Residual Effect Of Fertilizer Research Articles

Commercial forest fertilization causes long-term residual effects in ground vegetation of boreal forests

Due to an increasing demand of forestry products, nitrogen (N) fertilization of coniferous forests may in the future become a standard silvicultural practice in parts of the boreal region that is not too remotely situated. Beside positive effects on productivity, forest fertilization may induce changes in species composition of the ground vegetation. More information on the magnitude of such side effects is needed to evaluate whether commercial forest fertilization is in accordance with principles of sustainable forestry and preservation of biodiversity. We examined the effects of forest fertilization on ground vegetation in boreal forest by comparing species composition in unfertilized stands and stands fertilized twice (>20 years since the last fertilization) with 150 kg N ha −1 per event. By using stands that had been clear-felled and replanted 8–11 years ago, we addressed whether effects of fertilization persists over more than one forest generation. The ground vegetation in fertilized stands was denser, showed decreased species evenness, lower biodiversity, and higher Ellenberg N values. The abundance of dwarf shrubs was reduced by more than 40%, while grasses and some nitrophilous herbs increased by >100%. For bottom layer species, fertilization favoured litter-dwelling bryophytes (e.g. Brachythecium spp.), while Hylocomium splendens and ground living lichens were disfavoured. For the dwarf shrub Vaccinium myrtillus, fertilization reduced the density of current annual shoots by >60% and berry production by >70%. Fertilization had, however, no effect on berries produced per annual shoot. Leaf tissue N concentrations were higher in V. myrtillus, and Deschampsia flexuosa growing in previously fertilized stands, indicating N enrichment although more than 20 years had past since the last fertilization event. Because residual effects of commercial forest fertilization on forest ground vegetation appear to be substantial and extend over more than one forest generation, we question whether forest fertilization, as performed today in the Nordic countries, can be considered a long-term sustainable silvicultural practice that is in accordance with principles of preservation of biodiversity.

Residual effect of leguminous crops and inorganic fertilizer on soil properties and maize grain yield

Soil management practices that utilize organic matter have great potential to increase productivity in sub-Saharan Africa. Field studies were carried out between September 1995 and August 1998 to determine the effects of three leguminous crop species: velvet bean ( Mucuna pruriens var. utilis ), groundnut ( Arachis hypogaea L.) and cowpea ( Vigna unguiculata (L.) Walp), and inorganic fertilizer on the soil properties and succeeding maize grain yield when grown in rotation on a sandy soil classified as Haplic Lixisol in the forest-savannah transition zone of Ghana. The legumes were established in the minor seasons and maize in all the plots in the major cropping seasons. A 2 × 3 factorial design laid out in a randomized complete block was used. The main plots consisted of three leguminous crop residues and the sub-plots of two fertilizer levels (0 and 45 kg N ha −1 , 19 kg P ha −1 , 19 kg K ha −1 ). The control consisted of maize following maize with the recommended fertilizer rate (90 kg N ha −1 , 37 kg P ha −1 , 37 kg K ha −1 ). On average the Mucuna plots added 4.0 t ha −1 of crop residue to the soil in a season and cowpea 1.0 t ha −1 . The preceding crops had little effect on the soil properties. Leaf area index, total dry matter and maize grain yields were significantly affected by fertilizer. The best maize grain yield (6787 kg ha −1 ) was recorded in the first year on Mucuna plots with half the recommended rate of fertilizer. The cropping sequence with Mucuna residue was the most efficient. The gap in maize grain yield between the fertilized and unfertilized treatments widened each successive year. The interaction between organic matter and fertilizer may have been limited due to the surface application of the organic residue.

Residual Influence of Early Season Crop Fertilization and Cropping System on Growth and Yield of Cassava

