Turfgrass (Cynodon dactylon L.) sod production on sandy soils: I. Effects of irrigation and fertiliser regimes on growth and quality

The effects on growth, quality and N uptake by turfgrass (Cynodon dactylon L.) during sod production of four fertiliser types applied at three application rates (100, 200 or 300 kg N ha⁻¹ per ‘crop’) under two irrigation treatments (70% and 140% daily replacement of pan evaporation) were investigated. The fertiliser types were: water-soluble (predominately NH₄NO₃), control-release, pelletised poultry manure, and pelletised biosolids; and the experiment was conducted on a sandy soil in a Mediterranean-type climate. Plots were established from rhizomes, with the turfgrass harvested as sod every 16–28 weeks depending upon the time of the year. Four crops were produced during the study. Applying water-soluble and control-release fertilisers doubled shoot growth and improved turfgrass greenness by up to 10% in comparison with plots receiving pelletised poultry manure and pelletised biosolids. Nitrogen uptake into the shoots after four crops (averaged across irrigation treatments and N rates) was 497 kg N ha⁻¹ for the water-soluble fertiliser, 402 kg N ha⁻¹ for the control-release, 188 kg N ha⁻¹ for the pelletised poultry manure and 237 kg N ha⁻¹ for the pelletised biosolids. Consequently, the agronomic nitrogen-use efficiency (NAE, kg DM kg⁻¹ N applied) of the inorganic fertilisers was approximately twice that of the organic fertilisers. Increasing irrigation from 70% to 140% replacement of pan evaporation was detrimental to turfgrass growth and N uptake for the first crop when supplied with the water-soluble fertiliser. Under the low irrigation treatment, inorganic N fertilisers applied at 200–300 kg N ha⁻¹ were adequate for production of turfgrass sod. Section Editor: P. J. Randall     

Deep placement of Mn fertiliser on a sandy soil increased grain yield and reduced split seed in Lupinus angustifolius

Experiments were conducted over two years with Lupinus angustifolius L. on a site with acid sandy soil near Esperance, Western Australia to determine if deep placed manganese fertilizer increases lupin grain yield. Manganese at 4 and 8 kg ha⁻¹ was placed below the surface immediately before sowing at 4, 20 and 30 cm and 4, 8, 12, 16 and 20 cm in 1987 and 1988 respectively. Foliar Mn applied at 1 kg ha⁻¹ when the first order laterals were in mid-flowering stage, was also compared. Increasing the depth of Mn placement increased grain yield in both years. The deepest placed Mn increased grain yields by 255 kg ha⁻¹ (10%) and 430 kg ha⁻¹ (106%) in year 1 and year 2 over the shallow (4 cm) placed Mn. The higher responses to deep placed Mn occurred in year 2, the year with the driest spring and most intense aphid infestations. Foliar applied Mn was as effective as most deep placed Mn treatments, except for the highest rate (8 kg ha⁻¹) at the greatest depth (20 cm) in year 2. The higher rate of applied Mn gave the best grain yields. This revised version was published online in June 2006 with corrections to the Cover Date.     

Carbon, nitrogen and phosphorus in volcanic soils following afforestation with native birch (Betula pubescens) and introduced larch (Larix sibirica) in Iceland

Afforestation has become an important tool for soil protection and land reclamation in Iceland. Nevertheless, the harsh climate and degraded soils are growth-limiting for trees, and little is know about changes in soil nutrients in maturing forests planted on the volcanic soils. In the present chronosequence study, changes in C, N and total P in soil (0–10 and 10–20 cm depth) and C and N in foliar tissue were investigated in stands of native Downy birch (Betula pubescens Enrh.) and the in Iceland introduced Siberian larch (Larix sibirica Ledeb.). The forest stands were between 14 and 97 years old and were established on heath land that had been treeless for centuries. Soils were Andosols derived from basaltic material and rhyolitic volcanic ash. A significant effect of tree species was only found for the N content in foliar tissue. Foliar N concentrations were significantly higher and foliar C/N ratios significantly lower in larch needles than in birch leaves. There was no effect of stand age. Changes in soil C and the soil nutrient status with time after afforestation were little significant. Soil C concentrations in 0–10 cm depth in forest stands older than 30 years were significantly higher than in heath land and forest stands younger than 30 years. This was attributed to a slow accumulation of organic matter. Soil N concentrations and soil P_tot were not affected by stand age. Nutrient pools in the two soil layers were calculated for an average weight of soil material (400 Mg soil ha⁻¹ in 0–10 cm depth and 600 Mg soil ha⁻¹ in 10–20 cm depth, respectively). Soil nutrient pools did not change significantly with time. Soil C pools were in average 23.6 Mg ha⁻¹ in the upper soil layer and 16.9 Mg ha⁻¹ in the lower soil layer. The highest annual increase in soil C under forest compared to heath land was 0.23 Mg C ha⁻¹ year⁻¹ in 0–10 cm depth calculated for the 53-year-old larch stand. Soil N pools were in average 1.0 Mg N ha⁻¹ in both soil layers and did not decrease with time despite a low N deposition and the uptake and accumulation of N in biomass of the growing trees. Soil P_tot pools were in average 220 and 320 kg P ha⁻¹ in the upper and lower soil layer, respectively. It was assumed that mycorrhizal fungi present in the stands had an influence on the availability of N and P to the trees. Responsible Editor: Hans Lambers.     

