A Lethal Virus Disease of Lloyd George Raspberry in Scotland

Trials lasting nine years have been conducted on two types of magnesium- deficient apple rootstocks to assess the curative value of foliar sprays and/or soil applications of Epsom salt (MgS0₄.7H₂0).

After the first year, M.IV rootstocks sprayed with 2% Epsom salt solution produced more, larger, and better-rooted shoots than did the untreated plants, giving more than a 60% increase in numbers of high-quality rooted shoots, and three sprayings were as effective as nine. The implications of this finding are discussed.

In contrast to M.IV, spraying MM.102 rootstocks did not lead to a sustained improvement in quality of rooted shoots even though symptoms of magnesium deficiency were eliminated and the number of shoots increased. Elimination of foliar symptoms is therefore, of itself, no indication of economic improvements of growth. It is concluded that some other factor, perhaps potassium deficiency, limited growth.

Foliar sprays applied nine times annually to M.IV rootstocks raised the percentage of magnesium in the leaves in successive years and eliminated symptoms typical of magnesium deficiency. With only three sprays annually, the magnesium concentration in leaves was also increased, but to a less extent and not until after the second year ; the symptoms were reduced in severity but not eliminated. The percentage of potassium in the leaves fell as the percentage of magnesium rose.

Soil applications at the rate of 46 cwt. per acre spread over eight years markedly increased " available ” magnesium in the top 3 ft. of soil, but produced only small increases in the percentage of magnesium in the leaves. Symptoms were only slightly reduced and there was little increase in growth. Thus, under the conditions of this experiment, soil treatment with Epsom salt was ineffective in curing magnesium deficiency.     

福建柑桔园营养施肥状况及其施肥改进建议

以福建省永春等10县（市）70片（≥3．5hm2）柑桔示范园为代表,通过土壤、叶片分析及施肥状况的综合诊断得出的结果表明：84％的示范园土壤显著酸化（pH＜5．5）,主要是施用N、P、K化肥造成的;营养失调也普遍存在于示范围中,其中主要元素缺Ca、P吸收障碍及微量元素B、Cu的过量尤为普遍;施肥中有机肥不足,P、N肥滥用,Ca、Mg、K肥欠缺;叶片K、Mg并不简单受其土壤有效成分的影响,叶片K与土壤"全N／有效K"、"水解N／有效K",叶片Mg与土壤"代换Mg／代换Ca"呈极显著相关（P＜0．01,r=-0．36、-0．39、0．49）。据此,对以红壤为主要土壤类型的福建柑桔产区的施肥提出了改进建议。     

The Relation Between the Rate of Respiration of an Apple Fruit and its Content of Protein: I. The Value of this Relation Immediately After Picking

Tomato plants of two varieties (Potentate and Immuna) were grown for four seasons with different combinations of magnesium and potassium sulphate in heated glasshouses. Magnesium sulphate was applied either to the soil or as a foliar spray, with untreated plots as controls ; these treatments were combined factorially with two levels of soil potassium. The effects of the treatments on the magnesium and potassium contents of the soil, as extracted by 0 5N-acetic acid, are recorded.

Chlorosis of the leaves was widespread where magnesium was not applied. Foliar spraying effectively controlled the deficiency symptoms; treatment of the soil with magnesium sulphate was only partially successful in the first season but increasingly satisfactory thereafter.

In only one of the four seasons was there a significant increase in yield J due to the correction of magnesium deficiency. In that year (1959) the yields at the higher level of potassium were increased by 15%and 12%by the soil and spray treatments respectively (P=0·001).

The magnesium treatments slightly improved fruit quality as assessed by visual grading, mainly at the very low level of potassium in the last two seasons. The dominant factor affecting fruit quality was potassium, however, which markedly increased the proportion of uniformly coloured fruit and reduced the incidence of ripening disorders.

It is suggested that magnesium deficiency should be controlled by supplying this nutrient rather than by reducing the application of potassium salts below the quantity necessary for high fruit quality.

Variety Immuna gave higher yields and better quality fruit than Potentate throughout the trial.     

