Survival of plants of common sainfoin (Onobrychis viciifolia Scop.) in competition with two companion grass species

A 2-year experiment on competition between sainfoin ( Onobrychis viciifolia Scop.), meadow fescue ( Festuca pratensis ) and tetraploid perennial ryegrass ( Lolium perenne ) was conducted using plants grown in plastic containers outdoors. Root and shoot systems of sainfoin and the grasses were separated in order to investigate full and no competition of root and shoots, at two planting ratios (0·33 grass:0·66 sainfoin and 0·66 grass:0·33 sainfoin). Survival of sainfoin plants was lower at the higher grass:sainfoin ratio. More sainfoin plants died in the winter than during the growing season. Root competition had no effect on survival of sainfoin plants, but shoot competition reduced survival of sainfoin plants during one growing season. Companion grass species had no effect on survival of sainfoin plants, except in the first winter, when fewer sainfoin plants survived when grown with meadow fescue than perennial ryegrass.     

Impact of frost and plant age on compensatory growth in timothy and perennial ryegrass during winter

Two cultivars of each of two contrasting grass species, timothy ( Phleum pratense L.) and perennial ryegrass ( Lolium perenne L.), sown either in May or July, were sampled for dry matter (DM) weight of roots and herbage in late October (end of main growing season) and examined for regrowth when exposed to a frost treatment (−8 to −10°C in darkness for 48 h) in late January, early March and late April. The frost treatment caused compensatory root and herbage growth, and regrowth of roots in March and April was greater than regrowth of herbage. Early-sown plants had higher DM weights of roots and herbage than late-sown plants in October but had the lowest survival rate when exposed to the frost treatment in April. Compensatory growth of root and herbage in response to moderate frosts occurred in January and March in all cultivars, and in the most frost-resistant timothy cultivar in April. Concentration of total carbohydrates increased from October to March with the greatest increase in the most winter-hardy cultivar of each species, and then decreased in April. An indirect correlation between concentration of total carbohydrates and tolerance to moderate frost was indicated, and plant survival and ability for compensatory growth were also associated with differences in adaptation related to winter survival in the cultivars tested.     

多年生黑麦草对干旱-低温交叉适应的生理响应

草坪草在冬季的时候常常面临着干旱和低温的双重胁迫,严重影响着春季返青时草坪草的质量。为了探讨多年生黑麦草的干旱-低温胁迫交叉适应的生理机制,以多年生黑麦草“爱神特(Accent)”为植物材料,设置3个水分梯度,土壤相对含水量分别为30%(重度胁迫)、60%(中度胁迫)、100%(良好浇水)。处理5 d后在人工气候箱中进行低温处理(2℃)15 d。低温胁迫使多年生黑麦草的叶片相对含水量、叶绿素含量显著降低,电解质渗漏、脯氨酸、可溶性总糖、抗氧化酶的含量增加。3种水分处理条件下,经过中度干旱处理后的多年生黑麦草的叶片相对含水量、叶绿素含量的降低幅度减小,但脯氨酸、可溶性糖、抗氧化酶的含量增加显著。实验结果表明多年生黑麦草对干旱-低温胁迫具有交叉适应能力。适当地进行干旱处理有利于提高多年生黑麦草对低温胁迫的适应能力。但值得注意的是,严重的干旱处理会造成过度伤害,致使植株更快死亡。     

Weed flora and seed yield in quinoa crop (Chenopodium quinoa Willd.) as affected by tillage systems and fertilization practices

The effects of tillage system and fertilization regimes on weed flora in quinoa (Chenopodium quinoa Willd.) were evaluated by means of two field experiments in 2011 and 2012. The experiments were laid out in a split-plot design with two main plots (conventional and minimum tillage) and four sub-plots (fertilization regimes). The results indicated that weed biomass and density in quinoa were influenced by the different fertilization and tillage treatments. Moreover, seed yield in conventional was 5%–13% higher than that of minimum tillage, probably due to the lower weed density and biomass. Concerning fertilization treatments, total weed density and biomass increased under manure application and inorganic fertilization. Tillage effects on weeds were species specific. The density of perennial weeds such as purple nutsedge (Cyperus rotundus L.) and the density of small-seeded weeds such as redroot pigweed (Amaranthus retroflexus L.) and common purslane (Portulaca oleracea L.) were significantly lower under the conventional tillage than under the minimum tillage system.     

Weight loss in overwintering below‐ground parts of Sonchus arvensis under current and temperature‐elevated climate scenarios in Sweden

Weight loss in overwintering below‐ground parts of perennial weeds has been attributed to respiration, but neither its temperature dependence nor its relevance for biomass dynamics under changing climate conditions have been investigated. In two experiments, we quantified weight loss of the perennial weed Sonchus arvensis, by measuring weight changes over time of sprouting roots in dark rooms at temperatures of 4, 8 and 18°C. Dry weight loss rates were 0.47, 0.64 and 1.47% day^?1 at 4, 8 and 18°C, respectively, giving a half‐life time of 149, 110 and 47 days, respectively. A factor by which weight loss rates increase for every 10° rise in temperature (Q₁₀) was equal to about 2.3. Cumulative weight loss may comprise >40% of the below‐ground biomass during overwintering periods. Applying weight loss rates and Q₁₀ to elevated soil temperature projections showed that losses during winter seasons in central Sweden will remain basically constant, the effect of increased weight loss at higher temperatures being balanced by shorter winters. This implies that need for control of S. arvensis in a changing climate will persist, but that shorter winter seasons will provide a longer time window for control of S. arvensis prior to sowing crops.     

