渭北旱塬春玉米生产力及其水分条件评价

田间试验表明,渭北旱塬春玉米最大生产力为8350.5kg/hm~2,需水量为442.2mm。根据自然降水总量及降水分布与春玉米、冬小麦需水量及需水规律的关系,适当扩大春玉米种植面积,不仅可增加粮食产量,而且可保持农田良性的物质、能量循环体系。     

旱地小麦少耕沟播覆盖技术研究

１９９０～１９９３年的试验研究和生产示范表明，旱地小麦少耕沟播覆盖栽培技术具有明显的蓄水保墒和培肥土壤效果，少耕沟播覆盖比常规耕作的土壤含水量提高两个百分点以上，土壤有机质含量提高０．１２７～０．２５１百分点；土壤容重变小，比常规耕作增产小麦３６．６％。     

Comparison of Nitrogen Uptake,Transpiration Rate and Exudation Rate between Upland NERICAs and Japanese Cultivars

Abstract

Our previous study revealed that upland cultivars of New Rice for Africa (NERICAs) exhibited superior biomass production and N uptake compared with selected Japanese cultivars under upland conditions. The objective of this study was to examine whether the N uptake ability of upland NERICAs is attributable to their transpiration and exudation rates. Two NERICA cultivars (NERICA 1 and NERICA 5), two Japanese upland cultivars (Toyohatamochi and Yumenohatamochi), and a Japanese lowland cultivar Hitomebore were grown under rainfed upland conditions at two N levels. The NERICAs exceeded Japanese cultivars in the increment of aboveground dry weight and N content during the ripening stage. The transpiration rate and exudation rate of NERICAs tended to be higher than those of Japanese cultivars during the ripening stage. These results suggest that NERICAs are capable of maintaining higher water uptake ability during the ripening stage, leading to greater N uptake and biomass production at maturity.     

Plasticity in root system architecture of rice genotypes exhibited under different soil water distributions in soil profile

ABSTRACT

The root system architecture (RSA) has been reported to be determined by several root traits such as branching, elongation, and growth angle. This study aimed to evaluate the genotypic variation of plasticity in RSA in response to different soil water distributions in a soil profile. IR64 (shallow root system), YTH183 (adapted to rainfed lowland conditions due to high plasticity in root elongation), and Kinandang Patong (KP – deep root system) were grown in PVC root boxes for 34 days under continuously waterlogged conditions and with soil moisture fluctuations (SMF). For SMF, watering was done from the top of the root box (TI-SMF) or from the bottom of the root box (BI-SMF). A water gradient was observed more clearly in BI-SMF than in TI-SMF, while mean soil moisture content in the root box was kept at around 23% (v/v) after first irrigation in both SMF treatments. RSA changed drastically with SMF in all cultivars, all of which tended to shift root distribution to deeper soil layers in response to SMF. Such changes in RSA resulted from different degrees of plasticity exhibited mainly in nodal root and L-type lateral root development. YTH183 showed a greater ability to change its root growth angle and thus its root distribution in the deeper soil layer compared to IR64 and KP under SMF, indicating that YTH183 could help to improve RSA in cultivars adapted to SMF.     

Suppressing weeds in direct-seeded lowland rainfed rice: Effect of cutting dates and timing of fertilizer application

Weeds cause substantive yield losses in rainfed rice, particularly direct-seeded rice (DSR). Two field experiments were conducted in 2005 in north-east Thailand to examine the effects of cutting date and timing of fertilizer application on suppressed weed, growth and yield of DSR. Treatments consisted of two fertilizer applications to the main plots (top-dressing at the date of cutting and 15 days after cutting; DAC) and four cutting dates of the sub-plots. Rice and weed cutting was performed at 30, 45, 60 and 75 days after seeding (DAS), compared with an untreated control. Cutting resulted in a higher growth rate and improved grain yield of rice compared to the untreated control. Weed cutting at 60 DAS resulted in the greatest leaf area index, which contributed to the maximum number of tiller as well as maximum plant dry mass when observed at 30 DAC. Lower densities and dry weights of weeds at 30 DAC were observed when cutting was done 60 DAS, resulting in a higher grain yield than the other cutting dates. Timing of fertilizer application had no significant effect on the density and dry weight of grasses and broad-leaved weeds, but did have a significant affected on, resulting in the lowest density of sedges at 45 DAC was observed with fertilizer applied at cutting date. Rice grain yield was higher with top-dressing of fertilizer at 15 DAC than with fertilizer applied at cutting date. The cutting treatments resulted in higher net incomes than the untreated control. These results indicate that rice and weed cutting at an appropriate growth stage is an alternative method to chemical weed control for DSR in rainfed riceland.     

