Temporal course of net N mineralization and immobilization in topsoil following incorporation of crop residues of winter oilseed rape,peas and oats in a northern climate

The impact of incorporated residues of winter oilseed rape, peas and oats on soil N availability and the risk of N leaching during autumn and winter in a northern climate is not clear. Therefore, the aim was to determine the influence of incorporated residues on net N mineralization–immobilization in topsoil during autumn and winter. A field experiment carried out at three sites in South Sweden provided soil samples and crop residues for an interpretive, in situ incubation study. Topsoil corresponding to a 7‐cm soil layer from each site used for the field experiment was incubated with and without aboveground residues under natural temperature conditions at a single field location. On the basis of the incubation study, we concluded that in the field experiment, soil N dynamics during autumn and winter trials were the combined outcome of net N mineralization in the topsoil fraction not affected by aboveground residues and net N immobilization in the fraction in contact with aboveground crop residues. In the absence of aboveground residues, the net rate of N mineralization during early autumn was similar after both oilseed rape and peas, but values were larger than that after oats. After incorporation, aboveground residues of winter oilseed rape and peas made no contribution to soil mineral N in late autumn and thus did not increase the risk of N losses during winter. In fact, the residues of oilseed rape, peas and oats reduced the amount of soil mineral N by 7–14 kg N/ha during the main drainage period (October–March). Therefore, incorporating chopped aboveground residues should be encouraged before sowing winter wheat after peas and winter oilseed rape.     

Effect of sowing date and increasing sowing rates on plant density and yield of winter oilseed rape (Brassica napus L.) under Nordic climate conditions

Abstract

A five-year investigation on overwintering of winter oilseed rape (Brassica napus L.) cv. Wotan has been carried out in Estonia. Sowing in August was conducted four times at weekly intervals. Seeding rates of 100, 150, and 200 plants m^?2, at which respectively 47, 71, and 98 plants overwintered, gave different densities at harvest. A lower plant density (47 plants m^?2) produced yields just as high as those with higher density (98 plants m^?2). The optimal sowing date was mid August, which gave on average 98 plants m^?2 with various plant densities. Those plants also gave higher yield (1748 kg ha^?1), compared with the plots sown early or later in August.     

Importance of soil mineral N in early spring and subsequent net N mineralisation for winter wheat following winter oilseed rape and peas in a milder climate

Abstract

Nine biennial field experiments, 2000–2004, in south Sweden, 55–56°N, with winter wheat following winter oilseed rape, peas, and oats, were used to estimate the impact of a future milder climate on winter wheat production in central Sweden, 58–60°N. The trials included studies 1) on losses during winter of soil mineral nitrogen (N_min, 0–90 cm soil), accumulated after the preceding crops in late autumn, 2) on soil N mineralisation (N_net) during the growing season of the wheat (early spring to ripeness) and 3) on grain yield and optimum N fertilisation (Opt-N rate) of the wheat. Average N_min in late autumn following winter oilseed rape, peas, and oats was 68, 64, and 45 kg ha^?1, respectively, but decreased until early spring. Increased future losses of N_min during the winter in central Sweden due to no or very short periods with soil frost should enhance the demand for fertiliser N and reduce the better residual N effect of winter oilseed rape and peas, compared with oats. Their better N effect will then mainly depend on larger N_net (from March to maturity during the winter wheat year). Owing to more plant-available soil N (mainly as N_net) Opt-N rates were lower after oilseed rape and peas than after oats despite increased wheat yields (700 kg ha^?1) at optimum N fertilisation. In addition to these break crop effects, a milder climate should increase winter wheat yields in central Sweden by 2000–3000 kg ha^?1 and require about 30–45 kg ha^?1 more fertiliser N at optimum N fertilisation than the present yield levels. Increased losses and higher N fertilisation to the subsequent winter wheat in future indicates a need for an estimation of the residual N effect at the individual sites, rather than using mean values as at present, to increase N efficiency.     

