Fertilizer Input Levels Research Articles

Optimal fertilizer rates towards the improvement of nitrogen use efficiency and reduction of nitrogen export in paddy rice-wheat intensive farming

Introduction: Fertilizer application above plant nitrogen (N) requirements, leading to N use inefficiency, has become the primary source of N surplus, posing nonpoint pollution threats. Chao Lake has received N loadings, primarily from the agroecosystem that surrounds it. Based on 10 years of field monitoring and experiment, this study used optimum fertilizer rates (30% N reduction) to evaluate nitrogen use efficiency (NUE) and N export in the Chao Lake watershed of paddy rice-wheat rotational farming.Methods: Five treatments were tested, namely, the Blank Treatment (CK), Conventional Fertilization Treatment (CFT), High Fertilization Treatment (HFT), Reduced Fertilization Treatment (CFT), Reduced Fertilization Treatment plus Straw addition (RFTS). The parameters employed to measure NUE were 1) by calculating NUE indicators; Agronomic efficiency (kg kg-1), recovery efficiency (%), and partial factor productivity (kg kg-1) 2) using the European Union NUE framework as a comparison tool. N export was measured using N export parameters, namely, nitrogen loading (kg ha-1yr-1), nitrogen runoff loss ratio (%), and net nitrogen runoff loss ratio (%).Results and discussion: Results revealed that optimum N fertilizer input levels maintained high crop and biomass yields. The empirical model of y = y0 + a * exp (−0.5 * (x-x0)/b2) explains the relationships between input N fertilizer and corresponding yield returns. Low yield responses to increased N input beyond certain limits were observed, which may lead to N accumulations. N export was much lower from the reduced fertilization treatments than other treatments. N export increased in 10 years for both paddy rice and wheat seasons. Runoff volume influenced N export more than any other environmental factor studied.Conclusion: Overall, optimal fertilizer levels produced high NUE, maintained high economic yield, and produced lesser N exports; NUE was in the order of reduced > high > conventional fertilization treatments, while it decreased in 10 years (2008–2018) across all treatments. Such strategies that further reduce fertilizer levels by accounting for excess supplies are vital for consolidating effective N control measures.

Year-Round Production of Cotton and Wheat or Rapeseed Regulated by Different Nitrogen Rates with Crop Straw Returning

Double direct seeding of cotton (with wheat or rapeseed) is a new method for cotton-growing regions in the Yangtze River Basin to adapt to the development of mechanization. It would help to reduce manual labor, optimize the amount of nitrogen fertilizer to be used, reduce the physical and chemical production costs, and improve the benefits of cotton fields. We selected five counties from the major cotton-producing areas of Hubei Province for three consecutive seasons, from winter 2020 to spring 2022. The experimental sites used no tillage with straw returning to the field, double direct seeding, late sowing at high density, and one-time fertilization to study the effects of different nitrogen fertilizer rates on the yield characteristics of cotton, wheat, and rape and calculate the economic benefits of the two cultivation modes under different nitrogen fertilizer input levels through parameters such as land-use efficiency, production efficiency, and profitability. In both cotton–wheat and cotton–rapeseed cropping systems, the number of bolls per plant in cotton was the lowest in the N165 (90 cotton + 75 wheat/rape kg ha−1) treatment. The cotton yield was the highest at N247.5 (135 cotton + 112.5 wheat/rape kg ha−1) in the cotton after the wheat system and N412.5 (225 cotton + 187.5 wheat/rape kg ha−1) in the cotton after the rape system. The yield of wheat and rape increased with the increase in the levels of nitrogen fertilizer, with the N165 treatment showing the lowest values. With an increase in nitrogen fertilizer, the harvest index of wheat first maximized and then started decreasing. The harvest index in wheat was the highest at N247.5 (135 cotton + 112.5 wheat/rape kg ha−1) and N330 (180 cotton + 150 wheat/rape kg ha−1), whereas, in rape, it increased with nitrogen fertilizer application, with the highest value at N495 (270 cotton + 225 wheat/rape kg ha−1). Economically, the expenses and income of both cotton–wheat and cotton–rape systems increased as nitrogen fertilizer increased. The net profit and benefit ratio first increased and then decreased with increasing nitrogen fertilizer, with N247.5 (135 cotton + 112.5 wheat/rape kg ha−1) scoring the maximum values for both of these parameters. The land-use efficiency and production efficiency increased with the increase in nitrogen fertilizer, and the production efficiency of the N165 (90 cotton + 75 wheat/rape) treatment was significantly lower than that of the other four treatments. The profitability increased first and then decreased with the increase in nitrogen fertilizer, with the N247.5 (135 cotton + 112.5 wheat/rape) treatment showing the highest profit. The production cycle of cotton–rape was slightly shorter than that of cotton–wheat, and the system productivity was also lower. The expenses and land-use and production efficiency of the rapeseed system were lower than those of wheat, while the gross income, net profit, and productivity of the cotton–rape system were higher than those of cotton–wheat. The application of nitrogen fertilizer in the cotton–wheat double-cropping system under straw return can achieve the maximum net profit, production ratio, and yield at the low nitrogen level of N247.5, (135 cotton + 112.5 wheat/rape kg ha−1). Due to the price advantage of rape, the net profit, production ratio, and income of the cotton–rape production system are higher than those of the cotton–wheat production system.

