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Four-year growth response to nitrogen fertilization and thinning is reported for an experiment established in a 25-year-old Douglas-fir stand of medium site quality. Four levels of nitrogen (0, 112, 224, and 336 kg N/ha), in the form of urea, were tested at two thinning levels in a randomized 4 × 2 × 2 factorial design replicated in 2 Blocks. Fertilizer was applied in spring or fall. Basal area growth per hectare in the thinned stand significantly surpassed that of the unthinned stand in the fourth growing period. Increased rate of nitrogen fertilization resulted in increased growth 1 year after fertilization. Urea applied in the fall resulted in greater growth response than that applied in the spring for the first growing period and over a 4-year period. Increased rate of fertilization increased mortality significantly in the fourth growing period, but had no prior effect. Thinning decreased mortality in all four growing periods.

Blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Steud.] plants from a native shortgrass prairie were subjected to four treatments at three different temperatures in a growth chamber experiment to evaluate the dynamics of labile and nonlabile energy components in different plant organs. At high temperature regimes (24°/13° and 29.5°/18 °C day–night) blue grama plants accumulated comparatively greater amounts of labile and nonlabile energy in the three organs, viz., shoots, crowns, and roots, than at low temperature regime (13°/7 °C). The labile energy in shoots at the three temperature regimes continued to increase up to a peak value recorded at 90 days and then declined during the subsequent 30-day growth period. On the other hand, the accumulation of labile energy in roots and crowns continued till final harvest. Irrigated plus N-fertilized plants accumulated more labile and nonlabile energy in their shoots than did the irrigated plants, and the latter accumulated more than the fertilized and the control plants. The labile and nonlabile energy components in fertilized plants were at lower levels than the control plants during the 120-day growing period, resulting in net negative energy balance as compared with control plants. Higher temperature, irrigation, and irrigation plus nitrogen application decreased the nonlabile:labile ratios in the plants.

Variations in logistic growth curve among rice varieties were investigated using dry-mat-ter weight data from the International Rice Adaptation Experiment. Two major trends of variation were detected, one represented by the developmental stage at which growth rate beco-mes maximum (variation betweeh early- and late-vigor types), and the other represented by the durability of high growth rate (between sustained- and dash-vigor types). These varia-tions were found to be controlled by varietal genotypes. Early vigor contributes to the production of many spikelets, while late vigor contributes to the growth after heading and filling the spikelets with grain. Sustained-vigor types gave more grain yield than dash-vigor types. The pattern of changes in these vigor types due to fertilizer application also appeared to be varietal characteristics.

The results are reported of the effects of fertilizer and grazing or cutting for hay over a period of 6 years on the composition of an Agrostis/Festuca permanent pasture on low-lying land at Beghroke Hill. Applications of N up to 264 units/ac each year associated with frequent defoliation every 21 days produced only small changes in sward composition; Agrostis spp. declined and Poa trivialis increased. Lolium perenne did not increase from a small initial presence. Records of animal performance and hay yield showed that the mean output from the experiment as a whole was 530 Ib liveweight gain/ac and 0·5 ton hay/ac.

Monocalcium phosphate was broadcast at 0, 50, 100, and 200 kg P/ha to a calcareous soil, very low in NaHCO3-extractable P. Wheat (Triticum aestivum cv. Selkirk) and flax (Linum usitatissimum cv. Marine) were seeded in the 1st yr and barley (Hordeum vulgare cv. Montcalm) and flax were alternated in 3 subsequent yr. Subplot treatments consisted of 0, 5, 10, 20 and 40 kg P/ha applied as monoammonium phosphate with the seed. Wheat and barley responded well to broadcast or seed-drilled P. The latter was the most effective method of application; this was apparent even on plots receiving large amounts of broadcast P. In contrast, flax was not responsive to newly applied P, and yields decreased with application of seed-drilled P in combination with large amounts broadcast. The solubility of P in the untreated soil was between that of octacalcium phosphate (OCP) and hydroxyapatite (HA). The solubility of P in the treated soils was greater than in the untreated soils for the duration of the sampling period (3 yr) and was slightly less than that of OCP for the 50 kg/ha treatments, about that of OCP for the 100 kg P/ha treatment and greater than that of OCP for the 200 kg P/ha treatment. These studies indicate that the reaction product most likely governing the solution concentration of P was OCP.

