High Fertility Sites Research Articles

The structure and dynamics of old-growth Pinus sylvestris (L.) stands in the Wigry National Park, north-eastern Poland

The paper describes the structure and the developmental trends of old-growth Pinus sylvestris stands in the Wigry National Park, in north-eastern Poland. The stands represent a transitional zone between deciduous forests of Central Europe and boreal, coniferous forests of north-eastern Europe. Besides P. sylvestris, the most important tree species are Picea abies and Quercus robur. Among the subcanopy species, Corylus avellana and Sorbus aucuparia occur most frequently. On the basis of the data from 6 permanent sample plots (total size: 1.90 ha), several parameters and stand indices are analysed including species composition of the canopy and the regeneration, diameter distribution, age structure of main tree species, and the relationship between canopy and spatial dispersion of woody regeneration. The most striking feature of the stands studied is the almost complete absence of natural regeneration of P. sylvestris. This seems to be in contradiction with the apparently natural origin of this species in the stands, and a common occurrence of natural disturbances resulting in openings and gaps in forest canopy. The main tree species replacing P. sylvestris in the canopy are P. abies and Q. robur. Also increasing are some broad-leaved species typical of high fertility sites: Acer platanoides, Tilia cordata, Ulmus glabra, and Fraxinus excelsior. A shrub C. avellana occurs extensively competing with tree species and delaying tree replacement processes. While no direct data on the changes in the site conditions can be provided and the ‘recovery’ hypothesis appears to be the most straightforward explanation of the changes in P. sylvestris stands, the possible role of the allogenic changes in environmental conditions (climate warming, nitrogen deposition) is also discussed.

An in situ mini lysimeter with a removable ion exchange resin trap for measuring nutrient losses by leaching from grazed pastures

This study describes the construction, installation and evaluation of an in situ mini-lysimeter with a removable ion exchange resin trap for measuring nutrient losses by leaching from grazed pastures. The resin trap efficiently removed solutes from simulated drainage water at a flow rate of 14 mm h-1. Over 88% of each of the solutes was removed from synthetic nutrient solution containing 1.65 mM nitrate-N, 1.65 mM ammonium-N, 0.25 mM sulfate-S (SO2-4-S) and 0.6 mM potassium. In a further test of the system, sulfate leached in simulated rainstorm events from two undisturbed soil cores, taken from legume based pastures of contrasting superphosphate (SSP) fertilizer history following 495 mm of simulated rainfall, was all recovered using the resin trap. Seven times more SO2-4 (21.2 kg S ha-1) was leached and recovered from the resin trap of the core collected from the high fertility (HF, 375 kg SSP ha-1 year-1) site than from the low fertility (LF, 125 kg SSP ha-1 year-1) site (3.1 kg S ha-1). As part of the field evaluation of the technique, lysimeters with resin traps were placed in the field at four sites (8 lysimeters/site) contrasting in fertilizer history, landslope, and dung and urine return. Two additional lysimeters with drainage collection reservoirs (vessels) and eight soil solution samplers were placed on each site to collect drainage water and soil solution. The amount of SO2-4 present in drainage water was more closely related (1:1, R2 = 0.861) to the amount of SO2-4 collected by the resin traps over a period of 9 months than estimates made using soil solution samplers (1:1, R2 = 0.829). The advantages of the resin trap technique over alternative methods for estimating SO4-S leaching losses from field soils are discussed, as are applications of the technique for studying nutrient losses and cycling in grazed pastures.