Identification of Phosphorous Efficient Germplasm in Oilseed Rape

ABSTRACT

Plant species and genotypes within one species may significantly differ in phosphorus (P) uptake and utilization when they suffer from P starvation. The objective of this research was to screen P-efficient germplasm of oilseed rape (Brassica napus L.) and analyze the possible mechanism responsible for P efficiency by two-steps screening experiments and validation of P efficiency. Phosphorus efficiency coefficient at seedling stage, namely, ratio of shoot dry weight under low P to that under adequate P (PECS) of 194 oilseed rape cultivars varied from 0.050 to 0.62 and was significantly related with shoot dry weight under low P level (r = 0.859??, P < 0.01). Oilseed rape cultivar ‘Eyou Changjia’ presented the highest P efficiency coefficient in each growth stage and had the highest seed yield at low P, whereas oilseed rape cultivar ‘B104-2’ was the most sensitive to low P stress among the 12 candidate cultivars obtained from the two-steps screening experiments. Under low P condition in validation experiments of soil and solution cultures, ‘Eyou Changjia’ could produce much more dry matter and acquire more P than ‘B104-2.’ Moreover, P efficient coefficient obtained from the pot experiment was comparable to those from the field experiment. This might be attributed to high P uptake efficiency for ‘Eyou Changjia’ when it suffered from low-P stress. Comparison of results from the hydroponics with those from the pot and field experiments led to the conclusion that the P uptake efficiency in the hydroponics is highly related to that in soil culture conditions. These results show that there are large genotypic differences in response to phosphorus deficiency in oilseed rape germplasm (Brassica napus L.) and ‘Eyou Changjia’ is P-efficient and ‘B104-2’ is P-inefficient. By comparing these results further, the mechanism responsible for P efficiency was suggested to be mainly due to high P uptake efficiency by forming larger root system, and improving the ability of mobilizing and acquiring soil P in P-efficient oilseed rape under the condition of P starvation.     

Potassium‐fertilizer management in winter oilseed‐rape production in China

Optimal potassium (K) fertilization is beneficial for oilseed‐rape (Brassica napus L.) yield and quality. However, the discrepancy between the high K demand of winter oilseed rape and low soil fertility and insufficient potassium input has limited the sustainable development of oilseed‐rape production. A series of on‐farm experiments in the key winter oilseed‐rape domains of China was conducted from 2004 to 2010 to evaluate K‐fertilizer management for winter oilseed rape. Currently, the average NH₄OAc‐extractable K content in the 0–20 cm soil layer is 89.1 mg kg^–1 indicative of “slight deficiency”. In addition, farmers in China usually fail to use sufficient K fertilizer in oilseed‐rape production, the average mineral‐potassium‐fertilizer input in 2010 being only 35 kg K ha^–1, far lower than the recommended rate of potassium for winter oilseed rape. Adequate potassium fertilization significantly raises seed yield. The average yield‐increase rate for the major production regions due to K‐fertilizer application was 18.5%, and the average K fertilizer–use efficiency 36.1%. Based on the negative correlation between yield response to potassium fertilization and available soil K content, a soil‐K‐test index was established for winter oilseed rape with a threshold value for NH₄OAc‐extractable soil K of 135 mg kg^–1. When available soil K‐content is below this threshold value, more K fertilizer should be applied to achieve high seed yield and to increase soil fertility. The major challenge for K‐fertilizer management in winter oilseed‐rape production in China will be to guide farmers in the different regions in making reasonable use of K fertilizer through soil K‐testing technology in order to maintain both seed yield and soil fertility.     