In tests with sources of N, (NH4)2SO4, when banded in the soil, usually resulted in highest tuber yield. Yields with Nitroform and sulfur-coated urea were similar to each other, and somewhat less than those from urea. Application of Aqua Humus, a humic acid derivative, in addition to several sources of N, had no significant effect on yields. Nitrogen absorption was highest from (NH4)2SO4, as measured by NO3 content of the petioles or total N absorption by the entire plant. There was little difference in N absorption from Nitroform and sulfurcoated urea. These materials did not result in increased N absorption by plants during late growth. In Kern County experiments, about 80% of the N from (NH4)2SO4 and urea had nitrified and leached from the fertilizer band by 40 days after application. At 80 days after application, half of the N from Nitroform was still in place. In an experiment at Davis on a heavier soil, Nitroform had a slower rate of N release than sulfur-coated urea, followed in order by (NH4)2SO4 and urea.

Thatcher wheat was grown in tank-type lysimeters over a 7-yr period to determine the effect of fertilizer, two levels of available water and two cropping systems on the yield and nutrient content of grain and on some soil nutrients. Fertilizer did not change the yield of grain materially under natural rainfall. Added water only increased the yield by one-half and three-quarters of continuous wheat and fallow, respectively. Fertilizer with added water nearly doubled the yield of continuous wheat and increased by one-third the yield from the wheat-fallow rotation. The P content of the grain was not affected by fertilization, but was higher in the treatments to which additional water was applied than in those receiving natural rainfall only. It was also higher in continuous wheat than in fallow wheat. There was an interaction between the N and P uptake ratio and the N content of the grain. Fertilizer or additional water or both increased or decreased the N content, depending upon which way the N or P balance was shifted. Surplus available N not utilized by the crop grown with natural rainfall accumulated as nitrates at lower soil depths, particularly under the wheat-fallow system. All the NO3-N produced where supplemental water or water and fertilizer were applied was utilized and none accumulated. The organic N content of the surface soil increased along with a reduced loss in organic C where water and fertilizer were applied, as compared to the other treatments. Fertilizer application resulted in a sharp increase in NaHCO3 soluble P, particularly following the supplemental water plus fertilizer treatments where an excess of P was supplied with the fertilizer over that removed by the crop. There was an increased demand on soil P where water only was applied, and the soluble P content was appreciably reduced.

The K intensity in the soil was maintained adequate for chrysanthemum growth by applying a fertilizer solution containing K at 5 × 10-4 M/1 in a constant-drip fertilization system. A 10-fold increase or decrease changed the uptake of K probably because the soil solution was not in equilibrium with the fertilizer solution. Changing the concentration of K in the fertilizer solution also caused a reduction in Ca, Mg, P, and N absorbed by the plant.

The differential water use efficiency of maize crops grown during the summer and autumn period, in the central coastal plain of Israel, is analyzed in the light of the difference in radiative conditions and its effect on crop behaviour. Water-use efficiency appears to be adversely affected by high values of total radiation. Other environmental factors, such as soil fertility, have on the other hand a positive effect on water use efficiency, and this could be used as criterium in determining fertilizer application quantities in regions with limited water resources and high fertilizer costs.

Pot experiments were carried out to clarify the effect of K fertilizer on the growth of some vegetable crops in the volcanic ash soils with different levels of exchangeable K.1. On the soil with 94ppm exchangeable K, growth of spinach, lettuce, turnip and cucumber plants not receiving K fertilizer seemed to be inferior to those supplied with K, already from the cotyledon stage. In radish, carrot and snap beans, the increase of growth due to K supply did not become apparent until the mid-stage of growth. Howewer, at the harvest time, K application resulted in a marked increase in yield of all species investigated.2. On the soil with 255ppm exchangeable K, K application resulted in a noticeable increase in yield of spinach and cucumber. With lettuce and carrot there was a slight increase in yield due to K fertilizer.3. On the soil with 472ppm exchangeable K, there was no increase in yield due to K supply, with the exception of spinach.4. These results suggested that the exchangeable K level, below which yield increase due to K application would be expected, might be higher for vegetable crops on volcanic ash soils than that reported by other investigators. It seemed that the critical level of exchangeable K described above might be different by the plant species.