Problem Statement: In assessing fertilizer effects to sustain an intensive cropping system, the residual effects of fertilizer applied to preceding maize on the growth and yield of cassava and the effects of intercropping with soybean were studied in field experiments at Ibadan, Nigeria. Approach: Maize, established in April was fertilized using either organic manure or inorganic fertilizer or a mixture of organic manure and inorganic fertilizers. Organic manure was an equal mixture of domestic waste collected from a composted refuse dumping site applied at l0 t ha-1. Inorganic fertilizer was 150kg N supplied as urea and 50 kg P ha-1 as Single Super phosphate fertilizer. The mixture of organic and inorganic fertilizer treatment was 5 tonnes organic manure and 75kg N+25 kg P ha-1. Cassava was established in June and soybean planted in July, after harvesting maize. Results: Organic fertilizer treatment gave the tallest Soybean plants of 53 cm. Plants from sole inorganic fertilizer and from a mixture of organic and inorganic fertilizers had comparable heights but were significantly lower than plants from sole organic fertilizer application. Organic fertilizer application gave the highest seed yield of 481 kg ha-1 that was significantly higher than 380 kg ha-1 observed from a mixture of organic and inorganic fertilizers. Stover yield followed the same trend as seed yield. Cassava plant height was increased with fertilization but was reduced with intercropping. Sole organic fertilization had the tallest plants of 206 cm. Plant leaf area was neither significantly affected by fertilizer type nor cropping system. Fresh root yield was significantly reduced by 16% with soybean intercropping. Sole organic fertilizer application gave the highest yields of 22 tons ha-1 in sole crop and 18 tons ha-1 in intercrop with soybean. Conclusion: Cultivating an early season maize crop, followed by a cassava-soybean intercrop is more favored with application of 10 tons ha-1 organic fertilizer.

The Grass Garden in the Giant Mts. (Czech Republic): Residual effect of long-term fertilization after 62 years

The aim of the study was to investigate how plant species’ composition, soil parameters and nutrient concentrations in plant biomass differ between fertilized and control plots 62 years after the last fertilizer application on a sub-alpine grassland. A piece of land called the Grass Garden (GG), fertilized with wood ash and manure for at least 200 years, was rediscovered in the Giant Mts. (Krkonoše, Karkonosze) in 2006. The last fertilization was applied in 1944. The central part of GG (treatment A), the edge of GG (treatment B) and never-fertilized control plots outside of GG (treatment C) were distinguished. Sixty-two years after the last fertilization Nardus stricta was dominant in treatment C and Deschampsia cespitosa and Avenella flexuosa in treatments A and B. The predominance of these grasses was first described in 1786 and repeatedly during the 19th and 20th centuries and indicated the long-term stability of plant species’ composition in the sub-alpine grassland. In the case of GG, long-term fertilization has had a long-term “stable after-effect” upon differences in plant species’ composition. Ca concentration in the soil was more than two times higher in treatments A and B than in the control, indicating that it was very difficult to deplete applied Ca even on extreme podzol soils and under the climatic conditions of the sub-alpine vegetation belt. In above-ground plant biomass, Mg and P concentrations and N:P ratio were still significantly affected by treatment.

Long‐Term Integrated Nutrient Management for Rice‐Based Cropping Pattern: Effect on Growth, Yield, Nutrient Uptake, Nutrient Balance Sheet, and Soil Fertility

A 7‐year‐long field trial was conducted on integrated nutrient management for a dry season rice (Boro)–green manure (GM)–wet season rice (T. Aman) cropping system at the Bangladesh Rice Research Institute Farm, Gazipur during 1993–1999. Five packages of inorganic fertilizers, cow dung (CD), and GM dhaincha (Sesbania aculeata) were evaluated for immediate and residual effect on crop productivity, nutrient uptake, soil‐nutrient balance sheet, and soil‐fertility status. Plant height, active tiller production, and grain and straw yields were significantly increased as a result of the application of inorganic fertilizer and organic manure. Usually, the soil‐test‐based (STB) fertilizer doses for a high‐yield goal produced the highest grain yield of 6.39 t ha−1 (average of 7 years) in Boro rice. Application of CD at the rate of 5 t ha−1 (oven‐dry basis) once a year at the time of Boro transplanting supplemented 50% of the fertilizer nutrients other than nitrogen (N) in the subsequent crop of the cropping pattern. A positive effect of GM on the yield of T. Aman rice was observed. Following GM, the application of reduced doses of phosphorus (P), potassium (K), sulfur (S), and zinc (Zn) to the second crop (T. Aman) did not reduce yield, indicating the beneficial residual effect of fertilizer applied to the first crop (Boro rice) of the cropping pattern. The comparable yield of T. Aman was also observed with reduced fertilizer dose in CD‐treated plots. The total P, K, and S uptake (kg/ha/yr) in the unfertilized plot under an irrigated rice system gradually decreased over the years. The partial nutrient balance in the unfertilized plot (T1) was negative for all the nutrients. In the fertilized plots, there was an apparent positive balance of P, S, and Zn but a negative balance of N and K. This study showed that the addition of organic manure (CD, dhaincha) gave more positive balances. In the T4c treatment at 0–15 cm, the application of chemical fertilizers along with the organic manures increased soil organic carbon by (C) 0.71%. The highest concentration of total N was observed with T4c followed by T4d and T4b, where CD was applied in Boro season and dhaincha GM was incorporated in T. Aman season. The sixfold increase in soil‐available P in T4b‐, T4c‐, T4a‐treated plots was due to the addition of CD. Dhaincha GM with the combination of chemical fertilizer helps to mobilize soil‐available P by 3 to 6 ppm. The highest amount of soil‐available S was found in T4c‐ and T4a‐treated plots. It was 2.5 times higher than that of the initial soil. The application of CD and dhaincha GM along with chemical fertilizers not only increased organic C, total N, available P, and available S but also increased exchangeable K, available Zn, available iron (Fe), and available manganese (Mn) in soil.

