Frequency of defoliation and nitrogen and phosphorus fertilization on Andropogon gayanus Kunth. I. Yield,crude protein content,and in vitro digestibility

Abstract

An experiment was conducted in a semi‐arid region located in the State of Zulia, western part of Venezuela (10°32'N and 71°42'W, 600 mm average annual rainfall), to evaluate dry matter (DM) yield and in vitro organic matter digestibility (IVOMD), and crude protein (CP) content of Andropogon gayanus Kunth as affected by three frequencies of defoliation (every 42, 63, and 84 days) and fertilization with three levels of nitrogen (N) (0, 100, and 200 kg N ha^‐1‐year^‐1) and two levels of phosphorus (P) (0 and 75 kg P₂O₅ ha^‐1.year^‐1) in a factorial array using a split‐split‐plot experimental design with frequencies in the main plots, N in the sub‐plots, and P in the sub‐subplots with three replications. Soil was a sandy loam Aridisol with a pH of 5.5. Average soil calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), and P contents were 0.6, 0.3, 0.1 and 0.17 meq‐100g^‐1 soil, and 6 ppm, respectively. Data from six, four, and three cuttings for the frequencies of 42, 63, and 84 days were analyzed over the total duration of the study (252 days) as well as separately for periods with high (168 days, 384 mm) and low rainfall (84 days, 69 mm). Frequency of defoliation was the only factor that influenced (P≤0.05) the variables studied. In the overall analyses, the highest (P≤0.05) DM yield (3,656 kg#lbha^‐1.cutting^‐1) was obtained with harvests every 63 days. Mean IVOMD decreased (P≤0.05) from 54.2 to 51.7% with increasing harvest interval from 63 to 84 days, respectively. The average CP content was 7.9%. With low rainfall, mean DM yield was 2,209 kg#lbha^‐1, CP content declined (P≤0.05) from 7.5 to 3.9% as the cutting interval increased, and IVOMD decreased (P≤0.05) between 42 and 63 days. With high rainfall, the highest (P≤0.05) DM yield (4,872 kg#lbha^‐1) and IVOMD (56.5%) were found at 63 days of age. Mean CP content was 9.3%. These results confirm that A. gayanus is a highly productive forage grass. Lack of response to N and P fertilizers may be attributed partly to relatively low rainfall during the experiment, adaptation of the grass to low fertility soils, and long intervals between N applications and the next harvest.     

Frequency of defoliation and nitrogen and phosphorus fertilization on Andropogon gayanus Kunth. II. Macroelement concentrations

Abstract

An experiment was conducted in a semi‐arid region located in the State of Zulia, western part of Venezuela (10°32'N and 71°42'W, and 600 mm average annual rainfall), to evaluate ash and macroelement concentrations of Andropogon gayanus Kunth as affected by two frequencies of defoliation (every 42 and 63 days) and fertilization with three levels of nitrogen (N) (0, 100, and 200 kg N ha^‐1‐year^‐1) and two levels of phosphorus (P) (0 and 75 kg P₂O₅ ha^‐1#lbyear^‐1) in a factorial array using a split‐split‐plot experimental design with frequencies in the main plots, N in the sub‐plots, P in the sub‐sub‐plots, and two replications. Soil was a sandy‐loam Andisol with pH 5.5. Average soil calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), and P contents were 0.6, 0.3, 0.1, and 0.17 meq#lb100 g^‐1 soil and 6 ppm, respectively. Data from six and four cuttings for the frequencies of 42 and 63 days were analyzed over the total duration of the study (252 days) as well as separately for periods with “high”; (168 days, 384 mm) and “low”; rainfall (84 days, 69 mm). In the overall analysis, forage ash content was increased (P≤0.05) by increasing the cutting interval, whereas macroelement concentrations were not affected (P>0.05). Mean Ca, P, Mg, and Na were: 0.20, 0.11, 0.10, and 0.029 with over 90% of the samples inadequate for grazing ruminants. Only mean K content (1.2%) was considered adequate. Nitrogen fertilization did not influence (P>0.05) macromineral composition. Applied P fertilizer increased (P<0.05) forage P concentration from 0.09 to 0.12% and reduced (P≤0.05) the Ca:P ratio, but within the normal range. Most macroelement concentrations in A. gayamts are extremely low, indicating the need for mineral supplementation to prevent deficiencies in ruminants consuming this species.     

