Influence of rate and method of application of superphosphate on the growth and nutrient status of newly planted peach trees

A field experiment was carried out with newly planted peach trees to determine the influence of both rate and method of application of superphosphate on tree growth and nutrient status during the first growing season. Superphosphate was applied at planting at rates ranging from ¼ to 9 lb per tree, and applications were made either to the soil surface, in the planting hole, under tree roots, or in a band around the tree at a depth of 6 inches. Trees were grown under straw mulch and were irrigated as required.

Results showed that, in this soil of low initial ? content, trees receiving 9 lb superphosphate on the soil surface or in a ring band grew significantly larger than trees receiving ¼ lb superphosphate per tree (this applied for butt circumference only on surface-treated trees), but high rates of superphosphate in the planting hole or under tree roots resulted in tree death. No significant differences in growth were recorded at harvest between surface and ring-banded treatments at any phosphate rate, but leaf analysis in midsummer and tree analysis at harvest showed that the phosphate status of surface-treated trees was significantly higher than that of ring-banded trees.

At low rates of superphosphate (¼ and 1 lb per tree), surface treatment tended to give larger trees at the end of the growing season than band treatment, but differences were not significant. It is thought that this differential response occurred because the phosphate-fixing potential of the soil increased sharply with depth and hence band applications were inefficient unless very high rates of superphosphate were used.

The tree damage observed when high rates of superphosphate were applied in the planting hole or under tree roots was probably due to a combination of osmotic stress, acidity damage to the roots and possibly toxic nutrient levels in tree tissues. Hence high rates of superphosphate should not be placed close to tree roots at planting.

Leaf analysis in midsummer and tree analysis at harvest showed that the main effect of superphosphate application was on the ? status of the trees, and maximum tree growth in the surface and band treatments corresponded to a value of approximately 0.28% ? (dry weight basis) in the leaves. The efficiency of uptake of applied superphosphate was very low at all rates of application and was especially so at high rates. However, positive growth responses were recorded to 9 lb superphosphate per tree in surface and banding treatments. It is suggested that, although most of the applied superphosphate could not be utilized, tree growth rate was proportional to the concentration of ? in the soil zone which could be exploited by the roots.     

The Influence of Vigour and Nitrogen Status on the Fruitfulness of Talisman Strawberry Plants

In a study on the growth and cropping of strawberries under contrasting soil nitrogen conditions in a trial extending over six years, annual split applications of Nitrochalk maintained distinct regimes of mineral nitrogen in the soil but 30 tons/acre F.Y.M., prior to planting, had little additional effect. Nitrogen deficiency was achieved by preplanting applications of straw but this only lasted for one season.

There was a regular pattern in leaf nitrogen concentration associated with the different phases of strawberry growth. The concentration showed a linear response to increments of fertilizer nitrogen. Leaf colour gave visual evidence of these differences.

F.Y.M. did not affect plant growth or cropping but nitrogen applications resulted in small increases in both plant spread and number of crowns per plant.

Nitrogen at 200 lb. N/acre depressed the yields of marketable fruit in each of the four years. This was due only in part to an increase in wastage and it is suggested that a high nitrogen status in the plant could reduce the number of fruits per truss. The lower rate (50 lb. N/acre) gave yields generally similar to the nil control.

Nitrogen levels had little influence on the intensity of flowering in spring, whereas autumn flowering decreased sharply as nitrogen levels increased. Floral initiation thus appears much more sensitive to the nitrogen status of the plant in July than in September.     

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.     

Apple rootstock studies: growth of trees on three clonal rootstocks planted with or without roots

Trees of Cox's Orange Pippin on M.IXa, M.26 and MM. 106 were planted either normally with roots or without roots to simplify the planting operation. Pruning treatments were superimposed, the trees being cut back at planting, left unpruned the first year and cut back the second year, or left entirely unpruned. All trees survived. After two growing seasons the trees were lifted and weighed. Removal of all roots before planting reduced shoot growth, trunk girth increment, final tree weight and incremental weight. However, on all rootstocks, trees planted without roots and left unpruned were similar in size when lifted to those planted with roots and cut back at planting in the orthodox manner.

