Apparent Nitrogen Recovery Research Articles

Nitrogen Application Improved Photosynthetic Productivity, Chlorophyll Fluorescence, Yield and Yield Components of Two Oat Genotypes under Saline Conditions

: Understanding the interaction between salinity and nitrogen (N) nutrition is of great economic importance to improve plant growth and grain yield for oat plants. The objective of this study was to investigate whether N application could alleviate the negative effect of salinity (NaCl) stress on oat physiological parameters and yield performance. Two oat genotypes with contrasting salt tolerance response (6-SA120097, a salt-tolerant genotype SA and 153-ND121147, salt-sensitive ND) were grown under four N rates (0, 100, 200, and 400 mg N pot−1) in non-saline and saline (100 mM NaCl) conditions. The results showed that salinity, N fertilization and their interaction significantly affected the photosynthetic rate, transpiration rate, agronomic nitrogen use efficiency (aNUE), physiological nitrogen efficiency (pNUE) and apparent nitrogen recovery (ANR), seed number, and grain yield. Saline stress reduced gas exchange rate, nitrogen use efficiency (NUE), grain yield, and yield components. N fertilization increased photosynthetic productivity and chlorophyll fluorescence, resulting in improved grain yields and yield components for both genotypes. On average, the photosynthetic rate was increased by 38.7%, 74.1%, and 98.8% for SA and by 49.8%, 77.6%, and 110% for ND, respectively, under the N rates of 100, 200, and 400 mg N pot−1, as compared with non-fertilized treatment. In addition, grain yield was increased by 80.6% for genotype SA and 88.7% for genotype ND under higher N application rate (200 mg N pot−1) in comparison with the non-nitrogen treatment. Our experimental results showed that an increase of N supply can alleviate the negative effects induced by salinity stress and improved plant growth and yield by maintaining the integrity of the photosynthesis and chlorophyll fluorescence processes of oat plants, which provides a valuable agronomic strategy for improving oat production in salt-affected soils.

IMPROVEMENT OF SANDY SOIL CHARACTERISTICS AND ITS PRODUCTIVITY OF WHEAT CROP USING ORGANIC AND MINERAL-N FERTILIZATION

A field experiment was carried out on sandy soil at the Farm of Ismailia Agric. Res. Station, Ismailia Governorate, Egypt (Latitude, 30o 35' 41.901 N and longitude, 32o 16' 45.834 E) during the two successive growing winter seasons, i.e., 2016 / 2017 and 2017 / 2018 on wheat plant ( Triticum aestivum L.) variety Misr 1, to study the individual and combined effect of organic fertilizers (farmyard manure or potassium humate) and mineral nitrogen fertilization levels ( 0, 50, 75 and 100 kg N fed.-1 as ammonium nitrate 33.5 % N) on plant growth, yield and its components as well as nutrient contents, apparent nitrogen recovery efficiency (ANRE) and agronomical efficiency, also on some chemical and physical properties of the studied soil. Application rates of farmyard manure (FYM) were 0 and 5 ton fed.-1, while potassium humate at rates of 0 and 5 kg fed.-1. The layout of the experiment was a split- plot design, with the main plots arranged in a randomized complete blocks design, with three replicates. The results showed that, there are a significant increases of the estimated growth parameters, i.e. plant height (cm), spike length (cm), number of tillers/ plant, number grains/ spike as well as straw and grain yields of wheat plants and their content (concentration and uptake) of the determined macro- ( N, P and K) and micro- (Fe, Mn and Zn) nutrients and protein content as a result of N, FYM and K-humate applications in both individually and together. The highest values of these determinations were found in the plants fertilized by N + FYM followed by these resulted from the treatment of N + potassium humate, except weight 1000 grains, grain yield and K content which gave the highest values with the treatment of N + potassium humate. In addition, individual applications of N resulted in a decrease in the soil content of available macro- (N, P and K) and micro- (Fe, Mn and Zn) nutrients, but increased the soil content of available compared with the control treatment. On the other hand, there are an increase of soil content of available macro- and micro-nutrients under study as a result of individual applications of FYM and K-humate with the superior increase of FYM compared with that with K-humate, except the soil content of available K. Also, the soil content of OM was decreased with the increase of added N, but increased as a result of FYM and K-humate applications alone. Soil bulk density was increased in the fertilized by N alone and decreased in the soil fertilized by individual applications of FYM and K-humate. The obtained data from this study concluded that, under sandy soil conditions, organic fertilizers played a major role in sandy soil fertility and its productivity of wheat plants and it's become more efficiency if its application in combination with mineral nitrogen fertilization.