The Effect of A Vesicular-Arbuscular Mycorrhiza on The Uptake of Soil Phosphorus by Strawberry (Fragaria Sp. Yar. Cambridge Favourite)

Mycorrhizal and non-mycorrhizal strawberry plants, var. Cambridge Favourite, were grown in a soil low in available phosphorus as well as in the same soil dressed with KH₂PO₄. The soil was autoclaved and mycorrhizal plants were produced by inoculating young runner plants with sporo- carps of an Endogone sp. capable of producing vesicular-arbuscular mycorrhiza in strawberry. Leachings of sporocarps were also added to the non-inoculated plants.

In the P-deficient soil, the mycorrhizal plants absorbed significantly more P and gave significantly higher dry matter production than the nonmycorrhizal plants. The latter showed acute phosphorus deficiency symptoms. There were no differences in the P uptake and the growth of mycorrhizal and non-mycorrhizal plants in the phosphate-enriched soil.     

Production gradients in smallholder banana (cv. Giant Cavendish) farms in Central Kenya

Banana is an increasingly demanded food and cash crop in sub-Saharan Africa. Reported yields in smallholder farms vary substantially. The importance and spread of yield constraints have not been properly quantified. A study was carried out in Central Kenya to (i) quantify the yield levels, the primary yield constraints, and the spatial production gradients in such systems (ii) explore how soil fertility gradients relate to gradients in soil fertility management, and whether this is a function of farmer resource availability. Data was collected on crop management aspects, pests and diseases, and soil and plant tissue samples analyzed for nutrient contents. Bunch yields were higher near homesteads (29.8 t ha⁻¹ yr⁻¹) than at mid-distance (26.8 t ha⁻¹ yr⁻¹), or far away 20.2 t ha⁻¹ yr⁻¹. Yields were much higher than previously reported (11–14 t ha⁻¹ yr⁻¹) in Kenya. Both soil and tissue K levels were higher near and mid-distance, than far from the homestead. Gradients of soil pH, total N, available P and Organic carbon were found, being higher near the homestead, while Mg and Ca were lowest near the homesteads. K was the most deficient nutrient, with tissue K index (I_K) decreasing when moving away from the homesteads. P and Ca deficiencies were also observed. Resource-poor farmers’ soils were higher in exchangeable K and Mg, pH, and total N, and supported higher mat densities compared to resource-endowed farmers’ farms. Soil quality problems were the biggest yield loss factors and not pests and diseases.     

The Response to Epsom Salt Sprays of Mature Apple Trees of Three Varieties on Two Contrasting Rootstocks

Mature trees of Beauty of Bath, Tydeman’s Late Orange and Laxton’s Superb on M.VII rootstock, growing under commercial-type conditions, were severely deficient in magnesium as shown by leaf analysis and typical symptoms. Five sprays yearly of 2% Epsom salt (MgSO₄.7H₂ O) raised the concentration of magnesium in the leaves and largely eliminated symptoms: the concentrations of calcium and, to a lesser extent, of potassium in leaves were reduced. Over six years, there was little effect of Epsom salt on growth as measured, but crop weight was increased by 19–39% according to variety: this was largely, but not entirely, due to increase in fruit set. The proportion of fruit that dropped was decreased for Beauty of Bath and for Tydeman’s Late Orange sprayed with Epsom salt and the weight per 100 fruits of the late varieties Tydeman’s Late Orange and Laxton’s Superb was increased. Untreated trees on M.II rootstock, in contrast to those on M.VII, showed almost no foliar symptoms of magnesium deficiency, made more growth and produced larger crops; the concentrations of magnesium and calcium in the leaves were higher whereas potassium was usually lower. Epsom salt sprays did not increase growth or cropping; indeed, there was a tendency for sprays to reduce the crop weight of Beauty of Bath on M.II, indicating that they should not be used indiscriminately.

Epsom salt foliar sprays increased the “available” magnesium in the soil to a level considered to be medium—high; this effect was mainly shown in the top 6 in. of soil and gradually diminished to the 18–24 in. zone. Nevertheless, in the year following the termination of treatments, the proportion of foliage affected in Laxton’s Superb on M.VII, previously sprayed with Epsom salt, was almost as great as that of untreated trees and the concentration of magnesium in the leaves was as low. It appeared that magnesium in the soil did not reach the leaves.

The increase in “available” magnesium due to sprays was greater in soil carrying trees on M.II than M.VII, a result probably due to the extra quantity of spray required for these larger trees.     