In a complementary trial lasting one season Cox's Orange Pippin trees on M.26 were planted with or without roots. All trees were cut back at planting, and four times of planting were compared. The mid-April planting included trees that had been stored at 2.8 °C and trees that had been bedded-in outdoors. There were no tree losses attributable to removal of the roots before planting. Removing the roots at planting again reduced growth and weight of tree at lifting. Month of planting had no effect upon shoot growth or trunk girth increment.

The results are discussed, together with their practical implications in relation to mechanical tree planting for high density orchards.     

Root growth following defruiting improves peach tree water status

Summary

Tree growth and water status throughout the growing season and after fruit removal were studied in container-grown peach trees. Trees with fruit (F) and defruited (DF) trees were sampled destructively at bud break (8 March), 1 month after fruit removal (3 June), at harvest (6 August), and before leaf fall (15 October) to determine the mass of leaves, current season shoots, branches, trunk, and the entire root system. Tree water status was determined from the mid-day stem water potential (SWP) the day before each sampling date. Root growth in DF trees was greater than that observed in F trees, while the above-ground biomass was similar in DF and F trees. DF trees therefore had lower leaf:root biomass ratios than F trees throughout the fruit growing season. Environmental factors did not fully explain the seasonal variations in SWP, but there was a significant correlation between leaf:root biomass ratios and SWP. Reductions in leaf:root biomass ratios were accompanied by increases in SWP and, ultimately, DF trees had higher SWP values than F trees in mid-Summer. Improvements in tree water status following fruit removal can be explained, in part, by additional root growth.     

The Effects of Different Manurial Treatments on The Yield and Mineral Composition of Red Beet

Red beet was grown in factorial manurial experiments at two sites: at Wellesbourne annually from 1954 to 1964 in a rotation of vegetable crops and at Efford in 1959 only.

At Wellesbourne applications of FYM (20 tons per acre per crop), together with NPK fertilizers, consistently gave much higher yields than mineral fertilizers alone, but the relative effect of FYM did not increase as the experiment proceeded.

In the presence of FYM, yields of red beet increased with increasing rates of application of Nitrochalk (up to 124 lb. N per acre), but applications of phosphate and potash fertilizers did not affect yields.

In the absence of FYM, phosphate fertilizers did not increase yields significantly after 1959; there was an important interaction between the effects of the applications of Nitrochalk and SUlphate of potash. Each fertilizer applied alone produced small increases in yield, but when they were applied together at the highest rates used (186 lb. Nand 192 lb. K₂O per acre) large increases in yield were obtained and there was some indication that an even higher rate of application would have given a further increase in yield. At Efford, nitrogenous fertilizers increased yields significantly.

Applications of FYM increased the potassium and decreased the calcium and magnesium contents of red beet leaves and had only small effects on the nitrogen and phosphorus contents; in the roots, only the potassium content was altered (increased) by the FYM applications.

In general, in the absenc~ of FYM only potash fertilizer applications had large, consistent and significant effects on the mineral composition of the leaves and roots. At both sites, applications of sulphate of potash increased the potassium content of the leaves and had a much smaller depressing effect on the calcium and magnesium contents of the leaves but not, in general, of the roots.

The effects of the nitrogenous fertilizers on the total nitrogen content of the roots were relatively small, but could be important in relation to the processing quality of the beet.

The marked differences between the responses of red beet and early potatoes to the manurial treatments are discussed in relation to the nutrient contents of the plants.     