Integrated agronomic practices management improve yield and nitrogen balance in double cropping of winter wheat-summer maize

Crop production alters nitrogen balance in double cropping of winter wheat-summer maize in grain nitrogen content, soil nitrogen pool and nitrogen loss, ultimately affecting nitrogen use efficiency and environmental health. In comparison to the information on crop responses only limited knowledge exists on the response of nitrogen balance to integrated agronomic practices management (IAPM, defined as a comprehensive management framework consisted of tillage method, plant density, seeding and harvest dates, and fertilizer application) under field. Planting pattern will affect crop production and environmental costs. And how the nitrogen balance change under IAPM? In order to answer this question, four treatments (T1, T2, T3 and T4) were conducted on double cropping of winter wheat-summer maize for 4 years in North China Plain. Annual grain yield of T2, T3, and T4 was 22.0%, 51.2%, and 33.3%, respectively, higher than T1. And single grain yield of winter wheat or summer maize had the same trend as the annual grain yield. Dry matter accumulation of T2, T3, and T4 in summer maize season were 8.3%, 42.0%, and 23.0%, and those in winter wheat season were 3.9%, 25.7%, and 12.1%, respectively, higher than T1 at harvest. The grain yield of T4 was lower than that of T3 but higher than that of T1 and T2, and net profit and nitrogen use efficiency of T4 were higher than that of T3. Meanwhile the highest current and residual nitrogen recovery efficiency (CREN and REREN) were obtained by T4 treatment during the study period. The soil nitrogen content in 0–90 depth (SN), grain nitrogen content (GN), nitrogen apparent recovery efficiency (AREN) and fertilizer nitrogen loss (FNL) were measured for nitrogen balance. T4 treatment promoted nitrogen balance as higher GN, higher AREN and lower FNL. The GN kept stable and FNL was increasing slowly in all treatments, which mean the contribution to soil nitrogen pool was decreasing with experimental years. The grain yield for T4 treatment of winter wheat, summer maize and annual increased by 36.4%, 31.3% and 33.3% averagely in the past 4 years, compared with T1 treatment. While maintaining crop production, T4 treatment made an important contribution to promoting nitrogen use efficiency, improving the situation of nitrogen balance, and reducing nitrogen loss about 39.1–54.4%, compared with other treatments.

Nitrogen and phosphorus uptake from solid and liquid pig manure in perennial and annual cropping systems

Applying pig manure in excess of crop demand can result in nutrient loss to water bodies. We studied the effect of liquid and solid pig manures and their N- and P-based application rates on yield and nutrient uptake in annual and perennial cropping systems for 3 yr. The experiment had a split-plot design with five nutrient management treatments including liquid-N (annual N-based liquid pig manure), liquid-P (P-based liquid pig manure once every 5 yr), solid-N (annual N-based solid pig manure), solid-P (P-based solid pig manure once every 5 yr), and control (no manure). The liquid-P treatment showed high apparent nitrogen and phosphorus recovery (ANR and APR, respectively) in each cropping system and yields similar to that of the liquid-N treatment. The solid-N treatment had the smallest ANR in the perennial cropping system (9%–27%) and also the smallest APR in both cropping systems (typically <4%) possibly due to N deficiency and high P application rate. The current formula for estimating organic N mineralization overestimated the available N, particularly for solid pig manure, reducing crop yield. Based on the ANR obtained in this study, a more appropriate coefficient is 10%–15% of the organic N from solid pig manure for no-till perennial cropping systems.