Long-Term Effect of Manure and Mineral Fertilizer Application Rate on Maize Yield and Accumulated Nutrients Use Efficiencies in North China Plain

Overuse of mineral fertilizer has become common at the North China Plain. Simultaneously, more organic manure resources are available for smallholder farmers. In order to increase the use of organic manure and reduce mineral fertilizer applications, a 10-year fertilization experiment with maize took place between 2008 and 2017. We assessed the long-term effects of cattle manure (CM) application and a complete nutrient substitution with mineral fertilizer (MF) at four application levels (3, 6, 9 and 12 t ha−1 CM) on yield, macronutrients (N, P and K) use efficiencies and soil conditions. Results showed that maize yields from CM and MF treatments differed across time and were significantly different in the first year of the experiment to no significant differences with increasing experimental time. In addition, increased MF levels did not result in increased maize yields; this response was different with CM applications. The highest 10-year maize average yield was 7.7 t ha−1 obtained with 9 t ha−1 of CM. Our results also showed that at the lowest application level (3 t ha−1 CM), the partial factor productivity (PFP) and the agronomic efficiency (AE) of all macronutrients were significantly higher with MF than with CM applications. Nevertheless, these differences narrowed with increased fertilizer input levels. The MF and CM recovery efficiency (RE) of N, P and K performed differently. Generally, MF exhibited significantly higher N-RE than CM treatments. CM treatments had significantly higher P-RE, but no K-RE differences were found between CM and MF. Soil available N, P and K significantly increased when fertilizer levels raised. MF treatments exhibited similar levels of soil available N, but lower soil available P and K compared with CM treatments.

Simulation of a regional soil nitrogen balance in Swiss croplands

Nitrogen (N) management in cropping systems needs adjustments because constraints to crop production are mostly related to high inputs and low recovery of N fertilizers. We used the DayCent model to predict regional N inputs, outputs, and balances of Swiss soils under (1) a range of N fertilizer input levels (0–300% of recommended crop-specific rates) and (2) organic fertilization, reduced tillage or cover cropping at the recommended input of N. The crops included wheat, maize, and root/tuber crops and legumes. Decreasing N inputs reduced the environmental impact by 13.5–51.3 kg N ha $$^{-1}$$ , but it also reduced the yield by 6.8–44.8 kg N ha $$^{-1}$$ . Increasing N inputs led to an increase in yield by 5.6–29.5 kg N ha $$^{-1}$$ , but with additional losses of 14.9–181.8 kg N ha $$^{-1}$$ into the environment. Harvested crop N and $$\hbox {NO}_3^{-}$$ leaching accounted for 30–59% and 27–62% of fertilizer-derived changes in total N output, respectively. Converting conventional to organic cropping led to a mean increase in soil N balance by 0.3–62.6 kg N ha $$^{-1}$$ . The soil N balance increased the most by using partially decomposed organic fertilizer in combination with cover cropping and reduced tillage. However, this positive N balance was mainly due to a reduction in N removal with harvest and $$\hbox {NO}_3^{-}$$ leaching. The use of highly decomposable organic matter and cover cropping did not lead to any N yield penalty while decreasing $$\hbox {NO}_3^{-}$$ leaching. These results highlight that organic practices combined with reduced tillage and cover cropping can optimize the use and recovery of N resources.