Effect of hail nets on the microclimate,irrigation requirements,tree growth,and fruit yield of peach orchards in Catalonia (Spain)

Summary

Hail nets protect orchards from storm damage, but also offer potential water savings for fruit trees grown in arid areas. We investigated the effects of black nets on water use, growth, yield, and fruit quality in peach trees growing in Catalonia, Spain, over 2 years (2006 and 2007). Water savings were quantified by irrigating the netted trees to a similar midday stem water potential (Ψ_stem) as the control trees. This method was only partially successful in 2006, with the netted trees being over-watered early in the season (i.e., higher Ψ_stem than the controls), and under-watered (i.e., lower Ψ_stem than the controls) later in the season. A combination of water stress and a hail net resulted in lower yields because of a smaller fruit size. Skin colour was more enhanced in control fruit. In 2007, Ψ_stem values were similar between treatments. Any difference in tree performance was therefore due to the hail net per se. Fruit size was similar between treatments, and the lower yields of netted trees were due to decreased fruit number. There were no treatment differences in fruit skin colour or flesh firmness. Soluble solids concentrations were higher in nonnetted fruit. In both years, water savings amounted to approx. 25%, if irrigation replaced the potential evapotranspiration that was measured. Hail nets are therefore recommended for their effects on water saving in arid areas, despite lower fruit yields.     

The Effects of Different Manurial Treatments on The Yield and Mineral Composition of Early Potatoes

The effects of different manurial treatments on the yield and mineral composition of early potatoes are described. The crops were grown annually from 1954 to 1964 in a rotation of vegetable crops in a factorial manurial experiment on a sandy loam at Wellesbourne and, in i960 only, on a very fine sandy loam at Efford.

At Wellesbourne, farmyard manure (20 tons per acre per crop) with fertilizers consistently produced much higher yields than mineral fertilizers alone, and the relative effect of FYM increased from 1954 to 1959 but not subsequently. In years when moisture supplies were adequate, the larger part of the increase in yield could be attributed to effects of FYM on the early growth of the plants, and a smaller part to the increased rate of bulking of the tubers on the FYM plots. In dry years, however, growth during the harvest period was much slower on the fertilizer plots than on the FYM plots and the additional relative increase in yield on the latter during this period caused the overall effect of FYM to be larger than in the wetter years.

In the absence of FYM, each of the major nutrients N, P and K gave significant yield increases, but the need for adequate applications of phosphate and potash fertilizers together was emphasized by a marked interaction between their effects on yield. Applications of phosphate fertilizers had a particularly important effect early in the bulking period, whereas the effects of the nitrogenous fertilizers were greater at the later stages. In the presence of FYM, the fertilizer applications had significant effects only at the later stages of bulking, but at this time the amounts needed to give maximum yields were similar to those needed in the absence of FYM (124 lb. N, 36 lb. P₂O₅ 144 lb. K₂O (estimated), each per acre).

At Efford, applications of up to 4 cwt. per acre of sulphate of ammonia and 2 cwt. per acre of superphosphate (18% P₂2O₅) gave significant increases in yield, and higher rates would probably have given still higher yields. Potash fertilizers did not affect yields although they markedly increased the potash contents of the plants. The differences between the responses at the two sites are discussed in relation to soil conditions.

The leaves of plants manured with FYM (Wellesbourne) contained much more potassium and slightly more phosphorus than leaves from unmanured plants and, while the differences in potassium content were larger towards the end of the bulking period than at the beginning, the reverse was true of the phosphorus contents. Thus, to use leaf composition data to indicate possible shortages of nutrients in the soil, the samples of leaves for chemical analysis must be taken at several different times during the growth of the crop. The value, if any, of extra nutrients for FYM-manured plants cannot at present be assessed.

At Efford, applications of sulphate of potash increased the potassium content of the leaves to levels approaching those found in the manured plants at Wellesbourne and higher than those in the unmanured plants. Because of marked interactions between the effects of the phosphate and potash fertilizers at Wellesbourne and indications that phosphate applications at Efford may have been too low to ensure maximum yields, it does not seem possible to combine the data from the two experiments in order to suggest levels of the major nutrients in the potato leaves, at any particular stage or stages, which may be considered adequate for maximal yield production.