Calcium deficiency and CaCO3 on micronutrient status of plants grown in solution culture

Abstract

Plants were grown in solution culture with different levels of Ca to further evaluate Ca relationships to trace metal uptake and to toxicity of trace metals. When tomato plants (Lycopersicon esculentum L., Tropic) were grown at a low level of Ca, the Zn, Cu, Fe, Mn, Al, and Ti concentrations of leaves, stems, and roots were considerably increased. The use of an excess of CaCO₃ which increased pH did not influence the trace metal concentrations of plants any more than did Ca⁺⁺. In a factorial experiment with bush beans (Phaseolus vulgaris L. C.V. Improved Tendergreen) with Ca (10^‐4,10^‐2, 10^‐2 N) and Ni (0, 2 × 10^‐6 M, 2 X10^‐5 M), Ni phytotoxicity and Ni uptake were decreased somewhat at the highest Ca level. High Ni tended to decrease the Ca concentration in leaves. High Ca and Ni both tended to decrease Fe, Cu, Zn, and Mn concentrations in leaves. The Ni had some interactions on the P concentrations of shoots.     

Forage quality and yield increments of intensive managed grassland in response to combined sulphur-nitrogen fertilization Dedicated to Prof. em.Dr. Alois Kornher on his 75th birthday.

Abstract

A three-year experiment was carried out at three different sites in northern Germany to investigate the effects of combined sulphur (S, up to 50 kg S ha^?1 year^?1) and nitrogen (N, up to 300 kg N ha^?1 year^?1) fertilization on dry matter (DM) yield and forage quality. There was an interaction effect of site, year, S and N fertilization. The greatest DM yield increment relative to yield at the start of the experiment (1997) with no S and N applied was 10.2 t DM ha^?1 at Ostenfeld (arable grassland). Cattle slurry when applied to provide 50 kg N ha^?1 and 10 kg S ha^?1 did not noticeably increase yield. The S content in forage decreased significantly over the years without S fertilization. At 300 kg N ha^?1 and 0 kg S ha^?1, crude protein (CP) contents achieved 173 g kg^?1 DM and were diluted due to higher DM yields with S fertilization. The true protein content (TP% of CP) differed significantly at 300 kg N ha^?1. TP achieved 93% with 50 and 87% with 0 kg S ha^?1 year^?1, respectively. In conclusion, with N fertilizer intensities in the range of 300 kg N ha^?1, it is necessary to apply 25 kg S ha^?1 to improve forage yield and quality. On the other hand, with N fertilization levels below 300 kg N ha^?1, S fertilization could be omitted.     

Salinity and nitrogen fertilization affecting the macronutrient content and yield of sweet pepper plants

The effects of salinity due to sodium chloride (NaCl) and nitrogen (N) concentration in the nutrient solution were studied with sweet pepper plants. Four saline treatments combined with two N fertilization were used. Nitrate‐nitrogen (NO₃ ^‐‐N) presence in the nutrient solution produced an increase of sodium (Na) and potassium (K) contents in leaves as well as N. Salinity promoted a reduction of K, phosphorus (P) and Ca and increased the Na concentration in leaves. Calcium (Ca) concentrations were lower in the higher NO₃ ^‐‐N treatment although N level was reached adding calcium nitrate and salinity increased P, K, Na, Ca, and magnesium (Mg) contents in fruits. Yield was increased in the highest N treatment.     

