膜下滴灌条件下水分对棉花根系分布特征的影响

通过分层土柱挖掘法，研究膜下滴灌条件下不同滴灌量棉花（Gossypium hirsutum L．）根系的分布特征。结果表明：直径〉1mm的粗根只分布在40cm以上的土层；随着土层深度增加，棉花根系生物量逐渐减少；但随着滴灌量减少，土壤深层根系生物量有增加趋势。不同处理的根系生物量的分布与土层深度呈显著的负指数关系，棉花细根生物量、根长、根表面积在土壤中垂直分布都呈“单峰型”曲线变化规律；但随着滴灌量的减少，棉花根系消弱系数β呈增加趋势。     

Comparison of the adsorption of maize root mucilage and polygalacturonic acid on montmorillonite homoionic to divalent lead and cadmium

Summary Root mucilage material (RM) was isolated from maize plants grown in the field, and its affinity to montmorillonite (M) homoionic to Pb²⁺ and Cd²⁺ was compared with that of a commercial polygalacturonic acid (PGA). Adsorption isotherms of the commercial and natural materials on the two clay systems were compared in unbuffered systems at pH 3 and pH 6. Adsorption of PGA occurred only at pH 3, and was higher on M-Pb than on M-Cd. In contrast, the adsorption of RM was higher on M-Cd than on M-Pb. Total amounts of RM adsorbed at pH 3 were about 3 times lower on M-Cd and 20 times lower on M-Pb than the respective amounts of PGA adsorbed at the same pH. Polygalacturonic acid had a high content of relatively well dissociated (pKa = 3.5) carboxylic groups, and adsorbed on the clay surface at pH values lower than its pKa. At pH 6, the dissociation of the acid groups favoured its solubility, and the metal cations were then probably displaced by ion exchange. The lower affinity of RM to the clay materials was related to its average molecular weight, which was lower than that of PGA, and to its water solubility, which was higher than that of PGA. The low pH dependence of the adsorption of RM was related to its lower carboxylic acidity and higher content in hydroxyl and amino groups.     

Minirhizotron quantification of soybean root growth as affected by reduced A horizon in soil

Shallow soil A horizon (topsoil) caused by soil erosion and soil movement from cultivation is known to reduce soil and crop productivity. The reduction may be related to limitation of root growth. A field study was conducted to investigate the effects of topsoil thickness on distributions of root density and growth. Soybeans [Glycine max (L.) Merr.] were grown on plots of Mexico silt loam (fine, montmorillonitic, mesic Mollic Endoaqualfs) with topsoil thicknesses of 0, 12.5, 25.0, and 37.5 cm above the Bt horizons. Root density was measured 60 and 90 days after planting using a minirhizotron video‐camera system. Root density was significantly reduced as topsoil thickness decreased from 37.5 to 0 cm. Mean density and net change of the density across profile between 30 and 60 days of growth had a linear function of topsoil thickness. The reduction and lower activity induced by shallow topsoil were attributed to detrimental properties in the Bt horizons. Root distribution pattern and rooting depth were not significantly affected by topsoil thickness. The roots appeared to be accumulated on the upper layers of the Bt horizons. Roots growing in thicker topsoil were more active than roots growing without topsoil. High soil moisture content during the growing season may mitigate the detrimental effects of shallow topsoil, inhibit root penetration, and enhance root activity.     

Root growth and phosphorus efficiency among sweet potato genotypes under low phosphorus

Abstract

A column experiment was conducted to investigate the responses of root growth and phosphorus (P) efficiency among sweet potatoes—JiHei1 (JH1), NingZi2 (NZ2), SuShu11 (S11) and SuShu17 (S17)—under low P and normal P conditions. Root growth was inhibited by low P in root length and surface area across diameter classes, except for in S17. The P absorption was influenced and led to variations in P content among organs. A high correlation was observed in root dry matter (DM) and P uptake. The tuber DM declined among genotypes under low P, and different P efficiencies were determined. A higher phosphorus utilization efficiency was observed in S11 and S17, suggesting that more P was needed to maintain their normal growth. Physiological efficiency and phosphorus utilization efficiency were significantly positively correlated with the tuber DM, indicating that low P limited the growth of sweet potatoes. These results benefit the production and breeding of sweet potatoes in response to P deficiency.     

Increased plant density with reduced nitrogen input can improve nitrogen use efficiency in winter wheat while maintaining grain yield

ABSTRACT

Plant density and nitrogen (N) input level have notable effects on root development, distribution in the soil profile, and in turn, N-uptake of winter wheat. Our study objectives were to identify whether a high yield can be maintained with a reduced N input by increasing plant density. Field studies were conducted during four successive seasons (2014–2015, 2015–2016, 2016–2017, and 2017–2018) using a widely planted cultivar, Tainong18. Two regimes of N fertilization (180 kg ha^?1 and 240 kg ha^?1) and three planting densities (135, 270, and 405 plants per m²) were used. Higher plant density led to increased root length density (RLD) and enhanced N uptake from the whole soil profile. The RLD in the soil profile at 0–1.2 m, 0–0.4 m, and 0.4–0.8 m decreased while in the 0.8–1.2 m layer it increased in response to reduced N input. The combined effects of higher plant density and lower N input resulted in reduced N uptake, a lower nitrogen nutrition index (NNI), unchanged grain yield, and improved N use efficiency. In conclusion, it is possible and sustainable to maintain a high wheat yield with reduced N input by increasing plant density.     

