麦套春棉麦棉共生期水分变化动态研究

１９９２～１９９３年对麦套春棉麦棉共生期水分变化动态进行了研究。两年试验结果表明，４种套种方式共生期田间持水量变化动态均表现为：棉行间＞棉株间＞麦棉行间＞麦行间；在试验范围内麦棉间距≥０３０ｍ时，无论麦收前有无自然降雨，棉行间、棉株间持水量与纯作棉田（ＣＫ）差异不显著，而麦棉行间、麦行间持水量显著低于ＣＫ；３—２式和４—２式用水较为经济；套种田与ＣＫ持水量等同点分布区集中在距小麦边行０３０～０４０ｍ处，各套种方式麦棉间距以０３０ｍ为宜。     

土壤水分下限对番茄光合速率、品质及产量的影响

通过盆栽试验,研究了土壤水分下限对番茄苗期、初花期和结果期的光合速率、蒸腾速率及果实品质、产量和水分利用效率的影响,试验结果表明,当土壤水分下限控制在苗期45%、初花期55%、结果期75%田间持水量范围内,可以提高果实品质,获得较高的产量和水分利用效率。     

Effects of different land use types on infiltration capacity in a catchment in the highlands of Ethiopia

Infiltration capacity is an important variable for understanding and predicting a range of soil processes. This study investigated for different slope positions the effects of forest conversion to cultivation and grazing on soil infiltration capacity. Infiltration capacity was measured in the field in each land use type using a double‐ring infiltrometer. A total of 108 soil samples (3 slope positions × 3 land use types × 4 soil profiles × 3 soil depths) were collected to determine the variables that affect infiltration capacity viz. particle size distribution, organic carbon content, dry bulk density and soil moisture content. The results showed that in the cultivated and grazed land compared with forest, infiltration capacity and soil moisture content were 70 and 45% smaller respectively, and dry bulk density was 13–20% larger. Changes in soil structure caused by surface soil compaction because of tillage and animal trampling coupled with a smaller soil organic carbon content, are likely to be the principal factors causing the decline in infiltration capacity and soil moisture content after conversion of forest to cultivation and grazing.     

Nitrate leaching in a silage maize field under different irrigation and nitrogen fertilizer rates

Quantification of the interactive effects of nitrogen (N) and water on nitrate (NO₃) loss provides an important insight for more effective N and water management. The goal of this study was to evaluate the effect of different irrigation and nitrogen fertilizer levels on nitrate-nitrogen (NO₃-N) leaching in a silage maize field. The experiment included four irrigation levels (0.7, 0.85, 1.0, and 1.13 of soil moisture depletion, SMD) and three N fertilization levels (0, 142, and 189 kg N ha⁻¹), with three replications. Ceramic suction cups were used to extract soil solution at 30 and 60 cm soil depths for all 36 experimental plots. Soil NO₃-N content of 0-30 and 30-60-cm layers were evaluated at planting and harvest maturity. Total N uptake (NU) by the crop was also determined. Maximum NO₃-N leaching out of the 60-cm soil layer was 8.43 kg N ha⁻¹, for the 142 kg N ha⁻¹ and over irrigation (1.13 SMD) treatment. The minimum and maximum seasonal average NO₃ concentration at the 60 cm depth was 46 and 138 mg l⁻¹, respectively. Based on our findings, it is possible to control NO₃ leaching out of the root zone during the growing season with a proper combination of irrigation and fertilizer management.     

YTG型双向体积管在计量检定中的应用

体积管是检定流量计的标准器。ＹＴＧ型双向体积管，其外型尺寸、主体结构、检定速度、日常管理等方面，均比单向体积管有明显的优点，并具有独特的容积补偿性，给体积管的管理、使用带来极大方便。介绍了ＹＴＧ型双向体积管的结构、技术指标及其优越性，并建议在条件允许的情况下，尽可能使用双向体积管。     

水分湿热平衡关系式在提高通风储粮效果中的指导作用

运用水分和湿热相对平衡的数学关系式来指导储藏产品通风、密闭、干燥和冷却等保护技术的应用，控制储粮的温、湿度和水分含量，并采取必要的辅助措施，以提高通风储粮效果，对预防和消除储粮发热、抑制虫霉危害、延缓品质陈化或劣变、保持储藏稳定性具有十分重要的作用．     

