The effect of nitrogen catch crop species on the nitrogen nutrition of succeeding crops

Ten widely different plant species were compared for their ability to reduce soil mineral nitrogen levels in the autumn and their ability to improve the nitrogen nutrition of the succeeding crop. The species included monocots and dicots, crops that survived the winter (persistent) or were winter killed (non-persistent) as well as legumes and non legumes. Their ability to reduce soil mineral nitrogen content was dependent on both root depth and persistency of the crops in the autumn. For non-persistent catch crops most of the mineralization of plant nitrogen occurred during the winter, and for some of these so early as to allow leaching of some mineralized nitrogen. For persistent crops most of the mineralization occurred shortly after incorporation in the spring. The effect of the catch crops on nitrogen uptake by the succeeding barley crop varied from 13 to 66 kg N ha^–1 and the differences between the crops could not be related to any single character, but to a combination of root depth, persistency, plant nitrate accumulation, and depletion of the soil mineral nitrogen pool in spring.     

砂姜黑土区控释尿素与普通尿素掺混对小麦-玉米轮作定位产量及氮肥利用率的影响

在驻马店新坡村进行了小麦-玉米轮作制下的控释尿素与普通尿素掺混比例定位试验研究。结果表明:控释尿素与普通尿素掺混处理的小麦、玉米产量均以70%控释尿素+30%普通尿素处理最好,第1年和第2年的小麦产量分别比100%普通尿素处理增产17.0%和21.1%,玉米产量分别比普通尿素处理增产16.2%和16.2%;氮肥利用率与产量结果一致,均以70%控释尿素+30%普通尿素处理最高,分别为53.9%和54.5%。     

Simulation of the nitrogen balance in the soil and a winter wheat crop

A simulation model for winter wheat growth, crop nitrogen dynamics and soil nitrogen supply was tested against experimental data. When simulations of dry matter production agreed with measurements, nitrogen uptake was simulated accurately. The total amount of soil mineral nitrogen as well as the distribution of mineral nitrogen over the various soil layers were generally simulated well, except for experiments in which fertilizer was applied late in spring. In these experiments, applied nitrogen disappeared because it could not be accounted for by the model. Some explanations for this disappearance are briefly discussed.     

Simulation of the effects of nitrogen supply on yield formation processes in winter wheat with the model TRITSIM

An outline of the dynamic winter wheat model TRITSIM is given. The model describes in one-day steps growth, yield formation and development of a crop from post-winter tillering until harvest under various conditions of water and nitrogen supply. TRITSIM is coupled with a simple soil nitrogen model and a soil water model to describe effects of nitrogen and water on yield formation processes. Comparisons between model and experimental results for ontogenesis, grain biomass, nitrogen uptake and soil mineral nitrogen are given for a series of Dutch experiments. Simulations were satisfactory, except for the time course of soil mineral nitrogen.     

包膜控释氮肥对玉米增产效应的研究

采用包膜控释氮肥在玉米上进行肥效试验研究。结果表明,与普通氮肥(尿素)相比,控释氮肥由于其本身控制释放和缓慢释放的特点,能使耕作层土壤速效氮含量在玉米生育期内维持较高的水平,满足玉米生长对氮素的吸收需求,尤其能满足玉米中后期对养分高强度吸收的需求;显著提高玉米生长中后期植株体内氮素含量,加速氮磷钾向籽粒的转移,从而提高生物产量、经济产量和玉米品质。同等和减半施氮量条件下,玉米产量和氮素利用率都有显著提高。     

On-farm estimation of indigenous nitrogen supply for site-specific nitrogen management in the North China plain