Evaluating the effect of agronomic management practices on the performance of differing spelt (Triticum spelta) cultivars in contrasting environments

Abstract Spelt (Triticum spelta) is an ancient wheat which is attracting renewed interest with an increasing demand for wholegrains and ancient cereals in the diet. This study evaluates the yield and quality performance of four contrasting European spelt varieties (both landraces and modern cultivars) grown with different fertiliser types (cattle slurry, farm yard manure, and biogas digestate in comparison with mineral N) and rates (50 and 100 kg N ha−1) in contrasting environments, i.e. the UK and CZ in the 2014−15 and 2015−16 seasons. Grain yield was similar in both seasons but was greater in CZ than the UK (4.9 vs 3.2 t ha−1) which was also supported by a much greater harvest index (HI) of 40.4 vs 31.3 % and all yield components measured. The yield differences were largely related to differences in climate and disease levels, i.e. leaf blotch (S. tritici) and yellow rust (Puccinia striiformis), which were much greater in the UK. Clear varietal differences were evident between the two sites especially in susceptibility to yellow rust. Leaf chlorophyll data showed that the uptake efficiency of the biogas digestate was similar to that of mineral N resulting in greater grain yield when averaged across sites and seasons. Significantly lower levels of yellow rust were observed under the biogas digestate treatment in the UK relative to the other fertiliser types. Clear genotype (G) x environment (E) interactions show the benefits of selecting spelt varieties suited to particular environments. Although yields of spelt are lower than common wheat, the crop benefits from lower inputs of fertiliser and the use of biogas digestate where available can provide a clear opportunity for organic and reduced input growers. The ability of the crop to produce a high grain protein content from low levels of fertiliser input shows the clear potential of spelt production systems whereby wheat in the UK struggles to achieve13 % protein from much greater rates of N fertiliser.

Anammox bacterial abundance and biodiversity in greenhouse vegetable soil are influenced by high nitrate content

The anaerobic ammonium oxidizing (anammox) process has been found to play an important role in terrestrial ecosystems in recent years. However, the diversity and abundance of anammox bacteria in nitrogen (N)-rich agricultural soils under high fertilizer greenhouse conditions are still unclear. Two greenhouse fields with different N fertilizer input levels were chosen, and their soil profiles were studied with molecular technologies, including quantitative polymerase chain reaction assay, a clone library, and phylogenetic analysis based on hzsB (encoding anammox hydrazine synthase β-subunit) gene. Molecular analyses suggested that anammox bacteria were at their highest density at 10–20 cm soil depth, and that the anammox bacterial abundance was significantly lower at high N than at low N. Candidatus Brocadia was the sole anammox bacterial genus throughout the soil depth profiles. The highest diversity of anammox bacteria was found at 30–40 cm soil depth, and different phylotypic clusters of Candidatus Brocadia were associated with specific soil environmental factors, such as nitrates, soil depth, and total N. Correlation analyses and redundancy analyses confirmed that high nitrate content associated with high N fertilizer input had a significant negative influence on the abundance and biodiversity of anammox bacteria. These results imply that excessive use of N fertilizer would affect arid land soil N loss to the atmosphere by the anammox pathway.

Effects of straw management and nitrogen application rate on soil organic matter fractions and microbial properties in North China Plain

A 2-year field experiment was conducted on the North China Plain to assess the effects of two straw management practices and different nitrogen fertilizer addition levels on soil organic matter (SOM) fractions and microbial properties under a winter wheat-summer maize cropping system. Eight treatments (two straw management practices and four nitrogen fertilizer input levels) were established using a randomized complete block design. The straw management practices were no straw return and straw return. Each straw management practice received nitrogen fertilizer rates at 0 (N0), 270 (N270), 360 (N360), or 450 (N450) kg N ha−1 year−1. The soil properties measured included SOM fractionation, enzyme activities, community level physiology profile (CLPP), and microbial community abundance and composition, which were represented by phospholipid fatty acid (PLFA). Compared to no straw return, the addition of straw significantly increased soil total organic carbon and nitrogen, particulate organic carbon and nitrogen, and occluded particulate organic carbon and hot water extractable organic carbon by 7–29%. Invertase, protease, urease, and dehydrogenase activities increased by 22–40%. The biomasses of Gram-positive bacteria and fungi also increased. The increase in SOM fractions may be attributed to the decomposition of the added straw by more active enzymes, which may result from the shift of microbial community composition. In addition, hot-water extractable organic carbon, NO3-N, urease activity, and fungal biomass in the N270, N360, and N450 treatments significantly increased, independent of the nitrogen application rate, which indicated that N input level had a non-linear effect on soil properties in this area. Short-term straw return combined with a modest nitrogen fertilizer input (270 kg N ha−1 year−1) can increase SOM contents and microbial activity, which may help improve soil fertility in this region.