Impact of long-term nitrogen addition on carbon stocks in trees and soils in northern Europe

The aim of this study was to quantify the effects of fertiliser N on C stocks in trees (stems, stumps, branches, needles, and coarse roots) and soils (organic layer +0–10 cm mineral soil) by analysing data from 15 long-term (14–30 years) experiments in Picea abies and Pinus sylvestris stands in Sweden and Finland. Low application rates (30–50 kg N ha⁻¹ year⁻¹) were always more efficient per unit of N than high application rates (50–200 kg N ha⁻¹ year⁻¹). Addition of a cumulative amount of N of 600–1800 kg N ha⁻¹ resulted in a mean increase in tree and soil C stock of 25 and 11 kg (C sequestered) kg⁻¹ (N added) (“N-use efficiency”), respectively. The corresponding estimates for NPK addition were 38 and 11 kg (C) kg⁻¹ (N). N-use efficiency for C sequestration in trees strongly depended on soil N status and increased from close to zero at C/N 25 in the humus layer up to 40 kg (C) kg⁻¹ (N) at C/N 35 and decreased again to about 20 kg (C) kg⁻¹ (N) at C/N 50 when N only was added. In contrast, addition of NPK resulted in high (40–50 kg (C) kg⁻¹ (N)) N-use efficiency also at N-rich (C/N 25) sites. The great difference in N-use efficiency between addition of NPK and N at N-rich sites reflects a limitation of P and K for tree growth at these sites. N-use efficiency for soil organic carbon (SOC) sequestration was, on average, 3–4 times lower than for tree C sequestration. However, SOC sequestration was about twice as high at P. abies as at P. sylvestris sites and averaged 13 and 7 kg (C) kg⁻¹ (N), respectively. The strong relation between N-use efficiency and humus C/N ratio was used to evaluate the impact of N deposition on C sequestration. The data imply that the 10 kg N ha⁻¹ year⁻¹ higher deposition in southern Sweden than in northern Sweden for a whole century should have resulted in 2.0 ± 1.0 (95% confidence interval) kg m⁻² more tree C and 1.3 ± 0.5 kg m⁻² more SOC at P. abies sites in the south than in the north for a 100-year period. These estimates are consistent with differences between south and north in tree C and SOC found by other studies, and 70–80% of the difference in SOC can be explained by different N deposition.     

Root growth,macro-nutrient uptake dynamics and soil fertility requirements of a high-yielding winter oilseed rape crop

Shoot growth, root growth and macro-nutrient uptake by a high-yielding (5t/ha grain) winter oilseed rape crop have been measured. Maximum rooting density in the top 20cm of soil was 9.4 cm cm⁻³ and roots reached a depth of at least 1.8 m. Maximum nutrient uptakes were 364 kg ha⁻¹ for N, 43 kg ha⁻¹ for P, 308 kg ha⁻¹ for K, 287 kg ha⁻¹ for Ca and 16 kg ha⁻¹ for Mg. A 30-day drought coincided with the flowering period and root and shoot growth, as well as nutrient uptake rates, were reduced. Nutrient concentrations in the soil solution necessary to sustain the nutrient fluxes into the root system by diffusive supply have been calculated. Peak values were in the range 10 μM for P to 87 μM for N, lower than the observed concentrations, and it was concluded that nutrient transport to roots was not a limitation to uptake by this rape crop.     