The effects of three patented nitrification inhibitors on transformations of urea N in soils were studied by determining the effects of these compounds (10 μg/g of soil) on urea hydrolysis, ammonia volatilization. and production of ammonium, nitrite, and nitrate in soils incubated under aerobic conditions (30°C, 60% WHC) after treatment with urea (400 μg of urea N/g of soil). The inhibitors used (N-Serve, ATC, and CL-1580) had little, if any, effect on urea hydrolysis, but they retarded nitrification of the ammonium formed by urea hydrolysis and increased gaseous loss of urea N as ammonia. They also decreased the amount of (urea + exchangeable ammonium + nitrite + nitrate) — N found in urea-treated soils after various times. Two of the soils used accumulated substantial amounts of nitrite(> 160 μg of nitrite N/g of soil) when incubated under aerobic conditions after treatment with urea. Addition of nitrification inhibitors to these soils eliminated or substantially reduced nitrite accumulation and greatly retarded nitrate formation, but had little, if any, effect on the recovery of urea N as (urea + exchangeable ammonium + nitrite + nitrate + ammonia) — N after various times. This finding and other observations reported indicate that the “nitrogen deficits” observed in studies of urea N transformations in soils may not largely be due to gaseous loss of urea N through chemodenitrification and are at least partly due to volatilization and fixation of the ammonium formed by urea hydrolysis in soils. The work reported also indicates that N-Serve and other nitrification inhibitors may prove useful for reduction of the nitrite toxicity problems associated with the use of urea as a fertilizer but that application of such inhibitors in conjunction with fertilizer urea, when surface applied, may promote gaseous loss of urea N as ammonia.

In the rapid spectrophotometry method described, direct available P2O5 in fertilizer is determined in the presence of ammonium citrate, meta- and polyphosphates are hydrolyzed with a simple heating step, and coloring matter (other than organic material) is destroyed with the direct addition of HN03. Direct available extracts prepared from samples containing organic phosphorus can be effectively digested by a simple technique of heating an aliquot with acid in a special decomposition vessel. The method is rapid, accurate, and precise and would be readily adapted to automated techniques.

The effectiveness of substituted p-benzoquinones as inhibitors of urease activity in soils depends largely upon their substituent groups. Methyl, chloro-, bromo- and fluoro-substituted p-benzoquinones have a marked inhibitory effect on soil urease activity, whereas phenyl-, r-butyl-and hydroxy-substituted p-benzoquinones have little, if any, effect. Methyl-substituted p-benzoquinones differ from other substituted p-benzoquinones in that their effects on soil urease activity usually increase markedly with increase in their time of contact with soil. A study of the effects of selected substituted p-benzoquinones on urea hydrolysis and volatilization of urea N as ammonia in a sandy soil treated with urea showed that methyl- and chloro-substituted p-benzoquinones had very marked effects, whereas hydroxy- and phenyl-substituted p-benzoquinones had little or no effect. Gaseous loss of urea N as ammonia when this soil was incubated at 20°C for 14 days was reduced from 62.8 to 0.1 per cent by addition of 2,3-dimethyl-, 2,5-dimethyl-, or 2,6-dimethyl-p-benzoquinone (2.3 parts/100 parts of urea). The work reported indicates that, of the 34 substituted p-benzoquinones studied, 2,3-dimethyl-, 2, 5-dimethyl- and 2,6-dimethyl-p-benzoquinone are likely to prove the most effective for retardation of urea decomposition in soils and reduction of the problems caused by the normally rapid hydrolysis of fertilizer urea by soil urease.