Forage potential of wild populations of perennial ryegrass collected from southern New Zealand farms

A ryegrass breeding programme to improve the cool season activity and summer quality of perennial ryegrass (Lolium perenne L,) in southern regions was initiated in 1986. One of the strategies assessed wild ryegrass populations from 50 dairy and sheep farms in Southland, West Otago and Westland. The plants were collected and evaluated as spaced plants in a high and low fertility site at DSIR Grasslands Gore in comparison with current ryegrass cultivars. Principal Component Analysis was used to order the performance of the ryegrass populations in relation to the observed characters of seasonal growth, tillering, crown rust infection, recurrent ear emergence and endophyte presence. Ihe collection consisted of many short-leaved densely tillered prostrate plants with high levels of crown rust infection and recurrent flowering. In comparison the cultivars had fewer, but larger tillers, rapid leaf extension and good rust tolerance. There were no strong distinguishing features between plants from dairy and sheep farms and 30% of plants had no endophyte. Selected ecotypes hybridised with New Zealand and European cultivars produced plants with better cool season growth and summer quality than standard cultivars. The ecotype germplasm is an important source in the development of new cultivars suited to the southern region. Keywords plant evaluation, Lolium perenne, ryegrass hybrids, southern New Zealand ecotypes

Response of six-row barley to N and P2O5 fertilizer application in high fertility sites in Central Alberta

Two series of N and P2O5 fertilizer response trials were conducted at a total of five sites in Central Alberta in 1985 and 1986 to determine whether a range of barley (Hordeum vulgare) cultivars differed in their response to high levels of fertility application under high-yielding conditions. The cultivars included were two semidwarf (Samson, Duke) and three of conventional height (Leduc, Klondike and Johnston). No cultivar × fertility level interaction was obtained for grain yield in any of the trials, although significant interactions of minor magnitude were found for other agronomic traits in some trials. The most important of these traits was extent of lodging which was at a low level (less than 3 on the 0.2–9 Belgian Scale) in all trials, despite average grain yields ranging from 4000 to 6289 kg ha−1. Lodging was more severe in Johnston than in the other cultivars. Yields of the semidwarf s were no higher than those of Leduc in any trial, although minor lodging occurred for Leduc in some cases. Lack of significant cultivar × fertility interaction may be partially explained by the general lack of response to the higher fertility levels that were used, although good yield response was found to addition of 45 kg ha−1 of P2O5 in four of six trials, and to addition of up to 90 kg ha−1 of N in three of the six trials. No significant correlation was found between initial soil test N and P2O5 versus the mean year-site yield for different locations, suggesting that factors other than base soil fertility were more important in determining site-year yield potential. These results suggest that use of individualized fertilizer recommendations for targeting maximum yield for any of the cultivars studied is not warranted, since the cultivars demonstrated similar yield responses. The excellent straw strength advantage of the semidwarf cultivars was reconfirmed under these high yielding conditions, but yields over 6000 kg ha−1 with several taller cultivars were also recorded without lodging (e.g. Leduc). Key words: Target yields, lodging, Intensive Crop Management®, cultivar specific fertilizer recommendations

Temporal variations in some plant and soil P pools in two pasture soils of widely different P fertility status

Temporal variations in plant production, plant P and some soil P (and N) pools were followed over 21 months in two New Zealand pasture soils of widely different P fertility status. Plant growth rates, and herbage composition at the high-fertility site, were closely linked to soil water use, with growth rates falling when soil water deficits exceeded 60 mm. Herbage P concentrations reflected P fertility, and varied with season, being generally higher in winter and lower in summer.

High‐ vs. Low‐Stress Yield Test Environments for Selecting Superior Soybean Lines

An important factor in cultivar development is the choice of yield testing sites that permit the best discrimination among breeding lines. The objectives of this study were to test the hypotheses that: (i) there are genotypes that have superior yield potential in both low‐ and high‐stress edaphic conditions, and (ii) yield tests conducted exclusively in low‐stress environments can be used effectively for selecting such genotypes. Forty‐eight random F4‐derived soybean [Glyciue max (L). Merr.] lines were evaluated for yield over 4 yr on a low soil acidity, high fertility site (low‐stress) and on a high soil acidity, low‐medium fertility site (high‐stress) at each of two locations (Crossville and Milan, TN). In addition, low‐stress yield tests were conducted at five other locations during each of the last 2 yr. The grand mean of low‐stress tests was 2.25 Mg ha−1 compared to 0.62 Mg ha−1 for high‐stress tests. The 16 lines (33% selection intensity), which had overall mean yields above the grand means of combined high‐ and combined low‐stress tests were designated as the superior lines. Simulated selections revealed that 32 to 54% of the superior lines would have been selected using either type of nursery at either the Crossville or Milan location each year. At least one of the top three lines would have been chosen in every case, regardless of type(s) of nursery environment, location(s), or year(s) used. These results indicate that the low‐stress environments commonly used in soybean breeding programs should provide high probabilities for selecting genotypes that have superior yield potential in both low‐ and high‐stress edaphic conditions. Regression coefficients for line mean yield regressed on site mean were generally highest for the superior lines (b ≥ 1.0), but the deviations from regression were similar to the non superiors. The ranges for maturity and plant height were similar for both groups indicating that selection for superior lines would not have led to extremes for either trait.

