施氮深度对‘黄金梨’树氮素吸收、分配及利用效率的影响

以7年生‘黄金梨’树为试材,采用~(15)N示踪技术研究了3个施氮深度[0(表面施氮)、20和40 cm]处理下不同器官对氮素的吸收、分配及利用效率,并探讨了氮素在土壤中的残留及损失。结果表明,梨果实成熟期,果实的Ndff值最高,其他器官的Ndff值均表现为20 cm施氮深度处理显著高于其他处理。各施氮深度处理,~(15)N的分配率均为贮藏器官最高,生殖器官最低。20 cm施氮深度处理的梨树N利用率最高(26.23%),40 cm施氮深度处理最低(15.65%)。N损失率以表面施氮处理最高(54.21%),20 cm施氮深度最低;0~80 cm土层的N残留率以40 cm施氮深度处理最高(31.73%),表面施氮处理最低。因此,本研究中,20 cm深度施氮处理能提高梨树各器官对N肥的吸收征调能力,氮素损失少。     

秸秆深还机具特点和作业效率分析

秸秆深埋还田(秸秆深还)作为一种新兴的秸秆还田模式,其机具有别于地表覆盖还田和铧式犁翻压还田。为了科学管理、合理运用秸秆深还机械,提高机组的作业效率,在调查测试秸秆深还作业的基础上,对机具的特点进行了分析,同时对测试机组分别进行了时间利用率和作业效率分析。结果表明:对于各个机具的作业时间利用率和总作业效率影响因素有所不同。作业速度、幅宽、故障维修和地头转向是影响机械作业效率的主要因素。根据调查和分析的结果,针对秸秆深还作业中存在的问题提出了机组的合理运行模式。     

思澜二级公路改建工程石拱桥加固利用

公路改建工程主要依托老路进行,旧桥加固利用是公路改建工程中重要的环节,对降低工程造价、缩短施工周期、缓解施工中的保通压力有其现实意义,针对思澜公路石拱桥加固利用,对老石拱桥加固技术和经济效益进行探讨。     

近15年我国土地利用分区研究进展

通过查阅21世纪以来的大量文献和对比分析,总结了国内土地利用分区的研究动态。结果表明院国内土地利用分区类型呈多元化,以省、市、县级为尺度和采用聚类分析法、GIS技术的研究较多,基于个案研究提出了新的理论、方法模型等,有效地对土地利用分区进行了探索,但也存在问题和不足;并指出其发展趋势是分区理论深入化、分区制度完善化、分区方法集成化及信息化。     

浅议如何提高高校图书馆数据库利用率

当前各高校图书馆数据库的数量与日俱增．在数据库数量不断增加的同时．情况，发现并不是每个数据库的利用率都很理想，有不少数据库的利用率还一定的浪费。以贵州大学图书馆为例．通过研究贵州大学图书馆数据库的利利用率低的原因，并提出提高高校图书馆数据库利用率的一些措施和建议、，各高校开始关注数据库的使用比较低．对学校的投入造成了用现状．具体分析导致数据库     

郏县文庙片区更新中历史文化资源的保护与利用

对河南郏县文庙片区的环境背景进行了分析,立足于其核心历史价值,对片区进行了详细规划设计。将片区的核心历史文化特色通过设计,在建筑、景观等层面表达出来,在保护古建筑的同时,借其核心优势,驱动整个片区的经济,并将部分收益返回来用于保护历史遗迹。通过案例的解析来阐明历史文化资源的有效保护利用手段。     

硼对平邑甜茶幼苗硝态氮吸收、利用及分配特性的影响

以平邑甜茶幼苗为试材,运用~(15)N同位素示踪和非损伤微测技术,研究了不同供硼(硼酸0、1.0、2.0、3.0、4.0、5.0和6.0 mg·L~(-1))水平对平邑甜茶根系生长及氮素吸收、利用和分配特性的影响。结果表明,3.0 mg·L~(-1)硼酸处理的幼苗根系活力及根系形态指标显著高于其他处理,幼苗的全氮量及~(15)N吸收量增幅最大,分别比对照提高了19.4%和75.0%。随供硼水平的增加,植株氮素利用率呈现先增高后降低的趋势,在3.0 mg·L~(-1)硼酸处理时最大,为14.8%,是对照的1.8倍。施硼处理对幼苗的~(15)N分配率有一定的影响,3.0 mg·L~(-1)硼酸处理的根系~(15)N分配率达到最大,且显著高于对照。非损伤微测结果显示,3.0 mg·L~(-1)硼酸处理时,平邑甜茶根系对NO_3~-有强烈吸收且内流速度达到最大,在缺硼和高硼(硼酸0和6.0 mg·L~(-1))处理时有明显外排趋势。因此,3.0 mg·L~(-1)硼酸处理最有利于平邑甜茶根系的生长、根系活力的提高和氮素的吸收利用,而低硼和过量供硼均会抑制根系生长及氮素的吸收利用。     

Dietary fiber in a low-protein diet during gestation affects nitrogen excretion in primiparous gilts,with possible influences from the gut microbiota