Grass tetany, a Mg deficiency in ruminants, is responsible for large economic losses throughout temperate regions. Significant livestock losses occur in the semiarid western United States primarily when livestock are grazing the spring growth of Agropyron desertorum, an introduced grass species which provides much needed early spring forage. The objective of this study was to increase forage Mg to about 0.2% by Mg and N fertilization and thus meet animal needs and reduce losses from death. The field study was located on A. desertorum grassland which had previously produced grass tetany. Two calcareous aridisols were each fertilized with 0, 90, 200, and 600 kg Mg/ ha as MgSO?•7H?O, having split plots with 0 and 150 kg N/ha applied as NH?NO?. Forage was harvested at regular periods intended to bracket the spring occurrence of tetany for three seasons following fertilization. Fertilization with 600 kg Mg/ha was necessary to increase forage Mg to the recommended level (0.2%). Applying 150 kg N/ha increased forage Mg concentration as much as did 200 kg Mg/ha. The N and Mg fertilizers were additive in increasing forage Mg concentrations. Forage Mg concentrations decreased with increasing age of vegetatively growing grass, and the benefits from fertilization were less with each successive season following fertilization. Little residual effect of 600 kg Mg/ha or 150 kg N/ha fertilization on plant Mg concentration would be expected after 5 years. Rapid decreases in water-soluble soil Mg with the resulting formation of some unknown insoluble phase, as well as high investment costs, preclude Mg fertilization of these ranges to meet Mg requirements of grazing animals.

A pot experiment was made to study the effect of two seed pretreatments on the phosphorus uptake by alfalfa in two different soils. The results showed that the dry weight of both the tops and the roots as well as the total P-uptake of alfalfa in both soils increased when the seeds were previously soaked in 0.5 mol/l KH2PO4 or 150 ppm indoleacetic acid for 6 hours when compared with the control. The increase was much higher with the seeds soaked in the former than in the later solution. Both soil and fertilizer phosphorus taken up by alfalfa increased by seed soaking in the above mentioned solutions and the increase was most pronounced in the fraction that derived from the soil.

SUMMARY A land classification dividing the forest area of Forestier Peninsula in south eastern Tasmania into two land systems, the Blackman land system and the Murdunna land system, and several land units is described. Results from a trial to evaluate four component units of the land classification for establishment of a radiata pine plantation indicate different growth rates, nutrient deficiencies and responses on different units. On three of the four units there was a growth response to application of phosphorus and an interaction of nitrogen and phosphorus. On the fourth unit there was no growth response to application of phosphorus alone but there was a response to application of nitrogen and phosphorus together. Without treatment, radiata pine trees growing on the Murdunna land system had extremely low foliar concentrations of phosphorus, nitrogen and copper. On only one land unit was growth satisfactory without fertilizer.

Three cutting heights, 2±5, 7±6 and 12±7 cm (1, 2±5 and 5 in.) and three levels of fertilizer N, 168, 280 and 392 kg N/ha (150, 250 and 350 Ib N/ac) were imposed on a sward of Italian ryegrass (Lolium multiflorum) cv. Irish. Lowering the cutting height and increasing the level of applied N increased the yield of herhage DM. Increasing the level of applied N had a greater effect on the chemical composition of the herbage than altering the cutting height

SUMMARYPangola grass grown with and without sulphur fertilizer was cut as a 7-week regrowth to measure voluntary intake and digestibility by sheep. To determine the extent of a simple sulphur deficiency half the sheep on each feed were supplemented with 0·6 gsulphur daily. Retention time of feed in the reticulo-rumen and proportion of feed digested anterior to the duodenum was also determined.Sulphur fertilizer increased the sulphur content of the pasture from 0·09 to 0·15%, voluntary intake of dry matter from 44·4 to 64·1 g/kg W0·75/day and dry-matter digestibility from 55·2 to 60·2%. Sulphur fertilizer reduced the retention time in the reticulo-rumen by 16% and increased the extent of dry-matter digestion before the duodenum from 13 to 34%.Feeding a sulphur supplement increased dry-matter digestibility of the low sulphur feed to that found with sulphur fertilized pangola grass but only accounted for 63% of the difference in voluntary intake.It was concluded that fertilizer sulphur leads to large increases in both voluntary intake and digestibility of sulphur deficient grass and that the improvement in nutritive value may be more than can be achieved by feeding a sulphur supplement.

The effect of uncertainty due to imperfect information on the decision to adopt fertilizer responsive seed varieties is examined. Additional information and enhanced ability to "decode" information are shown to increase the likelihood of adoption. Relevant empirical evidence for the Philippines is summarized.