Effects of establishment method, seeding rate and soil fertility on the growth and persistence of a prairie grass pasture in the Waikato

The production and persistence of 'Grasslands Mama prairie grass were compared when direct drilled or oversown at a low or high seeding rate, and with or without extra fertiliser before planting. To estimate possible effects of insects on prairie grass persistence, insecticide was applied to a small area. Prairie grass growth during the first winter/spring was greater when direct drilled than when oversown, but thereafter treatment effects disappeared. High seed rate plots maintained higher prairie grass plant and tiller densities than low seed rate plots during the first year, but this did not affect annual herbage accumulation, Two years from sowing, prairie grass plant and tiller densities had declined to a low level in all plots. At this time, prairie grass tiller density and prairie grass content (% of DM) in insecticidetreated areas were about twice those in untreated areas. Mean total annual herbage accumulation in the second year had declined by 21% compared with the first. This work shows that prairie grass does not require extra fertiliser at planting when sown into a well maintained high fertility site, and that direct drilling at a low seed rate produces results similar to those of the traditional method of establishment of oversowing at a high seed rate. Insect attack contributed to poor prairie grass persistence. Keywords Bromus willdenowii Kunth, oversowing, direct drilling, pasture botanical composition, major element composition, tiller density, insect damage, annual herbage accumulation, root yields

Site fertility affects seasonal carbon reserves in loblolly pine

Concentrations of nitrogen, phosphorus and total non-structural carbohydrates were examined in loblolly pine foliage from control stands and stands fertilized with sludge containing 450 kg N ha(-1). Needles from the fertilized sites had higher N concentrations regardless of needle age. Fertilization increased P concentration in needles relative to the control sites. Seasonal patterns of change in sugar concentrations were similar among sites for both current-year and one-year-old needles, the highest concentration (126 mg g(-1)) occurring in February. Sugar concentrations were lowest in June and were generally lower in current needles than year-old needles. Starch concentrations and the amount of starch per fascicle varied both seasonally and among sites. Fertilization increased starch reserves in current needles at the end of the growing season (7 mg g(-1) and 14 mg g(-1) for the control and fertilized sites, respectively), and increased the rate of starch mobilization during the initiation of needle growth. In the growing season, starch concentrations were lower in current foliage from high fertility sites than low fertility sites. Carbon reserves accumulated during the growing season in mature one-year-old needles from control sites indicating a lower sink strength for carbon under low nutrient conditions. There was a positive relationship between starch and nitrogen concentrations during the dormant season whereas the relationship was negative during the growing season. The magnitude and direction of change in starch reserves with the onset of growth following the dormant season may indicate nutrient limitation and potential growth response to fertilization.