At Wellesbourne the standard error per plot was smaller for the manured series (8·1%) than for the unmanured (12·9%), indicating that growth was more uniform on the former.     

Factors influencing urban tree planting program growth and survival in Florida,United States

High levels of mortality after installation can limit the long-term benefits associated with urban tree planting initiatives. Past planting projects funded by the Florida Forest Service were revisited two to five years after installation to document tree survival and growth and assess program success. Additionally, various site (e.g., soil compaction, installed irrigation) and tree-related (e.g., species, nursery production method, initial size at planting) factors were noted to assess their impact on tree growth. Results show that the overall establishment rate for the 26 sites (n = 2354 trees) was high, with 93.6% of trees alive at the time of final inspection. On-site irrigation played a significant role in tree survival and growth, especially for Magnolia grandiflora (97.7% survival on irrigated sites; 73.8% survival on non-irrigated sites). Findings from this work validate the effectiveness of current program policies which include maintenance of tree quality within the first year after planting, and offer further insights regarding the impacts of season of planting and initial size of nursery stock on plant growth and development.     

Comparative movement of labelled nitrogen and zinc in 1-year-old peach [Prunus persica (L.) Batsch] trees following late-season foliar application

Summary

Late in the season, a double-labelled solution containing ¹⁵N-enriched urea and ⁶⁸Zn sulphate was painted on the entire leaf area of 15, 1-year-old ‘O’Henry/Nemaguard’ peach trees to quantify N and Zn movement out of leaves following foliar application, and redistribution of these nutrients to new growth in the following Spring. About 47% of the labelled N and only 7% of the labelled Zn painted on the leaf surfaces was recovered in the permanent structure of the trees after leaf fall. Thus, it is concluded that foliar applications of Zn in the Autumn are not very efficient at supplying Zn to peach trees, especially when compared to supplying N as urea sprays in the Autumn. These data raise the possibility that foliar applications of Zn may actually be considered as soil applications, because 90% or more of the foliar-applied Zn may be carried to the orchard floor at the time of leaf fall. Therefore, future research needs to focus on assessing the efficacy of foliar applications for Zn nutrition of fruit trees, and identification of potentially detrimental effects from possible excessive soil accumulation of Zn. Once within the tree, however, labelled Zn was quite mobile and was stored throughout the plant, including in the roots. Of the labelled N and Zn exported from treated leaves prior to leaf fall, a substantial redistribution from storage was evident by 2 weeks after bloom and, by 4 weeks after bloom, 38% and 56% of the labelled N and Zn, respectively, had been redistributed from storage in roots, trunk and 1-year-old shoots to new growth. The biomass of new, above-ground growth tripled between 2 – 4 weeks after bloom and was coincident with a conspicuous influx of both N and Zn from the soil.     

Rubus Stunt: A Virus Disease

In 1958, at three sites in the Vale of Evesham, a progressive increase in the yield of spring cabbage was obtained from increasing rates of application of nitrogenous fertilizers up to 279 lb. N per acre, as Nitrochalk. At a fourth, with later application of fertilizers and a relatively early cutting date, 6 cwt. per acre gave a yield response rather greater than at the other three sites, but higher rates of application of Nitrochalk produced no further increases in yield.

No yield advantage was gained by applying the fertilizer dressing in three doses during the growth of the crop rather than in one dose in the very early spring.

The uptake of potassium, phosphorus, magnesium and calcium by the plants increased as the rate of nitrogenous fertilizer increased. The need to maintain an adequate level of available potassium in the soil when using heavy dressings of nitrogenous fertilizers is emphasized.

The effect of a ploughed-in ley on the recovery of added nitrogen is discussed.     