Linking crop- and soil-based approaches to evaluate system nitrogen-use efficiency and tradeoffs

Increasing nitrogen (N)-use efficiency (NUE) is key to improving crop production while mitigating ecologically-damaging environmental N losses. Traditional approaches to assess NUE are principally focused on evaluating crop responses to N inputs, often consider only what happens during the growing season, and ignore other means to improve system efficiency, such as by tightening the cycling of soil N (e.g. with N scavenging cover crops). As the goals of improving production and environmental quality converge, new metrics that can simultaneously capture multiple aspects of system performance are needed. To fill this gap, we developed a theoretical framework that links both crop- and soil-based approaches to derive a system N-use efficiency (sNUE) index. This easily interpretable metric succinctly characterizes N cycling and facilitates comparison of systems that differ in biophysical controls on N dynamics. We demonstrated the application of this new approach and compared it to traditional NUE metrics using data generated with a process-based model (APSIM), trained and tested with experimental datasets (Iowa, USA). Modeling of maize-soybean rotations indicated that despite their high crop NUE, only 45% of N losses could be attributed to the inefficient use of N inputs, whereas the rest originated from the release of native soil N into the environment, due to the asynchrony between soil mineralization and crop uptake. Additionally, sNUE produced estimates of system efficiency that were more stable across weather years and less correlated to other metrics across distinct crop sequences and N fertilizer input levels. We also showed how sNUE allows for the examination of tradeoffs between N cycling and production performance, and thus has the potential to aid in the design of systems that better balance production and environmental outcomes.

Plastic film mulch increased winter wheat grain yield but reduced its protein content in dryland of northwest China

Plastic film mulch has been proved of great potential to enhance crop productivities in drylands, but there is still lacking insight into its underlying changes in crop grain nutritional quality. Therefore, field experiments were conducted to investigate the effects of different soil surface managements on grain yield and its protein content of winter wheat in 2014–2016 at different fertilizer input levels under no mulch and plastic film mulch at seven sites in dryland of the Loess Plateau in northwest China. Compared with no mulch, overall average grain yield was significantly increased by 13.7%, but its protein content was decreased by 7.8% with plastic film mulch. Apart from the dilution effects caused by the much more increase of grain yield, the decreased N remobilization from vegetative parts to grain and the lowered crop N uptake from soil during grain filling stage were found to be the main reasons, when the overall average of N remobilization efficiency, N harvest index and post-anthesis N uptake was respectively decreased by 16.0%, 5.7% and 24.0%. However, the winter wheat grain protein content was observed to increase more quickly with the N rate increase under plastic film mulch, compared to no mulch. This provides opportunity to increase the grain protein content under plastic film mulch to the same level of no mulch by increasing the N fertilizer application rates, and an estimation of optimal N application rates for winter wheat grain yield and its protein content was computed under plastic film mulch in drylands.

Tea planting affects soil acidification and nitrogen and phosphorus distribution in soil

Land use change from natural forest to agricultural land often affects the properties of soil, resulting in various environmental problems. A field study was conducted to evaluate the effects of land use change from forest to tea cultivation on soil acidification as well as the nitrogen (N) and phosphorus (P) leaching risk. The soil acidification and nutrient concentrations in soil at a depth of 0–200cm in two tea gardens with differing stand ages (10 and 100 years old), and three different fertilizer input levels (low-input, medium-input, and high-input), and in the forests adjacent to these tea gardens were measured at the Tea Research Institute of the Chinese Academy of Agricultural Sciences. Tea cultivation caused soil acidification throughout the 0–200cm soil profile, and the lowest soil pH was observed in the 20–40 or 40–60cm soil depth. Both nitrate (NO3−) and ammonia (NH4+) concentrations increased as the tea stand age and fertilizer input levels increased at the 0–90cm soil depth. Compared to the forests, significantly higher concentrations of NO3− and NH4+ were observed in the 90–200cm soil of the tea gardens, suggestive of a high risk of N leaching loss in the tea gardens. Longer tea cultivation times and higher input levels also increased the concentration of soil available P and CaCl2-P at 0–90cm soil depth, and a change point was observed in the relationship between soil available P and CaCl2-P. Depending on the relationship between soil available P and soil CaCl2-P, the soil CaCl2-P concentration dramatically increased when soil available P surpassed 75.1mgkg−1. This study also indicated that soil acidification could occur in deep soil profiles as a result of tea cultivation and excessive fertilization; thus, there is a high risk of N and P leaching loss in tea gardens.