Estimating indigenous nitrogen supply (INS) by measurement of crop N uptake in N omission plots for site-specific N management is not feasible on a routine basis because it involves destructive plant sampling and plant tissue analysis, which is time-consuming and expensive. The objective of this study was to determine the amount of INS and develop a method to estimate it using soil testing in the North China plain (NCP). On-farm experiments at 229 sites were conducted from 2003 to 2005 in seven key winter wheat (Triticum aestivum L.)/summer maize (Zea mays L.) production regions of the NCP. The mean INS during the wheat-growing season was129 kg N ha⁻¹ with a range from 62 to 212 kg N ha⁻¹, and it varied from 69 to 202 kg N ha⁻¹ with a mean of 142 kg N ha⁻¹ during the maize-growing season. Considering all sites, the variability of INS was not simulated by initial soil N _min or apparent N mineralization (N _organic) alone, while together they could explain about 38% and 60% of INS during the wheat and maize-growing seasons, respectively. During the wheat-growing season, mean N _organic was 63 kg N ha⁻¹, and 59% and 33% of its variation could be explained by SOM in high-yielding regions (mean yield, 7.6 t ha⁻¹) and low-yielding regions (mean yield, 5.3 t ha⁻¹), respectively. Mean N _organic during the maize-growing season was 109 kg N ha⁻¹, 22% of which could be explained by SOM across all sites. An average of 40% and 42% of INS variation could be explained by both SOM and initial soil N _min content during the wheat and maize-growing seasons, respectively. We conclude that the accuracy of estimating crop N requirement for site-specific N management will be increased by using initial soil N _min and SOM.     

Crop yield and the fate of nitrogen and phosphorus following application of plant material and feces to soil

Organic materials are the most important sources of nutrients for agricultural production in farming systems of semi-arid West Africa. However, reliance on locally available organic nutrient sources for both crop and livestock production is rapidly becoming unsustainable. A series of feeding and agronomic trials have been conducted to address the role of livestock in sustainable nutrient cycling. This paper reports results of a greenhouse study that evaluated the effects of applying crop residue and browse leaves, or feces derived from these feeds, at equal organic-N application rates (150 kg ha^-1), alone or with fertilizer-N (60 kg ha^-1), on pearl millet (Pennisetum glaucum [L.] R.Br.) dry matter (DM) yield, nitrogen (N) and phosphorus (P) uptake, on soil nutrients, and on total, labile and recalcitrant fractions of soil organic matter (SOM). Millet DM and cumulative N uptake were most affected by fertilizer-N, followed by plant species and amendment type, although various interactions among these treatments were noted due to variations in the composition of the applied amendments. Fertilizer-N increased total millet DM by 39%, N uptake by 58% and P uptake by 17%, and enhanced N mineralization from most organic amendments, but was applied insufficiently to totally offset N and P immobilization in pots containing leaves of low initial N and P content. Feces alone appeared to supply sufficient N to meet millet-N demands. Nitrogen use efficiency was, in most cases, higher in pots amended with feces than with leaves. Nitrogen in feces apparently mineralized more in synchrony with millet-N demands. Also, the relatively high cell wall content of feces may have provided an effective, temporary sink for fertilizer-N, which upon remineralization provided more N to millet than pots amended with leaves. Whereas most of the P contained in feces mineralized and was taken up by millet, most leaves immobilized P. Assessing the costs and benefits associated with the direct land application of biomass as a soil fertility amendment versus feeding biomass first to livestock then using feces (and urine) to fertilize the soil requires information on both crop and livestock production and associated impacts on nutrient cycling.     

Effect of irrigation and nitrogen fertilizer on yield,oil content,nitrogen accumulation and water use of canola (Brassica napus L.)

