Differential effect of transpiration and Ca supply on growth and Ca concentration of tomato plants

To determine the extent to which transpiration and Ca concentration in the nutrient solution affect the regulation of growth, two independent experiments with young tomato plants were carried out under fully controlled climate conditions and grown hydroponically. The first experiment consisted of the regulation of transpiration by three levels of relative air humidity (RH): 50%, 70% (control) and 95% (corresponding to 1.32, 0.79 and 0.13 kPa, respectively) during 7 days. The second experiment involved four periods of 1, 3, 7 or 14 days of low-calcium (0.5 meq L⁻¹) compared with the nutrient standard solution (9 meq L⁻¹). The results show that plant growth was affected more by RH than by the reduction of Ca in the nutrient solution. High humidity reduced the total plant dry matter and total leaf area, increasing the dry matter partitioning into the stems and reducing it into the leaves. However, the low-Ca supply did not affect those parameters. Plant Ca concentration was significantly reduced by low-Ca supply as well as by high RH, but to a much greater extent by the Ca supply than by high RH. Ca concentrations in leaves, stem, and roots were quickly reduced already after 1 day of low-Ca. After 14 days, Ca concentration in all plant organs (leaves, stems and roots) was reduced by approximately 70% compared to control plants. Our data show that calcium supply, and consequently Ca concentration in the tomato plant can be reduced drastically for short-term periods during the vegetative growth stage without any adverse effect on growth whilst higher humidity reduce both growth and Ca concentration in young vegetative tomato plants. Consequently, reduced Ca uptake at high air humidity is not the cause for the reduction in growth.     

Changes in nutrient concentrations and leaf gas exchange parameters in banana plantlets under gradual soil moisture depletion

Changes in mineral nutrient concentration, growth, water status and gas exchange parameters were investigated in young banana plants (Musa acuminata cv. ‘Grand Nain’) subjected to gradual soil moisture diminution. Experiments were performed in glasshouse under controlled temperature, and water stress was imposed by ceasing irrigation for 62 days. The data showed a parallel decrease of leaf gas exchange parameters and soil moisture initiated few days after the imposition of water stress. However, the leaf relative water content (RWC) showed a minor decrease in response to drought. The onset of growth reduction evaluated as plant height, pseudostem circumference, number of newly emerged leaves, leaf area, and leaf and root biomass took place approximately between 34 and 40 days after the beginning of the stress period. In addition, drought did not modify nitrogen and phosphorus concentrations in foliar and root tissues; however, it increased potassium, calcium, magnesium, sodium and chloride in leaves, and only calcium, sodium and chloride in roots. Collectively, the data reveal that banana plants show a drought avoidance mechanism in response to water stress. After a prolonged drought period, leaf RWC was hardly reduced, while gas exchange and growth parameters were reduced drastically. Increasing leaf mineral concentration could have help to maintain leaf RWC due to osmotic adjustment mechanism.     

The Effect of Iron Supply on Strawberry,Var. Royal Sovereign

Royal Sovereign strawberries, grown in sand culture with pure inorganic nutrients and controlled levels of iron supply, have shown that restriction of the iron supply can cause marked reduction in growth and crop yield before the onset of characteristic symptoms of iron deficiency. At the levels where visual symptoms first occur, fruit yield was reduced some 40% below that of plants adequately supplied with iron.

Visible deficiency symptoms were associated with an iron content of 50 p.p.m. Fe in the dry leaf at harvest. Leaves with a higher iron content did not show symptoms. Increasing the supply caused an increase in growth and crop yield, and the iron content in the leaf dry matter rose to 70 p.p.m. Fe. A still higher level of supply raised the leaf content of iron to 80 p.p.m. but did not increase growth or crop yield above that obtained with a leaf content of 70 p.p.m.

Eight other nutrient elements were determined by leaf analysis. Five of these (zinc, manganese, copper, magnesium, potassium) showed a decrease in percentage content in dry leaf matter as growth increased. This “dilution” effect could have produced a new nutrient limitation at the highest growth and yield levels. Nitrogen and phosphorus contents did not vary much, but the calcium content in the leaf showed a steady inGrease in percentage content as growth increased.     