The Effects of Nitrogen,Phosphorus, Potassium,Magnesium and Lime in Factorial Combination on the Yields of Glasshouse Tomatoes

Tomato yields and soil analyses from a 3² × 2³ factorial nutritional trial are summarized for six seasons of cropping in heated glasshouse borders. The varieties were Potentate for four seasons, and J168 and Moneymaker (split plot) in the last two seasons. The soil was steamed before planting except in the first and third years.

Deficiencies of nitrogen and phosphorus decreased the yields in five out of six seasons, as also did potassium deficiency in four seasons. Significant positive interactions were found between these three nutrients. The highest level of nitrogen (680–830 lb. N per acre) was favourable when both phosphorus and potassium were at adequate levels in unlimed soil. No yield response was found to potassium in excess of the intermediate level (870 lb. K₂O per acre). The main effect of magnesium was not significant, but a positive phosphorus-magnesium interaction was found for variety Moneymaker.

Lime (carbonate) decreased the yield significantly each season. A significant interaction was found between lime and nitrogen level, the adverse effect of lime occurring at the high and intermediate levels of nitrogen. This effect of lime, and the lime-nitrogen interaction, may be due to induced boron deficiency.     

Putting back what we take out,but how much?: Phosphorus and nitrogen additions to farmed Leucadendron ‘Safari Sunset’ and Leucospermum ‘Succession’ (Proteaceae)

Proteaceae are adapted to low-nutrient soils in the various regions where they occur. However, harvesting of flowering stems for the cut-flower industry must eventually cause soil nutrient depletion sufficient to reduce yields. Different N forms, and N and P concentrations were supplied to two Proteaceae cultivars (Leucadendron ‘Safari Sunset’ and Leucospermum ‘Succession’) in a controlled fertigation experiment, and appropriate concentrations for maximum growth with minimum nutrient accumulation or loss were determined. Small additions of N (0.025–0.1 mM) significantly improved growth of both cultivars growing on Strandveld sandy soil. Larger additions of N (up to 2 mM N) resulted in poor growth (both cultivars) and N accumulation in the soil (Safari Sunset). Small additions of P (<10 μM) significantly improved growth of both cultivars and resulted in no accumulation or loss of P in the soil. Larger additions of P (up to 500 μM) resulted in poor growth, P toxicity symptoms and P leaching from the upper soil layers. Best N forms in descending order of both plant visual appearance and vegetative yield were: urea ≥ ammonium nitrate > ammonium sulphate > calcium nitrate. Phosphorus toxicity symptoms were associated with increased concentrations of leaf P, Ca and Fe. Under conditions of maximum growth (10 μM P and 0.1 mM N) Safari Sunset removed 18 ± 0.6 g N, 1.5 ± 0.1 g P, 5.3 ± 0.6 g K and Succession removed 5.5 ± 0.2 g N, 0.3 ± 0.02 g P, 3.1 ± 0.5 g K over 6 months. At maximum growth, plants acquired more N and P amounts than were supplied, but supplying higher N and P concentrations adversely affected growth. Thus, a more complex or slow-release form of N and P than urea and soluble phosphate, respectively, may provide enough N and P to replace losses from the farm soil at the low concentrations required for proteas.     

黄土丘陵区仁用杏园不宜间作沙打

 〗在陕北黄土丘陵沟壑区对清耕和间作沙打旺(Astragalus adsurgens)6年、4年、2年仁用杏园0~500 cm土层土壤水分、有机质、全氮、全磷、速效氮、速效磷、速效钾含量及树体生长状况进行了测定，结果表明，间作沙打旺，除了在秋季提高了0~100 cm土层土壤水分以外，在春季、夏季和秋季均显著降低了0~500 cm土层土壤水分，且间作沙打旺年限越长，降低越显著。间作沙打旺提高了0~100 cm土层土壤有机质和全氮含量，间作年限越长效果越显著，但对100 cm土层以下的土壤有机质和全氮无显著影响。间作沙打旺对土壤全磷含量无显著影响。间作沙打旺显著降低了土壤速效养分含量，其中速效氮降低深度达500 cm土层，速效磷、速效钾达300 cm土层，且间作年限越长，降低越显著。间作沙打旺显著削弱了树体的长势，降低了坐果率和杏仁产量。间作沙打旺存在着与仁用杏争水争肥的矛盾，黄土丘陵沟壑区仁用杏园不宜间作沙打旺。     