Effects of N application and water supply on yield, oil content and N accumulation by canola, cultivar Marnoo, grown on a heavy clay soil in the Goulburn Murray Irrigation Region were investigated. Treatments were rainfed (R_f) or watered at a deficit of 50 mm (40–60 mm, I₅₀) beginning in the spring. N treatments were 0, 50, 100 or 200 kg N ha^–1 at sowing or as split applications of 20/80, and 50/50 kg N ha^–1 at sowing and rosette, respectively.Yield (Y_g) ranged from 170 to 520 g m^–2. Irrigation and N increased yield in both years. Grain yields were increased by N application on the irrigated treatments when 100 or 200 kg N ha^–1 was applied. Oil concentrations ranged from a maximum of 46.4% in treatment N₀ to a minimum of 40.6% in treatment N₂₀₀ and was inversely related to seed N concentration. Although fertilizer N decreased oil concentration, it increased the yield of oil.Nitrogen accumulation (N_b) limited yield of all treatments and was described by the equation, Y_g = 806[1-EXP(–0.039*N_b)]. This implied a decrease in yield per unit of N_b at the higher rates of fertilizer addition with consequent increases in grain N concentration.The efficiency of water use in the production of grain (WUE_g) and biomass (WUE_b) were 7.5 and 23 kg ha^–1 mm^–1 respectively. Nitrogen additions increased WUE_g and WUE_b in both seasons. Maximum values of 8.9 (WUE_g 1986) and 26.8 (WUE_b 1987) were measured from treatment N₂₀₀. These data suggest that the crops made efficient use of the applied water.     

Impact of planted fallows and a crop rotation on nitrogen mineralization and phosphorus and organic matter fractions on a Colombian volcanic-ash soil

Soil fertility replenishment is a critical factor that many farmers in the tropical American hillsides have to cope with to increase food crop production. The effect of three planted fallow systems (Calliandra houstoniana-CAL, Indigofera zollingeriana-IND, Tithonia diversifolia-TTH) and a crop rotation (maize/beans-ROT) on soil nitrogen mineralization, organic matter and phosphorus fractions was compared to the usual practice of allowing natural regeneration of native vegetation or natural fallow management (NAT). Studies were conducted on severely degraded Colombian volcanic-ash soils, 28 months after fallow establishment, at two on-farm experimental sites (BM1 and BM2) in the Cauca Department. Tithonia diversifolia had a significantly higher contribution to exchangeable Ca, K and Mg as well as B and Zn; the order of soil nutrient contribution was TTH > CAL > IND > NAT > ROT. On the other hand, lND had significantly higher soil NO₃⁻–N at both experimental farms as compared to all the other fallow system treatments. For the readily available P fraction, CAL and ROT had significantly higher H₂O–Po and resin-Pi, respectively, in the 0–5 cm soil layer; whereas TTH showed significantly higher values for both H₂O–Po and resin-Pi in the 5–10 cm soil layer. Significant effects were observed on the weights of the soil organic matter fractions which decreased in the order LL (Ludox light) > LM (Ludox intermediate) > LH (Ludox heavy). Indigofera zollingeriana showed greater C, N and P in the soil organic matter fractions than all the other fallow treatments, with NAT having the lowest values. It is concluded that planted fallows can restore soil fertility more rapidly than natural fallows.     

Nitrogen mineralization,nitrate leaching and crop growth following cultivation of a temporary leguminous pasture in autumn and winter

A field experiment was conducted to investigate the effect of timing and method of cultivation of a 3-year old ryegrass/white clover pasture on subsequent N mineralization, NO ₃ ^- -N leaching, and growth and N uptake of a wheat crop in the following season. The size of various N pools and decomposition of¹⁴C-labelled ryegrass material were also investigated. Cultivation method (mouldboard or chisel ploughing) generally had no significant effect on the accumulation of mineral N in the profile in the autumn or on the amount of NO ₃ ^- -N leached over winter.¹⁴C measurements suggested that initial decomposition rate of plant material was faster from May than March cultivation treatments. Despite this, overall net mineralization of organic N (of soil plus plant origin) increased with increasing fallow period between cultivation and leaching. The total amounts of mineral N accumulated in the soil profile before the start of leaching were 139, 119 and 22 kg N ha^–1 for the March, May and July cultivated soils respectively. Cumulative leaching losses over the trial calculated from soil solution samples were 78, 40 and 5 kg N ha^–1 for the March, May and July cultivated soils respectively. Differences in N mineralization over the season were generally not reflected by changes in amounts of potentially-mineralizable soil N (as measured by extraction or laboratory incubation) or levels of microbial biomass during the season. The amount of mineral N in the profile in spring increased with decreasing fallow period. This was reflected in an approximately 15% and 25% greater grain yield and N uptake respectively by the following wheat crop in plots cultivated in July rather than in March.     