Sprouting capacity from intact root systems of Cirsium arvense and Sonchus arvensis decrease in autumn

Perennial weeds are often controlled by mechanical means, which aim at stimulating axillary and adventitious buds to sprout. This happens when the apical dominance of the main shoot is removed by defoliation or when the underground system is fragmented. By repeating the measures, the result is a depletion of storage compounds, which weakens the plants and reduces their capacity to grow and reproduce. However, timing is critical. Earlier research has indicated that emergence from fragments of Sonchus arvensis cease during a period in autumn, while the seasonal pattern of sprouting in Cirsium arvense appears to be inconsistent. We studied the emergence pattern of defoliated plants with undisturbed root systems, from late summer to early spring. Potted plants grown outdoors were exhumed at regular intervals, put under forcing conditions for 4 weeks, after which shoots above and below soil level were counted and weighed together with the remaining root systems. In both species, the number and weight of emerged shoots decreased during a period in the autumn. In C. arvense, underground shoots were constantly produced during the same period, while fewer underground shoots were present in S. arvensis. For the latter species, apical dominance does not fully explain the effect; thus, endodormancy might be involved. Root weight increased until withering and did not explain the lack of emergence. Our results suggest an impaired sprouting capacity of undisturbed root systems of C. arvense and S. arvensis during September–October, which has implications for the timing and method of control of these species.     

多年生麻类作物种质资源研究进展

麻类作物是我国传统的栽培作物,麻纤维是人类最早使用的纺织材料之一,是纺织工业的重要原料。其中,苎麻、剑麻、罗布麻是我国代表性的麻类多年生作物,具有重要的经济价值。综述了苎麻、剑麻、罗布麻种质资源的搜集保存现状、选育及其在国内外的应用情况,并对其研究进展进行了探讨。     

多年生黑麦草抗逆性研究进展

多年生黑麦草是一种优良的冷季型草坪草。介绍了近几年来黑麦草抗逆性的研究进展,概括了干旱、高温、低温、盐碱、重金属等对黑麦草的危害及植物体的抗逆性应答反应,列举了提高黑麦草抗逆性的措施。同时袁总结了黑麦草抗逆性研究中存在的问题,为进一步研究提供思路。     

Nitrogen–Potassium Concentrated Complex Fertilizers versus Nitrogen–Potassium Blends: Effects on Potassium Uptake by Perennial Ryegrass

Abstract

It was hypothesized that supplying potassium (K) in concentrated complex fertilizer (CCF) form with nitrogen (N) (NK CCF) to all fertilizer microsites, rather than in NK‐blended fertilizer form to a fraction of the total fertilizer microsites, should enhance the rate of K uptake by perennial ryegrass. Two complementary pot experiments were conducted to test this hypothesis. The results demonstrated that plants fertilized with an NK CCF absorbed K at faster rates than those fertilized with an NK blend and that use of K₂SO₄ in place of KCl as the K source lowered the rate of K uptake by plants regardless of fertilizer form. Form of fertilizer (i.e., CCF or blend), however, had no effect on NH₄ ⁺ or NO₃ ^? uptake. Unfortunately, the positive effects of the CCF on K absorption were only manifest during the second 2 weeks of regrowth and did not result in significant improvements in dry matter production by the end of the 5‐week regrowth periods.     

Field and Laboratory Evaluation of the Cardy Nitrate-Nitrogen Meter for Measuring Soil Solution Nitrate Nitrogen in Hawaiian Soils

The estimation of plant-available nitrate nitrogen (NO₃-N) is essential for any nutrient-management plan but can be time-consuming and expensive. However, the efficacy of rapid methods to determine soil NO₃-N levels designed for grower use has received mixed reviews in the literature. Therefore, the objectives of this study were to (1) evaluate the Cardy electrode-based meter for measuring soil solution NO₃-N concentrations under a perennial peanut living mulch in two mixed orchard systems on O'ahu and (2) determine the influence of soil type on measurement accuracy and precision under laboratory conditions. To achieve the first objective, 24 lysimeters were installed 15–30 cm deep at each of two fruit tree orchards with different soils and climate on Oahu island. For the second objective, a replicated column study was conducted, in which NO₃-N solutions of varied concentrations were leached through three representative agricultural soils (Wahiawa, Loleka'a, and Waialua series). Field soil solution and column leachate were analyzed using the portable electrode-based meter and a standard laboratory colorimetric method. In the field samples, soil solution NO₃-N ranged from <1 to 110 mg/L, and there was a strong correlation (r²?=?0.92) between the portable meter and colorimetric values. Similarly, a strong correlation between the Cardy meter and the laboratory methods was observed in the column study, although r ² values varied with soil type. The data suggest that the Cardy meter can be used to rapidly and accurately measure soil solution NO₃-N, if its concentrations are relatively high and concentrations of interfering ions such as chloride (Cl^?) are low. Overall, the primary value of this rapid method may be in estimating relative changes in soil nitrate in response to nutrient management at a single site.