稻草覆盖还田对直播冬油菜生长及养分积累的影响

[目的]冬油菜产量常受限于季节性干旱、冬季低温以及土壤肥力较低等因素。考虑到秸秆还田有培肥土壤的优势以及长江中下游地区稻草过剩的现实,通过田间试验研究稻油轮作区稻草覆盖还田对直播冬油菜生长的影响,探讨稻草整株覆盖还田对直播油菜生育期内密度、株高、根茎粗的变化特征及其对油菜产量和养分吸收量的影响。[方法]试验于2014 2015和2015 2016年在湖北省武汉市华中农业大学试验场进行,共设置4个处理,分别为:1)对照,不施肥稻草不还田(CK);2)不施肥稻草覆盖还田(S);3)单施化肥(NPK);4)稻草覆盖还田配施化肥(NPK+S)。施肥处理(NPK、NPK+S)肥料用量为N 180 kg/hm^2、P2O5 60 kg/hm^2、K2O75 kg/hm^2、硼砂15 kg/hm^2。分别于油菜苗期、蕾薹期、花期、角果期和成熟期取样,测定油菜地上部生物量,氮磷钾含量和积累量,并在田间监测油菜生育期内密度、株高和根茎粗。[结果]稻草覆盖还田提高土壤最低温度0.6~1.2℃(播后95天),降低土壤最高温度0.8~1.8℃(播后184天),缩小土壤温度变幅2.3℃(播后95~184天),提高土壤平均含水量8.0%~8.9%(播后48~184天)。与稻草不覆盖相比,稻草覆盖还田减少冬油菜80%以上的出苗密度;与出苗密度相比,成熟期CK、S、NPK和NPK+S处理的密度分别降低71.3%、40.3%、69.5%和32.1%,稻草还田处理的油菜生育期内密度降低幅度小于稻草不还田处理。油菜成熟期S处理的根茎粗和株高分别比CK显著提高了22.7%和8.3%,NPK+S和NPK处理株高和根茎粗无明显差异。两年结果表明,S处理的最大生物量较CK平均增加了88.6%,与NPK处理相比,NPK+S处理的地上部苗期生物量降低3.7%~27.9%,角果期生物量平均增加28.1%。CK和S处理氮、磷和钾素积累量均在蕾薹期花期差异较大,成熟期S处理的氮、磷积累量分别较CK高28.6%~268.2%、93.3%~253.1%,两年增产率分别为218.8%和28.5%;施肥处理(NPK、NPK+S)冬油菜氮、磷和钾积累量随生育期持续增加,均在角果期达到最大值,与NPK相比,NPK+S处理分别提高成熟期油菜氮、磷和钾积累量18.1%~19.1%、23.7%~36.9%和28.3%~56.9%,两年分别增产1811和1032 kg/hm^2,增产率分别达到25.6%和20.3%。[结论]稻草覆盖还田能缓解气温骤变对土壤温度的影响,保持土壤含水量,缓解土壤干旱。稻草覆盖还田前期抑制直播冬油菜的出苗密度,后期可维持冬油菜密度的稳定,同时对冬油菜的生长、生物量、产量和养分吸收量有促进作用。     

Changes in N leaching and crop production as a result of measures to reduce N losses to water in a 6‐yr crop rotation

The effects of various measures introduced to increase nitrogen (N)‐use efficiency and reduce N losses to water in a 6‐yr crop rotation (winter wheat, spring barley, green manure, winter wheat, spring barley, spring oilseed rape) were examined with respect to N leaching, soil mineral N (SMN) accumulation and grain yield. An N‐use efficient system (NUE) with delayed tillage until late autumn and spring, direct drilling of winter wheat, earlier sowing of winter and spring crops and use of a catch crop in winter wheat was compared with a conventional system (CON) in a field experiment with six separately tile‐drained plots in south‐western Sweden during the period 1999–2011 (two crop rotation cycles). Total leaching of NO₃‐N from the NUE system was significantly 46 and 33% lower than in the CON system during the first and second crop rotation cycle, respectively, with the most pronounced differences apparently related to management strategies for winter wheat. Differences in NO₃‐N leaching largely reflected differences in SMN during autumn and winter. There was a tendency for lower yields in the NUE system, probably due to problems with couch grass. Overall, the measures for conserving N, when frequently used within a crop rotation, effectively reduced NO₃ concentrations in drainage water and NO₃‐N leaching losses, without severely affecting yield.     

