⁵NH₄ ⁺ oxidation in N₂ gas headspace, although the oxidation was depressed by the N₂ gas headspace itself. Therefore, the accumulation of NO₃ ^– would inhibit further nitrification of NH₄ ⁺ at micro-aerobic sites in paddy soils, especially in paddy soils with a low denitrification rate. On the other hand, NO₃ ^– would lead to oxidation of NH₄ ⁺in anaerobic bulk soils.     

溴虫腈土壤和甘蓝微量残留量的气相色谱法测定

采用气相色谱法定量分析溴虫腈土壤和甘蓝微量残留量。样品经丙酮提取 ,液 液分配及氧化铝柱层析法净化后 ,以GC ECD测定 ,DB 170 1毛细管柱 ,氮气为载气 ,柱温 2 6 0℃ ,汽化室温度 2 5 0℃ ,检测器温度 2 80℃ ,外标法定量。该方法快速、准确 ,在 0 0 1～ 2 0 0mg/L范围内线性相关系数r2 =0 9999,平均回收率 90 0 %～ 10 3 6 7% ,变异系数 4 4 8%～ 5 89% ,最小检测量 2× 10 12 g ,最低检出浓度 3 3× 10 4mg/kg。     

Effects of Microbial Utilization of Phenolic Acids and their Phenolic Acid Breakdown Products on Allelopathic Interactions

Reversible sorption of phenolic acids by soils may provide some protection to phenolic acids from microbial degradation. In the absence of microbes, reversible sorption 35 days after addition of 0.5–3 mol/g of ferulic acid or p-coumaric acid was 8–14% in Cecil A_p horizon and 31–38% in Cecil B_t, horizon soil materials. The reversibly sorbed/solution ratios (r/s) for ferulic acid or p-coumaric acid ranged from 0.12 to 0.25 in A_p and 0.65 to 0.85 in B_t horizon soil materials. When microbes were introduced, the r/s ratio for both the A_p and B_t horizon soil materials increased over time up to 5 and 2, respectively, thereby indicating a more rapid utilization of solution phenolic acids over reversibly sorbed phenolic acids. The increase in r/s ratio and the overall microbial utilization of ferulic acid and/or p-coumaric acid were much more rapid in A_p than in B_t horizon soil materials. Reversible sorption, however, provided protection of phenolic acids from microbial utilization for only very short periods of time. Differential soil fixation, microbial production of benzoic acids (e.g., vanillic acid and p-hydroxybenzoic acid) from cinnamic acids (e.g., ferulic acid and p-coumaric acid, respectively), and the subsequent differential utilization of cinnamic and benzoic acids by soil microbes indicated that these processes can substantially influence the magnitude and duration of the phytoxicity of individual phenolic acids.     

腐植酸物质对盐碱化中低产田土壤理化性质及玉米影响的研究

通过田间试验探讨了复合改良制剂、草炭、风化煤等腐植酸类物质施用对盐碱化中低产田土壤理化性质及生长作物的影响，结果表明：复合改良制剂、草炭、风化煤施用对土壤理化性质均有积极的影响，与对照相比达到显著水平。玉米产量的方差分析表明，复合改良制剂处理与草炭、风化煤等处理差异显著，与对照差异极显著，增产率均达到30．67％以上。     

The effect of ionic strength on soil P reactions is negligible

The electrolyte concentration of the soil solution affects the availability of some nutrients in the soil, especially of P, but it is not know at what salt concentration the reactions start to be significantly affected and their magnitude. This study was carried out to evaluate the effect of rates of potassium chloride (KCl) on some soil parameters that determine supplying of P, K, Ca, Mg, and Al in an unlimed acid soil. Increasing rates of KCl (from zero up to 2000 mg K kg^–1) were applied to soil samples fertilized with 360 mg P kg^–1. Solution (C_li) and exchangeable (C_si) forms of P, Ca, Mg, K, and Al were determined in the treated soil samples after 30-days of incubation; cation activity in solution and their selectivity coefficients were then calculated. Addition of KCl at rates equal to or above 500 mg K kg^–1 caused a large relative increase on P in the soil solution (P_li) but a small and insignificant increase on the absolute value of P_li. All forms of soil K increased with increases on K applied, and buffer power for K varied according to the range of soil K. At all KCl rates, K displaced Ca, Mg, and Al from the solid phase to the soil solution, but had no effect on the extractable values. The relative preference of cations for the adsorption sites increased with increase on cation valency, and only those selectivity coefficients involving K were affected by K applied.