Relationship between tipburn and leaf mineral composition in strawberry

Malformation of emerging leaves with distortion of leaf tips, a condition known as tipburn, is frequently observed in strawberry. Calcium (Ca) deficiency has been considered the main cause of tipburn. The aim of the present study was to analyse the relationship between leaf mineral composition and the incidence of tipburn in three short-day strawberry (Fragaria x ananassa Duch.) cultivars (‘Ventana’, ‘Camarosa’ and ‘Candonga’) submitted to different concentrations of Ca. The studies were conducted in a hydroponic system in a greenhouse. Calcium was added as Ca(NO₃)₂ at 2 mM, 3 mM, 4 mM and 5 mM. A completely randomized block design (4 Ca concentrations × 3 cultivars) with three replications was used. Each replicate consisted of 12 plants grown in a polyethylene bag (100 cm × 18 cm × 3 cm) filled with coconut peat. Crown diameter and tipburn incidence were evaluated throughout the experimental period, and at the end of the experiment leaf mineral composition was assessed. In general, plants with larger crown diameters had a greater incidence of tipburn. The ‘Candonga’ cultivar had the smallest incidence of tipburn, while the ‘Camarosa’ and ‘Ventana’ cultivars were more susceptible. There was no correlation between level of Ca applied and incidence of tipburn. The incidence of tipburn was associated with foliar K:Ca and K:Mg ratios. Ratios above 3.40 for K:Mg and 1.77 for K:Ca represented a risk of more than 50% of tipburn incidence, when overall means for all cultivars and levels of Ca were used.     

The Response of Magnesium-Deficient Edward VII Apple Trees to Variations in the Timing and Composition of Foliar Sprays

Magnesium-deficient Edward VII apple trees were used to study the effect of pre-blossom sprays of magnesium sulphate and urea, and to compare the efficiency of post-blossom sprays of magnesium sulphate and chloride.

Two pre-blossom sprays of 2% Epsom salt (MgSO_4·7H,O) prevented the development of early-season magnesium deficiency symptoms but did not increase fruit set. Similar sprays of 0· 5%urea had no effect on symptoms but increased the set of fruit.

Five post-blossom sprays of 2% Epsom salt largely eliminated both early and late symptoms and produced consistent increases in the magnesium content of the leaves (% dry wt.). There was also a large increase in crop, due mainly to a greater fruit set which could be detected after the second spray application. Growth responses also were associated with this treatment.

Five post-blossom sprays of 0·83% magnesium chloride, i.e. containing only half the amount of magnesium, produced similar responses, except that growth was not affected. Reducing the number of magnesium chloride sprays to three, but applying them over the same time interval, resulted in similar' crop responses even though less magnesium was taken up and symptoms were slightly less effectively controlled.     

The Magnesium Content and Potassium Magnesium Ratio of Tomato Leaves in Relation to Degree of Chlorosis

The magnesium and potassium contents of the leaves of two tomato varieties have been studied for three seasons in a replicated nutritional trial in heated glasshouses. Magnesium sulphate was applied either to the soil or as a foliar spray, with untreated plots as controls, in combination with high and low levels of soil potassium.

The samples analysed consisted of upper (5th from the top) leaves in the first season, 5th and 15th leaves in the second, and lower (15th) leaves in the third; the lower leaves proved more responsive to added magnesium.

The treatments supplying magnesium increased the magnesium content of the foliage slightly in the first season and highly significantly in the subsequent years. Potassium had no effect on the magnesium content in the first season, but tended to depress it subsequently.

The degree of chlorosis, assessed visually, was closely related to the magnesium content of the lower leaves of both varieties. The relationship was approximately linear for values up to about 0· 4% Mg, above which little chlorosis was ever found; the correlation coefficient for values up to 0·5% Mg in the leaves was –0·94 (P=0·001). Severe chlorosis occurred below 0·25%–0·30% Mg.

The K{Mg ratios in the leaves were also significantly correlated (P=0· 001) with degree of chlorosis (r=+0·87 for values up to 0·5% Mg and +0·91 overall). Calculation of the multiple regression of chlorosis on % Mg and % K showed, however, that the regression coefficient of chlorosis on potassium content was not significant. The magnesium content of the lower leaves is thus regarded as a more satisfactory criterion of magnesium status than their K{Mg ratios.     