钠钾替代对甜菜生长的影响

以甜菜ST13092、SD13829、25和H10474为材料。通过盆栽水培研究了不同钠钾比作用下对甜菜幼苗的干物质重、叶面积、总叶绿素含量及光合速率的影响。结果表明,当Na＋替代K＋50％时,耐盐品种甜菜幼苗的干物质量、叶面积、叶绿素含量和光合速率均有所提高;而耐盐弱品种甜菜幼苗的干物质量、叶面积均有所下降,叶绿素含量和光合速率均有所提高。随着钠钾替代率的增加。所有甜菜幼苗的干物质量、叶面积、叶绿素含量和光合速率均有所下降。研究结果表明：钠钾替代对于耐盐品种的效果要明显优于耐盐弱品种,Na＋只能部分替代K＋,不能完全替代K＋的功能。     

除草剂对毛桃幼苗生长与光合的影响

以毛桃[Prunus persica（L.）Batsch.] 1年生幼苗为材料,研究土施除草剂对其生长发育、根系结构以及光合作用等的影响。结果表明：土施百草枯后,毛桃幼苗根系细胞电解质渗透率在初期显著升高,随后受损伤程度减轻;处理后40 d叶片蒸腾速率升高,叶片水分利用率、地上部干物质量显著降低。施用草甘膦对幼苗外部形态影响较明显,处理后7 d,幼叶变黄、向上卷曲,根系细胞电解质渗透率始终显著高于清水处理对照;处理后40 d,根总体积、总根长、总表面积以及根尖数显著减少,叶片净光合速率、气孔导度、蒸腾速率下降,植株干物质积累量也显著降低,表明草甘膦可通过根部传导危害地上部,桃园应尽量避免草甘膦等内吸性除草剂的使用。     

莲藕干物质积累与氮磷钾吸收分配特征

以山东莲藕地方品种"齐头"为试材,采用田间池栽试验,在莲藕不同生育期动态取样,测定各器官的干物质量和氮、磷、钾养分含量,计算各生育时期养分积累量,明确莲藕干物质积累及氮、磷、钾的吸收规律,以期为黄河中下游地区莲藕合理施肥提供参考依据。结果表明:莲藕干物质积累呈"慢-快-慢"的变化趋势。膨大茎形成期是莲藕干物质积累最快的时期,积累速率为每株29.27 g·d^-1。根状茎膨大之前,干物质主要集中在叶片和叶柄中,膨大之后,叶片和叶柄中的营养物质逐渐向膨大茎中转移,膨大茎中干物质最终积累量占全株的66.68%。不同时期莲藕氮、磷、钾的吸收积累量不同。膨大茎形成期莲藕对氮、磷、钾的积累速率最大,分别为每株0.46、0.18、0.56 g·d^-1,积累量分别占全生育期的49.50%、31.49%、39.56%。整个生育期莲藕氮、磷、钾吸收积累量的比例为1∶0.62∶1.53。根状茎膨大之前,莲藕氮和磷主要集中在叶片中,钾主要集中在叶柄中,之后随着地下根状茎的膨大,叶片和叶柄中的养分逐渐向地下部分转移,成熟期地下膨大茎中氮、磷和钾积累量分别占全株积累总量的71.97%、69.54%和87.89%。综上所述,莲藕前期以营养生长为主,根状茎膨大之后,以贮藏生长为主,膨大茎形成期为莲藕生长的关键时期。     

Impact of Mononychellus progresivus and Oligonychus gossypii (Acari: Tetranychidae) on cassava growth and yield in Central Africa

Growth of cassava was investigated in Central Africa (Congo) on crops attacked by two phytophagous mites: Mononychellus progresivus and Oligonychus gossypii. Change and distribution of dry matter in leaves, stems and roots were monitored for the 24 month crop cycle on infested and mite-free plants. Leaf dry matter increased during the rainy season and decreased during the dry season. Stems contain the reserves used for initiating plant growth after the dry season. Dry matter increased in the roots which form true storage organs. At the start of the second year of cultivation, one third of the root biomass was used to support the recovery of plant growth and development. Mite densities fewer than 50 mobile forms per leaf (maximum number of mites) were not sufficient to cause significant loss of leaf, stem and root dry matter. Nevertheless the mites diverted part of the biomass allocated to the roots thereby reducing the efficiency of storage root production in the infested plot.     