Variation in root system architecture and drought response in rice (Oryza sativa): Phenotyping of the OryzaSNP panel in rainfed lowland fields

Root growth at soil depths below 30 cm may provide access to critical soil water reserves during drought in rainfed lowland rice. In this study, the OryzaSNP panel, a set of 20 lines representing genetic diversity in rice used for the discovery of DNA sequence polymorphisms, was evaluated for root characteristics in the field over three seasons varying in drought severity. Root length density (RLD) at a depth of 30–45 cm varied up to 74–92% among genotypes under drought stress (2008–2009 dry seasons), ranging from 0.024 to 0.23 cm cm⁻³ in 2008 and from 0.19 to 0.81 cm cm⁻³ in 2009. Real-time monitoring of soil moisture profiles revealed significant differences among genotypes, and these differences were correlated with RLD at those soil depths. Among the lines evaluated, the Aus isozyme group, particularly the genotype Dular, showed greater drought resistance associated with deep root growth and the highest drought response index (less reduction in yield by drought stress). Since the set of genotypes used in this study has been completely sequenced for SNP markers, the phenotypic information on root growth and drought avoidance responses presented here could be used in initial analysis of the genetic basis of dehydration avoidance traits and in facilitating improvement in drought resistance in rice.     

雨养条件下玉米穗位叶与产量关系研究

华北地区是我国夏玉米主产区,但该地区地下水超采严重,玉米生育期内经常干旱缺水,雨养玉米已经成为节水农业发展的趋势。筛选简单易行的抗旱指标,对抗旱节水高产玉米品种的评价和选育有重要意义。在雨养水分亏缺条件下,对华北地区广泛种植的10个玉米品种穗位叶性状与产量关系进行相关研究,结果表明,在10个参试品种中浚单20的叶面积中等、叶鲜重和叶干重较重,物质的转运能力较高,其产量最高,具有抗旱节水高产特性。穗位叶各性状间呈极显著正相关,其中叶面积对叶干重的影响较大,穗位叶干重与产量呈显著正相关并具有共线性关系。因此,建议将穗位叶干重作为雨养条件下品种鉴定及选育的指标进行应用。     

山西省太原市旱作农区大气活性氮干湿沉降年度变化特征

鉴于大气氮素沉降对整个生态系统的重要影响,我国近年来陆续开展了不同尺度的大气氮素干、湿沉降的研究,但少有农业区多年连续监测的资料。本研究利用DELTA系统、被动采样器和雨量器在山西省太原市郊区阳曲县河村旱作农业区进行了4年的监测试验,观测大气氮素干、湿沉降的时间变异。结果表明:2011年4月—2015年3月,河村4年大气活性氮NH_3、HNO_3、NO_2、颗粒态NO_3~-(pNO_3~-)、颗粒态NH_4~+(pNH_4~+)平均沉降量分别为4.50 kg(N)·hm~(-2)·a~(-1)、3.54 kg(N)·hm~(-2)·a~(-1)、2.56 kg(N)·hm~(-2)·a~(-1)、1.62 kg(N)·hm~(-2)·a~(-1)、2.75 kg(N)·hm~(-2)·a~(-1),大气氮素干沉降总量为12.38~18.95 kg(N)·hm~(-2)·a~(-1),以2011年的氮干沉降量最高,2014年的最低。2011年4月—2015年3月各月氮干沉降量与氨气沉降量之间存在显著正相关,相关系数在0.809 8~0.937 1,由此可知,该地区活性氮沉降主要受农业氨气排放的影响。河村4年雨水中NO_3~-、NH_4~+平均浓度分别为3.20 mg(N)·L~(-1)和2.43 mg(N)·L~(-1),大气氮素湿沉降11.67~41.31 kg(N)·hm~(-2)·a~(-1)。年度间氮素湿沉降存在很大差异,以2012年氮素年湿沉降量最高,2014年最低,每年大气氮素湿沉降占氮总沉降量的份额超过50%。此外,4年湿沉降中不仅NO_3~--N和NH_4~+-N之间、且二者与降雨量也呈显著线性或二次相关关系,说明降雨量对NO_3~--N和NH_4~+-N的湿沉降影响较大。本研究表明太原市旱作农区不同年份间氮素湿沉降比干沉降差异更大,且总沉降数量较高。虽然是旱作区,该地区氮素干沉降略低于湿沉降。研究结果为该地区农田氮肥施用和氮素循环监测提供了理论依据。     

荒漠草原区灌溉和旱作条件下蒙古冰草和新麦草产草量的构成因素

对荒漠草原区灌溉和旱作条件下蒙古冰草和新麦草的适应性、单株产草量构成因子及其贡献率进行了研究。结果表明:灌溉条件下蒙古冰草和新麦草单株产草量及其各构成因子产量或数值皆大于旱作条件下;旱作条件下蒙古冰草产草量构成因子对单株产草量的贡献率大小顺序为,茎重>株高>穗重>分蘖数>叶重,新麦草为茎重>分蘖数>株高>叶重>穗重;灌溉条件下蒙古冰草产草量构成因子对单株产草量的贡献率大小顺序为,茎重>分蘖数>株高>穗重>叶重,新麦草为茎重>株高>分蘖数>叶重>穗重。     

玉米渗水地膜覆盖效应及增产作用

研究了玉米田覆盖渗水地膜后的增温调温、保墒提墒和增产效应,结果表明:渗水膜覆盖具有增温效应,对于夏季土壤的极端温度有一定的调节作用;生育期内土壤平均含水量为15.2%,与其他处理的差异达极显著水平;渗水膜覆盖增产幅度达25%~60%,与其他处理比较,差异均达极显著水平。