Residual fertilizer effects on dry‐matter yield and nutritive value of Mediterranean pastures

SummaryFive pastures in an Mediterranean environment in southern Italy were fertilized for 6 years (1993–1998) with nitrogen (N) fertilizer, phosphorus (P) fertilizer and two levels low (L) and high (H) of combined nitrogen and phosphorus fertilizer (N‐P), and compared with a no‐fertilizer control treatment, and the effects on soil variables, dry matter (DM) yield of herbage and floristic composition of the pastures measured. From 1998–2002, half of each plot was fertilized with the same treatments (continued treatment) while the other half received no fertilizer (discontinued treatment). In the year 2001–2002, the plots on the discontinued fertilizer treatments and the plots on the control treatment were used to evaluate the residual effects of the fertilizer treatments. The P and N‐P fertilizer continued and discontinued treatments, in comparison to the control treatment, had a higher content of available P2O5 in the soil while under the N fertilizer treatment it decreased. The N and P fertilizer treatments and the residual effects of these treatments led to higher DM yields and proportions of Gramineae and Leguminosae, respectively, compared to the control treatment. Furthermore, differences in the nutritive value of the herbage and floristic composition were observed between the N‐P fertilizer treatments and the control treatment. The residual effect of the N, P and N‐P fertilizer treatments increased DM yield proportionately by 0.063, 0.385 and 0.404, respectively, and reduced the crude protein content of the herbage. The residual effects of the fertilizer treatments on milk forage units (MFU) were 261 for N, 1107 for P and 1003 MFU ha−1 for N–P fertilizer treatments. Among fertilizers, the residual effect of the N‐P fertilizer treatment promoted an increase in DM yield but produced little variation in floristic composition of the pasture. In general, the fertilizer treatments increased DM yield and nutritive value of herbage and reduced floristic composition in pastures on these Mediterranean sites.

Simulating Long‐Term and Residual Effects of Nitrogen Fertilization on Corn Yields, Soil Carbon Sequestration, and Soil Nitrogen Dynamics

Soil carbon sequestration (SCS) has the potential to attenuate increasing atmospheric CO2 and mitigate greenhouse warming. Understanding of this potential can be assisted by the use of simulation models. We evaluated the ability of the EPIC model to simulate corn (Zea mays L.) yields and soil organic carbon (SOC) at Arlington, WI, during 1958-1991. Corn was grown continuously on a Typic Argiudoll with three N levels: LTN1 (control), LTN2 (medium), and LTN3 (high). The LTN2 N rate started at 56 kg ha(-1) (1958), increased to 92 kg ha(-1) (1963), and reached 140 kg ha(-1) (1973). The LTN3 N rate was maintained at twice the LTN2 level. In 1984, each plot was divided into four subplots receiving N at 0, 84, 168, and 252 kg ha(-1). Five treatments were used for model evaluation. Percent errors of mean yield predictions during 1958-1983 decreased as N rate increased (LTN1 = -5.0%, LTN2 = 3.5%, and LTN3 = 1.0%). Percent errors of mean yield predictions during 1985-1991 were larger than during the first period. Simulated and observed mean yields during 1958-1991 were highly correlated (R2 = 0.961, p < 0.01). Simulated SOC agreed well with observed values with percent errors from -5.8 to 0.5% in 1984 and from -5.1 to 0.7% in 1990. EPIC captured the dynamics of SOC, SCS, and microbial biomass. Simulated net N mineralization rates were lower than those from laboratory incubations. Improvements in EPIC's ability to predict annual variability of crop yields may lead to improved estimates of SCS.