Alternate partial root-zone drip irrigation improves water\u2013 and nitrogen\u2013 use efficiencies of sweet-waxy maize with nitrogen fertigation

Alternate partial root–zone drip irrigation (ADI) or fertigation has favorable effect on crop water- and nitrogen- use efficiencies (WUE and NUE). However, the advantage of combined application of ADI and nitrogen fertigation on crop WUE and NUE remains unclear. A pot experiment was conducted to investigate the impact of three irrigation methods (CDI conventional drip irrigation (both halves of pot irrigated), ADI (both halves of pot alternatively irrigated) and FDI fixed partial root–zone drip irrigation (fixed half of pot irrigated)) and five nitrogen treatments (F0 no N supplied, F1-F4 0.2, 0.18, 0.16 and 0.14 g N per kg soil via fertigation) on sweet-waxy maize. Compared with CDI, ADI reduced water consumption by 19.9%, but increased water use efficiency based on dry seed yield (WUEs) by 32.3%, and also enhanced nitrogen apparent recovery fraction (Nrf) and nitrogen agronomic efficiency (NAE). F1-F4 augmented dry mass accumulation, dry seed yield and total nitrogen uptake if compared to F0. Moreover, F2-ADI had higher shoot and total dry masses, WUEs, total nitrogen uptake, Nrf and NAE. Thus ADI increased nitrogen uptake, WUE and NUE of sweet-waxy maize with nitrogen fertigation of 0.18 g N per kg soil in this study.

Nitrogen use efficiency in spring wheat: genotypic variation and grain yield response under sandy soil conditions

SUMMARYAgricultural practices are likely to lower nitrogen (N) fertilization inputs for economic and ecological limitation reasons. The objective of the current study was to assess genotypic variation in nitrogen use efficiency (NUE) and related parameters of spring wheat (Triticum aestivumL.) as well as the relative grain yield performance under sandy soil conditions. A sub-set of 16 spring wheat genotypes was studied over 2 years at five N levels (0, 70, 140, 210 and 280 kg N/ha). Results indicated significant differences among genotypes and N levels for grain yield and yield components as well as NUE. Genotypes with high NUE exhibited higher plant biomass, grain and straw N concentration and grain yield than those with medium and low NUE. Utilization efficiency (grain-NUtE) was more important than uptake efficiency (total NUpE) in association with grain yield. Nitrogen supply was found to have a substantial effect on genotype; Line 6052 as well as Shandawel 1, Gemmiza 10, Gemmiza 12, Line 6078 and Line 6083 showed higher net assimilation rate, more productive tillers, increased number of spikes per unit area and grains per spike, extensive N concentration in grain and straw, heavier grains, higher biological yield and consequently maximized grain yield. The relative importance of NUE-associated parameters such as nitrogen agronomic efficiency, nitrogen physiological efficiency and apparent nitrogen recovery as potential targets in breeding programmes for increased NUE genotypes is also mentioned.

Response of No‐Till Grain Crops to Pig Slurry Application Methods and a Nitrification Inhibitor

Core Ideas Mineral N fertilization of no‐till crops may be replaced by pig slurry. Pig slurry with and without dicyandiamide was injected or broadcast in a no‐till soil. Pig slurry injection in a no‐till soil increased grain yield and crop N use efficiency. Dicyandiamide added to slurry improved crop yield and N use efficiency only in winter crops. The effects of application methods and nitrification inhibitors on the fertilizer value of pig slurry (PS) in no‐till crops are still poorly documented. We evaluated grain and straw yield, and N accumulation of no‐till corn (Zea mays L.), oat (Avena strigosa Schreb.), and wheat (Triticum aestivum L.) from 2011 to 2015 on a loam soil under a subtropical climate. The crops received either: (i) no fertilizer, no dicyandiamide (DCD) (control), (ii) surface‐broadcast of urea‐N (reference treatment), (iii) surface‐broadcast pig slurry (PSs), (iv) PSs + DCD, (v) shallow‐injected pig slurry (PSi), or (vi) PSi + DCD. Broadcast applications were performed manually whereas injection in furrows (≈10 cm) was made with a commercial applicator. Corn and wheat grain yields were similar with pig slurry and mineral fertilizer, confirming the good fertilizer value of pig slurry for no‐till grain crops. Compared with surface broadcast, shallow injection of pig slurry increased grain yields of corn (+1.5 Mg ha−1) and wheat (+0.3 Mg ha−1), nitrogen agronomic efficiency (NAE) of corn (+9 kg grain kg−1 total N applied) and wheat (+2 kg grain kg−1 N), and apparent nitrogen recovery (ANR) in corn (46–68%) and wheat (29–38%). Crop performance was generally not affected by DCD, except for wheat in 2013 with increased yield (+15%), NAE (+2.7 kg grain kg−1 N), and ANR (31–39%). Pig slurry injection improved yield and N use efficiency of no‐till grain crops, whereas DCD addition to pig slurry appeared more favorable for winter than summer crops.