Effects of tree age at planting,root manipulation and trickle irrigation on growth and cropping of apple (Malus pumila) cultivar Queen Cox on M.9 rootstock

Summary

The apple cultivar Queen Cox on M.9 rootstock cropped more precociously when planted as two year old trees than when planted as one year old trees, even though there were no significant differences in the sizes (leader height and branch length) of the trees at the time of planting. However, the two year old trees had larger root systems at planting. As the trees aged, those planted as one year olds grew more vigorously and bore higher cumulative yields than those planted as two year olds. Annual root pruning of the trees, commencing 15 months after planting, reduced extension shoot growth, crown volume and grubbing weights (final fresh weights of scions) severely. In some seasons root pruning increased the number of spur and terminal floral buds produced and also the final sets and yield efficiencies on the treated trees. Planting trees within semi-permeable fabric membranes also reduced extension shoot growth and tree size, but less severely than the root-pruning treatment. Root restriction increased the efficiency of fruit set and yields and also improved the grades of fruits produced. Trickle irrigation treatments increased shoot growth and tree fresh weight at the time of grubbing, but had inconsistent and small effects on fruit set and yields. Interactions between tree age at the time of planting and the root manipulative treatments were significant.     

Root and shoot growth of newly-transplanted apple trees as affected by rootstock cultivar,defoliation and time after transplanting

Summary

An experiment with Malus demonstrated that a large proportion of the transplanted root system was lost through death and decomposition soon after transplanting in the open ground. Mortality of the roots was not influenced by the rootstock cultivars or by defoliation but increased significantly with time. In the first month, shoots of maiden trees of Malus transplanted in June when in-leaf grew, but roots did not. Subsequently, most of the new roots on the rootstock M.9 regenerated from the rootstock stem, whereas with MM.106 the old coarse roots (>2.0 mm diameter) initially present at planting were most important. Root growth occurred in concert with shoot growth such that a functional balance was maintained as shown by the existence of a constant root length:leaf area ratio over a large part of the growing season. Following transplanting, the trees appear to re-establish their optimal ‘functional’ ratio by way of a co-ordinating pattern of growth tending to correct any disturbance to the ratio resulting from transplanting. Defoliation in the early establishment phase caused only a temporary initial reduction in the root growth, but reduced all the shoot growth variables measured and increased the root length:leaf area ratio throughout the growing season.     

Two new planting systems for early ripening peaches (Prunus persica L. Batsch): Yield and fruit quality in four low-chill cultivars

Summary

Trees of peach cvs Flordastar, Flordaprince, Flordacrest and Maravilha, low in chill requirement (Flordaprince 150; Flordacrest 350 C.U.), with a short fruit development period (Flordaprince 90; Flordacrest 110 d) and a very early ripening time (Flordastar mid May; Flordacrest first week of June), were planted in Sicily (37° 30′ Lat. N) both in a medium (667 trees per ha) and a high density (2000 trees per ha) plantation system. In the medium density planting system, the trees were trained to a Fusetto, and in the high density to a Y-shape. Both in the Fusetto and Y, the size of the trees was controlled by severe pruning soon after harvest, consisting in the shortening of most of the one year old wood. From mid June to October, the trees of all four cultivars were able to recover a “fruiting canopy”; flower bud density, flower fertility, fruit set, fruit quality and crop efficiency were not affected by the severe summer pruning. Due to the planting density and the pruning, the tree growth was restricted: no platforms or ladders were required to perform the cultivation techniques at the top of the Fusetto nor was the wire-trellis necessary to sustain the Y-shaped trees. To distinguish these training systems from the original ones, Fusetto and Tatura trellis, we called them “dwarfed Fusetto” (dF) and “free standing Tatura” (fsT), respectively. Although production per tree was higher in the dF, due to planting density fsT yielded more per hectare.     