Climate-induced overwintering challenges for wheat and rye in northern agriculture

Abstract

Winters are typically harsh in the northernmost agricultural areas of Europe, and winter rye (Secale cereale L.) and wheat (Triticum aestivum L.) are the only winter grain crops that can be grown. However, climate change is projected to result in milder winters, which may enable cultivation of winter crops to a greater extent in the future than is possible today. In this study we aimed at identifying main temperature, precipitation events and characteristics that have resulted in past poor overwintering of rye and wheat in their current production areas in Finland. Using long-term (1970–2006), multi-location datasets, we compared our findings with the projected major changes attributable to climate change. Mixed models were used to estimate mutually comparable overwintering damage to all experiments and logistic regression was used to determine whether climatic parameters are related to high levels of overwintering damage. Severity of overwintering damage, and associated yield penalties, fluctuate considerably on a year-to-year basis and no consistent reduction in variability was recorded during the study period. Particularly for wheat, severity of winter damage in any one year was associated negatively with area sown in the following year. There was no evidence of consistent genetic improvements in winter hardiness, but rye was more winter hardy than wheat. Current risks associated with rye production related to low temperatures could be alleviated in the future, although overwintering damage currently enhanced by high autumn precipitation could increase due to climate change. For wheat, fluctuating conditions hampered overwintering, which may be an even harder challenge in future when weather variation is projected to increase and extreme weather events are projected to become more common.     

The role of tillage and crops on a soil loss of an arable Stagnic Luvisol

The poor physical, chemical and biological properties make Stagnic Luvisol highly susceptible to water erosion on sloping terrains. The objective of this paper is to estimate the effect of different tillage treatments and crops (maize, soybean, winter wheat, spring barley, oilseed rape) on water erosion. The highest erosion in investigation period (1995–2014) was recorded in the control treatment with fallow, followed by the treatment that involved ploughing and sowing up and down the slope. Significantly, lower soil losses were recorded in no-tillage and treatments with ploughing and sowing across the slope. Regarding the crops significantly higher soil losses were recorded in spring row crops (maize and soybean) compared to high-density winter crops (wheat and oilseed rape) and double crop (spring barley with soybean). In the studied period, an average loss of 46 mm of the plough layer was recorded in the control treatment, while in treatment with ploughing and sowing up and down the slope average annual soil loss was 10 mm. According to the results of this study no-tillage and tillage across the slope are recommended as tillage which preserves soil for the next generations in agro-ecological conditions of continental Croatia.     

A review of fertilizer, lime and organic manure use on farm crops in Great Britain from 1983 to 1987

Abstract. In 1983, an annual Survey of Fertiliser Practice in England and Wales was extended to Scotland, to provide comprehensive information on inorganic fertilizer, lime and also organic manure use in mainland Britain. It was based on an annual sample of about 1500 farms, selected from the Agricultural Census and stratified by farm type and size. Results from the first fifteen years (1983–97) show that fertilizer nitrogen (N) rates on both tillage crops and grassland peaked at 157 and 132 kg ha^–1, respectively, in the mid 1980s and subsequently decreased by c.10%. The majority of N was applied in straight form (without P or K) to tillage crops and in compound form (containing two or more nutrients e.g. NPK; NK) to grassland. Total N use on cereals showed little change but autumn‐applied N decreased on both winter cereals and winter oilseed rape. Total N rates decreased on oilseed rape and, to a smaller extent, on maincrop potatoes and sugarbeet. Between 1983–87 and 1993–97, mean phosphate (P₂O₅) rates declined by almost 10% on both tillage crops (from 58 to 53 kg ha^–1) and on grassland (from 25 to 23kg ha^–1). The corresponding mean potash (K₂O) rates decreased slightly on both tillage crops (from 64 to 62 kg ha^–1), and on grassland (from 32 to 31 kg ha^–1), although annual usage was more variable on grassland. Sulphur use increased appreciably on cereal and oilseed rape crops between 1993, when S data were first recorded in the survey, and 1997 when 13% and 30%, respectively, of these crop areas received S‐fertilizer. However, on grassland, S use remained very low. Average lime use increased on both tillage crops and grassland between the mid 1980s and mid 1990s, from 10 to 12% and 4 to 7% of the total area, respectively. The proportion of land receiving organic manures remained at c. 16% for tillage cropping but increased slightly for grassland, from a mean of 40% in 1983–87 to 44% in 1993–97. Manures were applied throughout the year but about half the applications to tillage land, and a quarter of those to grassland, were made in autumn when the risk of subsequent nitrate leaching loss is greatest.     