葡萄锰中毒症及其相关营养元素分析

以玉溪市葡萄生产上出现的锰中毒症株及正常株为研究对象,采用田间调查与室内检测分析、锰中毒株与正常株比较相结合的方法,研究了葡萄锰中毒株及正常株叶片的N、P、K、Ca、Mg、Mn、Fe等指标,以及根际土壤的pH、有效态Mn、Fe、Ca、Mg等指标,以期为玉溪市葡萄生产上锰中毒症的防控提供技术依据。结果表明:与正常株比较,葡萄发生锰中毒株的叶片锰含量平均高达1 501.3 mg·kg^-1,比正常株的552.6 mg·kg^-1提高了1.7倍之多;P、K含量也极显著提高1倍多,而Ca、Mg含量则极显著降低近40%;锰毒株的Ca/Mn、Mg/Mn很低,分别为17.7、2.1,均显著低于正常株的98.3、10.5。葡萄发生锰中毒株的根际土壤的pH为4.29~4.35(为强酸性),有效Mn含量高达159.8~178.2 mg·kg^-1;土壤的Ca/Mn、Mg/Mn也很低,分别为7.1、0.6,均显著低于正常株的180.2、13.3。在玉溪市葡萄生产上发生的以"叶片主脉、支脉及叶脉附近的叶肉组织呈褐色状"为典型症状的锰毒株,其叶片锰吸收量过高,分析其原因是由于根际土壤pH较低为强酸性,土壤有效Mn含量过高,有效态Ca、Mg含量过低,Ca/Mn、Mg/Mn也很低所致。为葡萄生产上选择适宜土壤及其pH调节、合理平衡施肥提供参考依据。     

The Effects of Tillage,Non-Tillage and Nitrogen on Yield and Fruit Composition of Citrus

Over the period 1947 to 1965 studies were made of the effects of four cultural treatments and four levels of ammonium sulphate on crop growth and fruit composition of Washington Navel and Late Valencia oranges, budded on to either Rough Lemon or Sweet Orange rootstocks. In terms of yield and quality, the best treatment combination was weed control by kerosene oil sprays together with 4 lb. of ammonium sulphate per tree per annum. For this treatment combination the average annual yield over the five-year period 1961–65 approached 500 lb. per tree.

Almost all the nitrogen requirements of mature citrus trees were obtained from clover grown during March to September and then rotavated into the soil. Repeated ammonium sulphate applications caused soil acidity, aggravating an inherent soil phosphorus deficiency. Basal superphosphate applications, made since 1955 at an average annual rate of 4 lb. per tree, gradually improved fruit quality.

From 1955 to 1965 small annual calcium carbonate applications of up to 30 lb. per tree were made to half the trial area. Although these applications only partially neutralized soil acidity there was a consistent tendency since 1961 for yield and fruit quality to be higher on limed plots. As there was no evidence of calcium deficiency, it is considered that liming treatments stimulated crop growth mainly by raising soil pH and increasing soil phosphorus availability.

Soil analytical results showed that considerable differences existed between the fertility status of inter-tree and under-branch-spread areas: base exchange capacities and soil pH were considerably higher under the leaf canopy than in inter-tree areas.

A study of fruit quality indices, summarized for four periods each of four years duration, suggests that the juice content of an orange is a more sensitive index of fruit quality than skin thickness or sugar and acid contents.     

渭北高原苹果根区土壤养分变化及对果树再植植株生长的影响

对渭北高原地区苹果园距树干横向水平0～200 cm、纵向垂直0～80 cm土层深度范围内的果树根区空间土壤养分的盈亏变化进行了研究,并结合盆栽试验,分析了不同根区土壤对苹果再植植株的影响。结果表明: 在水平方向上,随距树干距离的增加,土壤养分含量呈增高趋势;垂直方向上,除水溶性Ca、Mg外,其他养分随土层加深呈下降趋势。果园根区土壤速效P、水溶性Ca、水溶性Mg、有效Zn、有效Mn有亏缺现象,N/P、K/P、Ca/P、Ca/Mg、Ca/Mn、Ca/Zn存在养分比例失调。果园土壤的盆栽幼树株高、新梢长度、粗度、叶面积和根活力较生茬土壤的分别减少44.93%、34.46%、23.88%、49.48%和11.40%,表现明显的重茬障碍症状,土层愈深的土壤,症状愈重,距树干愈远的土壤,症状愈轻。果园土壤中Zn元素亏缺和Ca/Zn比例失调可能是造成渭北高原苹果再植病害发生的重要原因之一。距树干横向水平100～200 cm、纵向垂直0～40 cm土层土壤养分含量较高,盆栽幼树再植病害较轻,是老果园更新再植应选择的栽植区域。     