Mulberry nutrient management for silk production in Hubei Province of China

The silk industry is important for south China's rural economy. Leaves of mulberry (Morus spp.) are used for silkworm production. Hubei province is one of the main silk‐producing provinces in China. The objectives of this research were to survey the fertilization practices in the mulberry‐producing regions in the province and to determine the best nutrition‐management practice for mulberry plantations. A survey and a series of field experiments with N, P, K, and micronutrients were conducted from 2001 to 2002. In addition, a silkworm‐growth experiment was also conducted by feeding leaves harvested from various fertilization treatments. The results indicate that poor soil fertility and unbalanced fertilization were the main factors limiting mulberry‐leaf yield and quality in Hubei province. Nitrogen fertilization of mulberry has reached a high level (454 kg ha^–1 y^–1) in Hubei province, but P‐ and K‐fertilization rates have not been matched with N‐fertilization rates as farmers are not aware of the significance of P and K. Balanced fertilization showed positive nutrient interactions with respect to mulberry yield and quality. Potassium application increased yield and quality (protein and sugar concentration) of mulberry leaves. Silkworm growth and cocoon quality were improved when silkworms were fed with the leaves derived from K‐fertilized plants in comparison with those taken from control plots. Application of Mg, S, and B also significantly improved leaf sugar, essential and total amino acid concentrations, but did not increase leaf yield significantly. It is concluded that a fertilizer dose of 375 kg N ha^–1, 66 kg P ha^–1, and 125 kg K ha^–1 is suitable for the cultivation of mulberry in the Hubei province along with Mg, S, and B, wherever necessary, for the improvement of yield and quality of mulberry leaves.     

Distribution profiles of dry matter and total nitrogen in leaves and stems of oriental field‐grown tobacco plants at different nitrogen levels

Oriental tobacco plants (Nicotiana tabacum L. cv Myrodata Agrinion) were grown without nitrogen (N) fertilization (N₀) and with added ammonium nitrate at a rate of 50 kg‐ha^‐1 (N₁) and 100 kg‐ha^‐1 (N₂). Non‐uniform patterns for leaf FW and DW changes per node showed a decreasing trend from lower to upper nodes during the vegetative stage. From approaching flowering to fruit set, these patterns became more uniform. Plants which were fertilized with N had increased leaf FW and DW accumulation levels and non‐uniform distribution patterns, primarily during the reproductive stage, and leaves of the lower nodes were found in the older plants. By contrast, the median values of leaf FW for the unfertilized plants were reduced during the reproductive period. The DW/FW×100 ratio values revealed a stable relationship between leaf FW and DW from the vegetative to the reproductive stage, while modified patterns of DW/FW×100 appeared later in the plant cycle. Nitrogen fertilization resulted in an early appearance of modified patterns of DW/FW×100 in the plant life cycle and higher accumulation of dry matter per unit leaf area. Patterns of total leaf N concentration showed an increasing trend from the lower to the upper nodes for all plant ages and treatments. Total N concentration values varied from 1.6%, 1.9%, and 1.8% on a dry matter basis, for the lower node up to 5.5%, 6.3%, and 6.1% for the upper node in young tobacco plants in the N _o , N₁, and N ₂ treatments, respectively. After fruit set, a more uniform distribution of total leaf N was observed among the leaves in all treatments. Concentration values for total leaf N in older plants varied from 1.9%, 2.1%, and 2.2% for the lower node up to 3.4%, 3.3% and 3.2% for the upper node in the N ₀ , N₁, and N₂ treatments, respectively. These results suggest a progressive decrease with plant age for total leaf N concentration in the plant as a whole. The increased N fertilizer level affected the total N level in young plants but not in the older ones. Inflorescence and fruit set periods are critical for plant N balance except for the plants which received the increased N fertilization. The determined total stem N concentration was less than that for the leaves. This change in the stem, similar to leaves, showed an increasing trend from the basal to the upper part and a decreasing trend from the vegetative to the reproductive stage. The total stem N level declined from 1.0–1.2%, 1.6–1.7%, and 2.2–2.9% on a dry matter basis to 0.5–0.6%, 1.0–1.2%, and 1.2–1.6% for the basal, middle, and upper part of the stem, respectively.     