2022年夏收粮油作物生育期气象条件及其影响分析

基于主产区气象观测站和农业气象站实测气象资料和作物发育期资料,计算冬小麦和油菜生长季的气候适宜度和灾害指数等参数,评价该阶段气象条件对夏收粮油作物的利弊影响。结果显示：2021/2022年度冬小麦、油菜生育期内,产区大部光热充足、土壤墒情适宜,冻害、干旱等农业气象灾害影响程度偏轻,气候适宜度高于上年和近5a平均值,气象条件利于夏收粮油作物生长发育和产量形成;成熟收获期间多晴好天气,收获进度快、质量高。但北方冬麦区秋播期多雨渍涝,冬小麦播种期明显推迟,冬前壮苗比例偏少、分蘖不足。江南和贵州等油菜产区冬季持续阴雨寡照,影响油菜发育进程。     

轮作体系下冬油菜养分利用效率的区域研究

Fertilization is essential for oilseed rape because it is sensitivity to nutrient deficiency, especially for winter oilseed rape(Brassica napus L.). To investigate regional nutrient efficiency and nutrient uptake-yield relationship of winter oilseed rape in an intensive cropping system, this study used data from 619 site-year on-farm experiments carried out in the winter oilseed rape planting area of the Yangtze River Basin, China from 2005 to 2010, with large yield in the range of 179–4 470 kg ha~(-1). Currently recommended application rates of N, P and K fertilizers increased rapeseed yield at different levels of soil indigenous nutrient supply(INS) in this region. Boundary values of plant nutrient uptake were established to analyze the nutrient uptake-yield relationship of winter oilseed rape(internal nutrient efficiency), i.e., 128 kg N ha~(-1), 24 kg P ha~(-1), and 122 kg K ha~(-1). The internal nutrient efficiency declined by 48.2%–64.1% when nutrient uptake exceeded the boundary value, resulting in excessive nutrient uptake(i.e., low yield response with high nutrient uptake), especially for K. In the intensive cropping system, agronomic efficiencies of N, P, and K were 5.9, 3.4, and3.6 kg kg~(-1), and recovery efficiencies of N, P, and K were 35.6%, 24.1%, and 36.8%, respectively. These findings showed that the fertilization rate should be optimized by considering INS, nutrient status, and nutrient efficiency of winter oilseed rape. In this study,considering the lower yield improvement to high K uptake levels and low K fertilizer efficiency, application rate of K fertilizer should be reduced since soil K deficiency has already been mitigated.     

Analysis of Genetic Diversity in the Brassica napus L. Gene Pool Using SSR Markers

Genetic diversity throughout the rapeseed (Brassica napus ssp. napus) primary gene pool was examined by obtaining detailed molecular genetic information at simple sequence repeat (SSR) loci for a broad range of winter and spring oilseed, fodder and leaf rape gene bank accessions. The plant material investigated was selected from a preliminary B. napus core collection developed from European gene bank material, and was intended to cover as broadly as possible the diversity present in the species, excluding swedes (B. napus ssp. napobrassica (L.) Hanelt). A set of 96 genotypes was characterised using publicly available mapped SSR markers spread over the B. napus genome. Allelic information from 30 SSR primer combinations amplifying 220 alleles at 51 polymorphic loci provided unique genetic fingerprints for all genotypes. UPGMA clustering enabled identification of four general groups with increasing genetic diversity as follows (1) spring oilseed and fodder; (2) winter oilseed; (3) winter fodder; (4) vegetable genotypes. The most extreme allelic variation was observed in a spring kale from the United Kingdom and a Japanese spring vegetable genotype, and two winter rape accessions from Korea and Japan, respectively. Unexpectedly the next most distinct genotypes were two old winter oilseed varieties from Germany and Ukraine, respectively. A number of other accessions were also found to be genetically distinct from the other material of the same type. The molecular genetic information gained enables the identification of untapped genetic variability for rapeseed breeding and is potentially interesting with respect to increasing heterosis in oilseed rape hybrids.     