The consequences of cultural practices on growth and cropping of peach trees subjected to localized irrigation: Effects of soil management,nitrogen fertilization and tree density

SUMMARY

Cultural practices were studied in peach tree orchards irrigated with microsprinklers, herbicide strips being maintained along the tree rows. Differences in fruit cropping between treatments varied in the same way as tree vigour, the most vigorous trees having the highest production capacities. Concerning soil management, ground cover vegetation (permanent or temporary) improved fruit production compared with soil cultivation. According to leaf analysis, ground cover vegetation appeared to ameliorate the conditions of trees nutrition. This effect was probably mainly due to increasing soil resistance to compaction; applying organic matter was not effective in improving the performance of trees grown with soil cultivation compared with those grown with ground cover vegetation. Increasing fruit tree density also contributed to increased fruit production. Nevertheless, more than 600 trees per hectare did not allow further increase in fruit yield for the experimental cultivar. Lastly, nitrogen fertilization seemed particularly important for improving the fruiting of peach trees.     

Status,determinants and challenges of tree planting in Dodoma district,Tanzania

Climate change, human population growth, the energy crisis, and food insecurity negatively drive livelihoods in developing countries. The trend seems to be severe in arid and semi-arid areas where some livelihood strategies are naturally constrained. Tree planting is one of the mitigation and adaptation approaches applied to climate variability and change for sustainable development in sub-Saharan Africa. The current study assessed the status, determinants, and challenges of tree planting in Nkuhungu, Msalato, and Hombolo villages in the Dodoma district, Tanzania. A household questionnaire survey (HQS) was used to collect data from 213 household respondents. In-depth interviews and focus group discussions were used to supplement data from HQS. Results indicate that tree planting is practiced at household and institutional levels during the wet season and was promoted after the government shifted from Dar es Salaam to Dodoma. Approximately 5111 planted trees were recorded in the study villages, with an average of 24 ± 5 trees planted per household. Fruit and shade trees are widely planted in residential areas, and privately owned nurseries and the Tanzania Forest Services Agency (TFS) are the major sources of seedlings. Level of education (+), type of employment (-), seedling price (-), water availability (+), and the importance of the tree (+) were found to influence the number of trees planted by household respondents. The main challenges of tree planting are inadequate land size, water scarcity, high pricing of seedlings, lack of improved seeds, and insufficient extension services. Knowledge on tree planting determinants would be instrumental in strengthening the current governmental strategies for greening Dodoma. The study suggests increasing water sources such as boreholes and digging wells/ponds for watering trees; improvement of extension services; and provisioning of affordable improved and adaptive seeds to semi-arid areas.     

A Long-Term Manurial Trial on Dessert Apple Trees

A factorial NPK fertilizer trial was started in 1931 with newly planted dessert apple trees. Two varieties (Cox’s Orange Pippin and Beauty of Bath) and four rootstocks (M.I, M.V, M.IX and M.XII) were represented. By 1953. after the orchard was thinned in two stages, only one experimental tree, of Cox’s Orange Pippin on M.XII, remained in each plot; at this time a fourth factor was added by establishing a sward (S) in half the plots and continuing to cultivate the remainder during each spring and summer.

Severe deficiency symptoms developed early in the trial on plots receiving no potash. Recovery followed the overall annual application from 1937 of 2 cwt. per acre sulphate of potash, additional to the treatment comparison of nil v. 2 cwt. per acre, but large differences in tree size and cropping persisted. These differences were not greatest with the variety or the rootstock showing the most severe leaf scorch symptoms.

The overall potash application was discontinued in 1953, but the levels of “ available” potassium in the soil had by then been raised, and the trees of Cox on M.XII did not develop potassium deficiency over the next ten years. On the contrary, there was evidence that the higher level was now harmful, perhaps because of induced incipient magnesium deficiency.

Superphosphate (18% P₂O₅, 5 cwt. per acre per annum) did not affect the performance of the trees and only slightly increased the phosphorus concentration in the leaves. Much greater increases in leaf phosphorus were brought about by grassing down, particularly in the absence of nitrogen applications.