Relationship between Remote Sensing Data, Plant Biomass and Soil Nitrogen Dynamics in Intensively Managed Grasslands under Controlled Conditions.

The sustainable use of grasslands in intensive farming systems aims to optimize nitrogen (N) inputs to increase crop yields and decrease harmful losses to the environment at the same time. To achieve this, simple optical sensors may provide a non-destructive, time- and cost-effective tool for estimating plant biomass in the field, considering spatial and temporal variability. However, the plant growth and related N uptake is affected by the available N in the soil, and therefore, N mineralization and N losses. These soil N dynamics and N losses are affected by the N input and environmental conditions, and cannot easily be determined non-destructively. Therefore, the question arises: whether a relationship can be depicted between N fertilizer levels, plant biomass and N dynamics as indicated by nitrous oxide (N2O) losses and inorganic N levels. We conducted a standardized greenhouse experiment to explore the potential of spectral measurements for analyzing yield response, N mineralization and N2O emissions in a permanent grassland. Ryegrass was subjected to four mineral fertilizer input levels over 100 days (four harvests) under controlled environmental conditions. The soil temperature and moisture content were automatically monitored, and the emission rates of N2O and carbon dioxide (CO2) were detected frequently. Spectral measurements of the swards were performed directly before harvesting. The normalized difference vegetation index (NDVI) and simple ratio (SR) were moderately correlated with an increasing biomass as affected by fertilization level. Furthermore, we found a non-linear response of increasing N2O emissions to elevated fertilizer levels. Moreover, inorganic N and extractable organic N levels at the end of the experiment tended to increase with the increasing N fertilizer addition. However, microbial biomass C and CO2 efflux showed no significant differences among fertilizer treatments, reflecting no substantial changes in the soil biological pool size and the extent of the C mineralization. Neither the NDVI nor SR, nor the plant biomass, were related to cumulative N2O emissions or inorganic N at harvesting. Our results verify the usefulness of optical sensors for biomass detection, and show the difficulty in linking spectral measurements of plant traits to N processes in the soil, despite that the latter affects the former.

Prediction of nutrient digestibility and energy concentrations in fresh grass using nutrient composition

Improved nutrient utilization efficiency is strongly related to enhanced economic performance and reduced environmental footprint of dairy farms. Pasture-based systems are widely used for dairy production in certain areas of the world, but prediction equations of fresh grass nutritive value (nutrient digestibility and energy concentrations) are limited. Equations to predict digestible energy (DE) and metabolizable energy (ME) used for grazing cattle have been either developed with cattle fed conserved forage and concentrate diets or sheep fed previously frozen grass, and the majority of them require measurements less commonly available to producers, such as nutrient digestibility. The aim of the present study was therefore to develop prediction equations more suitable to grazing cattle for nutrient digestibility and energy concentrations, which are routinely available at farm level by using grass nutrient contents as predictors. A study with 33 nonpregnant, nonlactating cows fed solely fresh-cut grass at maintenance energy level for 50 wk was carried out over 3 consecutive grazing seasons. Freshly harvested grass of 3 cuts (primary growth and first and second regrowth), 9 fertilizer input levels, and contrasting stage of maturity (3 to 9 wk after harvest) was used, thus ensuring a wide representation of nutritional quality. As a result, a large variation existed in digestibility of dry matter (0.642–0.900) and digestible organic matter in dry matter (0.636–0.851) and in concentrations of DE (11.8–16.7 MJ/kg of dry matter) and ME (9.0–14.1 MJ/kg of dry matter). Nutrient digestibilities and DE and ME concentrations were negatively related to grass neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents but positively related to nitrogen (N), gross energy, and ether extract (EE) contents. For each predicted variable (nutrient digestibilities or energy concentrations), different combinations of predictors (grass chemical composition) were found to be significant and increase the explained variation. For example, relatively higher R2 values were found for prediction of N digestibility using N and EE as predictors; gross-energy digestibility using EE, NDF, ADF, and ash; NDF, ADF, and organic matter digestibilities using N, water-soluble carbohydrates, EE, and NDF; digestible organic matter in dry matter using water-soluble carbohydrates, EE, NDF, and ADF; DE concentration using gross energy, EE, NDF, ADF, and ash; and ME concentration using N, EE, ADF, and ash. Equations presented may allow a relatively quick and easy prediction of grass quality and, hence, better grazing utilization on commercial and research farms, where nutrient composition falls within the range assessed in the current study.