Residual Effect of Copper and Zinc from Fertilizers on Plant Concentration, Phytotoxicity, and Crop Yield Response

To avoid toxicity resulting in reduced crop yields and/or phytotoxic symptoms on the foliage, information on the residual effect of micronutrient fertilization after periods of application is desirable. This article includes discussion on the micronutrients copper (Cu) and zinc (Zn), because they are essential and are of concern from plant and animal standpoints. In general, no detrimental effects in yield reduction or phytotoxicity were noted from Cu applications of up to 50 kg Cu ha−1 to barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.). Barley was an exception where 50 kg Cu ha−1 decreased yield by about 12% in the first‐year crop. The Cu levels in plants did not exceed 9 mg kg−1. Studies showed that Zn applications of 50 kg ha−1 for 2 years in succession and the resulting crop tissue Zn levels as high as 105 mg kg−1 did not cause any phytotoxicity in cereals. The results of this study suggest that cereals can tolerate high levels of Cu and Zn.

Nutrient runoff from a Korean rice paddy watershed during multiple storm events in the growing season

Summary The concentrations and loading characteristics of total nitrogen (TN) and total phosphorous (TP) in runoff from a 50.1-ha rice paddy field watershed in South Korea were investigated for eight storm events during the 1998–2001 growing seasons. TN concentrations in total runoff were inversely related to discharge, except in periods with high fertilization rates. In contrast, TP concentrations were strongly proportional to discharge under non-ponded paddy conditions, but not correlated with discharge under most ponded paddy conditions. Stormflow and irrigation return flow were separated from total runoff using the constant-discharge method. The flow-weighted mean TN concentration in stormflow was lower than that in irrigation return flow, mainly because of rainwater dilution, except for periods with a residual fertilizer effect. The flow-weighted mean TP concentration in stormflow, however, was always higher than that in irrigation return flow, likely a result of sediment-associated phosphorus transport. The ratio of mean TP concentration in stormflow to that in irrigation return flow under ponded paddy conditions (1.6) was approximately one-half that under non-ponded conditions (3.1), suggesting that ponding on paddy fields played an important role in reducing soil erosion-related phosphorus export. Relationships between TN loads and stormflow runoff volumes were found except during a storm event in the high fertilization period (p

Direct and residual effects of sulphur fertilization on productivity of sugarcane

The experiment was carried out during 1999 to 2001 on two plant and two ratoon crops of sugarcane at Sugarcane Research Station, Jalandhar. The direct effects of application of sulphur @ 0,20,40,60 and 80 Kg S/ha were studied on plant crop and the residual effects on succeeding ratoon crops. The sulphur application did not increase the cane yield in the first year as this experimental site contained 14 ppm of available sulphur that was above the critical limit of 10 ppm. In the second year the soil contained 10 ppm of available sulphur and the crop responded only upto 20 Kg/ha of applied sulphur. The sulphur content of the index leaf as well as the number of tillers and millable canes showed a pattern similar to that of cane yield. In the ratoon crop, significant residual effects wee observed during both the years due to 40 and higher levels of sulphur applied to plant crop. Thee was no residual response to 20 K S/ha. Though the experimental sites contained 14 and 10 kg of available S/ha, in the first and second years suggesting thereby that the critical levels of soil S may be higher for ratoons that for the plant crop.

Residual effects of NPK fertilization on shrub growth in a Yukon boreal forest

Residual effects of nutrient additions were sustained in shrubs 4–8 years after fertilization stopped in a northern boreal forest in Yukon, Canada. We measured the growth rate of grey willow (Salix glauca L.) and bog birch (Betula glandulosa Michx.) twigs during the growing seasons of 1998, 2001, and 2002, 4–8 years after NPK fertilization from 1987 to 1994 had ceased. We also measured the nitrogen concentration of the 1998 growth tissue. Willow twigs had significantly higher growth rates in previously fertilized shrubs than control shrubs in these 3 years, even greater than differences observed during fertilization. Willow also had higher N concentration in fertilized twigs than control twigs. Birch growth was negatively correlated with hare abundance during the snowshoe hare (Lepus americanus) abundance cycle. Birch growth rate was higher in fertilized twigs than control twigs in 1998 during the hare peak, but fertilized birch twigs approached control levels by 2002 following the hare decline.Key words: Salix, Betula, productivity, nitrogen, fertilizer, herbivory.