SEASONAL NUTRIENT DYNAMICS, NUTRIENT RESORPTION, AND MYCORRHIZAL INFECTION INTENSITY OF TWO PERENNIAL FOREST HERBS

Patterns of mycorrhizal infection, seasonal foliar nutrient concentrations, nutrient allocation to shoots and rhizomes, and nutrient resorption were measured in relation to soil nutrient availability in two species of perennial forest herbs, Geranium maculatum L. and Polygonatum pubescens Pursh., in four forest stands in southern and central Ohio. The percentage of plants with V‐A mycorrhizae and the proportion of root length colonized by VAM structures increased with decreasing nutrient availability in both species. Foliar N and P concentrations in plants from lower fertility sites were as high, or higher, than those in plants from higher fertility sites; as a result, tissue nutrient enrichment ratios (foliar concentration/soil available concentration) increased with decreasing fertility. Proportional resorption of N and P generally decreased with decreasing nutrient availability, a pattern inconsistent with those exhibited by woody plants in these forest stands. We hypothesize that the inverse relationship between nutrient uptake efficiency (via mycorrhizae) and nutrient use efficiency (resorption) exhibited by these forest understory herbs, but not by trees or herbs from high‐light environments, may be related to low‐light limitation of energy reserves in the forest understory.

The effect of soil nitrogen on grain legume yield and nitrogen fixation

SUMMARYTwo field experiments examined the influence of soil nitrogen on grain yield, wateruse efficiency and residual nitrate accumulation of four winter grain legumes in a legume–fallow–wheat rotation. In the first experiment, conducted on a clay soil with a high total soil nitrogen content (0·194%), the three legumes Cicer arietinum, Vicia faba and Pisum sativum gave similar yields, with Lupinus angustifolius showing poor yields. Water-use efficiencies followed similar trends to the grain yields. Wheat yields and concentration of nitrogen in the grain, following a fallow after the legume crops, showed no differences from a full 2-year fallow. In the second experiment on a low fertility soil (0·081 % total soil nitrogen), Cicer arietinum gave the highest yield and the greatest water-use efficiency. All legumes and long fallow resulted in a similar increase in wheat yield when compared with a wheat-fallow-wheat rotation. The legume crops generally increased soil nitrate status between their sowing and the sowing of a wheat crop 2 years later; such increases were greatest with Pisum sativum at the high fertility site, with a suggestion of the reverse occurring at the low fertility site.

Comparative Rents for Farmland and Timberland in a Subregion of the South

AbstractThis study compares equivalent annual rents for two alternative land uses in a region where farming and timber plantations coexist. The comparison is motivated by the possibility that rising timber prices may stimulate timber processors to compete for farmland. Prices, costs, and market rents are assumed to first follow existing trends and then to reach steady state values. Market rents are projected and capitalized for agriculture. Internal soil rents are capitalized for timber. The results show timber to have a comparative advantage on high fertility sites and suggest that timber might become a competitive land use at the intensive margin of the region's farmland base.

BIONOMICS OF PLATYLYGUS LURIDUS (HEMIPTERA: MIRIDAE) IN WISCONSIN JACK PINE SEED ORCHARDS

AbstractPlatylygus luridus (Reuter) causes conelet abortion and reduces seed production in jack pine, Pinus banksiana Lamb., seed orchards in northern Wisconsin. One generation a year occurs and the insect overwinters as an egg that hatches during late May. The nymphs pass through 5 instars within 5 to 6 weeks. Adults were abundant during July and early August 1982. Eggs were laid singly within the phloem tissues of current year's shoots just below the bases of needle fascicles. The nymphs fed predominantly on the tender tissues of shoots or needles. The adults preferred to feed on ovules in the conelets, and conelet abortion resulted. About 74% of the total abortion occurred during adult feeding periods. Conditions favoring P. luridus population increases in the jack pine seed orchards included: densely planted seed orchards on high fertility sites; trees 6 to 10 years old with closed crowns or in shade; vigorously growing trees that were well watered and fertilized. Natural enemies included predators Deraeocoris albigulus, D. (possibly) laricicola, Evarcha nr. hoyi, and Misumenops asperatus.