Effects of long-term mineral fertilization on microbial biomass,microbial activity,and the presence of <Emphasis Type="Italic">r</Emphasis>- and <Emphasis Type="Italic">K</Emphasis>-strategists in soil

Long-term effects of mineral fertilization on microbial biomass C (MBC), basal respiration (R _B), substrate-induced respiration (R _S), β-glucosidase activity, and the r–K-growth strategy of soil microflora were investigated using a field trial on grassland established in 1969. The experimental plots were fertilized at three rates of mineral N (0, 80, and 160 kg ha⁻¹ year⁻¹) with 32 kg P ha⁻¹ year⁻¹ and 100 kg K ha⁻¹ year⁻¹. No fertilizer was applied on the control plots (C). The application of a mineral fertilizer led to lower values of the MBC and R _B, probably as a result of fast mineralization of available substrate after an input of the mineral fertilizer. The application of mineral N decreased the content of C extracted by 0.5 M K₂SO₄ (C _ex). A positive correlation was found between pH and the proportion of active microflora (R _S/MBC). The specific growth rate (μ) of soil heterotrophs was higher in the fertilized than in unfertilized soils, suggesting the stimulation of r-strategists, probably as the result of the presence of available P and rhizodepositions. The cessation of fertilization with 320 kg N ha⁻¹ year⁻¹ (NF) in 1989 also stimulated r-strategists compared to C soil, probably as the result of the higher content of available P in the NF soil than in the C soil.     

Effect of Nitrogen Fertilizer Rate and Harvest Season on Forage Yield,Quality, and Macronutrient Concentrations in Midland Bermuda Grass

Bermuda grass [Cynodon dactylon (L.) Pers.] is a major forage for grazing and hay production in the southern United States. The objectives of this study were to determine effects of nitrogen (N) fertilization rate (0, 112, 224, 336, and 448 kg ha^?1), split spring and summer applications of N at the 224 and 448 kg ha^?1 rates, and harvest periods (spring and summer) on forage yield, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), total digestible nutrients (TDN), and concentrations of phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca in Midland Bermuda grass. Data were collected from 2002 to 2008 as part of an ongoing, long-term soil fertility experiment in southern Oklahoma. Repeated measures analysis of these long-term data showed that forage yield responses to N rate varied with year and harvest time with up to 2.5-fold yield differences among years. Nitrogen fertilization increased CP, TDN, and macronutrient P and Mg and decreased ADF and NDF. Crude protein was increased by ≥50%, and ADF and NDF dropped by up to 25% with the greatest N rate. In general, split N applications did not affect forage yield but produced low-quality forage compared to single N application in spring. Split application of 448 kg N ha^?1 gave forage with CP, TDN, ADF, and NDF similar to the Bermuda grass receiving 336 or 448 kg N ha^?1 as a single application. Spring forage had better forage quality than summer harvests. While N fertilization increased forage Mg and P concentrations by more than 50% during both spring and summer, it had no effect or slight increased K and Ca concentrations. In the southern Great Plains, despite the weather-dependent variability in forage yield of Bermuda grass, N application increase forage quality.     

Nitrate leaching loss under annual and perennial pastures with and without lime on a duplex (texture contrast) soil in humid southeastern Australia

Mineral N accumulates in autumn under pastures in southeastern Australia and is at risk of leaching as nitrate during winter. Nitrate leaching loss and soil mineral N concentrations were measured under pastures grazed by sheep on a duplex (texture contrast) soil in southern New South Wales from 1994 to 1996. Legume (Trifolium subterraneum)‐based pastures contained either annual grass (Lolium rigidum) or perennial grasses (Phalaris aquatica and Dactylis glomerata), and had a control (soil pH 4.1 in 0.01 m CaCl₂) or lime treatment (pH 5.5). One of the four replicates was monitored for surface runoff and subsurface flow (the top of the B horizon), and solution NO₃^– concentrations. The soil contained more mineral N in autumn (64–133 kg N ha^?1 to 120 cm) than in spring (51–96 kg N ha^?1), with NO₃^– comprising 70–77%. No NO₃^– leached in 1994 (475 mm rainfall). In 1995 (697 mm rainfall) and 1996 (666 mm rainfall), the solution at 20 cm depth and subsurface flow contained 20–50 mg N l^?1 as NO₃^– initially but < 1 mg N l^?1 by spring. Nitrate‐N concentrations at 120 cm ranged between 2 and 22 mg N l^?1 during winter. Losses of NO₃^– were small in surface runoff (0–2 kg N ha^?1 year^?1). In 1995, 9–19 kg N ha^?1 was lost in subsurface flow. Deep drainage losses were 3–12 kg N ha^?1 in 1995 and 4–10 kg N ha^?1 in 1996, with the most loss occurring under limed annual pasture. Averaged over 3 years, N losses were 9 and 15 kg N ha^?1 year^?1 under control and limed annual pastures, respectively, and 6 and 8 kg N ha^?1 year^?1 under control and limed perennial pastures. Nitrate losses in the wet year of 1995 were 22, 33, 13 and 19 kg N ha^?1 under the four respective pastures. The increased loss of N caused by liming was of a similar amount to the decreased N loss by maintaining perennial pasture as distinct from an annual pasture.     