Weed biodiversity and rice production during the irrigation rehabilitation process in Cambodia

A phytosociological survey of weed species was conducted during the rainy season in 2008 in paddy fields at different distances from the main irrigation canal in the Kamping Puoy Irrigation Rehabilitation Area in northwestern Cambodia. The spatial variation in water depth was large between upstream (shallower) and downstream (deeper) paddies, which resulted in different weed, with many Poaceae and Cyperaceae species observed on levees in upstream and aquatic herbs in downstream paddies. Chemical fertilizer input levels were generally small and average rice yield was relatively low (ca. 2.3t/ha). Traditional and less intensive weed management options such as hand weeding, mid-season tillage, and post-harvest straw burning were common, while the herbicide 2,4-D was also widely used. Weed species in the paddy ecosystem used by villagers included Ipomoea aquatica, Nymphaea nouchali, and Monochoria vaginalis (occasional, for human consumption) and graminoid species (frequent, for cattle feed in addition to rice straw). Greater inorganic fertilizer input was associated with a lower diversity of weed species, but grain yield and weed diversity indices had no negative relation among different locations. This survey revealed relatively small extent of intensification in the irrigation rehabilitation area in Cambodia, which led to high weed diversity, including numerous plant species available for use to support farmers’ livelihoods in the area.

土壤水分和氮添加对华北平原高产农田有机碳矿化的影响

A highly productive soil from the North China Plain was used for a homoeothermic incubation study at 25 ℃ for105 d to identify the characteristics of soil organic C mineralization and investigate the impacts on that mineralization of soil moisture,and addition of inorganic and organic nitrogen. Four fertilizer input levels and four moisture gradient treatments were used in the experiment,including a control( S0),inorganic nitrogen( urea,S1),inorganic and organic nitrogen( 50% urea+50% chicken manure,S2) and organic nitrogen( chicken manure,S3). The N application rate of the S1,S2 and S3 treatments was 200 kg N /hm2,with 20% field capacity( M0),50% field capacity( M1),75% field capacity( M2) and 100% field capacity( M3) used with each soil treatment,giving a total of sixteen treatments with three replicates. The soil organic C mineralization rate of all treatments sharply declined at the first day of incubation,decreased by 57. 2% —75. 0% over the first 7 d,and appeared as secondary peaks at the 20 thday of incubation. Soil organic C mineralization ranged from 208. 8 to 1161 mg /kg and mainly happened in the first 50 days,especially in the first 30 days( accounting for 59.1%—69.9% of the total mineralized soil C). The net mineralization rate of all treatments ranged from0. 07% to 2. 01%. According to simulation using a double exponential model,the potential organic C mineralization flux and rate were 219. 1—1204 mg /kg and 1. 75% —9. 66%,respectively. The active and resistant pools were 53. 0—135. 1mg /kg and 156. 9—1069 mg /kg,respectively. Organic C mineralization of soil with fertilizer was significantly affected by the soil water content( P 0. 05). The higher the soil water content( from 25% to 100% of field capacity),the more organic C accumulated in the soil under the same fertilizer addition conditions. The relationship between organic C mineralization and soil water content was well fitted by a quadratic function equation( P 0. 05). When the soil water content increased from M0 to M3,the average organic C mineralization rate significantly increased to 18. 4 mg·kg-1·d-1,20. 9 mg·kg-1·d-1,22.3 mg·kg-1·d-1and 23. 5 mg·kg-1·d-1from 4. 47 mg·kg-1·d-1,4.64 mg·kg-1·d-1,4.61 mg·kg-1·d-1and 4. 88 mg·kg-1·d-1,respectively. However,the increasing rate gradually reduced to 30.0%—43.9% and-3.08%—12. 4% from 66. 9% —261%. The amount of C mineralized in the soils amended with fertilizer was significantly higher than that in the control treatment. The average mineralization rates of the S1,S2 and S3 treatments increased above that in the S0 treatment by 3. 86% —27. 9%,3. 28% —39. 5% and 9. 27% —31. 5%,respectively. However,there were no significant differences among the S1,S2 and S3 treatments at the same soil water content conditions. Thus there were no significant differences between the forms of added nitrogen,i. e. organic nitrogen( chicken manure) or inorganic nitrogen( urea). The amounts of soil organic C mineralization were linearly related to the microbial biomass carbon( P0.01) and mineral nitrogen( P0. 05),indicating that the contents of microbial biomass carbon and mineral nitrogen were the key factors affecting the mineralization of C. It can be concluded that soil organic C mineralization was significantly affected by soil moisture and nitrogen addition,and that there was a significant interaction with soil moisture and nitrogen addition( P0. 05).