Fe2+/Fe3+和Mn2+对低氧曝气过程总氮去除与转化途径的影响

为短期快速实现实际生活污水自养脱氮,采用含有厌氧氨氧化菌的实际污水处理厂活性污泥,针对Fe²⁺/Fe³⁺和Mn²⁺对低氧曝气过程中氮的去除效果进行了研究,分析确定了氮素转化的途径。研究结果表明,Fe²⁺/Fe³⁺和Mn²⁺均可提高活性污泥中厌氧氨氧化菌（AnAOB）丰度,但由于Fe²⁺/Fe³⁺对氨氧化菌（AOB）也存在一定抑制作用,因此,短期投加Fe²⁺/Fe³⁺条件下,低氧曝气过程中总无机氮去除率为25%,但投加Mn²⁺条件下总无机氮去除率可达44%。通过氮素平衡分析,发现投加Fe²⁺/Fe³⁺条件下,氮素主要通过反硝化作用去除;而投加Mn²⁺条件下,氮素主要通过厌氧氨氧化（anammox）作用去除。因此,传统活性污泥可通过短期投加Mn²⁺增强厌氧氨氧化活性,促进低氧曝气过程中氮的去除,利于快速实现一体化自养脱氮。     

Effect of the timing and rate of nitrogen fertilization on the growth and recovery of fertilizer nitrogen within the potato (Solanum tuberosum L.) crop

The effect of the timing of N fertilizer application on the uptake and partitioning of N within the crop and the yield of tubers has been studied in two experiments. In 1985 either none, 8 or 12 g N m^–2 was applied and in 1986 none, 12 or 18 g N m^–2. Fertilizer N was applied either at planting, around the time of tuber initiation or half at planting and the remainder in four foliar sprays of urea during tuber bulking.¹⁵N-labelled fertilizer was applied to measure the recovery of fertilizer N in the crops.There was an apparent pre-emergence loss of nitrate from the soil when N was applied at planting in 1986, thereby reducing the efficiency of fertilizer use. Applying the N at tuber initiation delayed and reduced the accumulation of N in the canopy compared with crops receiving all their fertilizer at planting. Foliar sprays of urea slightly increased both tuber yields and tuber N contents when compared to a single application at planting. The proportion of the fertilizer N recovered in the crop was little affected by the rate of N application, but a greater proportion of foliar-applied N was recovered than N broadcast at planting, due partly to pre-emergence losses of nitrate in 1986. It is suggested that late applications of N was foliar sprays can be of benefit to crops with a long growing season and reduce environmental losses of N.     

Response to nitrogen application and interval between harvests in five grasses — I Dry-matter yield,nitrogen content and yield,numbers and weights of tillers,and proportion of crop fractions

Effects of five levels of applied nitrogen on field swards of each of five grasses were studied in the year of sowing, in the first full harvest year and part of the second harvest year. The plots were cut at 4-week intervals during the year of sowing; subsequently 4- and 8-week intervals between cuts were compared.Differences between grasses in dry-matter yield response to applied N were sufficiently large to suggest that commercially-important varieties should be tested at more than one level of applied N. In Melle and R v P the percentage increase in weight per tiller due to applying N was much greater, and in Aberystwyth S.24, Sabrina and Aberystwyth S.170 only slightly greater, than the percentage increase in number of tillers. Sabrina had a low number of tillers, with a negative effect of the final increment of applied N on number of tillers. The results for the five grasses in respect of number of tillers, weight per tiller, dry-matter yield, N yield and light penetration all emphasized the case for more frequent defoliation the higher the level of N applied. The application of N greatly increased the proportion of stem in the harvested herbage on 16 September 1977, evidently at least partly by reducing the proportion of stem which escaped defoliation. On that date, with the 8-week interval, the application of moderate amounts of N reduced the N content of the harvested herbage, evidently because of a large reduction in the proportion of green leaf blade and an increase in the proportions of stem and dead leaf blade.     