Yield and nutritional evaluation of the banana hybrid ‘FHIA-18’ as influenced by phosphate fertilization

Abstract

The ‘FHIA-18’ hybrid banana is an alternative for producers as it is resistant to Black Sigatoka and Panama disease. However, few studies report the nutritional requirement of this hybrid, especially phosphorus. It is known that the efficiency of phosphorus use can be improved, reducing the need for application, depending on the genotype cultivated. Therefore, this study aimed to evaluate the yield and mineral nutrition of ‘FHIA-18’ hybrid banana on phosphate fertilization. A banana orchard with the cultivar ‘FHIA-18’ was conducted on a Typical Red Latosol. Then, triple superphosphate fertilizer was applied on plants at 0, 20, 30, 40, 50, and 60?kg ha^?1?year^?1, over three productive seasons. At the time of flowering the macro and micronutrient contents of the leaves were evaluated. Subsequently, the nutrient contents of the fruits were evaluated. For this, fruit pulp samples from the third and fourth hands were collected. In addition, yield was estimated considering cluster mass and plant density. The following dose 36?kg ha^?1 of P₂O₅ year^?1 increased the content of phosphorus in the leaf, despite that banana hybrid cultivar FHIA 18 demanded 50% of the recommended fertilizer to achieve its maximum yield (29.4 t ha^?1?year^?1). Phosphate fertilization promoted significant changes in P, Ca, Cu, and Zn contents of leaves and fruits. Therefore, it is concluded that the mineral nutrition of banana ‘FHIA-18’ is affected by phosphate fertilization, as well as requiring less P than recommended to achieve higher yield.     

Nitrogen and phosphorus fertilization leads to soil arbuscular mycorrhizal fungal diversity changes and rainfed crop yield increase on the Loess Plateau of China: A 37-year study

More than 80% of plants form mutualistic symbiotic relationships with arbuscular mycorrhizal fungi (AMF), and the application of fertilizers, such as nitrogen (N) and phosphorus (P) fertilizers, is a common agricultural management practice to improve crop yield and quality. However, the potential effects of long-term N and P fertilization on the AMF community in the rainfed agricultural system of the Loess Plateau of China are still not well understood. In this study, a long-term field experiment was conducted based on orthogonal design, with three N levels (0, 90, and 180 kg ha^-1 year^-1) and three P levels (0, 90, and 180 kg ha^-1 year^-1) for wheat fertilization. Changes in AMF community and correlations between AMF community composition, soil environmental factors, and wheat yield component traits were analyzed using traditional biochemical methods and high-throughput sequencing technology. The results showed that long-term N and P addition had a significant effect on the AMF community structure and composition. Nitrogen application alone significantly reduced the richness and diversity of AMF community, whereas the combined application of N and P significantly increased the richness and diversity of AMF community. The AMF community was driven mainly by soil available P, total P, and pH. There was a significant positive correlation between Glomus abundance and wheat yield and a significant negative correlation between Paraglomus abundance and wheat yield. Long-term N and P addition directly increased crop yield and affected yield indirectly by influencing soil chemical properties and the AMF community. Combined application of N and P both at 90 kg ha^-1 year^-1 could improve the ecological and physiological functions of the AMF community and benefit the sustainable development of rainfed agriculture.     