The effect of biostimulators on the content of crude oil and total protein in winter oilseed rape (Brassica napus L.) seeds

The objective of the study was to determine the effect of the experimental factors on the seed quality of three winter oilseed rape cultivars. The following factors were studied: I-three winter oilseed rape morphotypes: population, hybrid restored characterised by a semi-dwarf growth pattern, hybrid restored characterised by a conventional growth pattern; II-two sowing methods: a spacing of 22.5?cm, a spacing of 45.0?cm; III-four types of biostimulants: control-no biostimulants, the biostimulant Tytanit^®, Asahi^®SL, Silvit^®. Seed samples were subjected to chemical analysis to determine: crude oil, total protein and crude fibre. Natural stimulants of plant growth and development contributed to an increase in crude oil ranging from 7.4 to 9.5?g?kg^–1 d.m., on average, compared with control. The biostimulants applied did not affect total protein content which was, however, affected by meteorological conditions in individual study years as well as the genetic factor. Biostimulants increased crude fibre content compared with control.     

冬前积温和春化处理对不同春化发育特性小麦品种幼穗分化的效应

以3个春性、半冬性和冬性小麦品种为材料,采用分期播种和春化处理,以热时间为尺度,研究了冬前积温对不同春化发育特性小麦品种幼穗分化进程及主要穗分化期累积GDD(生长度日,growingdegree days)的影响。结果表明,随着冬前积温的减少,不同幼穗分化时期累积GDD减小,冬前积温对小麦幼穗分化的影响主要表现在单棱期和二棱期,护颖分化期后幼穗分化受冬前积温的影响较小,冬性品种幼穗分化累积GDD对冬前积温最敏感,半冬性品种次之,春性品种则对冬前积温不敏感。春性品种幼穗分化前期适宜温度的上限为14℃,当14℃以下累积GDD达到232~243时,幼穗可正常分化进入二棱期,半冬性品种幼穗分化适宜温度的上限为12℃,12℃以下GDD达到261~277后,幼穗分化可正常进入二棱期,高于上限的GDD不能满足小穗原基正常分化的需求。在田间条件下小麦小穗原基的分化对特定温度范围的累积GDD有稳定的需求,这种需求因品种的春化发育特性而异。     

Effect of air temperature on common bunt (Tilletia caries) infection in winter wheat

Abstract

During the period 1993–2006 experiments designed to study the peculiarities of common bunt infection in winter wheat were carried out in a nursery with artificial inoculation at the Lithuanian Institute of Agriculture. The effects of air temperature from sowing to resumption of vegetation were determined using correlation analysis on the infection level of common bunt in winter wheat. A significant correlation between the mean nursery infection and daily mean temperature had a maximum value on the 36th day (r=0.60) at a 30–190-day interval after sowing. The minimum value was detected on the 150th day (r = -0.65) at a 150–190-day interval after sowing. The calculation of multi-intervals of mean temperatures allowed us to highlight the actual influence of temperature on the final level of common bunt infection. Cross-comparison of 6 contrasting years indicated that the impact of post-sowing temperatures was low. This was proved in 1994, 1998, and 2006 with similar temperatures but considerable differences in final infection levels – 46.9, 6.8, and 80.9%, respectively. Of the 6 test years only post-sowing temperatures in the autumn of the year 2003 were unfavourable for initial infection. The mean infection level was low when heavy frosts occurred together with a thin snow cover in 1995 (8.6%), 1998 (6.8%), and 2004 (8.9%). A high infection level occurred when heavy frosts coincided with a thicker snow cover in 1994 (46.9%), 1999 (22.9%), and 2006 (80.9%).     

Effects of seedbed properties on crop emergence. 4. Inhibitory effects of oxygen deficiency

Abstract

For studies of the effects of seedbed properties on crop emergence, experiments were carried out in shallow plastic boxes. In some experiments, it was examined whether rainfall after sowing could cause oxygen deficiency in the seedbed sufficiently severe to hamper emergence. Crops studied were barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), oilseed rape (Brassica napus var. oleifera, L., Metzg.) and pea (Pisum sativum L.). For harmful oxygen deficiency to develop it appeared that rainfall would need to cause structural collapse of the surface layer followed by continuously wet weather accompanied by slow drainage and high oxygen consumption in the soil; in the experiments the latter was achieved by large amounts of easily decomposable organic matter. It was concluded that such conditions are rare in the field. Therefore, unless rainfall after sowing generates surface water for an extended period, the poor crop emergence often observed after such rainfall is nearly always caused not by oxygen deficiency, but by surface layer hardening when this layer dries.     