The leaf concentrations of N, P, and K were primarily influenced by the respective fertilizer nutrient, except P, vhich also was influenced by the fertilizer N. Increasing rates of the nutrients well above those recommended for normal corn production increased the leaf nutrient concentrations, but not yields after the first increment of fertilizer. The effect of dry veather reduced yields 0.7 quintals per hectare per day and also vas negatively correlated with the leaf N and leaf P concentrations (0.01 probability level).

Tomatoes1) Tomatoes, cv.‘Shin-Hogyoku No. 2’were grown under constant temperature regimes of 17, 15 and 13°C and at two levels of N, P and K in 1964 to study the interaction of those factors on the differentiation and subsequent development of flower buds.2) The plant growth both in bed soil at 2(NPK) (high level of fertilizer) and in volcanic loam at NPK (low level of fertilizer) was promoted at 17°C and restricted in the lower temperature ranges of 15 to 13°C. The seedlings in the 2(NPK) plot grown under the same temperature were larger than those in the NPK plot. The growth was found to be most remarkable at 17°C in the high level of fertilizer as in the previous report (7).3) The differentiation and its subsequent development of flower buds both in bed soil at 2(NPK) and in NPK plots were accelerated at 17°C and retarded in the lower temperature ranges of 15 to 13°C.4) The differentiation and its subsequent development of flower buds in bed soil at 2 (NPK) plot were earlier than those at NPK plot. The most favorable conditions for them were combination of temperature range of 17°C and high level fertilizer (bed soil at 2(NPK)).5) The number of flower buds per plant was increased at 17°C in high level of fertilizer (the bed soil at 2(NPK)) plot, and decreased at the lower temperature of 15 to 13°C. At the lower level of fertilizer (NPK) plot, it was fewer and there was no difference among the temperature ranges of 17, 15 and 13°C.6) From the results in 1963 and 1964 of tomatoes, it was found that effect of high level of fertilizer on the growth, the differentiation and development of flower buds were most marked at 17°C in the temperature ranges from 30 to 13°C (30, 24, 17, 15 and 13°C).Eggplants1) Eggplants, cv.‘Kisshin No. 2’were grown under constant temperature regimes of 30, 24, and 17°C and two levels of N, P and K in 1965 to study the interaction of those factors on flower bud differentiation and their subsequent development.2) The plant growth both in bed soil at 2(NPK) and in volcanic loam at NPK was promoted most remarkably at 30°C and restricted in the temperature ranges of 24 to 17°C. The seedlings in the 2(NPK) plot were larger than those in the NPK plot.3) The differentiation and its subsequent development of flower buds both in bed soil at 2(NPK) and NPK plot were promoted at 30°C and retarded in the temperature ranges of 24 to 17°C.4) The differentiation and its subsequent development of flower buds in the 2(N PK) plot were earlier than those in the NPK plot. The morphological differentiation of flower buds was not found at the temperature of 17°C in low level of fertilizer (NPK) in this experiment.5) The number of flower buds both in bed soil at 2(NPK) and in NPK was greatest at 30°C and fewer at 24 and 17°C. The 2(NPK) plot had much more flower buds than the NPK plot.6) In case of eggplants, the effect of high level of fertilizer on growth and the differentiation, development and number of flower buds was small under the low temperature of 17°C, but it was very great under the high temperature of 30°C.

Biomass and nutrient content of natural stands of northern hardwood regeneration were measured 4 years after clearcutting. Pin cherry and shrubs made up a significant proportion of the biomass in both unfertilized and fertilized stands. Yet these stands are well stocked with large numbers of desirable commercial species, especially paper and yellow birch. However, fertilizer greatly stimulated pin cherry to the detriment of the commercial species. Paper birch was the only commercial species to increase in average dry weight on the fertilized area.

An experiment using 40 lactating dairy cows was conducted for 3 successive years to examine the effects of fertilizer N applied at 400 and 700 kg/ha (358 and 627 lb/ac) at stocking rates of 4.94 and 7.41 cows/ba (2 and 3 cows/ac). The animals were grazed in groups of 10 per treatment, using a fixed rotational grazing system, for 22 weeks in each year. Milk ontput/cow and/ha was significantly affected by stocking rate, the mean milk outputs being 2499 and 2218 kg/cow (5498 and 4880 lb/ cow) and 12313 and 16396 kg/ha (11032 and 14691 lb/ac) at the lower and higher stocking rates, respectively. Milk yield/cow at the lower stocking rate was not affected by N level. At tbe higher stocking rate, increasing the amount of N resulted in a 7.4% increase in milk output/cow and/ha. This response to N declined from 1.7% in the first year of the trial to 2.4% in the third year. The response in milk yield to N appeared to he greatest during the first part of the grazing season. Milk composition, liveweight change, and herbage availahilities and intakes were also recorded.