Fertilization regulates soil enzymatic activity and fertility dynamics in a cucumber field

Different fertilizers may affect soil enzymatic activity and soil fertility dynamics. These effects were investigated in a field experiment with cucumber (Cucumis sativus L.) and the relationship with yield and soil nutrient availability was assessed. Soil enzymatic activity, measured as phosphatase, catalase, invertase and urease activities, decreased in the early growth stages of cucumber, but increased in the late ones, when plant were supplied with partially decomposed horse manure. Chemical N fertilizer inhibited soil enzymatic activity but P and K fertilizers enhanced it. Activity of different soil enzymes was positively correlated with soil NH₄⁺–N and available P concentration, but negatively correlated with leaf N and P concentration. Cucumber yield was also positively correlated with the soil enzymatic activity. Our results demonstrate that soil enzymatic activity acted as a useful indicator of soil fertility dynamics.     

Comparison of three pea cultivars (Pisum sativum) regarding their responses to direct and bicarbonate-induced iron deficiency

The aim of this work was to explore leaf characteristics underlining the difference in the sensitivity of pea cultivars (cv. Kelvedon, Douce and Lincoln) to Fe deficiency. Plants were grown in a greenhouse under controlled conditions in continuously aerated solution. Three treatments were used: 30 μM Fe (+Fe), 0 μM Fe (−Fe); direct deficiency and 30 μM Fe + 10 mM NaHCO₃ (+Fe+Bic); indirect deficiency for 12 days. Growth parameters, iron status, potassium content, chlorophyll fluorescence and photosynthetic capacity were studied. Our results showed that Fe deficiency led to a significant decrease of chlorophyll index (SPAD readings) and bivalent iron content in all Pisum sativum cultivars. The lower reduction was observed in Fe-deficient plants of Kelvedon and Douce. In addition, shoot length and whole plant dry weight were not affected by Fe deficiency in the latter cultivars. Both tolerant cultivars showed higher accumulation of potassium content in their leaves compared with the sensitive one. Moreover, both chlorophyll fluorescence ratios (F_v/F_m and F_v/F₀) were significantly decreased in all cultivars under both Fe deficiency treatments. The photosynthetic electron transport activity was reduced in the sensitive cultivar, especially in the absence of iron. The adverse effect of bicarbonate-induced Fe deficiency on the above mentioned parameters were more pronounced than that of the direct one. The capacity of both tolerant cultivars to preserve adequate chlorophyll synthesis, photosynthetic capacity and plant growth under iron-limiting conditions is related to the suitable nutrition of their leaves in ferrous iron, due to (at least partially) their higher potassium content.     