Effect of nitrogen management modes on grain yield, nitrogen use efficiency and light use efficiency of wheat

A nitrogen management experiment with three nitrogen levels (0, 120, and 180 kg·hm-2, namely N0, N120, N180) and three nitrogen allocation modes (NA: base fertilizer 100%; NB: base fertilizer 70% + seedling fertilizer 30%; NC: base fertilizer 60% + jointing fertilizer 40%) was conducted at four sites (Chongqing, Renshou, Guanghan and Xichang) during two consecutive years, the SPAD value, canopy photosynthetic rate (CAP), photosynthetically active radia-tion (PAR) interception efficiency and grain yield were determined, and the nitrogen use efficiency and PAR use efficiency were calculated. The results showed that the SPAD of upper-most three leaves, CAP, PAR interception efficiency and grain yield were promoted with increasing nitrogen fertilizer, but nitrogen fertilizer use efficiency, productivity efficiency, uptake efficiency and use efficiency were decreased. The promoting effects of nitrogen fertilizer postponing were different among nitrogen levels, with the highest SPAD in N180 treatment and the highest CAP in N120 treatment. The light use efficiency of different nitrogen fertilization patterns differed among four sites. Furthermore, nitrogenous fertilizer postponing significantly increased nitrogen agricultural fertilizer use efficiency, productivity efficiency, uptake efficiency and apparent nitrogen recovery efficiency, but declined nitrogen use efficiency, and the performance of NC was better than NB. Among different sites, Guanghan had the highest SPAD, CAP, PAR interception efficiency and grain yield, Xichang had higher SPAD and nitrogen use efficiency, lower CAP and PAR use efficiency, Chongqing and Renshou had the lowest SPAD, light use efficiency, nitrogen use efficiency and grain yield. Biomass had significant positive relationships with grain yield, CPA, SPAD, and PAR interception efficiency. Therefore, the increase of nitrogen fertilizer could promote yield at all sites, and nitrogenous fertilizer postponing could further optimize grain yield component and improve nitrogen and light use effi-ciency. But the effects depended on the years and sites, thus a target nitrogen management mode should be site-specifically made.

Early Fall Planting Increases Growth and Nitrogen Uptake of Winter Cereals

Core Ideas Double cropping of forages can increase yield per ha and reduce nutrient loss. Timely planted winter cereals can take up N leftover from the summer crop. Timely planted winter cereals also provide a safe window for fall‐applied manure. Late planting of winter cereals in corn silage rotations will limit fall N uptake. Winter cereals such as triticale (× Triticosecale) have shown to be excellent cover and double crops in the northeastern United States due to beneficial environmental and economic qualities, including the potential to scavenge residual N and take up N from fall‐applied manure. Total fall N uptake is impacted by fall seeding date and available N supply. Here we determined the impact of fall planting date and available N on pre‐frost biomass accumulation and N uptake of triticale. Two planting dates, ranging from late August to early October, were evaluated at four locations in upstate New York. Trials were arranged in a split‐plot design, with planting date as the main treatment and N application rate (0, 34, 67, 101, 135 kg N ha−1) as the split plot treatment. All plots were harvested in November prior to frost. With no added N, earlier planting (before 20 September), on average, resulted in 21% greater biomass and 45% greater N uptake. Nitrogen addition did not increase biomass or fall N uptake for later planting dates, averaging 13 to 30 kg N ha−1 across all sites. Earlier planting dates had greater nitrogen use efficiency (NUE) and apparent nitrogen recovery (ANR), with an average N uptake of 70 to 90 kg N ha−1, suggesting early planted triticale can scavenge nutrients leftover from the previous crop and provide a more environmentally friendly opportunity for spreading manure in the fall. Additional research is needed to examine the potential for N loss in these scenarios.