Spinach was grown in the greenhouse in soil with the pH adjusted to 5.0, 5.5, 6.0, 6.5, and 7.0, N fertilizer rates of 0, 50 and 200 mg N/Kg soil, and Mo fertilizer rates of 0, 0.3 and 1.2 mg Mo/Kg soil. The NO3‐N concentration of the tissue increased with fertilizer N or a rise in pH from 5.0 to 7.0. The addition of Mo at either rate reduced the NO3 concentration of spinach grown at pH 5.0 and 5.5 but had no effect on plants grown at pH 6.5 or 7.0. At pH 6.0 the 1.2 mg Mo/Kg soil rate was effective at the 50 and 200 mg N/Kg soil fertilizer rates but had no effect on spinach grown without a N application. At the same pH, the 0.3 mg Mo/Kg soil rate had no effect on NO3 content of spinach grown with the 50 mg N/Kg rate but did reduce the NO3 content of spinach grown without N added or with the 200 mg N/Kg soil. The 1.2 mg Mo/Kg soil rate was more effective than 0.3 mg Mo/Kg rate in reducing NO3 content of spinach grown with 200 mg N/Kg soil at pH 5.0–6.5 inclusive but gave variable results when no ...

A comparison of steer performance, as measured by body weight gains, carcass weight and quality, from ladino clover-timothy or grass pastures was carried out. Two pasture management systems were used, an extensive one with a stocking rate of 1.85 heads/ha and a moderate rate of fertilizer application, and an intensive one with stocking rate of 3.70 heads/ha and a heavy fertilizer application. Steer development followed a linear trend throughout the grazing season and steer growth was slower on the intensively managed timothy-ladino pastures than on the other pastures. The liveweight gains of the animals, per head, over the season was 10.3% greater on the grass swards than on the timothy-ladino swards, and 7.7% greater on the pastures under an extensive management system than on the other ones. Increase in stocking rate was not completely compensated for by heavy fertilization of pastures since steers grazing on high stocking rate pastures did not gain weight as rapidly as the ones on low stocking rate pastures. The amount of beef meat produced per steer (233 kilos) was not influenced by treatments. Beef carcasses from 3.70 head/ha pastures were as heavy as the ones from 1.85 head/ha pastures indicating that high stocking rate effect was balanced out by doubling the amount of fertilizers applied to pastures.

SummaryThree experiments (1970–2) on calcareous sandy loan tested all combinations of four plant densities (18500–124000 plants/ha), two amounts of potassium (0, 156 kg/K/ha) and sodium (0, 247 kg/Na/ha) fertilizer and two watering treatments on yield and chemical composition of sugar beet. The main effects of the treatments in all three experiments confirmed that at least 75000 plants/ha were needed for maximum sugar yield, that sodium fertilizer increased sugar yield more than potassium (+0.76 and +0.29 t/ha respectively) and that the crop responded to irrigation in some years (+1.35 t sugar/ha in 1970 and +1.67 t/ha in 1972).Analysis of the growth of the crop showed that increasing the plant density increased leaf growth per unit area from singling onwards and giving irrigation increased it from July; the effects persisted until harvest and were reflected in increased sugar yields. Fertilizer increased leaf growth early in the season but the effect disappeared later, although sugar yield was still increased. Interactions between plant density, fertilizer treatment and irrigation were small every year but there were some consistent effects on sugar yield. The results suggest that in commercial practice the optimum density is 75000 plants/ha; where irrigation is not practised, 247 kg/ha of sodium and 70 kg/ha of potassium fertilizer should be given. Where irrigation is applied, only 247 kg/ha of sodium needs to be given as the extra water increases the uptake of soil potassium.

