Evaluation of two N cycle models for the prediction of N mineralization from grassland soils in the UK

Abstract. The ability of two nitrogen cycle models, of contrasting complexity, to predict N mineralization from a range of grassland soils in the UK, was evaluated. These were NCYCLE, a simple mass balance model of the N cycle in UK grasslands, and CENTURY, a more complex model simulating long-term C, N, P & S dynamics in grassland ecosystems. The models were tested using field measurements of net N mineralization from a range of grassland soils (differing in soil type, history & management practice), obtained over a 2 year period using a soil core incubation technique. This method was considered to measure the total net release of mineral N from the soil organic matter over a specified time, including N which may have been recycled several times. NCYCLE consistently under-estimated mineralization rates at all sites. By contrast, there was some correlation between CENTURY predictions of net N mineralization and field measurements. This may have reflected the different abilities of the two models to simulate N recycling. Neither model, however, was able to predict adequately the effect of cultivation and reseeding on net N mineralization.     

Nitrogen uptake by ryegrass from organic wastes applied to a sandy loam soil

Sandy‐textured Mediterranean soils are invariably depleted in organic matter and supply only small amounts of N to crops. To compensate for these deficiencies, we tested the N supply from six organic wastes applied to a Cambic Arenosol in pots growing ryegrass. The results showed that the behaviour of the wastes in supplying N to a ryegrass crop grown in this soil can be predicted by observing their performance in laboratory aerobic incubations. The N made available during these incubations fitted well to a one‐pool kinetic model.     

Response of Mustard to Ethrel Spray and Basal and Foliar Application of Nitrogen

In a field trial conducted during 1992–93 and 1993–94, the effect of basal (B) nitrogen (N) (45 and 60 kg N ha⁻¹) and foliar application (F) of water (W) or 10 kg N ha⁻¹ and 400 or 600 ppm ethrel (E) (2-Chloro ethyl phosphonic acid) at 70 days after sowing was studied on leaf area index and dry mass at 90 days and pod number per plant, seeds per pod, 1000 seed weight, seed yield, oil content and oil vield at harvest of mustard ( Brassica juncea L. Czern & Coss.) cv. T-59. Recommended basal (B) application of 90 kg N ha (BN₉₀) was used as control. On the basis of 2 year data it was found that basal application of 60 kg N and foliar spray of 10 kg N ha ⁻¹ and 600 ppm ethrel gave higher values for growth and yield characteristics and enhanced seed yield and oil yield by 12.5 and 14.8%, respectively over control BN_90.     

氮肥对黑小麦“运黑161”产量及氮素利用效率的影响

为了研究不同施肥水平对黑小麦产量和氮利用率的影响,在洪洞县小麦试验基地开展大田试验。试验以“运黑161”为供试品种,采用单因素完全随机设计,设0 kg/hm²（N0）、144 kg/hm²（N144）、192 kg/hm²（N192）、240 kg/hm²（N240）4 个施氮水平,研究黑小麦在不同氮肥水平下的株高、产量、籽粒蛋白质含量和氮利用率的变化。研究表明,与不施肥相比,施氮可增加黑小麦孕穗至成熟期株高。随施氮量的增加,成熟期穗数和穗粒数也增加,产量以施氮量240 kg/hm²最高,达6 048.45 kg/hm²,较其它氮肥提高6.04%~134.30%,但与施氮量192 kg/hm²处理间差异不显著。氮肥农学利用率以施氮量192 kg/hm²最高,达16.26%。总之,施氮量为192 kg/hm²更利于“运黑161”降低氮肥投入,节约成本,实现产量和氮效率的同步提升。     

不同时期一次性施肥对夏玉米产量和氮肥效率的影响

在河南省鹤壁和原阳采用田间试验,研究不施氮(CK)、种肥同播(T1)、5叶期一次性施肥(T2)和10叶期一次性施肥(T3),对夏玉米生长发育、氮素积累转运及产量的影响,明确夏玉米包膜尿素1∶1配施普通尿素适宜的一次性施肥时期。结果表明,鹤壁和原阳T1处理产量最高,分别为12 700 kg/hm²和10 945 kg/hm²,但与T2处理间差异不显著,较T3处理分别提高14.2%和10.9%;干物质积累量较其他处理分别提高5.6%～25.1%和1.6%～21.2%。不同生育期T1处理叶片SPAD值和叶面积指数均达最高。鹤壁和原阳T1氮肥表观利用率最高,分别为35.2%和35.5%,较其他处理分别提高5.6～14.7个百分点和3.2～13.6个百分点;氮素积累量较其他施氮处理分别提高13.8%～34.5%和14.5%～41.5%。T1处理土壤氮素依存率低于T2和T3处理。综上,种肥同播提高了夏玉米产量、氮肥效率、叶片SAPD值和叶面积指数,保持较高的氮素吸收速率,降低了土壤氮依存率,满足夏玉米整个生育期的氮素需求,实现了夏玉米高产和高效施肥。     

循环流化床中塑料粉与稻壳共燃生成NO的研究

为研究塑料与稻壳共燃的氮氧化物生成规律,在自行设计的循环流化床装置上进行了二者的共燃实验。研究了温度、塑料粉和稻壳的混合比例及过量空气系数对NO生成量的影响。实验结果表明,随温度升高,NO生成量升高;随塑料粉与稻壳混合比例增加,NO生成量呈降低趋势,且NO的生成量低于二者单独焚烧时生成量的线性叠加;随着过量空气系数增加,NO生成量降低。为寻找二者共燃NO生成的一般性规律,采用径向基神经网络建立了NO生成的预测模型,预测结果显示该模型具有很高的精度。     