堇叶山梅花营养缺乏症状的研究

通过石英砂培法,研究了堇叶山梅花幼苗在缺N、P、K、Ca、Mg条件下的缺素症状及生理变化情况。结果表明:在N素缺乏时最先表现出叶边缘有黄色斑点症状;K素缺乏处理15 d表现生长良好,但处理后期40 d左右最先出现缺素焦枯现象,说明该植物前期需钾肥相对较少;缺Ca处理的堇叶山梅花新叶先表现出轻微失绿,有的叶尖干枯且呈螺旋形,其它4种元素亏缺的植株均是老叶先表现症状;N、P、K、Ca、Mg 5种营养元素缺乏的植株叶绿素含量、可溶性蛋白质含量均低于全素(CK)处理,该研究结果可作为堇叶山梅花苗期营养诊断的依据。     

Nutrient uptake of pepino plants in soilless cultivation

Summary

This study addresses vegetative growth and the uptake of nutrients and their accumulation in the vegetative and reproductive tissues of pepino (Solanum muricatum Ait.). The study was conducted in soilless plastic house conditions, with a planting density equivalent to 25.000 plants ha^–1 during two seasons (1997–98 and 1998–99). The plants were sampled, fractionated into leaves, stems, fruits and roots, then dried and weighed and the macronutrient content was analysed every 30.d for 300.d after transplanting. The yield obtained was 2.kg of fruit per plant, which is 30% of the total dry weight. The relative growth rate (RGR) ranged from 0.0028 to 0.0451.d^–1. The highest N, K, Ca and Mg concentrations were recorded in the leaves, and the highest P concentration in the roots. The nutrient accumulation of this yield was 10.64, 1.12, 16.06, 10.0 and 1.58.g of N, P, K, Ca and Mg per plant respectively. The highest accumulation of all nutrients was found in the leaves. The nutrient with the highest specificuptake rate was K, which ranged from 0.0037 to 0.0838.g g^–1 d^–1.     

Nitrogen uptake,partitioning and remobilization in ‘Kotata’ blackberry in alternate-year production

Summary

Mature ‘Kotata’ trailing blackberry plants growing in the alternate-year (AY) system in the field, were treated with ammonium sulfate depleted in ¹⁵N in early April, 1997. Based on the whole plant, excluding roots, accumulation of new dry matter over the two year AY production cycle averaged 5.96 kg plant^-1. On average, 28, 64 and 8% of this new dry-matter accumulation could be attributed to harvested fruit; loss from the crop as prunings and leaf senescence; and increased dry matter in the crowns for the next growth cycle, respectively. On average, 46% of new dry matter accumulation occurred in the off-year (non-producing). Whole plant (excluding roots) accumulation of new N (labelled and non-labelled) over the two-year AY production cycle averaged 63.7 g N plant” . Over a two-year production cycle, 44% of new N accumulation occurred in the off-year. Of the newly accumulated N, 37% was in harvested fruit, 58% was lost from the crop as prunings, and 5% was accumulated in crowns for the next growth cycle. For both the on-year and the off-year plants fertilized with labelled N, near maximum nitrogen derived from fertilizer (NDFF) accumulation occurred by August. At this time, 45% of the applied fertilizer could be accounted for in the non-root portion of on-year plants. A portion of this maximum on-year accumulation was either lost from the system or translocated to the roots. At the time of maximum accumulation, 39, 37,19, 3 and 2% of the accumulated NDFF was contained in the fruit, laterals, primocanes plus primocane leaves, floricanes, and crowns, respectively. Labelled N applied in the off-year was used primarily for primocane and primocane leaf growth. A large portion of the nitrogen stored in the off-year was used for early growth of floricanes, fruiting laterals and fruit in the following on-year. Excluding roots, by the end of the 1997 season, almost 30% of the applied fertilizer was accounted for in the non-root portion of off-year plants. There was also evidence of remobilization of N among plant tissues at different times during the production cycle. Results of this study suggest fertilizer N is an important N source for fruiting lateral and fruit growth in the on-year and for new primocane and primocane leaf growth in the off-year. N accumulated in the off-year is also an important source for early growth of floricanes, fruiting laterals and fruit the following year.     

