施氮量对旱地胡麻养分积累、转运及氮素利用率的影响

通过田间试验,研究不同施氮量对胡麻产量、氮素积累转运及氮肥利用率的影响。结果表明, 在本试验土壤肥力条件下,无论施氮与否,胡麻各器官不同生育阶段氮素养分吸收、累积和转运规律的基本趋势一致,但其变化量与施氮量有极大关系。施氮量为55.2kg/hm2时,叶和茎中的氮素向籽粒的转移量、转移率及对籽粒氮素的贡献率最大;叶中氮素向籽粒的转移量、转移率及贡献率要比茎高出89.18%、83.36%和86.36%。胡麻籽粒中47.10%～57.66%的氮素来源于叶,22.46%～30.94%的氮素来源于茎,21.00%～30.48%来自籽粒生长后期从土壤中的吸收。施氮量为27.6、55.2、82.8 kg/hm2时,胡麻籽粒产量分别比不施氮增加了10.21%、16.92%和15.55%。施氮量为27.6～55.2 kg/hm2时,氮肥的表观利用率、偏生产力分别为：51.10%～68.63%和51.54～97.16 kg• kg-1。本试验条件下,综合考虑产量、氮肥利用率及生态环境,施氮量在27.6～55.2 kg/hm2为宜。     

Identification of sorghum genotypes suitable for specific end uses: Semolina recovery and popping

There has always been an interest in devising breeding programs for designer foods that would benefit both the producer and consumer. The challenge today is transformation of agriculture from “subsistence farming” to “market and income generation oriented” production system for which sorghum with its diverse end uses can assume significant role. Breeding for end-use identity-specific genotypes is needed for increased profitability to the farmers. In the present study, 60 sorghum genotypes were evaluated over two years to identify genotypes suitable for semolina recovery and popping properties, i.e. popping efficiency and pop volume expansion. Semolina recovery ranged from 20.7% to 48.3%, while popping efficiency ranged from 0 to 77.5%. Semolina recovery had positive and significant association with endosperm texture (r = 0.62), grain density (r = 0.49) and grain hardness (r = 0.55) indicating that genotypes with corneous endosperm yield high semolina. Also, semolina recovery had significant positive correlation with popping efficiency (r = 0.49) indicating that genotypes suitable for semolina can also be used for popping. Genetic divergence studies indicated that out of three clusters formed, cluster II having guinea race germplasm lines are suitable for semolina and popping. The information generated and the genotypes identified will help in enhancing the demand for sorghum as an industrial crop.     

Soluble organic nitrogen in agricultural soils

 The existence of soluble organic forms of N in rain and drainage waters has been known for many years, but these have not been generally regarded as significant pools of N in agricultural soils. We review the size and function of both soluble organic N extracted from soils (SON) and dissolved organic N present in soil solution and drainage waters (DON) in arable agricultural soils. SON is of the same order of magnitude as mineral N and of equal size in many cases; 20–30 kg SON-N ha^–1 is present in a wide range of arable agricultural soils from England. Its dynamics are affected by mineralisation, immobilisation, leaching and plant uptake in the same way as those of mineral N, but its pool size is more constant than that of mineral N. DON can be sampled from soil solution using suction cups and collected in drainage waters. Significant amounts of DON are leached, but this comprises only about one-tenth of the SON extracted from the same soil. Leached DON may take with it nutrients, chelated or complexed metals and pesticides. SON/DON is clearly an important pool in N transformations and plant uptake, but there are still many gaps in our understanding. Received: 10 June 1999     

Evaluation of the RZWQM-CERES-Maize hybrid model for maize production

The root zone water quality model (RZWQM) was developed primarily for water quality research with a generic plant growth module primarily serving as a sink for plant nitrogen and water uptake. In this study, we coupled the CERES-Maize Version 3.5 crop growth model with RZWQM to provide RZWQM users with the option for selecting a more comprehensive plant growth model. In the hybrid model, RZWQM supplied CERES with daily soil water and nitrogen contents, soil temperature, and potential evapotranspiration, in addition to daily weather data. CERES-Maize supplied RZWQM with daily water and nitrogen uptake, and other plant growth variables (e.g., root distribution and leaf area index). The RZWQM-CERES hybrid model was evaluated with two well-documented experimental datasets distributed with DSSAT (Decision Support System for Agrotechnology Transfer) Version 3.5, which had various nitrogen and irrigation treatments. Simulation results were compared to the original DSSAT-CERES-Maize model. Both models used the same plant cultivar coefficients and the same soil parameters as distributed with DSSAT Version 3.5. The hybrid model provided similar maize prediction in terms of yield, biomass and leaf area index, as the DSSAT-CERES model when the same soil and crop parameters were used. No overall differences were found between the two models based on the paired t test, suggesting successful coupling of the two models. The hybrid model offers RZWQM users access to a rigorous new plant growth model and provides CERES-Maize users with a tool to address soil and water quality issues under different cropping systems.     