Residual N and P fertilizer effect and fertilizer recovery on intercropped and sole-cropped corn and bean in semiarid northeast Brazil

The effects of a single 15N and P fertilizer application (16 and 12 kg ha–1) on intercropped and sole-cropped corn and beans was followed over three consecutive years. Grain (0.1–0.9 ton ha–1 yr–1) and straw productions (0.2–2.5 ton ha–1 yr–1) were limited by rainfall and showed small responses to fertilizer. In the first year, plant N uptake was more than twice the fertilizer amounts, while P uptake was less than half the fertilizer amounts. Plant N derived from fertilizer was low (9–19%). Sole corn took up more (34%) than beans (16%) and the combined intercrop (26%) and also had higher recovery of fertilizer in the soil than single beans (50% against 28%). The distribution of fertilizer N and P in the soil showed a similar pattern in all treatments, with a high concentration around the application spot and decreasing concentrations at greater distances and above and below this point. Total P increases in a soil volume 10 cm around the application spot corresponded to 60% of the amount applied. Fertilizer contributions to the second crop were < 3% of total plant N and represented <6% of the applied amount. Therefore, the residual fertilizer effect on production was attributable to P. The patterns of fertilizer N and P distribution in the soil remained similar but N recoveries decreased 14–18%. Despite low rainfall, low productivities and reasonable proportions of fertilizer N remaining in the soil, the residual effects of the applied fertilizer N were too low to justify a fertilizer recommendation based on economic returns on the investment.

Current and residual effects of nitrogen fertilizer applied to grass pasture on production of beef cattle in central Saskatchewan

Four rates of nitrogen fertilizer (0, 50, 100 and 200 kg N ha-1) were applied for 4 yr to two replications of a 32-yr-old crested wheatgrass (Agropyron cristatum) pasture at Lanigan, Saskatchewan, after which no fertilizer was applied for a further 4 yr. The pastures were grazed by pregnant yearling Hereford heifers using a “put-and-take” stocking system. Soil cores (0–60 cm) were taken to monitor soil NO3-N concentrations either in early spring, before grass growth commenced, or in late fall, after grass growth had ceased. Pasture measurements included available forage at the start of the grazing season, total forage production and the concentrations of crude protein, acid detergent fiber (ADF), ash, Ca, P, Mg, K, Cu, Zn, Fe and Mn. Heifers, fistulated at the esophagus, were used in 1984 and 1985 to obtain samples of the grazed herbage, which were analyzed for organic matter digestibility (OMD), protein and minerals, except P and K. Heifer intakes of digestible organic matter (DOMI), protein and minerals, except P and K, were estimated from their concentrations in fistula extrusa and estimates of intake obtained from extrusa digestibility and fecal output using Cr2O3 as a fecal marker. Phosphorus intake was estimated from fecal P concentration. Plasma samples were also collected and analyzed for concentrations of minerals.

Selecting Iodine-Enriched Vegetables and the Residual Effect of Iodate Application to Soil

A greenhouse pot experiment was conducted to select vegetables for iodine uptake. The residual effect of iodate fertilization on the growth of and iodine uptake by spinach plants were also investigated. Six vegetables, including leafy vegetables (pakchoi [Brassica chinensis L.], spinach [Spinacia oleracea L.]), tuber vegetables (onion [Allium cepa L.]), shoot vegetables (water spinach [Ipomoea aquatica Forsk.], celery [Apium graveolens L.]), and root vegetables (carrot [Daucus carota var. sativa DC.]) were examined. Results showed that the concentrations of iodate in soil had significant effect on the biomass of edible parts of pakchoi and spinach (p<0.01), whereas the concentrations of iodate in soil had no significant effect on that of carrots, water spinach, celery, and onion. Iodine concentrations in edible parts of vegetables and the transfer factors (TFedible parts) of soil-to-edible parts of vegetables significantly increased with increasing iodine concentrations in soil (p<0.001), and iodine concentrations in edible parts and TFedible parts of spinach were much higher than those of other vegetables at any treatment. Both transfer coefficients for edible parts (TCedible parts) and for aerial parts (TCaerial parts) of vegetables changed differently with increasing iodine concentrations in the soil, and TCedible parts and TCaerial parts of spinach were higher than those of other vegetables. Therefore, spinach was considered as an efficient vegetable for iodine biofortification. Further experiment showed that there is considerable residual effect of soil fertilization with iodate.

