Root storage of nitrogen applied in autumn and its remobilization to new growth in spring of persimmon trees (Diospyros kaki cv. Fuyu)

This study was conducted to understand the effect of N supply in autumn on its uptake and distribution in tree parts and the utilization of reserve N the following year in persimmon trees (Diospyros kaki cv. Fuyu). The treated trees received 22.5-g N each for two successive years as a 3.5% urea solution from September 18 at 5-day intervals. Trees absorbed about 30% on average of the N applied in autumn. Sixty four to 83% of the N absorbed in autumn was in perennial parts, and 65–72% of that was in roots. Total N in perennial parts of the tree fertilized with N increased by over 4.28 g while leaf N changed little during senescence, indicating that the reserve N was constituted mostly by the N absorbed in autumn. Total N in the new growth was about the same as the amount of N declined in spring from perennial parts, indicating that there was little contribution by soil N to sustain new growth. Total dry weights of new growth the following year in a with-N tree were greater by over 34 g than those in a without-N tree.     

不同铵硝配比对辣椒产量、养分积累和氮肥利用率的影响

通过设施大棚辣椒盆栽试验,设置不施氮肥(CK)、铵态氮与硝态氮的氮质量比分别为0:100(A0N100)、25:75(A25N75)、50:50(A50N50)、100:0(A100N0)5个处理,研究不同铵硝态氮配比对辣椒产量、养分积累和氮肥利用率的影响.结果表明,与CK相比,不同铵硝配比处理增加了辣椒的果实数、鲜果...     

苹果分根交替灌溉不同水量对树体生长和水分利用效率的影响

以3 a生分根盆栽嘎拉苹果为试材,研究了不同根域交替灌溉不同水量对树体生长和水分利用效率的影响。结果表明,灌水量调控了苹果新梢二次生长的发生、生长时间和速率,每一根域每次灌水量为500 mL时,仅4/4根域灌水处理的新梢出现二次生长;灌水量为750 mL时,2/4、3/4和4/4根域灌水处理的新梢均出现二次生长;灌水量为1 000 mL时,1/4、2/4、3/4和4/4处理的新梢均有二次生长,其二次生长随着灌水根域的增多而时间提早,生长速率加快。每一根域灌水量相同时,植株主干、枝条、叶片、根系和总生物量随灌水根域增多而提高,750 mL与1 000mL根域灌水处理差异不显著。植株的水分利用效率随灌水根域的增多而降低。从确保树体正常生长和提高树体水分利用效率综合分析,2/4根域每次灌水750 mL为最佳灌溉方案。     

Effect of different drip irrigation methods and fertilization on growth,physiology and water use of young apple tree

A pot experiment was conducted to investigate the effect of three drip irrigation methods (i.e. conventional drip irrigation (CDI), both sides of the root-zone irrigated with full watering, alternate drip irrigation (ADI), both sides of the root-zone irrigated alternatively with half of the full watering, and fixed drip irrigation (FDI), only one side of the root-zone irrigated with half of the full watering) on growth, physiology, root hydraulic conductance and water use of young apple tree under different nitrogen (N) or phosphorus (P) fertilization (i.e. CK (no fertilization), N₁ (0.2 g N/kg), N₂ (0.4 g N/kg), P₁ (0.2 g P₂O₅/kg) and P₂ (0.4 g P₂O₅/kg)). Results show that compared to CDI, ADI and FDI reduced mean root dry mass, daily transpiration, root hydraulic conductance (K_r), leaf photosynthesis rate, transpiration rate and stomatal conductance of young apple tree by 6.9 and 27.7, 29.3 and 45.0, 6.8 and 37.9, 2.5 and 4.8, 32.6 and 33.0, 22.1 and 22.3%, but increased leaf water use efficiency (WUE) by 31.3 and 29.8%, respectively when they saved irrigation water by 50%. Compared to the CK, N or P fertilization significantly increased K_r, and K_r was increased with the increased N or P fertilization level. There were parabolic correlations between K_r and root dry mass, daily transpiration and stomatal conductance. Our results indicate that ADI reduced transpiration rate significantly, but it did not reduce photosynthesis rate and K_r significantly, thus alternate drip irrigation improved WUE and the regulation ability of water balance in plants.     