Total nitrogen and phosphorus balance sheet in a typic ustochrept soil under intensive cropping and fertilizer use

Summary Balance sheets were computed for total nitrogen and phosphorus in plough layer (0–15 cm) of a Typic Ustochrept soil under continuous multiple cropping for seven years (1971–72 to 1977–78) with a fixed rotation of pearl millet (Pennisetum typhoideum L.) wheat (Triticum aestivum L.) (Vigna sinensis Savi.) The treatments considered of soil test-based rates of N, P and K, applied both singly and in combinations together with farm yard manure, sulphur and zinc superimposed over optimum rates (100%) of NPK. Heavy, losses of N (762–899 kg ha⁻¹) occurred in the plots which received high rates of Nviz. 150% of recommended NPK and 100% NPK plus FYM. Application of N alone accelerated N losses whereas addition of P, PK, PKS to N minimised such losses. Enrichment of P (66 to 198 kg ha⁻¹) occurred in all phosphate-treated plots. A marginal net decrease (29–54 kg ha⁻¹) in P levels was observed in control and N alone treatments.     

The Impact of Nitrogen Placement and Tillage on NO, N2O, CH4 and CO2 Fluxes from a Clay Loam Soil

To evaluate the impact of N placement depth and no-till (NT) practice on the emissions of NO, N₂O, CH₄ and CO₂ from soils, we conducted two N placement experiments in a long-term tillage experiment site in northeastern Colorado in 2004. Trace gas flux measurements were made 2–3 times per week, in zero-N fertilizer plots that were cropped continuously to corn (Zea mays L.) under conventional-till (CT) and NT. Three N placement depths, replicated four times (5, 10 and 15 cm in Exp. 1 and 0, 5 and 10 cm in Exp. 2, respectively) were used. Liquid urea–ammonium nitrate (UAN, 224 kg N ha⁻¹) was injected to the desired depth in the CT- or NT-soils in each experiment. Mean flux rates of NO, N₂O, CH₄ and CO₂ ranged from 3.9 to 5.2 μg N m⁻² h⁻¹, 60.5 to 92.4 μg N m⁻² h⁻¹, −0.8 to 0.5 μg C m⁻² h⁻¹, and 42.1 to 81.7 mg C m⁻² h⁻¹ in both experiments, respectively. Deep N placement (10 and 15 cm) resulted in lower NO and N₂O emissions compared with shallow N placement (0 and 5 cm) while CH₄ and CO₂ emissions were not affected by N placement in either experiment. Compared with N placement at 5 cm, for instance, averaged N₂O emissions from N placement at 10 cm were reduced by more than 50% in both experiments. Generally, NT decreased NO emission and CH₄ oxidation but increased N₂O emissions compared with CT irrespective of N placement depths. Total net global warming potential (GWP) for N₂O, CH₄ and CO₂ was reduced by deep N placement only in Exp. 1 but was increased by NT in both experiments. The study results suggest that deep N placement (e.g., 10 cm) will be an effective option for reducing N oxide emissions and GWP from both fertilized CT- and NT-soils.     

The response ofAzolla pinnata R. Brown to the split application of phosphorus and the transfer of assimilated phosphorus to flooded rice plants

A field experiment was conducted at the Bangladesh Rice Research Institute, Joydebpur, Dhaka during the late wet season. Basal application of P at both 5 and 10 kg ha⁻¹ significantly increased total biomass production and nitrogen fixation byAzolla pinnata R. Brown (local strain). Addition of both 5 and 10 kg P ha⁻¹ in equal splits at inoculation and at six day intervals thereafter during growth periods of 12, 24 and 36 days increased biomass production and nitrogen fixation by Azolla over that attained with the basal application. Biomass and nitrogen fixation using a split application of 5 kg P ha⁻¹ exceeded that attained with basal application of 10 kg P ha⁻¹ and split application of 10 kg P ha⁻¹ resulted in 0.58, 11.2, and 18.3 t ha⁻¹ more biomass, and 0.47, 18.9, and 18.3 more kg fixed N ha⁻¹ at 12, 24 and 36 days, respectively, than the same amount applied as a basal application. Analyses indicated that the critical level of dry weight P in Azolla for sustained growth was in the range of 0.15–0.17%. Compared with the control, where no P was added, and additional 30 and 36 kg N ha⁻¹ were fixed after 24 and 36 days, respectively, when P was provided at 10 kg ha⁻¹ using a split application. A separate field study showed that flooded rice plants received P from incorporated Azolla with about 28% of the P present in the supplied Azolla being incorporated into the rice plants.     