Rendimento de milho em área de integração lavoura-pecuária sob o sistema plantio direto, em presença e ausência de trevo branco, pastejo e nitrogênio

O trabalho experimental foi realizado no campo, na Estação Experimental da Fundação Agrária de Pesquisa Agropecuária (FAPA), em Guarapuava (PR), Brasil, nos anos agrícolas de 1999 e 2000, com o objetivo de verificar a influência da adubação nitrogenada residual na cultura do milho, em Sistema Plantio Direto, cultivado em seqüência, em áreas que no inverno tinham presença e ausência de trevo branco e de animais em pastejo. O delineamento experimental foi o de blocos ao acaso com três repetições. Os tratamentos foram arranjados em parcelas subdivididas. No inverno, nas parcelas, foram aplicados quatro doses de nitrogênio (N-TI = 0, 100, 200 e 300 kg ha-1 de N) e, nas subparcelas, a combinação de presença e ausência de trevo branco e de pastejo (CT = com trevo; ST = sem trevo; CP = com pastejo e SP = sem pastejo). No verão, em cada subparcela proveniente do inverno, foram aplicadas cinco doses de N (N-TV = 0, 60, 120, 180 e 240 kg ha-1 de N), em cobertura, e cultivado o milho. A máxima eficiência técnica de rebrote da cultura de inverno, avaliada dezoito dias após a retirada dos animais, foi obtida com a aplicação de 231 kg ha-1 de N (N-TI). As áreas CP/N-TI apresentaram maiores produtividades do milho que as áreas SP; contudo, estes resultados não foram estatisticamente significativos. As áreas sem N-TI produziram mais milho em subparcelas SP. As parcelas que receberam 300 kg ha-1 de N N-TI não mostraram resposta do milho ao N-TV, comprovando o efeito residual do N-TI. Conclui-se que a interação entre pastejo e N-TI contribui para a nutrição nitrogenada da cultura do milho.

Effect of Direct and Residual Effects of Different Sulfur Fertilizers on Groundnut and Wheat Cropping System on Typic Haplaquent Soils

A field experiment was conducted on sulfur deficient soil during kharif dry seasons of 1993, 1994, and 1995 to study the comparative efficacy of selected sources of sulfur to groundnut (Arachis hypogaea L.). The results of the experiment were tested on farm trial in cultivator's field during the kharif season of 1999. The yield of groundnut crop in experimental field increased significantly with increasing levels of sulfur up to 40 kg S ha−1. Among the various sources tested, gypsum was the best with respect to yield, followed by single super phosphate and ammonium sulfate. In on‐farm trial the application of gypsum at 20 kg S ha−1 increased the yield parameters and yield over un‐treated control. The residual effect of different sulfur sources on wheat (Triticum aestivum) grain yield, the effect of treatments was non significant but the levels of sulfur and the interaction between source and levels were significant.

Impact of organic residue management on nitrogen use efficiency in an annual rice cropping sequence of lowland Central Thailand

Field experiments were conducted in Central Thailand under a rice–fallow–rice cropping sequence during consecutive dry and wet seasons of 1998 to determine the impact of residue management on fertilizer nitrogen (N) use. Treatments consisted of a combination of broadcast urea (70 kg N ha−1) with rice straw (C/N 67) and rice hull ash (C/N 76), which were incorporated into the puddled soil 1 week before transplanting at a rate of 5 Mg ha−1. Nitrogen-15 balance data showed that the dry season rice recovered 10 to 20% of fertilizer N at maturity. Of the applied N, 27 to 36% remained in the soil. Loss of N (unaccounted for) from the soil–plant system ranged from 47 to 54% of applied N. The availability of the residue fertilizer N to a subsequent rice crop was only less than 3% of the initial applied N. During both season fallows NO3-N remained the dominant form of mineral-N (NO3+NH4) in the aerobic soil. In the dry season grain yield response to N application was significant (P=0.05). Organic material sources did not significantly change grain yield and N accumulation in rice. In terms of grain yields and N uptake at maturity, there was no significant residual effect of fertilizer N on the subsequent rice crop. The combined use of organic residues with urea did not improve N use efficiency, reduced N losses nor produced higher yields compared to urea alone. These results suggested that mechanisms such as N loss through gaseous N emissions may account for the low fertilizer N use efficiency from this rice cropping system. Splitting fertilizer N application should be considered on the fertilizer N use from the organic residue amendment.