Effects of nitrogen deficiency on leaf photosynthesis,carbohydrate status and biomass production in two olive cultivars ‘Meski’ and ‘Koroneiki’

The effects of nitrogen deficiency on CO₂ assimilation, carbohydrate content and biomass were studied in two olive (Olea europaea L.) cultivars (‘Meski’ and ‘Koroneiki’). One-year-old plants were grown in pots and subjected to four nitrogen levels for 58 days.     

A comparative study of young ‘Thompson Seedless’ grapevines (Vitis vinifera L.) under drip and furrow irrigation. II. Growth, water use efficiency and nitrogen partitioning

The response of 3-year-old grapevines (Vitis vinifera L. cultivar ‘Thompson Seedless’) to furrow and drip irrigation was quantified in terms of water status, growth, and water use efficiency (WUE). Drip irrigation was applied daily according to best estimates of vineyard evapotranspiration while furrow irrigations were applied when 50% of the plant available soilwater content had been depleted. Drip and furrow irrigated vines showed similar water status (midday leaf water potential, Ψ₁) and shoot growth patterns throughout the season. Dry weight partitioning was not significantly different between treatments but root mass was somewhat larger for the furrow than drip irrigated vines. Nitrogen concentrations of the fruit and roots were significantly (P < 0.05) less for the drip irrigated vines when compared with the furrow treatment. Similar WUE (kg water kg⁻¹ fresh fruit wt.) were obtained for both treatments indicating that furrow irrigation was as efficient as drip irrigation under the conditions of this study. The data indicate that drip irrigation may increase the potential for control of vine growth by making vines more dependent on irrigation and N fertilization than furrow irrigation.     

Influence of no-tillage and organic mulching on tomato (Solanum Lycopersicum L.) production and nitrogen use in the mediterranean environment of central Italy

In conservation tillage systems based on legume mulches it is important to optimize N management strategies. The present study evaluated the effect of some winter legume cover crops converted into mulches on the following no-tillage tomato (Solanum Lycopersicum L.) yield, tomato nitrogen uptake, tomato use efficiency (NUE), soil nitrate and the apparent N remaining in the soil (ARNS) in a Mediterranean environment. Field experiments were carried out from 2002 to 2004 in a tomato crop transplanted into: four different types of mulches coming from winter cover crops [hairy vetch (Vicia villosa Roth.), subclover (Trifolium subterranem L.), snail medic (Medicago scutellata L. Miller), and Italian ryegrass (Lolium multiflorum Lam.)]; a conventional tilled soil (CT); and a no-tilled bare soil (NT). All treatments were fertilized with three different levels of nitrogen (N) fertilizer (0, 75, and 150 kg N ha⁻¹). Cover crop above-ground biomass at cover crop suppression ranged from 4.0 to 6.7 t ha⁻¹ of DM and accumulated from 54 to 189 kg N ha⁻¹, hairy vetch showed the highest values followed by subclover, snail medic and ryegrass. The marketable tomato yield was higher in no-tilled legume mulched soil compared to no-tilled ryegrass mulched soil, CT, and NT (on average 84.8 vs 68.7 t ha⁻¹ of FM, respectively) and it tended to rise with the increase of the N fertilization level. A similar trend was observed on tomato N uptake. Hairy vetch mulch released the highest amount of N during tomato cultivation followed by subclover, snail medic, and ryegrass (on average 141, 96, 90 and 33 kg N ha⁻¹). The tomato NUE tended to decrease with the increase of the N fertilization rates, it ranged from 39 to 60% in no-tilled legume mulched soil and from −59 to 30% in no-tilled ryegrass mulched soil when compared to the CT. The soil NO₃-N content and the ARNS was always higher in the soil mulched with legumes compared to the soil mulched with ryegrass and in NT and CT. This study shows that direct transplanting into mulches coming from winter legume cover crops could be useful for improving the yield and the N-uptake in a no-tillage tomato crop. Furthermore, considering the high N content in the upper soil layer and the remaining N content in the organic mulch residues after tomato harvesting, there is a large amount of N potentially available which could be immediately used by an autumn–winter cash crop.     