Changes in Chemical Composition of Australian Waxflowers Due to Soil Applications of Nitrogen and Assessment of Nitrogen Status by Tissue Analysis

Abstract

Three field experiments were conducted to investigate the effects of soil‐applied nitrogen (N) on plant chemical composition, nutrient removal, and the use of plant analysis to assess N status of Australian waxflowers. Experiments were conducted in commercial plantings of Chamelaucium uncinatum cultivar Alba and a Chamelaucium hybrid (C. floriferum × C. uncinatum) known locally as Walpole wax, at 3 sites in South Australia. Nitrogen, as ammonium nitrate, was applied at rates up to 160 g plant^?1 over several side dressings during the growing season. To assess plant nutrient status, stem tips (25–40 mm long tips of stems) were sampled during the growing season and whole stems at harvest.

Nitrogen concentration in both stem tips and whole stems was sensitive to variations in N supply; however, the magnitude of the effect varied between sampling times and sites. In stem tips sampled during spring, the increase in N concentrations ranged from 19.8% at site 2 to 74.6% at site 1. Nitrogen concentrations in stem tips were consistently greater than concentrations in whole stems. The application of N decreased phosphorus (P) concentrations in whole stems and copper (Cu) concentrations in stem tips and whole stems. There was no consistent effect of applied N on potassium (K), calcium (Ca), magnesium (Mg), boron (B), zinc (Zn), and manganese (Mn) concentrations in either plant part sampled. Nutrient removal by flowering stems, in order from greatest to least, was N > K > Ca > P > Mg > Mn > B > Zn > Cu.

Based on 1800 plants ha^?1, it was estimated that for N, P, and K, 121.9, 15.4, 60.1 kg ha^?1, respectively, was removed in harvested stems. Based on poor sensitivity, the lack of a sharp transition zone between deficient and adequate N concentrations and the lack of consistent relationships between N concentration in stem tips and yield response, it is concluded that N concentration in stem tips is not a useful indicator of the N status of waxflower plants.     

Compositional Nutrient Diagnosis in Maize Grown in a Calcareous Soil

ABSTRACT

Preliminary compositional nutrient diagnosis (CND) norms for maize (Zea mays L.) were developed from a small database as means and standard deviations of row-centered log ratios V _X of five nutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] and a filling value R, which comprised all nutrients not chemically analyzed and quantified in 72 leaves of hybrid ‘Pioneer 3044.’ Norms were derived from maize grain yields higher than 7.7 t ha^?1. Principal-component analysis performed using CND nutrient indexes allowed us to identify an antagonism between N and Mg explained by the calcareous nature of the soil and the relevant N fertilization with ammonium (NH₄ ⁺), and a positive interaction between P and K, and P-Ca and K-Ca antagonisms. Maize plants tended to take up lower amounts of N and K and higher amount of Mg in our calcareous soil than the concentrations of these nutrients reported to be optimum.     

Long-term effects of tillage, cover crops, and nitrogen fertilization on organic carbon and nitrogen concentrations in sandy loam soils in Georgia, USA