Phosphorus form and bioavailability in the pine rotation following fertilization: P fertilization influences P form and potential bioavailability to pine in the subsequent rotation

Soils in some parts of the world are known to be severely phosphorus (P) deficient. As little as 20 kg P ha −1 have produced large growth responses in forest stands. If increased tree growth and augmented P cycling are caused by a one-time P application, a valid question is whether the effect of the initial fertilization will be evident in the regenerating forest, thereby reducing the need for P fertilization early in the second rotation. The objective of this study was to evaluate the P status of the forest floor and inorganic P status of mineral surface soil of two long-term fertilizer trials in order to determine if there were increases in soil P amount and bioavailability that benefits the next rotation. Long-term fertilizer trials in Georgia, USA and New Zealand (29 and 22 years after fertilization) were the study sites. In Georgia, forest fertilization increased the mass of the F horizon by 239% and its P content by 318%. Anion exchange membranes measured up to a 47% increase in bioavailable P in the mineral soil in a fertilized treatment. While bioassays did not show significant residual P in the mineral soil under the fertilized plots, soil from an adjacent operationally fertilized stand, which had the forest floor bedded into its planting rows, showed a 100% increase in seedling P content. At the New Zealand site, the mineral soil contained 142% more P in the anion exchange membrane form than in the unfertilized soils. Bioassays indicated a 224% increase in seedling P content when grown in fertilized soil at the highest fertilization rate. Operational levels of fertilization did not yield a significant bioassay result. The data show that there can be a residual effect of fertilizer P in the rotation following fertilization. The bioassays, anion membrane exchangeable P and forest floor P from Georgia suggest that there is enough P in the soil system to support the needs of a regenerating stand of loblolly pine, while residual bioavailable P in the mineral soil from operational levels of fertilization at New Zealand site would require residual P in the forest floor or immediate fertilization to meet the demands of newly planted seedlings. Conservation of the forest floor is an important part of P management in these P deficient sites.

Soil nutrient contents, microbial properties and maize yield under long-term legume-based crop rotation and fertilization: a comparison of residual effect of manure and NPK fertilizers

A study was conducted in a field experiment that has been ongoing for over 60 years at the University of Pretoria, South Africa. The aim was to compare the residual effects of manure and NPK fertilizers on selected soil nutrients, microbial properties, C and N inputs, maize tissue nutrient concentration and yield under long-term crop rotation. Total organic C, total N and available P levels were increased owing to residuai effects of manure alone or in combination with NPK fertilizers. C input in NPK-fertilized plots was about 47% higher than in manured plots. The estimated fixed N ranged from 52 kg ha−1 in the NPK plots to 164 kg ha−1 in the control plots. Increases in nutrient contents of manured plots were not reflected in microbial properties of the soil. Microbial biomass and numbers were generally higher in the NPK-fertilized than in the manured plots. The differential responses were attributed largely to differences in decomposability of organic materials. Organic material in the NPK treatment appeared to have higher turnover rates than in other treatments, suggesting that C limitation in soils of low C but good nutrient supply may be compensated by the high turnover rate of available organic materials.

Efeito residual da adubação efetuada no cultivo da batata sobre a produção do feijão-de-vagem

Foi avaliado o efeito do adubo residual da batata sobre a produção do feijão-de-vagem em cultivo sucessivo. A batata, cv. Achat, plantada no espaçamento 0,80 m x 0,40 m, foi adubada nas doses: 0; 2 e 4 t ha-1 da fórmula 4-16-8. Posteriormente cultivou-se o feijão-de-vagem, cultivar Macarrão Rasteiro 274 (Horticeres) no delineamento experimental de blocos casualizados, com quatro repetições e no esquema de parcelas subdivididas, tendo nas parcelas a adubação residual do cultivo da batata e nas subparcelas a adubação de plantio do feijão-de-vagem (adubado e não adubado). Observou-se que o aumento das doses da adubação mineral da batata aumentou também os teores de fósforo, potássio e cálcio trocáveis no solo sem alteração do pH. A produção e demais componentes da produção analisados tiveram incremento positivo em função deste efeito residual. É viável a produção do feijão-de-vagem apenas com o resíduo da adubação da batata.