The impact of crop growth sub-model choice on simulated water and nitrogen balances

It is the aim of this study to analyse how different crop growth model routines affect the simulation of water flow and nitrogen transport of a crop rotation in agricultural fields. The model system Expert-N is briefly described and used to test the crop growth sub-models against data of a six-year field experiment on sandy soils. Expert-N is a modular soil–plant–atmosphere model system, which comprises different sub-models to simulate one-dimensional vertical transport of water, solute and heat in the unsaturated zone. It includes several sub-models to describe organic matter turnover and has three generic crop growth sub-models. The latter are derived from the crop models CERES, SPASS and SUCROS. Simulations were performed using the different sub-models for each of the cereal crops in the sugar beet, winter wheat, winter barley, winter rye crop rotation. Results show the impact of crop model choice on simulated water balances and turnover of C and N. It is concluded that the simulation of root growth and plant residue mineralisation needs some improvement.     

Residual effects of growing mungbean and uridbean on the yield and nitrogen uptake of a succeeding wheat crop

A two year field experiment was carried out at the Indian Agricutural Research Institute, New Delhi - 110012, India to assess the effect of mungbean (Vigna radiata L.) and uridbean (Vigna mungo L.) residues on the yield and N uptake of a succeeding wheat crop as compared to sorghum fodder. Sorghum produced 3.5–7.5 times more dry matter and removed 2–3 times more nitrogen than mungbean or uridbean during same duration (80 ± 10 days) of their growth. Without N application the grain yield of wheat following mungbean and uridbean (without residue incorporation) was 0.45 and 0.48 t ha^–1 more than the yield of wheat following sorghum fodder. These yields were equivalent to that predicted when 36 and 38 kg urea-N ha^–1, respectively, was directly applied to wheat. The residual effects of these grain legumes were higher when succeeding wheat was fertilized with 60 kg urea-N ha^–1; at this level mungbean and uridbean spared 52 and 43 kg urea-N ha^–1, respectively, in succeeding wheat. The residual effect of mungbean and uridbean further increased when their residue was incorporated in soil; with this practice they spared 94 and 115 kg urea-N ha^–1, respectively, without N application to wheat and 74 and 82 kg urea-N ha^–1, respectively, with an application of 60 kg urea-N ha^–1 to wheat.Mungbean and uridbean, without residue incorporation, increased aboveground plant-N uptake of succeeding wheat by 11.5–34.9 and 10.8–34.0 kg N ha^–1, respectively; whereas with residue incorporation, they increased aboveground plant-N content of succeeding wheat by 26.1–45.8 and 32.7–47.7 kg N ha^–1, respectively.The results of the present study indicate that there is both an indirect sparing effect and a direct residual effect of mungbean and uridbean on the nitrogen needs of succeeding wheat, more so when their residues are incorporated in soil.     

Effect of nitrogen and water uptake on yield of wheat

For 2 years, field experiments were conducted to study the direct and interactive effects of water and nitrogen uptake at different growth stages on grain yield of wheat, grown on coarse textured alluvial soil of Ludhiana. Twelve treatments comprising 3 irrigation regimes and 4 rates of N were imposed. The N and irrigation regimes showed significant interaction, especially during the drier year. Grain yield was better explained with water uptake and N uptake, when partitioned over different growth stages than with total uptake. The sensitivity factor for water uptake was higher at the reproductive stage ( = 1.60) than at the vegetative ( = 1.05) and maturation ( = 0.38) stages. Contrary, yield was more sensitive to N uptake during the vegetative stage than the reproductive and the maturation stages. Sensitivity of grain yield to water uptake was higher at higher N application rates. Yield predictability was much better (R² = 0.98) when N and water uptake at different growth stages were combined.     