Field trials assessing the effect of inoculating agricultural soils with endomycorrhizal fungi

SummaryFour field experiments were established to gauge the effect of inoculating white clover with selected strains of vesicular-arbuscular mycorrhizal (VAM) fungi. The four sites chosen ranged in fertility from undeveloped, phosphorus-impoverished tussock grassland to high fertility alluvial flats. As far as practicable conventional agronomic practices were followed prior to and during sowing. The soils were otherwise untreated and contained the normal complement of indigenous VAM fungi. Infested soil pellets were used to introduce the fungi into the soils as this was considered more appropriate to pastoral farming than for example transplanting infected seedlings.Initially the introduced fungi tended to have little or no effect on dry-matter yields but by the end of the first season there were significant responses to Gigaspora margarita, Glomus mosseae, Glomus macrocarpum or a mixed inoculum of Glomus pallidum and Glomus tenue. In the second season, dry-matter yields were increased on the two tussock grassland sites by up to 760 kg D.M./ha (ca. 30%), 825 kg D.M./ha on the moderately fertile site (14%) and 640 kg D.M./ha (5%) on the high fertility site. The growth responses tended to decrease with time probably owing to the spread of fungi from the inoculated to the control plots though growth responses were still present at the end of the 3rd year on two of the sites. Within each experiment the application of up to 50 kg P/ha per year did not reduce the size of the responses to inoculation. This and herbage chemical analyses suggested that a more efficient use of phosphatic fertilizers may have been only part of the reason for the responses to inoculation.

Effect of soil fertility, weed competition, defoliation and legume seeding rate on establishment of tropical pasture species in south-east Queensland

An experiment was sown at two contrasting sites in south-east Queensland to study the response of tropical pasture species in the establishment and second year to treatments imposed during the establishment year. Sowing was into fully prepared seed-beds on a nitrogen deficient low humic gley at Beerwah and a fertile prairie soil at Samford. Limiting nutrients, other than nitrogen, were supplied by fertilizer. The treatments were: two pastures (Macroptilium atropurpureum cv. Siratro/Setaria anceps and Desmodium intortum cv. Greenleaf/setaria anceps), three legume seeding rates, two defoliation systems in the establishment year, and presence or absence of severe annual grass weed competition. In the establishment year there were large treatment effects on the yields of sown pasture species. Sown weeds had a great effect, particularly on the high fertility site where they reduced setaria, desmodium and siratro yields by factors of approximately 50, 10 and 2 respectively. Legume yields increased with legume seeding rates. The sum of legume yields from the regularly cut treatments was only one-half to one-quarter that of the single end of season cut, whereas total grass yields were similar in both treatments. However, all first year treatments had much less effect in the second year, when legumes comprised about 70 per cent of mixtures at the low fertility site and 30 per cent of mixtures at the high fertility site. Some comments are made about this role of soil fertility in the dynamics of pasture establishment and about future lines of research. Results from this and other experiments suggest that pasture establishment problems on fully prepared seed-beds are not a major limitation to the wider use of tropical pastures in south-eastern Queensland.

Response by wheat to phosphorus and nitrogen, with particular reference to 'haying-off'

Heron wheat was grown with four levels of phosphorus (as superphosphate) and five levels of nitrogen (as ammonium sulphate) on two pairs of sites in the Riverina of New South Wales, to examine the 'haying-off' phenomenon. Within each pair of sites there was a large difference in soil fertility, as a result of contrasting pasture and cropping histories. Various attributes of crop growth and yield were measured. The crops responded more to phosphorus than to nitrogen. Phosphorus increased grain yield on two sites, and 1000-grain weights on all sites ; nitrogen increased grain yield on one very nitrogen-deficient site, and decreased 1000-grain weights on all sites. In each pair of sites, vegetative growth was considerably greater on the higher fertility one ; however, the difference in grain yield was much less. The failure of the crops on the higher fertility sites to achieve the grain yield potential indicated by their vegetative growth, is possibly an expression of the phenomenon commonly called haying-off. In the absence of adequate soil and plant moisture measurements, it cannot be stated unequivocally that the observed possible expression of haying-off was caused by a soil moisture deficiency induced by increased vegetative growth responding to higher fertility. The nature of the responses to phosphorus and nitrogen on the individual sites suggests that other factors besides induced moisture deficiency may be involved.