Studies on yield and economics of sunflower (Helianthus annuus L.) hybrids andvarieties as influenced by different fertilizer levels

A field experiment was conducted during the rainy season of 2008, 2009 and 2010 on Vertisol at Oilseeds Research Station, Latur to assess the productivity and response of sunflower (Helianthus annuus L.) hybrid and varieties to fertilizer inputs. Three hybrids along with two varieties were evaluated with four levels of fertilizer inputs. The result indicated that hybrids were superior over varieties. Sunflower hybrid LSFH-35, gave highestseed yield and monetary returns. The response to fertilizer was significant up to 150% RDF (90:45:45 NPK kg/ha).

Nitrogen fixation and transfer in grass-clover leys under organic and conventional cropping systems

Symbiotic dinitrogen (N2) fixation is the most important external N source in organic systems. Our objective was to compare symbiotic N2 fixation of clover grown in organically and conventionally cropped grass-clover leys, while taking into account nutrient supply gradients. We studied leys of a 30-year-old field experiment over 2 years in order to compare organic and conventional systems at two fertilization levels. Using 15N natural abundance methods, we determined the proportion of N derived from the atmosphere (PNdfa), the amount of Ndfa (ANdfa), and the transfer of clover N to grasses for both red clover (Trifolium pratense L.) and white clover (Trifolium repens L.). In all treatments and both years, PNdfa was high (83 to 91 %), indicating that the N2 fixation process is not constrained, even not in the strongly nutrient deficient non-fertilized control treatment. Annual ANdfa in harvested clover biomass ranged from 6 to 16 g N m−2. At typical fertilizer input levels, lower sward yield in organic than those in conventional treatments had no effect on ANdfa because of organic treatments had greater clover proportions. In two-year-old leys, on average, 51 % of N taken up by grasses was transferred from clover. Both, organically and conventionally cropped grass-clover leys profited from symbiotic N2 fixation, with high PNdfa, and important transfer of clover N to grasses, provided sufficient potassium- and phosphorus-availability to sustain clover biomass production.

Yield Potential and Physiological and Morphological Characteristics Related to Yield Performance in Oryza glaberrima Steud.

Oryza glaberrima has mostly been used as a source to improve stress resistance of Oryza sativa. Improvement of this species could be an approach to use its adaptability to local environments in Africa such as multiple resistance to several indigenous constraints. The yield of O. glaberrima was inferior to that of O. sativa under favorable growth conditions but not under unfavorable conditions. Moreover, spikelet number before grain shattering was no less in O. glaberrima than in O. sativa at any fertilizer input levels, suggesting that the yield potential of O. glaberrima is as high as that of O. sativa. Inferior yield of O. glaberrima reported in favorable environments could result from grain shattering enhanced by such growth environments where higher incidence of lodging, which is another undesirable character of O. glaberrima, can occur. Regarding characteristics associated to yield generation, O. glaberrima seemed to possess: higher dry matter production and greater leaf area than O. sativa at least until heading; a lower photosynthetic rate per leaf area but a higher rate against the same leaf nitrogen content in a low content range; higher responsiveness of dry matter, leaf area and leaf photosynthesis to increases in nitrogen inputs; lower water-use efficiency on dry matter accumulation and gas exchange bases; faster progress of leaf senescence during maturity; and faster completion of grain filling during maturity than O. sativa.