Organically grown Brassica napus – use of border strips and Trichoderma

Oilseed rape (Brassica napus L.) is a very difficult crop to cultivate organically. Only few organic methods are effective in reducing damage from insects and diseases. The current investigation assessed the use of the beneficial ascomycete Trichoderma asperellum (Samuels, Lieckf & Nirenberg) and a trap crop of Brassica rapa L. turnip rape cv. “Brachina,” both with and without an application of slurry fertilizer, for pest suppression and yield enhancement of winter oilseed rape cv. “Californium.” The presence of the trap crop significantly increased 1000 grain weight but not total yield or lipid content of the oilseed rape because turnip rape was not attractive enough to prevent colonization of the principal crop. Increase in 1000 grain weight, lipid content, and total seed yield were found in oilseed rape sprayed with three applications of T. asperellum, but the ascomycete had no influence on the insect pests observed. The effects of the fertilizer are about equal to the effects of the fungus on 1000 grain weight and on lipid content.     

Optimizing seed crops of common bent (Agrostis capillaris) by sowing rate

Abstract

As part of a project to stimulate Norwegian seed production of common bent (syn. browntop, US: colonial bentgrass, Agrostis capillaris L. syn. A.tenuis Sibth.) field trials comparing sowing rates of 2.5, 5.0, 7.5 or 10 kg ha^?1 were conducted at Landvik, south-east Norway, (58°N) from 1989 to 1994. Three trials were laid out of the forage cultivar ‘Leikvin’ and three trials of the lawn cultivar ‘Nor’, each trial being harvested for three consecutive years. While the average per cent ground cover in spring increased from 87% at 2.5 kg ha^?1 to 94–96% at 7.5 kg ha^?1, seed yields decreased with increasing sowing rate in both cultivars. On average for all harvests, quadrupling the sowing rate from 2.5 to 10 kg ha^?1 reduced seed yield by 9% in ‘Leikvin’ and 15% in ‘Nor’, the stronger effect probably being associated with a greater competition between tillers in the lawn cultivar. Seed yield reductions with increasing sowing rate showed no relationship with crop age, but were less accentuated for crops undersown in spring wheat in a dry year than for crops established without cover crop in years with ample rainfall in early summer. Increasing sowing rates reduced plant height and panicle number in ‘Nor’, but had no effect on seed weight or germination in any of the cultivars. It is concluded that seed crops of common bent should be established with a sowing rate of 2–5 kg ha^?1, with the lowest rate in lawn cultivars, under ideal seedbed conditions and when seed crops are sown without cover crop.     

EFFECT OF EXTERNAL NITRATE CONCENTRATIONS ON NITRATE EFFLUX FROM ROOTS AND ACCUMULATION IN TWO BRASSICA NAPUS L. CULTIVARS

The nutrient solution was replaced on day 72 after sowing, and then the relationship between nitrate (NO₃)-nitrogen(N) concentration in plants and nitrate efflux from roots of two oilseed rape cultivars (Brassica napus L. cv. ‘Zhongyou 821’ (‘ZY821’) and “D89”) was compared on days 73, 74, and 75, respectively. Nitrate-N concentration in petioles of “ZY821” was significantly greater than in “D89”. Nitrate-N concentrations in the nutrient solution and petioles were high on day 73 and nitrate efflux from roots of “D89” was greater than from “ZY821”. On day 75, as nitrate-N concentrations in the nutrient solution declined, both the maximum cumulative efflux and efflux rate of “ZY821” was higher than “D89.” We hypothesized that “ZY821” could remobilize more nitrate-N from the petioles to meet its N needs. This would result in a decline in translocation of nitrate from roots to shoots and an increase in root cytoplasm nitrate concentrations and root efflux.