Optimisation of fertiliser rates in crop production against energy use indicators

Optimising mineral nitrogen (N) use in crop production is inevitable target as mineral fertilisers reflect one of the highest inputs both in terms of economy and energy. The aim of the study was to compare the relationship between the rate of N fertiliser application and different measures of energy parameters exemplary data for spring-wheat in boreal climate condition in Estonia in 2006–2010. The effect of mineral N with rates 0, 40, 80, 120 and 160 kg N ha⁻¹ was studied on the background of composted cow manure and without organic fertilisers. Univalent parameters, energy gain (EG) (energy output − energy input) and energy ratio (ER) (energy output/energy input) were calculated. To aggregate parameters with different units (ER and EG) we proposed two standardisation approaches for combined indices. ER maximisation gave both organic fertilisation background optimum N norms significantly lower than EG (p < 0.05) optimisation. Both the new combined indices gave optimum N norms in between the rate of ER an EG. Composted cow manure background did not affect mineral N optimisation significantly. We suggest optimisation of mineral N according to bi-dimensional parameters as they capture important features of production efficiency and are more objective using as advisory tool for sustainable production systems.     

Effect of Euchsaena mexicana Schrad Diets on Nutrient Digestibility and Nitrogen Metabolism for Wulong Goose

One trial was conducted to study nutrition digestibility of Euchsaena mexicana Schrad (EMC) diets for Wulong Goose.Thirty-two geese of 9 months old were selected and divided into four groups randomly, with eight geese in each group.Four groups were fed with the isocaloric and isonitrogenous diets of different EMC contents (12, 19, 25 and 31%),respectively. The results showed that, as dietary EMC increased, dry matter (DM) digestibility was decreased significantly,meanwhile the digestibility of crude fiber (CF), neutral detergent fiber (NDF) and acid detergent fiber (ADF) increased significantly (P＜0.05). The ratio of apparent essential amino acid (EAA) digestibility (except Leu) among the four groups had significant difference (P＜0.01). the content of NH3-N in feces dropped (P＞0.05). There were no significant differences in net protein utilization (NPU), N apparent digestibility, N deposition and Ca apparent digestibility in different groups (P＞0.05). The apparent digestibility of P in different groups elevated, while there was significant difference between group D and A (P＜0.01), and there was significant difference between group D and B (P＜0.05).     

施氮与株丛切割对退化新麦草草地的改良效果

本文研究了施氮肥和株丛切割对退化新麦草人草地生产性能的影响,结果表明,施氮肥和株丛切割提高了新麦草草地生产性能和生产力。此外,施氮肥可改善牧草品质及土壤牮氮能力。株丛切割和施氮肥（１２０ｋｇ／ｈｍ＾２）相结合与单施氮肥相比,成本较低,对退化新麦草草地的改良效果良好,年均产草量２６７９．５ｋｇＤＭ／ｈｍ＾２。     

基于单螺杆膨胀机的发动机排气余热回收系统

针对发动机排气余热的特点,设计了有机朗肯循环(ORC)排气余热回收系统,采用单螺杆膨胀机作为动力输出装置,采用R245fa作为工质,提出了发动机排气余热利用率的概念和计算方法。结合发动机的试验数据,分析了ORC工质蒸发压力和发动机转速对ORC系统性能的影响,确定了适用于ORC系统的工质蒸发压力的最佳值。研究结果表明,当工质蒸发压力为3.0 MPa时,ORC系统能够在发动机全转速范围内正常工作,并且ORC系统的净输出功率最高可达12.1 kW,热力学第一定律效率最高可达11.27%,热力学第二定律效率最高可达25.8%,发动机排气余热利用率最高可达8.9%,发动机排气余热回收效果明显。     

有效微生物与调理剂在奶牛粪堆肥中的保氮与除臭效应

[目的]探索一套经济有效的奶牛粪堆肥除臭和保氮措施。[方法]采用正交设计设9个处理,在常温培养条件下研究了有效微生物EM和2种调理剂稻草、蚯蚓粪在奶牛粪堆肥中的保氮和除臭效应。[结果]试验设计的9个处理均有良好效果。在试验的第5d进行的第1次检测中,各试验处理比CK组降低了1～2个臭味等级,NH3去除率达21.09%～78.04%,H2S去除率达23.00%～73.39%;到第20d,大部分处理中检测不到H2S的释放量;到第25d试验结束时,所有处理均检测不到NH3的释放量。统计分析表明,奶牛粪堆肥中保氮除臭效果的最佳组合为:添加3%EM、30%稻草和7%蚯蚓粪。EM、稻草和蚯蚓粪在降低奶牛粪NH3和H2S释放量的效果上均随着添加量的增加而增加。[结论]EM、稻草和蚯蚓粪均对奶牛粪具有良好的除臭和保氮效应。