We investigated the effects of dietary fiber (DF) supplementation in normal or low crude protein (CP) diets on reproductive performance and nitrogen (N) utilization in primiparous gilts. In total, 77 Landrace × Yorkshire pregnant gilts were randomly allocated to four dietary treatments in a 2 × 2 factorial design. The groups comprised 1) equal intake of normal CP (12.82% and 0.61% total lysine), 2) low CP (LP) (10.53% and 0.61% total lysine), and 3) with or 4) without DF supplementation (cellulose, inulin, and pectin in a 34:10:1 ratio). A low-protein diet during gestation significantly reduced daily weight gain from days 91 to 110 of pregnancy (−162.5 g/d, P = 0.004). From N balance trials conducted at days 35 to 38, 65 to 68, and 95 to 98 of pregnancy, DF addition increased fecal N excretion at days 65 to 68 (+24.1%) and 95 to 98 (+13.8%) of pregnancy (P < 0.05) but reduced urinary N excretion (P < 0.05), resulting in greater N retention at each gestational stage. DF increased fecal microbial protein levels and excretion during gestation. An LP diet also reduced urinary N excretion at different gestational stages. An in vitro fermentation trial on culture media with nonprotein N urea and ammonium bicarbonate (NH₄HCO₃) as the only N sources revealed that microbiota derived from feces of gestating gilts fed the high DF diet exhibited a greater capacity to convert nonprotein N to microbial protein. Microbial fecal diversity, as measured by 16S rRNA sequencing, revealed significant changes from DF but not CP diets. Gilts fed an LP diet had a higher number of stillbirths (+0.83 per litter, P = 0.046) and a lower piglet birth weight (1.52 vs. 1.37 kg, P = 0.006), regardless of DF levels. Collectively, DF supplementation to gestation diets shifted N excretion from urine to feces in the form of microbial protein, suggesting that the microbiota had a putative role in controlling N utilization from DF. Additionally, a low-protein diet during gestation negatively affected the litter performance of gilts.     

Influence of amount and frequency of protein supplementation to ruminants consuming low-quality cool-season forages: efficiency of nitrogen utilization in lambs and performance of gestating beef cows

We evaluated the influence of amount and crude protein (CP) supplementation frequency (SF) on nitrogen (N) use by wethers and the performance of late-gestation beef cows. In exp. 1, seven Western whiteface wethers (31.8 ± 1.4 kg) were used in an incomplete 7 × 4 Latin square to evaluate intake and N use. Wethers received one of the seven treatments in a 2 × 3 factorial design containing two levels of supplemental soybean meal offered at a rate of 100% (F) or 50% (H; 50% of F) of the estimated CP requirement daily, once every 5, or once every 10 d, plus a non-supplemented control (CON). Low-quality cool-season forage (4.9 % CP; dry matter [DM] basis) was provided daily for ad libitum intake. Experimental periods lasted 30 d. In exp. 2, 84 Angus × Hereford cows (560 ± 35 kg) were stratified by age, body condition score (BCS), and expected calving date and allocated to 1 of the 21 feedlot pens (three pens per treatment). Pens were randomly assigned to receive the same treatments as in exp. 1 and cows had free access to low-quality cool-season forage (2.9% CP; DM basis). Cow body weight (BW) and BCS were measured every 14 d until calving and within 24 h after calving. In exp. 1, supplementation did not alter total DM and organic matter (OM) intake (P ≥ 0.26), but both parameters linearly decreased as SF decreased (P = 0.02). Supplementation increased DM, OM, and neutral detergent fiber (NDF) digestibility (P ≤ 0.02). Additionally, F feeding linearly increased DM, OM, and NDF digestibility as SF decreased (P ≤ 0.04). Digestibility of N, N balance, and digested N retained were greater with supplementation (P < 0.01), and N digestibility linearly increased as SF decreased (P = 0.01). Mean plasma urea-N concentration was not only greater (P < 0.01) for supplemented vs. CON wethers but also greater (P = 0.03) for F vs. H. In exp. 2, pre-calving BCS change was greater (P = 0.03) for supplemented cows. A linear effect of SF × supplementation rate for pre-calving BCS change was noted (P = 0.05), as F-supplemented cows lost more BCS compared with H as SF decreased. When considering supplementation intervals greater than 5 d, reducing the quantity of supplement provided, compared with daily supplementation, may be a feasible management strategy to maintain acceptable nutrient use and animal performance while reducing supplement and labor costs.     

宁夏回族自治区养殖粪污资源化利用现状调查与分析

畜禽粪污资源化利用,是农村生态环境保护工作的重点和难点,对于改善农村生态环境质量、提高农业绿色发展水平、促进农产品增产提质具有重要意义。本文为进一步了解宁夏回族自治区（简称“宁夏”）畜禽粪污资源化利用现状,在宁夏银川市、石嘴山市、吴忠市、中卫市、固原市5 市,对四大产业主导区畜禽养殖产业基本情况、全区及各市不同类型和规模的畜禽养殖粪污资源化利用现状及问题、不同养殖类型和规模的资源化主推技术及典型案例等情况进行了实地调研。结果表明：2020年,宁夏畜禽存栏总量2 046.0 万头（只）,其中,奶牛57.4 万头、肉牛120.7 万头、羊596.1 万只、生猪90.0 万头、家禽1 181.8 万只。畜禽粪污产生量3 025.3 万吨,全区粪污资源化利用总量为2 961.6 万吨,综合利用率达到97.9%,规模养殖场设施配套率达99.0%,该地区畜禽粪污综合利用主要途径有肥料化利用、能源化利用、清洁再生回用等。