Effect of different sources of iron and sulphur on nutrient concentration and uptake by groundnut

The C and N mineralization characteristics of two organic N fertilizers were determined in a soil-less incubation system at three temperature regimes. Protox (derived from activated sewage sludge) initially degraded more rapidly by microbial action compared with dried blood. However, dried blood released more CO₂-C and inorganic N towards the end of the incubation periods. The rate of microbial degradation increased with temperature. Mineralization characteristics of protein-based N sources are discussed in relation to organic N nutrition of vegetable crops.     

The effect of low‐power microwaves on the growth of bacterial populations in a plug flow reactor

A plug flow reactor (PFR) which permits the growth of bacteria in a microwave environment is described. The apparatus is used to analyse the effect of microwave radiation at the frequency of 2.45 GHz and at 37°C on the growth rate of three bacterial species: Bacillus clausii, Pseudomonas aeruginosa, and Staphylococcus aureus. The growth constant is determined for reacting mixtures irradiated with microwaves of different powers ranging from 0 to 400 mW. Analyses show that (a) the apparatus is able to perform the experimental runs maintaining an aseptic environment; (b) under the microwave power levels examined in the present study, no effects are detected for the Bacillus clausii and Pseudomonas aeruginosa species, while for the Staphylococcus aureus species, a few small effects are found (a minimum value of the growth constant at 200 mW and an increase of the constant between 200 and 400 mW). © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Effects of varying nitrogen supply at different growth stages on nitrogen uptake and nitrogen partitioning efficiency in two wheat cultivars

The objective of this work was to determine the effect of N availability upon N uptake and nitrogen partitioning efficiency and its relationship with %N in the grain in two wheat cultivars, differing in their grain protein content.Plants were grown in a nutrient solution with 2 nitrogen levels, 200 ppm (H) and 40 ppm (L). Four treatments were imposed: HH, HL, LH and LL. Nutrient solution exchange was done at maximum floret number. Plants were harvested at terminal spikelet stage, maximum floret number, 10 days after anthesis and maturity.Nitrogen content, N uptake and N distribution at maturity were significantly affected by N supply. Nitrogen content in the grain was similar in both cultivars, but varied significantly between treatments and decreased as follows: LH; HH; LL and HL. In both cultivars a low leaf %N was observed in HL 10 days after anthesis, which suggest early N utilization and its premature depletion, resulting in a low %N in the grain. Total %N in the plant, for both cultivars was higher in HH and LH than other treatments. When N availability was high during the whole crop cycle (HH), N distribution to the ear was improved.It is concluded that late N availability is necessary to achieve high %N in the grain. On the other hand if high and initial N availability is not maintained, %N in the grain decreased in a significant way.     

Effects of drying and rewetting on carbon and nitrogen mineralization in soils and incorporated residues

An understanding of nitrogen mineralization from residues and soil organic matter is important to understand the quantity of N available from the soil for crop production. The objective of this study was to determine effects of repeated wetting and drying of soils on rates of N mineralization. The study compared mineralization rates in three kaolinitic, low organic matter soils, utilizing cotton leaves or compost as residues. One set of treatments was subjected to repeated drying and rewetting, whereas the other was kept at constant moisture content. Mineralized N was measured by leaching with 0.01 M CaCl₂ periodically, for 185 days. Rates of C mineralization were measured in the treatment containers by periodic measurement of CO₂ respiration rates. In constant moisture conditions, soils with cotton leaf residue mineralized between 25% and 40% of N applied as residue, whereas soils with compost mineralized between 3.8% and 9.3%. In fluctuating moisture conditions, soils with cotton leaf residue mineralized between –1.3% and 6.9%, whereas soils with compost mineralized from 1.6% to 3.3%. Moisture effect was not significant in soils without residue, with soils mineralizing between 16 and 47 mg N kg^–1. Carbon mineralization rates were not significantly affected by moisture. Both residue and soil type affected rates of C mineralization.