高寒半干旱区油菜与豆科牧草混播草地施肥效应

油菜与豆科牧草混播草地施肥效应表明，氮磷合理配施促进土壤水分消耗，干草、植物量和施肥产投比显著提高。坡梁地最高植物产量施肥量Ｎ为７８．０６ｋｇ／ｈｍ２，Ｐ２Ｏ５为６１．１５ｋｇ／ｈｍ２，最高干草产量施肥量Ｎ为７６．６５ｋｇ／ｈｍ２，Ｐ２Ｏ５为５７．２９ｋｇ／ｈｍ２，增产效果Ｎ＞Ｐ２Ｏ５；旱滩地最高植物产量施肥量Ｎ为５８．３３ｋｇ／ｈｍ２，Ｐ２Ｏ５为５５．６８ｋｇ／ｈｍ２，最高干草产量施肥量Ｎ为５３．６０ｋｇ／ｈｍ２，Ｐ２Ｏ５为５９．１１ｋｇ／ｈｍ２，增产效果Ｐ２Ｏ５＞Ｎ；且氮磷具有明显的正交互效应。氮磷合理配施还显著提高了水分利用效率，坡梁地和旱滩地分别提高３．０５和２．６７ｋｇ／（ｍｍ．ｈｍ２）。     

湘南红壤区牧草生产的气候模型

利用湖南省祁阳县的长期气象数据，结合不同牧草的生长特性，建立了一个反映当地牧草生长状况的气候模拟模型，并据此气候模型评价了当地气候条件对牧草生产的影响，鉴定了牧草周年生长的限制性因子。根据气候模型预测出温带牧草的最佳播种时期在１０月中旬至１１月下旬，热带牧草最好在３月下旬至４月中旬播种。牧草生长气候模型还可用于指导牧草品种筛选及牧草生产管理。     

基于土壤墒情模拟的农业干旱动态评估

已有的农业干旱研究中,土壤墒情的模拟与干旱程度的动态评估常常是独立进行的,二者并没有统一起来。基于此,建立了田间土壤水分平衡模型,通过作物生育期内的土壤水分模拟农业干旱过程。为了将土壤墒情模拟与农业干旱的动态评估统一起来,引入了阶段性的作物水分生产函数,通过干旱缺水对农业产量影响的定量分析,反推得出作物不同生育阶段土壤水分状况对应的干旱程度和缺水权重,从而将土壤墒情模拟与农业干旱评估结合起来,达到农业干旱动态模拟与评估的目的,为从土壤墒情状况实时动态评估农业干旱程度提供了一种便捷可行的方法。最后将提出的模型方法结合某灌区进行了应用,效果较好。     

Tomato yield, biomass accumulation, root distribution and irrigation water use efficiency on a sandy soil, as affected by nitrogen rate and irrigation scheduling

Florida is the largest producer of fresh-market tomatoes in the United States. Production areas are typically intensively managed with high inputs of fertilizer and irrigation. The objectives of this 3-year field study were to evaluate the interaction between N-fertilizer rates and irrigation scheduling on yield, irrigation water use efficiency (iWUE) and root distribution of tomato cultivated in a plastic mulched/drip irrigated production systems. Experimental treatments included three irrigation scheduling regimes and three N-rates (176, 220 and 230 kg ha⁻¹). Irrigation treatments included were: (1) SUR (surface drip irrigation) both irrigation and fertigation line placed right underneath the plastic mulch; (2) SDI (subsurface drip irrigation) where the irrigation line was placed 0.15 m below the fertigation line which was located on top of the bed; and (3) TIME (conventional control) with irrigation and fertigation lines placed as in SUR and irrigation being applied once a day. Except for the “TIME” treatment all irrigation treatments were controlled by soil moisture sensor (SMS)-based irrigation set at 10% volumetric water content which was allotted five irrigation windows daily and bypassed events if the soil water content exceeded the established threshold. Average marketable fruit yields were 28, 56 and 79 Mg ha⁻¹ for years 1-3, respectively. The SUR treatment required 15-51% less irrigation water when compared to TIME treatments, while the reductions in irrigation water use for SDI were 7-29%. Tomato yield was 11-80% higher for the SUR and SDI treatments than TIME where as N-rate did not affect yield. Root concentration was greatest in the vicinity of the irrigation and fertigation drip lines for all irrigation treatments. At the beginning of reproductive phase about 70-75% of the total root length density (RLD) was concentrated in the 0-15 cm soil layer while 15-20% of the roots were found in the 15-30 cm layer. Corresponding RLD distribution values during the reproductive phase were 68% and 22%, respectively. Root distribution in the soil profile thus appears to be mainly driven by development stage, soil moisture and nutrient availability. It is concluded that use of SDI and SMS-based systems consistently increased tomato yields while greatly improving irrigation water use efficiency and thereby reduced both irrigation water use and potential N leaching.