Effects of fertilizer application on summer usage of cereal fields by farmland birds in central Hungary

Capsule Despite negative effects of inorganic fertilizer on weeds and invertebrates in cereal fields, impacts on bird usage were weak and non-linear. Aim To assess the effects of inorganic fertilizer application to winter cereals on breeding-season usage by farmland birds. Methods We measured bird usage of winter-sown cereal fields across a gradient of inorganic fertilizer inputs and tested for influences of management intensity and availability of semi-natural habitat on species richness and abundance of farmland birds. Results Avian species richness and bird abundance were unrelated to fertilizer inputs, and declined at higher levels of total vegetation cover. Sky Lark abundance increased, while Yellow Wagtail counts declined with the extent of semi-natural habitat. Sky Lark abundance increased with vegetation cover and peaked at an intermediate level of weed species richness. Yellow Wagtail counts peaked at intermediate levels of fertilizer inputs. Conclusions Compared with much of western Europe, cereal production in central Hungary is characterized by modest fertilizer inputs and large areas of semi-natural habitat. There was little evidence that increased applications of fertilizer are likely to have negative impacts on farmland birds, although increased application might reduce habitat suitability for Yellow Wagtails. Loss of semi-natural habitat is likely to have negative impacts on Sky Larks.

Impact of variable nitrogen fertilisation on arthropods in cotton in Georgia, USA

Reducing fertiliser applications can reduce production costs for cotton ( Gossypium hirsutum L.) growers, as well as nitrogen (N) leaching into the soil and contamination of surface and ground water. But altered N fertilisation may also affect pests and their natural enemies. In this study, plots with four different levels of fertiliser input (0, 45, 90 and 135 kg ha −1 N) were used to investigate the influence of N on cotton pest and beneficial arthropod populations, and on cotton yield in Tifton, GA, USA. We predicted that (1) N fertilisation will correlate positively with cotton plant growth; (2) increased N fertilisation will increase pest populations because plants with more N will be more nutritious for and attractive to herbivores; (3) populations of beneficial arthropods and predation of pests will decline with increased N fertilisation because of reduced plant signaling; (4) increased N fertilisation will increase pest mortality due to parasitoids because of increased host quality. Cotton plant growth was enhanced by N fertilisation but yield was unaffected. N fertilisation significantly affected some pest arthropods but inconsistently. Mirids were most abundant in the high N treatment in 1 year of the study and cotton aphids were most abundant in the highest N treatment in the other year of the study. Arthropod predators were generally more abundant in the high N treatment but only spiders and Geocoris spp. were significantly affected by N treatment, with highest numbers present in the highest N treatment but the significant differences were each only in a single year. The greatest mortality of sentinel pest eggs ( Spodoptera exigua) due to predation occurred under low N conditions. N fertilisation had no significant effects on parasitism of feral or sentinel caterpillars.

Modelling spatial–temporal covariance structures in monocropping barley trials

In long-term trials, not only are individual plot errors correlated over time but there is also a consistent underlying spatial variability in field conditions. The current study sought the most appropriate covariance structure of errors correlated in three dimensions for evaluating the productivity and time-trends in the barley yield data from the monocropping system established in northern Syria. The best spatial–temporal model found reflected the contribution of autocorrelations in spatial and temporal dimensions with estimates varying with the yield variable and location. Compared with a control structure based on independent errors, this covariance structure improved the significance of the fertilizer effect and the interaction with year. Time-trends were estimated in two ways: by accounting the seasonal variable contribution in annual variability (Method 1), which is suitable for detecting significant trends in short data series; and by using the linear component of the orthogonal polynomial on time (year), which is appropriate for long series (Method 2). Method 1 strengthened time-trend detection compared with the method of Jones and Singh [J. Agri. Sci., Cambridge 135 (2000), pp. 251–259] which assumed independence of temporal errors. Most estimates of yield trends over time from fertilizer application were numerically greater than the corresponding linear trends estimated from orthogonal polynomials in time (Method 2), reflecting the effect of accounting for seasonal variables. Grain yield declined over time at the drier site in the absence of nitrogen or phosphorus application, but positive trends were observed fairly generally for straw yield and for grain yield under higher levels of fertilizer inputs. It is suggested that analyses of long-term trials on other crops and cropping systems in other agro-ecological zones could be improved by taking spatial and temporal variability into account in the data evaluation.