A clonal line of orchard grass (Dactylis glomerata L.) was fertilized during early spring of 1972 with a fertilizer consisting of a mixture of KCl, MgSO4, K2HPO4, CuSO4, ZnSO4, and MnSO4. At mid-anthesis, shoots from unfertilized and fertilized plants were separated into the inflorescence and the individual leaf blades, leaf sheaths, and internodes. Tissues were analyzed for elements to ascertain distribution in the individual shoot parts and whether differential accumulation occurred among shoot parts with fertilization. No significant difference existed between unfertilized and fertilized plants in dry matter (DM) yields of comparable shoot parts or in length of the inflorescence or internodes. Fertilization with K, Cl, S, P, Mg, Zn, Mn, and Cu increased the concentration of these elements more in one plant fraction than in another, except for P and Cu. Concentrations in the inflorescence were not influenced by fertilization, except for an increase in Zn and Mn. With fertilization, largest increases in concentrations of Cl and Zn occurred in the total leaf blades, in the total internodes for K, and in the total sheaths for Mg. Increases in S and Mn were similar in both the total leaf blades and sheaths. Concentrations of N were increased in all plant fractions of fertilized plants, even though N was applied uniformly to all plants, presumably because S was applied in the mineral mixture. Highest concentrations of K, S, Mg, Cu, N, Ca, Fe, and Al in both unfertilized and fertilized plants occurred in the total leaf blades. Highest concentrations of Cl and Mn occurred in the total leaf sheaths and for P, Zn, and B in the inflorescence. Concentrations of Ba were similar in each of the plant fractions. Elemental distribution among the leaf blades, leaf sheaths, and internodes of the shoot are discussed.

In direct seeded tomato density experiments with constant rectangularity of 1.0 carried out at Preston and Simcoe Research Stations, Ontario, Canada in 1971, the effect of increasing plant density from 4.2 to 62.1 plants/m2 was to increase total plant weight, total fruit weight and ripe fruit weight per unit area. The proportion of ripe fruit to total fruit increased with increased density, and ripe fruit yields from a single harvest of up to 14 kg/m2 were obtained. Using the reciprocal yield-density equation 1 W = Aϱ + B (when W is the mean weight per plant (or plant part) at density ϱ, A and B are constants, and density is the only variable) to analyse the experiments, showed that both the A and B constants were influenced by cultivar while the A constant was influenced more by fertilizer application than was the B constant. In general the effect of increased fertilizer was to increase the yield potential ( 1 A ) for total plant weight and total fruit weight, but this effect was not so marked for ripe fruit weight.

The reciprocal yield/density equation 1 w = α + βϱ (when w is the mean weight per plant, or plant part, at density ϱ, and α and β are constants when ϱ is the only variable) was used to interpret the results of two plant density experiments with populations ranging from 15–280 plants/m2. In a fertilizer experiment the level of fertilizer used had a major effect on the β parameter, while the α parameter was influenced mainly by harvest date. In a cultivar/rectangularity experiment no effect of rectangularity was detected, and the cultivar mainly affected the α parameter, the β parameter being not significantly different between cultivars. Density was shown to have a major effect on the yield/tenderometer relationship. Yields in excess of 9.9 tonnes/ha (8 800 lb/acre) at a tenderometer reading of 120 (T120) were obtained.

When averaged over a wide range in soil nitrogen and moisture conditions, cultivar differences in yield and protein content of non-inoculated field peas (Pisum sativum L.) were relatively small. The inherent differences in seed weight were responsible for most of the variations in yield among the three cultivars. Nitrogen fertilization in the growth room experiment markedly increased plant weight, seed yield and protein content, and water-use efficiency was substantially improved. When maintained within the upper half of the available range, soil moisture supply had only a limited influence on plant growth. Periodic wilting did cause a severe reduction in plant weight and seed yield, but there was little change in protein content. For these fertilizer and moisture treatments, responses in seed yield were primarily due to changes in number of pods per plant; the seeds per pod and seed weight were relatively stable. It appeared that field peas were efficient converters of soil nitrogen to seed protein and, in the absence of nitrogen-fixing bacteria, nitrogen fertilization was the principal factor influencing the protein content of field peas. The correlation coefficient between yield and protein content was very low.