Acidification of Soil in a Dry Land Winter Wheat-sorghum/corn-fallow Rotation in the Semiarid U.S. Great Plains

Soil pH is decreasing in many soils in the semiarid Great Plains of the United States under dry land no-till (NT) cropping systems. This study was conducted to determine the rate of acidification and the causes of the acidification of a soil cropped to a winter wheat (Triticum aestivum L.)-grain sorghum [Sorghum bicolor (L.) Moench]/corn (Zea mays L.)-fallow rotation (W-S/C-F) under NT. The study was conducted from 1989 to 2003 on soil with a long-term history of either continuous NT management [NT(LT)] (1962–2003) or conventional tillage (CT) (1962–1988) then converted to NT [NT(C)] (1989–2003). Nitrogen was applied as ammonium nitrate (AN) at a rate of 23 kg N ha⁻¹ in 1989 and as urea ammonium nitrate (UAN) at an average annual rate of 50 kg N ha⁻¹ from 1990 to 2003 for both NT treatments. Soil samples were collected at depth increments of 0–5, 5–10, 10–15, and 15–30 cm in the spring of 1989 and 2003. Acidification rates for the NT(LT) and NT(C) treatments were 1.13 and 1.48 kmol H⁺ ha⁻¹ yr⁻¹ in the 0–30 cm depth, respectively. The amount of CaCO₃ needed to neutralize the acidification is 57 and 74 kg ha⁻¹ yr⁻¹ for the NT(LT) and NT(C) treatments, respectively. A proton budget estimated by the Helyar and Porter [1989, Soil Acidity and Plant Growth, Academic Press] method indicated that NO₃⁻ leaching from the 30 cm depth was a primary cause of long-term acidification in this soil. Nitrate leaching accounted for 59 and 66% of the H⁺ from the acid causing factors for NT(LT) and NT(C) treatments, respectively. The addition of crop residues to the soil neutralized 62 and 47% of the acidity produced from the leaching of NO₃⁻, and 37 and 31% of the acid resulting from NO₃⁻ leaching and the other acid-causing constituents for the NT(LT) and NT(C) treatments, respectively. These results document that surface soils in dry land W-S/C-F rotations under NT are acidifying under current management practices. Improved management to increase nitrogen uptake efficiency from applied fertilizer would help reduce the rate of acidification. The addition of lime materials to prevent negative impacts on grain yields may be necessary in the future under current management practices. A contribution of the university of Nebraska Agricultural Research Division, Lincoln, NE 68583. Journal series No. 15120     

Development of ground vegetation biomass and nutrient pools in a clear-cut disc-plowed boreal forest

Nutrient leaching from forest substrate after clear-cutting and subsequent soil preparation is strongly influenced by the capacity of ground vegetation to sequester the released nutrients. We studied the rates and patterns of biomass and nutrient accumulation in ground vegetation growing on ridges, in furrows and on undisturbed surfaces for 2–5 years after disc-plowing in eastern Finland. The biomass of mosses on ridges remained significantly lower than that in furrows and on undisturbed surfaces. Field layer biomass on ridges and in furrows was significantly lower than on undisturbed surfaces throughout the study period. Field layer biomass increased more on ridges than in furrows. Root biomass on ridges and undisturbed surfaces was considerably higher than in furrows. Five years after disc-plowing, total biomass and nutrient pools for ridges (biomass 4,975 kg ha⁻¹, N 40 kg ha⁻¹, P 5 kg ha⁻¹, K 20 kg ha⁻¹ and Ca 18 kg ha⁻¹) and undisturbed surfaces (biomass 5,613 kg ha⁻¹, N 43 kg ha⁻¹, P 5 kg ha⁻¹, K 22 kg ha⁻¹ and Ca 18 kg ha⁻¹) were similar, but considerably lower for furrows (biomass 1,807 kg ha⁻¹, N 16 kg ha⁻¹, P 2 kg ha⁻¹, K 10 kg ha⁻¹ and Ca 6 kg ha⁻¹). Ridges covered 25% of the area, furrows 30 and 45% was undisturbed surfaces. Taking into account the proportion of each type of surface, values for the whole prepared clear-cut area were 4,312, 34, 4, 18 and 14 kg ha⁻¹ for biomass, N, P, K and Ca, respectively. Biomass and nutrient pools had not returned to uncut forest levels at the end of the 5-year study period. The results indicate that mosses and field layer vegetation respond differently to soil preparation, that the development of biomass on ridges, in furrows and on undisturbed surfaces proceeds at different rates, and that the biomass and nutrient uptake of ground vegetation remains below pre-site preparation levels for several years. However, ridges, which are known to be the most susceptible to leaching, revegetate rapidly. Responsible Editor: Tibor Kalapos.