Response of potatoes to different nutrient solution management in a closed hydroponic system

Ion control of nutrient solutions to control nitrogen (N), phosphorus (P), and potassium (K) was developed for Superior (medium-to-early maturing) and Atlantic (mid-late) potato cultivars grown in closed hydroponic systems in which solutions were replenished and recirculated. Results were compared with conventional nutrient solution management strategies. In the “solution replacement” treatment, nutrient solutions were completely replaced each week. In the “electrical conductivity (EC) control” treatment, water use by potato plants was compensated by adding ground water to achieve the original volume (water replenishment) and the diluted EC of the solution was adjusted to the target levels using stock solution. In “ion control” treatment, ammonium dihydrogen phosphate (NH₄H₂PO₄) and potassium nitrate (KNO₃) were added to the EC-controlled nutrient solution. The amounts increased with plant age in both cultivars. The concentrations of nitrate (NO₃), P, and K in the ion control nutrient solution could be maintained at target levels. In water replenishment, recycling of nutrient solution resulted in a progressive decrease in EC and an increase in pH. Root activity increased by 93% and 59% in the Superior and Atlantic cultivars, respectively, compared with the nutrient solution replacement. These changes decreased photosynthesis, plant growth, water use, and thus tuber growth in the Superior cultivar. Decreased growth of shoots and tubers occurred without affecting photosynthesis in the Atlantic cultivar. Although there were no significant differences in root activity, photosynthesis, or plant growth between the ion control treatment and the EC control treatment, increased tuber growth was observed in the ion control treatment, possibly as a result of the constant supply of nutrients. High tuber growth and the capability to maintain solution nutrient concentration in the ion control treatment are highly desirable for closed hydroponic systems.     

Vesicular-arbuscular mycorrhizal status of various crops in different agricultural soils of northern Greece

Summary This paper reports the results of a survey of the occurrence of vesicular-arbuscular mycorrhizas and spores of the associated fungi in a variety of soils in Northern Greece. The roots of several crop species were examined for the presence of mycorrhizal structures and all samples showed evidence of infection, though to varying degrees. Cotton plants, in particular, had heavy arbuscular infection. Intact and presumably viable spores were relatively infrequent and empty non-viable spores were much more common. Soil characteristics at each sample site are reported also, but only broad generalizations are made at this stage with respect to correlations between mycorrhizal occurrence and edaphic factors.     

Improvement of rice (Oryza sativa L.) growth in upland conditions with deep tillage and mulch

The productivity of upland rice in Japan as well as in the world is low and unstable owing to scarce and unpredictable rainfall. The objective of this study was to examine whether agronomic methods could enhance grain yield of upland rice. Four field experiments were conducted from 2001 to 2003 in Nishitokyo, Japan, under upland conditions with different water supplies, in order to quantify the effects of deep tillage combined with deep placement of manure (50-cm depth), straw mulch (6 t ha⁻¹), or their combinations on the growth and grain yield of rice. Mulch kept surface soil moisture higher than without mulch even at reproductive stage, and it increased yield to the greatest extent under the most favourable conditions with much rainfall before heading (i.e., 2003). Deep tillage with deep placement of manure induced deep root proliferation and higher nitrogen uptake, increasing biomass production, and panicle number, and consequently grain yield was enhanced under the two lowest yielding environments with less rainfall before heading. Rice plants with deep tillage with deep manure application without mulch tended to have lower leaf water potential and higher diffusion resistance during drought, and negative effects on grain filling and harvest index in some experiments compared with the control. When deep tillage with deep placement of manure was combined with mulching in two experiments in 2002 and 2003, grain yield always enhanced compared with the control (P < 0.10, 6.0 t ha⁻¹ versus 5.4 t ha⁻¹ on average), suggesting their synergetic mechanisms for yield increase and stabilization. The results showed that deep tillage or mulching can improve grain yield of rice under drought-prone rainfed upland conditions in a temperate climate on an Andosol, and their combination had more consistent and greater positive effects.     

Agri-star松土促根剂对烤烟生长发育及经济性状的影响

采用大田对比试验,以中烟100为材料,研究了Agri-star松土促根剂对烤烟生长发育、主要病害及经济性状的影响。结果表明,与不施松土促根剂相比,施用Agri-star松土促根剂处理烟株的农艺性状均有提高,移栽后45 d,株高增加4.4 cm,茎围增加0.26 cm,叶片数增加0.8片,叶面积增加184.1 cm2,其中叶面积提高最明显;降低了烟草花叶病和气候斑点病的发病率,二者分别下降14.3、7.5个百分点,提高了烟株的抗病能力;增加了烟株根、茎、叶干物质质量和根系体积,促进了根系发育;使得烟叶的经济性状有了明显提高。     

砷污染下菌根接种对番茄生长和砷吸收的效应

为研究砷(As)污染条件下菌根真菌对番茄植株生长和砷吸收的效应,采用盆栽法,以全生育期的番茄植株为材料,对生长在不同砷浓度土壤中的番茄植株接种菌根真菌进行研究。结果表明:无论是接种还是不接种处理,基质砷添加水平增加植株总根长和比根长均呈现减少趋势;砷添加浓度从0 mg/kg增加到100mg/kg时,植株根冠比增加,但砷添加浓度为200 mg/kg时,对照植株根冠比在整个生育期明显增加,而在开花期和坐果期接种显著降低了植株根冠比;添加砷显著增加地上部分和根系砷含量,加砷后结果率显著降低,未接种植株结果量明显减少且质量下降,在200 mg/kg时,接种还是未接种植株均不结果实,但加砷条件下接种降低番茄果实中的含砷量和砷吸收量。