Effect of humidity and nutrient feed K/Ca ratio on physiological responses and the accumulation of dry matter,Ca and K in tomato

Summary

Two levels of humidity, high, 0.1 kPa vapour pressure deficit (vpd) and control 0.5 kPa vpd, and four nutrient feed K/Ca mM ratios (4/7, 10/7, 4/2 and 10/2) were applied in all factorial combinations to a nine-week old tomato (Lycopersicon esculentum Mill.) crop for 63 d. The effect on gas exchange, water relations, vegetative growth, yield and accumulation of Ca and K in the shoot was examined. High humidity had a deleterious effect on leaf expansion, delayed truss and fruit maturity and reduced fruit yield. Water uptake was reduced and the Ca concentration of leaf and fruit tissue was increased under high humidity compared with plants grown under control humidity; K accumulation was unaffected. The accumulation of K and Ca in the shoot appeared to be poorly related to the rate of transpiration. The high (10/2 mM) K/Ca ratio nutrient feed had little effect on vegetative growth and yield compared with the low (4/7 mM), but restricted Ca uptake to the fruits at both the high and the control humidity. During the measurement period, 0900–1300 hours, stomatal conductance and leaf water status remained high at elevated humidity, compared with a progressive reduction in leaf water status and low stomatal conductance in the control humidity. A/c_i gas exchange analysis where A is the net CO₂ assimilation rate and c_i is the intercellular partial pressure of CO₂ suggested that, at high humidity, the photosynthetic capacity of the leaves was reduced because of a lower in vivo carboxylation efficiency. However, the mechanism(s) responsible for reduced leaf expansion remains unclear. The complex interrelations between physiological responses, leaf expansion and the uptake and distribution of K and Ca to the shoot, are discussed.     

Growth and productivity of potato as influenced by cultivar and reproductive growth: I. Stomatal conductance,rate of transpiration,net photosynthesis,and dry matter production and allocation

The effect of cultivar and reproductive growth on leaf gas exchange, water relations, dry matter production and allocation in potato was the subject of investigation. Debudded, flowering and fruiting plants of cultivars Al-624, Al-436, CIP-388453-3(A) and CIP-388453-3(B) were evaluated under field condition of a sub-humid tropical highland of Ethiopia during 2003. Cultivars exhibited differences with respect to leaf stomatal conductance, rate of transpiration and net photosynthesis rate. Cultivars Al-624 and CIP-388453-3(A) showed higher stomatal conductance and rate of leaf transpiration than CIP-388453-3(B) and Al-436. CIP-388453-3(A) exhibited higher net photosynthesis than Al-624 while Al-436 is intermediate. Fruiting plants had higher leaf stomatal conductance and higher rate of leaf transpiration and net photosynthesis. Fruit development promoted early plant maturity and without affecting total dry matter production it reduced the amount partitioned to the leaves, stems, and tubers. The experiment demonstrated that cultivar and fruit development influence on water relations, rate of net photosynthesis and source–sink interactions in the potato.     

The photoperiodic control of rooting,growth, and dormancy in Cornus alba L.

Cuttings from 2 cultivars of Cornus alba propagated in late September produced more and longer roots in long days (LD) than in natural days (ND). The effects of photoperiod on rooting were much less when cuttings were propagated in mid-August. LD during propagation in mid-August delayed the onset of leaf senescence and bud dormancy so that heavier and taller plants were obtained. Bud dormancy did not develop if the plants were grown under LD throughout the winter. Such treatment produced very tall plants and resulted in a greater proportion of their dry matter being distributed to the stems.Short-day (SD) treatment hastened bud dormancy development followed eventually by leaf senescence. Returning the plants to LD after more than 3 months of SD-treatment did not overcome the bud dormancy regardless of whether the plants still had leaves.It is recommended that if material of Cornus alba is propagated in August, the natural photoperiod should be extended during propagation so as to improve plant growth.     

Stimulating productivity of hydroponic lettuce in controlled environments with triacontanol

Triacontanol (1-triacontanol) applied as a foliar spray at 10(-7) M to 4-day-old, hydroponically grown leaf lettuce (Lactuca sativa L.) seedlings in a controlled environment increased leaf fresh and dry weight 13% to 20% and root fresh and dry weight 13% to 24% 6 days after application, relative to plants sprayed with water. When applied at 8 as well as 4 days after seeding, triacontanol increased plant fresh and dry weight, leaf area, and mean relative growth rate 12% to 37%. There was no benefit of repeating application of triacontanol in terms of leaf dry weight gain.     