氮磷追肥配施对云南松幼苗根系生长的影响

云南松是我国西南地区主要的造林树种,在区域经济发展和生态环境建设中发挥着重要作用。但目前云南松苗期生长缓慢,这使得云南松经济效益与生态效益的发挥受到了阻碍。氮磷添加是目前农林业促成培育中一种常见技术手段,通过对云南松苗木在不同氮、磷施肥处理下其生长状况的研究,以期为云南松苗木培育提供依据。本次试验以90d生的云南松幼苗为试验材料,对其进行氮磷根部追肥配施试验,比较不同氮磷浓度水平下云南松幼苗根系生长的变化规律。研究表明,氮磷配施后,随着氮磷用量的增加,云南松幼苗根冠比降低。地下部分的生长优势降低,地上部分的生长优势升高,且氮元素对于地上部分的增长作用强于磷元素。     

Effects of shading and NO3:NH4 ratio on the yield,quality and N metabolism in strawberry

The effect of 50% shading and NO₃:NH₄ ratio (0:100, 75:25, 50:50, and 25:75) in the nutrient solution on growth, yield, quality and N metabolism in hydroponically grown strawberry (Fragaria × ananassa var Camarosa) was evaluated. Both fresh and dry weights of leaves were significantly lower when a high concentration of either NO₃ (100%) or NH₄ (75%) was the sole N source in the nutrient solution. In unshaded plants, increasing of both NH₄ and NO₃ ratio in the nutrient solution reduced photosynthetic (Pn) rate, however in shaded plants the reduction of Pn became more pronounced at a higher ratio of NH₄ in the nutrient solution. The yield in terms of fresh and dry weight of fruit per plant was significantly increased at the 75:25 and 50:50 (NO₃:NH₄) treatments. Fruit size was significantly affected by the treatments, so that the biggest fruits in both shaded and unshaded plants were obtained under the 75:25 and 50:50 (NO₃:NH₄) treatments. Total soluble solid (TSS) in unshaded plants was increased with increasing NH₄ ratio in the nutrient solution, however in shaded plants it was reduced at high NH₄ ratio in the nutrient solution. In both shaded and unshaded plants, higher concentration of NH₄ significantly reduced the post-harvest life of the fruits. The increase of tissue N concentration was nearly proportional to the NH₄ concentration in the nutrient solution. The activity of nitrate reductase (NR) was increased by increasing NH₄ from 0 to 50% and then reduced at a higher ratio of NH₄ in the solution. Shading increased NH₄ concentration so that the shaded plant had nearly twice as high NH₄ concentration in the leaves. The increase of NH₄ concentration induced by shading could be partially the reduction of NH₄ assimilate because of the shortage of carbohydrate.     

日粮添加蛋氨酸对幼兔生长发育、免疫性能及血液生化指标的影响

选择100只断奶新西兰兔,随机分成5组,在日粮中分别添加不同水平的蛋氨酸（0、0．2％、0．4％、0．6％、0．8％）,研究其对生长性能、氮代谢、免疫性能及血液生化指标的影响。结果表明：日粮添加蛋氨酸能显著提高日增重和饲料转化率（P〈0．05）,添加蛋氨酸0．4％时,日增重和料重比达最佳水平．分别为30．8g、3．29：1;蛋氨酸水平对氮代谢的影响差异不显著（P〉0．05）;蛋氨酸对胸腺指数的影响差异显著（P〈0．05）,当添加量为0．4％时,胸腺指数达到最大,但是对肝脏指数和脾脏指数无显著影响（P〉0．05）。对免疫球蛋白A、G、M含量也无显著影响（P〉0．05）;蛋氨酸对血清中总蛋白、白蛋白和血清尿素氮的含量无显著影响（P〉0．05）．     

外源氮对紫花苜蓿固氮酶活性和酰脲含量的影响及其相关关系研究

以‘甘农3号’为研究材料,采用室外(防雨网室)盆栽营养液砂培法,模拟土壤中2种氮素形态(NO₃^--N和NH₄⁺-N)的存在形式,研究混合态氮(NO₃^--N:NH₄⁺-N为1:1)的5个供氮水平(0,105,210,315,420 mg·L^-1)对紫花苜蓿固氮酶活性和酰脲含量的影响并筛选出最佳氮浓度;在筛选出的最佳氮浓度下研究2种形态(NO₃^--N和NH₄⁺-N)氮的7种不同的配比NO₃^--N:NH₄⁺-N(1/7,1/3,3/5,5/5,5/3、3/1,7/1)对紫花苜蓿固氮酶活性和酰脲含量的影响;并对根瘤固氮酶活性和酰脲含量之间的相关关系进行了分析。研究表明:最能促进紫花苜蓿酰脲累积和根瘤固氮能力的外源氮浓度为210 mg·L^-1;最佳混合型态氮配比为NO₃^--N:NH₄⁺-N=1/3。2种试验处理下紫花苜蓿地上部分酰脲含量(y)与固氮酶活性(x)之间分别存在显著正相关关系(P < 0.01),可分别用y=0.0321x+0.4759(R=0.911)和y=0.0313x+0.5545(R=0.960)表示,且2模型高度相似,这为寻求生产中评估紫花苜蓿固氮能力的简便方法提供理论依据。