Maintaining and/or conserving organic carbon (C) and nitrogen (N) concentrations in the soil using management practices can improve its fertility and productivity and help to reduce global warming by sequestration of atmospheric CO₂ and N₂. We examined the influence of 6 years of tillage (no-till, NT; chisel plowing, CP; and moldboard plowing, MP), cover crop (hairy vetch (Vicia villosa Roth.) vs. winter weeds), and N fertilization (0, 90, and 180 kg N ha⁻¹) on soil organic C and N concentrations in a Norfolk sandy loam (fine-loamy, siliceous, thermic, Typic Kandiudults) under tomato (Lycopersicon esculentum Mill.) and silage corn (Zea mays L.). In a second experiment, we compared the effects of 7 years of non-legume (rye (Secale cereale L.)) and legume (hairy vetch and crimson clover (Trifolium incarnatum L.)) cover crops and N fertilization (HN (90 kg N ha⁻¹ for tomato and 80 kg N ha⁻¹ for eggplant)) and FN (180 kg N ha⁻¹ for tomato and 160 kg N ha⁻¹ for eggplant)) on soil organic C and N in a Greenville fine sandy loam (fine-loamy, kaolinitic, thermic, Rhodic Kandiudults) under tomato and eggplant (Solanum melogena L.). Both experiments were conducted from 1994 to 2000 in Fort Valley, GA. Carbon concentration in cover crops ranged from 704 kg ha⁻¹ in hairy vetch to 3704 kg ha⁻¹ in rye in 1999 and N concentration ranged from 77 kg ha⁻¹ in rye in 1996 to 299 kg ha⁻¹ in crimson clover in 1997. With or without N fertilization, concentrations of soil organic C and N were greater in NT with hairy vetch than in MP with or without hairy vetch (23.5–24.9 vs. 19.9–21.4 Mg ha⁻¹ and 1.92–2.05 vs. 1.58–1.76 Mg ha⁻¹, respectively). Concentrations of organic C and N were also greater with rye, hairy vetch, crimson clover, and FN than with the control without a cover crop or N fertilization (17.5–18.4 vs. 16.5 Mg ha⁻¹ and 1.33–1.43 vs. 1.31 Mg ha⁻¹, respectively). From 1994 to 1999, concentrations of soil organic C and N decreased by 8–16% in NT and 15–25% in CP and MP. From 1994 to 2000, concentrations of organic C and N decreased by 1% with hairy vetch and crimson clover, 2–6% with HN and FN, and 6–18% with the control. With rye, organic C and N increased by 3–4%. Soil organic C and N concentrations can be conserved and/or maintained by reducing their loss through mineralization and erosion, and by sequestering atmospheric CO₂ and N₂ in the soil using NT with cover crops and N fertilization. These changes in soil management improved soil quality and productivity. Non-legume (rye) was better than legumes (hairy vetch and crimson clover) and N fertilization in increasing concentrations of soil organic C and N.     

Alfalfa Responses to Combined Use of Lime and Limiting Nutrients on an Acidic Soil

An on-farm field experiment was conducted on an acidic soil to investigate the effects of combined use of lime and deficient nutrients on herbage yield of alfalfa (Medicago sativa L.). Omitting lime and limiting nutrients led to elevated concentrations of aluminium (Al), iron (Fe), and manganese (Mn) in alfalfa leaves and stems and caused severe reductions in herbage yield of alfalfa. Combined use of lime (2 t ha^?1) and nutrients [phosphorus (P): 20 kg ha^?1, sulfur (S): 20 kg ha^?1, zinc (Zn): 4 kg ha^?1, and boron (B): 2 kg ha^?1] had the maximum increase in groundcover, root biomass, nodulation, leaf retention, leaf-to-stem ratio, herbage yield, crude protein, and nutrient composition of alfalfa. These beneficial effects were due to raised soil pH; improved calcium (Ca), P, S, Zn, and B nutrition; and reduced Al, Mn, and Fe toxicity. Aluminium and all the nutrients except copper (Cu) were more concentrated in alfalfa leaves than stems.

Aluminum concentration was about three times greater in the lower leaves than in upper leaves. Lower leaves also had much greater concentrations of Ca, Mg, K, S, Fe, Mn, Cu, and B compared with upper leaves. In contrast, P and Zn concentrations were greater in the upper leaves than in lower leaves. Results suggest that the combined use of lime and all the limiting nutrients may realize potential beneficial effects of alfalfa on acidic soils where more than one essential nutrient is deficient. This may increase growth potential, nitrogen contributions, and groundcover by alfalfa and reduce soil erosion and runoff.     

Effects of solid phase from pig slurry on soil chemical characteristics,nitrate leaching,composition, and yield of wheat

A two years lysimeter experiment was carried out using wheat plants (Triticum aestivum L. cv. Lotti) on two texturally contrasting soils. The main purpose of this study was to evaluate the influence of increasing applications (5,10, 15,20, and 25 t.ha^‐1) of solid phase (SP) from pig slurry on soil nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na) content, nitrate‐N (NO₃‐N) leaching as well as on wheat composition and yield. As the control, a basic dressing of NPK fertilizer was applied. Results showed that plant growth was stimulated by increasing amounts of SP, yet the additions of 15 to 20 t SP ha^‐1 led to similar effects on yield as that for the control. An accumulation of P on both soils was observed as well as a significant increase on NO₃‐N leaching due to increasing rates of SP added to the soils. The N and P content in wheat plants (straw and grain) increased with increasing rates of applied SP.     