VA 菌根真菌对酸枣实生苗抗旱性的影响

 在盆栽条件下, 研究了VA 菌根对酸枣实生苗生长和抗旱性的影响。结果表明, 在土壤相对含水量为20 %、40 %、60 %条件下, VA 菌根能显著增加酸枣实生苗的生长量(株高、叶面积、鲜样质量、干样质量等) , 降低叶片自然饱和亏和脯氨酸含量, 提高植株叶片气孔导度、蒸腾速率、光合速率, 显著增强了植株的抗旱能力。在土壤相对含水量相同状况下, 接种菌根真菌植株制造1 g 干物质的需水量低于不接种的处理, 节水效果为16. 5 %～29. 8 %。干旱条件对VA 菌根的侵染影响不大。播种时进行控水处理和在播种后40 d 开始控水两个水分试验对菌根的侵染率、植株的生长及水分状况影响差异不大。     

Effect of salinity on uptake and distribution of chloride and sodium in some citrus scion-rootstock combinations

The effect of scion on Cl and Na accumulation and the transport properties of rootstocks was investigated using grafted plants. The combinations of Navel orange (C. sinensis (L.) Osb.) and Clementine (C. clementine Hort. ex Tan) scions on Cleopatra mandarin (C. reticulata Blanco) and Troyer citrange (C. sinensis X P. trifoliata) rootstocks, were used in all experiments. Plants were grown under glasshouse conditions for 14 weeks supplied with nutrient solution containing 0-60 mM NaCl. Relative growth and defoliation were studied. The reduction in relative growth caused by salt, treatments was more scion- dependent, whereas defoliation was more rootstock-dependent. Changes in leaf and root ionic contents were measured. Scions on Cleopatra mandarin accumulated less Cl in their leaves and roots than did scions on Troyer citrange. The distribution of Cl in the whole plant showed that Clementine had a reduced ability to transport Cl from roots to leaves. However, sodium content was lower in scions on Troyer citrange than Cleopatra mandarin. The distribution of Na in the whole plant showed that Troyer citrange restricted the transport of Na to the scion. There was little difference in P content in all combinations. Salinity decreased sharply the N content of leaves and roots in plants on Troyer citrange, but there was only a slight effect in plants on Cleopatra mandarin. The pattern of N accumulation was inversely correlated with the pattern of Cl accumulation. Salinity decreased K, Ca and Mg contents in leaves and roots of all combinations.     

Yield,chemical composition,growth and maturity of ‘Williams’ banana fruit in relation to supply of potassium,magnesium and manganese

In New South Wales, banana plantations are subject to shortages of K, Mg and possibly high Mn. We investigated the effects of a low supply of K and Mg and high Mn on ‘Williams’ banana grown in drainage lysimeters over 3 crop cycles. Low K supply reduced yield by 73%, low Mg reduced it by 17% and high Mn had no effect. The bunch-weight component, mean finger weight, was reduced most (57 and 13% by low K and Mg, respectively) and the fruit number per hand was reduced least (16 and 8%, respectively). Fruit growth was exponential, and the relative fruit growth rate was influenced by K supply and seasonal conditions.High Mn supply decreased fruit maturity (greenlife) by 23%. Low K supply increased greenlife 79%, but only in relation to its effect on fruit size. The concentrations of K and Mg in the fruit dry matter were largely independent of the concentration in the solution around the roots. Mn concentration in fruit dry matter was directly proportional to Mn supply. The concentration of Ca in fruit dry matter showed a significant (P = 0.01) positive association with greenlife over all treatments.     

Effect of iron supply and nitrogen form on growth,nutritional status and ferric reducing activity of spinach in nutrient solution culture

This study was carried out in order to give some information that could improve spinach nutritional status and productivity. In this paper, the effect of two N forms (N was added either as 100% nitrate or as 80% nitrate and 20% ammonium) and three Fe levels (0 μM Fe; 20 μM FeEDDHA; 3 μM FeEDDHA + 10 mM NaHCO₃) on the growth, chlorosis symptoms and shoot nutrient element accumulation was studied in spinach plants (var. Viroflay), grown in hydroponics; six treatments and three harvests (at about 20 days interval each, until plants reached their commercial size) were applied in total. The results indicated that under conditions of Fe sufficiency (20 μM Fe), mixed N nutrition induced higher production of dry matter as well as improved Fe, Mn and Zn plant nutritional status. In plants grown under Fe deprivation (0 μM Fe), shoot Fe concentration was not significantly affected by the N form until the end of the experiment despite mixed N nutrition induced higher dry matter production up to harvest 2; plants grown under Fe deprivation and with mixed N nutrition presented also higher shoot Mn and Zn concentration. Under conditions of high concentration of bicarbonates and low level of Fe (3 μM Fe + 10 mM NaHCO₃), the N form had not a significant influence on total dry matter production whereas shoot Fe and Mn accumulation in 100% NO₃-fed plants was found to be significantly reduced compared to mixed N nutrition; regardless of the N form, those plants presented the least dry matter production, highest intensity of leaf chlorosis as well as highest root ferric reducing activity compared to plants grown under Fe deprivation.     