Leaf development,net assimilation and leaf nitrogen concentrations of five Prunus rootstocks in response to root temperature

Rootstocks differentially influence tree physiology and these differences may be due to varying responses to root zone temperature (RZT). To determine if this is the case, the physiology, leaf development and nitrogen relationships of five different Prunus rootstocks with chill requirements between 100 and 1100 h were examined during and after growth at RZTs of 5, 12 and 19 °C for 6 weeks. RZT correlated positively with leaf numbers, expansion rates and final leaf area, and significant differences existed among the rootstocks in the magnitude of these parameters at different RZTs. In particular, leaf expansion and area were less affected at low RZT in the low chill varieties. Net assimilation (A_n), leaf nitrogen (N%) and photosynthetic nitrogen use efficiency (A_n/N) also correlated positively with RZT: again, there were differences in the magnitude of these parameters among the rootstocks. No associations amongst A_n, N% or A_n/N could be found for the rootstocks; hence, they all differed in their physiological responses to RZT. Low RZT alone was sufficient to reduce A_n and decreased both leaf area and photosynthetic activity. Leaf expansion was related to N%, as the varieties with the lowest N% also had the lowest expansion rates. Infrared thermography of the cv. Golden Queen showed a negative correlation between RZT and leaf temperature with leaves of plants at the lowest RZT being 2 °C warmer than ambient whilst those at the highest RZT were 2 °C cooler than ambient. These differences were due to transpiration, as transpiration for the variety used decreased with reducing RZT. Transpiration from the other rootstock varieties was lowest at the 5 °C RZT but, depending on variety, at 12 °C was either higher, lower or the same as that from plants whose roots were at 19 °C. Together, the results of this study explain some of the rootstock-induced changes in tree growth and suggest the need to incorporate seasonal changes in RZT into development models for peaches.     

Effect of different fertilisation and irrigation practices on yield,nitrogen uptake and fertiliser use efficiency of white cabbage (Brassica oleracea var. capitata L.)

The effect of different fertilisation (i.e. broadcast application and fertigation) and irrigation practices (tank sprinkler and drip irrigation) on yield, yield quality (nitrate content), nitrogen uptake of white cabbage (Brassica oleracea var. capitata L.) and the potential for N losses was assessed on sandy-loam agricultural soil. ¹⁵N-labelled fertiliser was used as a tracer. It was found that different practices significantly affected yield, nitrate content in plants, N uptake, as well as fertiliser use efficiency. The highest yield (93 t ha⁻¹), plant N uptake (246 kg ha⁻¹), and fertiliser use efficiency (42%) were obtained under treatment with broadcast fertilisation with farmer's practice of irrigation (tank sprinkler). The N surplus after harvest was −41 kg N ha⁻¹, indicating the lowest potential for N losses. Treatment by fertigation and drip irrigation covering 100% of the crop's water requirements did not result in the highest yield as expected (72 t ha⁻¹), the N surplus after harvest was about +38 kg ha⁻¹. The lowest yield (58 t ha⁻¹), fertiliser use efficiency (30%) and hence the highest potential for N losses (N surplus after harvest +68 kg ha⁻¹) were found in treatment with broadcast fertilisation and drip irrigation covering 50% of the crop's water requirements.     

Nitrogen distribution,remobilization and re-cycling in young orchard of non-bearing ‘Rocha’ pear trees

In newly planted orchards, special attention must be paid to fertilization to build up the permanent structure of the trees so that high yield and fruit quality can be reached later on. Nitrogen (N) plays a major role in the fertilization plan, although few studies have assessed its use efficiency in young non-bearing trees, especially in field conditions. In this work, 1–3 years old ‘Rocha’ pear trees, grafted on quince BA29, were planted in a Mediterranean region, and fertigated with 6 g N tree⁻¹ year⁻¹ as ammonium nitrate with 5 at.% ¹⁵N enrichment to study the fertilizer N uptake during the vegetative cycle, the overall fertilizer N use efficiency at the end of each year, and the plant–soil N balance for this period. Nitrogen remobilization and the re-cycling of N from senescent leaves were also studied by fertilizing some pear trees with 10 at.% ¹⁵N enrichment.