Responses of eastern gamagrass [Tripsacum dactyloides (L.) L.] forage quality to nitrogen application and harvest system

Eastern gamagrass is a warm-season perennial with good forage yield and quality, but both may be increased with nitrogen (N) fertilization. The effects of N and harvest management on neutral- and acid-detergent fibers (NDF and ADF), lignin, in vitro dry matter digestibility (IVDMD), and crude protein (CP) were studied. Nitrogen (0, 50, or 100 kg ha^?1) was applied by broadcasting or knife placement, and forage was harvested from 1- or 2-cut systems. Data were obtained during four years of N treatment, and three intervening years with no N treatment. Neutral- and acid-detergent fibers and lignin were usually lower, and IVDMD and CP were generally higher in the 2-cut than in the 1-cut system. Increasing N affected forage quality in minor ways, except for CP. When 100 kg ha^?1 was applied, CP was increased over no N by 0.14 in the 1-cut system and by 0.25 in cut 1 of the 2-cut system.     

Contribution of red alder to soil nitrogen input in a silvopastoral system

Studies on Alnus rubra Bong. (red alder) were carried out to assess its potential for use as a component of a silvopastoral system. Comparison was between two treatments: red alder at 400 stems ha⁻¹ (silvopasture) and red alder at 2,500 stems ha⁻¹ (forestry control). δ¹⁵N values close to zero were recorded in all red alder plant parts except for root nodules, indicating that a large proportion of N in red alder was fixed from the atmosphere. Overall, it was estimated that there was 63.45 kg N ha⁻¹ fixed N accumulated in red alder trees, and the rate of N fixation was estimated at 30.95 kg ha⁻¹ year⁻¹ in the silvopasture treatment. The total amount of N that could potentially be added to the soil in the silvopasture treatment as a result of decomposition of senescent leaves, roots, and dead nodules was estimated at 40.56 kg ha⁻¹ year⁻¹. Of the total N added to the soil, 27.1 kg ha⁻¹ year⁻¹ was due to N fixation from the atmosphere. These results show that red alder has a potential to improve and maintain soil fertility in a silvopastoral system.     

Effects of Liming and Fertilization (N,PK) on Chemistry and Nitrogen Turnover in Acidic Forest Soils in SW Sweden

SW Sweden has very acidic forest soils because of deposition ofair-borne pollutants. Large-scale liming and fertilization have been proposed as countermeasures against a possible future development of forest decline. To test the effects of suggested treatments, liming (3 or 6 t ha¹) and fertilization with easily soluble PK (25 or 50 kg P, 80 or 160 kg K ha¹) or N(20 kg N ha¹ annually in the form of NH₄ NO₃) were applied in different combinations in four experiments in 30–60 yr-old Picea abies forests in SW Sweden. Four yearsafter the initial application of the fertilizers, samples were taken from the O-horizon and the two uppermost 5 cm thick layersof the mineral soil. Their pH(H₂O) and easily extractable Ca, Mg, K, P and inorganic N contents were analyzed. Samples werealso incubated to estimate net N mineralization and potential nitrification rates. Liming increased the pH by 0.6–1 unit in the O-horizon, and by 0.1 unit in the mineral soil. The Ca + Mg content increased by 15–25 kmol_c ha¹ (4–8 foldincrease) in the O-horizon of the limed plots, while an increaseof 5 kmol_c ha¹ (two-fold increase) was observed in theuppermost 5 cm of the mineral soil. Liming did not affect extractable P, K or inorganic N contents. Net N mineralization and potential nitrification rates in the O-horizon were enhanced 1.5- and 6-fold, respectively, by liming, but it had no apparenteffect in the mineral soil. N fertilization caused a slight increase (1.5 kg ha¹) in the content of inorganic N, buthad no effects on the other variables measured. The amount ofextractable P was raised by 16 kg ha¹ in plots given the high P dose (50 kg ha¹), but no other effects of PK fertilization were detected.