Phosphorus toxicity in the Proteaceae: A problem in post-agricultural lands

South African Proteaceae are adapted to the low soil phosphorus (P) concentrations of the Cape Floristic Region. The efficient P uptake by Proteaceae means that these plants experience phosphorus (P) toxicity at lower rhizosphere [P] than crop plants. This is only problematic when cultivating Proteaceae (and many plants from this region) on previously agricultural land with high residual soil [P]. In this study we hypothesize that P toxicity will result in element imbalances in leaves of Proteaceae and information from this study aims to facilitate ameliorative treatments. Phosphorus toxicity was induced on-farm in Leucadendron ‘Safari Sunset’ (Proteaceae) with subsequent mapping of element distribution in non-necrotic leaf tissue using micro particle-induced X-ray emission spectrometry. Phosphate supply up to 0.01 mM in a fertigation solution resulted in increased stem length of Leucadendron ‘Safari Sunset’ while P concentrations in excess of this resulted in decreased stem length, increased leaf [P] up to 0.25% (w/w) and, between 1 mM and 5 mM P supply, typical P toxicity symptoms were observed. High P supply (5 mM P) resulted in increased leaf [P] in most leaf tissues including the epidermis, where calculations from an equilibrium speciation model indicated that there was 30% more dissolved PO₄³⁻ in the epidermis compared to leaves at low P supply (0 mM added P on soil with 34 mg P kg⁻¹). Concomitantly, bundle sheath and epidermal [Ca] were reduced and 10% more Ca was predicted to be adsorbed and precipitated as hydrapatite at high P supply. High P supply resulted in increased leaf [Cl] and [Mn] in all tissues studied; decreased total leaf [Fe], bundle sheath, xylem, phloem and epidermal [Fe] and decreased total leaf [Zn] and xylem and phloem [Zn]. The observed symptoms of P toxicity in Leucadendron ‘Safari Sunset’ (necrosis in some plants, chlorosis and leaf rosetting) co-occurred with (1) excess PO₄³⁻, which may bind Ca in the epidermis (leading eventually to necrosis); (2) reduced [Fe] and increased [Mn] (leading to chlorosis) and (3) reduced total and vascular [Zn] (leading to leaf rosetting).     

增施氮肥和地面管理对酸樱桃园土壤营养状况的影响

在一个连续进行了 ８年Ｎ肥定位试验的酸樱桃园,调查了每年施用 Ｎ６０ ｋｇ· ｈｍ~(－２)和行间生草制对土壤营养状况的影响。结果表明：在肥沃土壤里ＮＨ_４~＋是速效Ｎ的主要存在形式,而ＮＯ_３~－的含量很低。生草地土壤中含有较多的 ＮＨ_４~－,而清耕带土壤中含有较多的 ＮＯ_３~－。施肥增加土壤速效 Ｎ的含量。土壤 ＮＯ_３~－的季节性变化表明 ５至 ６月份土壤中 ＮＯ_３~－的含量高,而花前和 ７月份土壤中 ＮＯ_３~－含量低。 Ｐ、Ｋ在清耕带 １０ ｃｍ以下土壤的含量低于生草地土壤,但在 ０～ １０ｃｍ土层中Ｋ的含量高于生草地。Ｐ的含量不受影响。施Ｎ减少了土壤Ｐ、Ｋ的含量。土壤中Ｍｇ的含量分布均匀,不受施Ｎ和地面管理制度的影响。     

Nursery inoculation of tomato with arbuscular mycorrhizal fungi and subsequent performance under irrigation with saline water

Protected horticultural crops as well as those planted in open fields particularly in the Mediterranean region have to cope with increasing salinization of irrigation water. High salinity of the supply water has detrimental effects on soil fertility and plant nutrition and reduces crop growth and yield. This study was conducted to determine if pre-inoculation of transplants with arbuscular mycorrhizal (AM) fungi alleviates salt effects on growth and yield of tomato (Lycopersicon esculentum Mill. Cv. Marriha) when irrigated with saline water. Tomato seeds were sown in polystyrene trays with 20 cm³ cells and treated with AM fungi (AM) or without (nonAM) Glomus mosseae. Once the seedlings were reached appropriate size, they were transplanted into nonsterile soil in concrete blocks (1.6 m × 3 m × 0.75 m) under greenhouse conditions. The soil electrical conductivity (EC_e) was 1.4 dS m⁻¹. Plants were irrigated with nonsaline water (EC_w = 0.5 dS m⁻¹) or saline water (EC_w = 2.4 dS m⁻¹) until harvest. These treatments resulted with soil EC at harvest 1.7 and 4.4 dS m⁻¹ for nonsaline and saline water treatments, respectively. Root colonization with AM fungi at flowering was lower under saline than nonsaline conditions. Pre-inoculated tomato plants with AM fungi irrigated with both saline and nonsaline water had greater shoot and root dry matter (DM) yield and fruit fresh yield than nonAM plants. The enhancement in fruit fresh yield due to AM fungi inoculation was 29% under nonsaline and 60% under saline water conditions. Shoot contents of P, K, Zn, Cu, and Fe were higher in AM compared with nonAM plants grown under nonsaline and saline water conditions. Shoot Na concentrations were lower in AM than nonAM plants grown under saline water conditions. Results indicate that pre-inoculation of tomato transplants with AM fungi improved yield and can help alleviate deleterious effects of salt stress on crop yield.