In the nitrogen treatment sulphate of ammonia was applied initially at 1½ cwt. per acre per annum, but this rate was increased to 3 cwt. per acre in 1941 and then to 6 cwt. per acre in 1953 ; from 1958 Nitrochalk at an equivalent rate was applied instead of sulphate of ammonia. This nitrogen treatment increased the total crop per plot over the first I7 years by 15%, and the total crop of the Cox on M.XII over the period 1953-62 by 25*#x0025;. The response was especi~lly marked in the last few years when the trees with and without nitrogen were still virtually indistinguishable in leaf colour ; values for nitrogen concentration on a dry-weight basis in mid-shoot leaves for August 1962 were 2·9% and 2·8% respectively.

Trees receiving nitrogen were grassed down in 1953 without reduction in total crop over the next ten years, though nitrogen status was depressed in the first few seasons. This depression was much more severe and persistent with the trees not receiving nitrogen, despite the abundance of clover in the swards on those plots.

The advantages of grassing down on fruit quality may be largely due to the restriction of nitrogen supply to the tree.     

Nitrogen fertilization during planting and establishment of the urban forest: A collection of five studies

Today's urban forest increasingly consists of planted trees, especially as native forest fragments yield to urban sprawl. These trees are usually larger (over 2-m tall) than typical reforestation trees and grow very little for the first few years after planting. Stressful urban sites exacerbate this effect and many practitioners hope to shorten the time required to reach environmentally functional size by fertilizing at planting. This is a controversial practice since nitrogen (N) application creates the potential for water quality impairment and effectiveness is uncertain. It is not clear how nitrogen application affects large trees with radically altered root:shoot ratios or how nursery production methods and restrictive sites affect response. In a series of five separate studies, we tested several N rates on ten shade tree species (both field- and container-grown) and transplanted to a range of urban sites, from a relatively undisturbed forest fragment to a highly compacted cutover soil with an absent A horizon. Trunk diameter increase, as an integrative metric of tree biomass accumulation, was followed for up to 4 years on each experiment. Overall, we saw little effect from fertilizing at planting at any rate we tested, regardless of location. Three studies that included leaf analysis with a SPAD-502 chlorophyll meter indicated that neither SPAD meter values or N concentration within leaves was increased by fertilizing at planting, suggesting that the newly planted shade trees took up very little of the applied N. Overall, SPAD-502 readings correlated well with actual leaf N concentration (r=0.692). This group of studies indicates that fertilization at planting does not increase post-transplant growth, even in stressful urban sites and it is therefore not effective at shortening the establishment period of transplanted shade 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.     

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

The effects of nutrition on the incidence of fruit ripening disorders are described, based on studies of three varieties of tomato (Potentate, Moneymaker and J168) grown with 72 combinations of fertilizers in heated glasshouse borders. The treatments included three levels each of nitrogen and potassium in factorial combination with two levels of phosphorus, magnesium and lime.

Potassium sulphate markedly decreased the overall percentage of unevenly ripened fruit from all three varieties. Magnesium sulphate had a similar but smaller effect; the response to magnesium was greatest at low levels of potassium. The higher level of phosphorus increased the proportion of unevenly ripened fruit, the combination of low potassium and high phosphorus having a particularly adverse effect. The responses to nitrogen were complex and differed between varieties. Lime increased the proportion of unevenly coloured fruit from varieties Moneymaker and J168, significantly in the high nitrogen plots. Numerous other interactions between nutrients were found.

The effects of the treatments on specific forms of ripening disorder were recorded, including greenback, yellow and green blotch, and waxy fruit. Potassium decreased the incidence of all forms of ripening disorder. High phosphorus increased the proportion of blotchy and waxy fruit, but significantly decreased the incidence of greenback in variety Potentate.

Although the intermediate level of potassium in this trial (871 lb. K₂ 0 per acre) had previously been found sufficient for maximum yield, significant improvements in fruit quality were obtained at the highest level (1,742 lb. K₂O per acre).