Photosynthetic and growth responses of juvenile Chinese kale (Brassica oleracea var. alboglabra) and Caisin (Brassica rapa subsp. parachinensis) to waterlogging and water deficit

Chinese kale (Brassica oleracea var. alboglabra) and Caisin (Brassica rapa subsp. parachinensis) are leafy vegetable crops grown in south-east Asian countries where rainfall varies dramatically from excess to deficit within and between seasons. We investigated the physiological and growth responses of these plants to waterlogging and water deficit in a controlled experiment in a glasshouse. Juvenile plants were subjected to waterlogging or water deficit for 19 days in case of Chinese kale and 14 days in case of Caisin and compared with well-watered controls. Caisin tolerated waterlogging better than Chinese kale because it produced hypocotyl roots and gas spaces developed at the stem base. In Chinese kale, waterlogging reduced plant fresh weight (90%), leaf area (86%), dry weight (80%) and leaf number (38%). In contrast, waterlogging had no impact on leaf number in Caisin and reduced plant fresh and dry weights and leaf area by 60–70%. Water deficit reduced leaf area, fresh weight and dry weight of both species by more than half. Leaf number in Chinese kale was reduced by 38% but no effect occurred in Caisin. Water deficit increased the concentration of nitrogen in the leaf dry matter by more than 60% in both species and the leaf colour of water deficient plants was dark green compared with the leaf colour of well-watered plants. Soil water deficit delayed flowering of Caisin while waterlogging accelerated it. Thickening and whitening of the cuticle on the leaves of Chinese kale probably increased its ability to retain water under drought while Caisin adjusted osmotically and Chinese kale did not. Waterlogging and water deficit had strong effects on leaf gas exchange of both Brassica species. Water deficit closed the stomata in both species and this was associated with a leaf water content of 9 g g⁻¹ DW. In contrast, waterlogging reduced conductance from 1.0 to 0.1 mol H₂O m⁻² s⁻¹ in direct proportion to changes in leaf water content, which fell from 11 to 5 g g⁻¹ DW. This separation of the effects of water deficit and waterlogging on conductance was reflected in transpiration, internal CO₂ concentration and net photosynthesis. In conclusion, Chinese kale and Caisin showed rather different adaptations in response to waterlogging and water deficit. Caisin was more tolerant of waterlogging than Chinese kale and also showed evidence of tolerance of drought. There is genetic variation to waterlogging within the Brassica genus among the leafy vegetables that could be used for cultivar improvement.     

The Effects of Nitrogen,Potassium and Sub-Irrigation on the Yield,Quality and Composition of Single-Truss Tomatoes

The effects of nitrogen and potassium on the growth of single-truss tomatoes and on the yield and quality of the fruit have been examined. Two successive crops of cv. Minicraigella were grown with sub-irrigation in a tiered-trough system, the troughs containing a 7:3:2 mixture of loam, peat and grit. Four concentrations of nitrogen in solution (100, 150, 200 and 250 ppm N) were tested in factorial combination with three concentrations of potassium (200, 300 and 400 ppm K), the treatments being replicated four times.

Plant height and leaf length increased markedly with N concentration, as also did the numbers of flowers and marketable fruits per plant, the mean weight per fruit and the total yield. Low N levels delayed harvesting. The proportion of unevenly ripened fruit decreased with increasing concentrations both of N and K. The percentage of hollow fruits was decreased by high K but increased with N concentration.

The titratable acidity of the expressed fruit juices increased significantly with N concentration (P<0.001) but was little affected by K treatment. The N concentration of the nutrient solution also largely controlled the percentage of K in the leaves and the total uptake of this nutrient. These unexpected results were attributed to stimulation of growth by N, leading to increased water requirement and hence to increased application of both N and K by the automatic sub-irrigation system.

The highest yields and best quality fruit were obtained with 250 ppm N and 400 ppm K in the solution, although lower concentrations of K might be preferable after continued cropping in the same compost.