Reducing nitrogen losses through ammonia volatilization and surface runoff to improve apparent nitrogen recovery of double cropping of late rice using controlled release urea.

Controlled release fertilizer can reduce nitrogen losses to the environment while increasing grain yield and improving apparent nitrogen recovery (ANR) of rice. However, few studies have evaluated the comparative efficacy of different polymer-coated urea products on nitrogen (N) losses, ANR, and N uptake of rice. A 2-year field experiment was conducted to compare the effects of three different types of polymer-coated urea fertilizer on nitrogen losses through NH3 volatilization and surface runoff to the environment, ANR, grain yield, and N uptake as compared to conventional urea of rice. Six treatments including (1) control with 0kg N ha-1 (CK), (2) basal application of urea (Ub), (3) split application (Us) of urea (50% at transplanting, 25% at tillering, and 25% at panicle stages), (4) CRU-1 (polyurethane-coated urea), (5) CRU-2 (degradable polymer-coated urea), and (6) CRU-3 (water-based polymer-coated urea) all applied at 165kg N ha-1. It was found that CRU-2 resulted in the highest grain yield and panicle numbers among the N fertilization treatments in 2013 and 2014. Applying CRU could help increase N uptake in rice, reduce N losses through NH3 volatilization and surface runoff, and hence improve ANR. Its single dose can meet the nutrient demand of the rice plant. Controlled release urea could be adopted as an effective mitigation alternative to retard N losses through NH3 volatilization and surface runoff while improving ANR of double cropping of late rice.

Long-term P and K fertilisation strategies and balances affect soil availability indices, crop yield depression risk and N use

The last century has seen a large increase of fertiliser use, along with a subsequent rise of crop productivity. However, in many places its intensive use has become a burden to the environment, and legislation has been introduced to restrict nutrient applications. In combination with changing production scenarios as a result of climate change, this means an improved understanding is needed of how low nutrient availability and climatic stress factors affect yields and yield stability.We examined the long-term effects mineral and organic fertilisation on a nutrient-depleted field, and observed large annual variations: depending on the year, average spring barley yields under unfertilised management (U) were between 17-75% lower than the reference N1/2P1/2K1/2 (60-10-60 kg ha(-1)). Yields increased up to 174% under N1P1K1 (120-20-120 kg ha(-1)), while animal manure applications at an N availability level corresponding to N-1 were between 79 and 137%. No temporal yield trends could be observed, but long-term changes of Olsen-P and exchangeable K were related to the nutrient balances (inputs-offtake) (r(2) = 0.60 and 0.59, respectively, P < 0.001).Multiple linear regression analysis was used to examine the effects of the treatments in combination with annual weather variations. The results could be split into two outcomes, 1) a general relation between yields and temperatures for the periods of early spring (P < 0.01, multiple R-2 = 0.31) and summer (P < 0.001, multiple R-2 =0.45), and 2) an interaction between temperature and nutrient applications during crop establishment, leading to a diverse response of relative yields (P < 0.001 multiple R-2 =0.64), i.e. relative yield losses under the unfertilised treatment (U) were greater in years with lower spring temperatures, and, conversely, the increased nutrient availability in the fully mineral and organically fertilised treatments could partially alleviate the negative effects.After 13 years of repeated fertilisation, inputs were suspended for a single year and only N was applied to evaluate the residual effects. Yields were significantly affected by the different fertilisation histories (P < 0.001). Likewise, apparent nitrogen recovery tended to improve with previous inputs, but the observations were highly variable.Overall, the analyses agree with the notion that brief periods of stress at a critical stage may significantly affect yields, and confirmed that management of sufficient nutrient availability is critical for maintaining high and stable yields. (C) 2017 Elsevier B.V. All rights reserved.

Do no-till and pig slurry application improve barley yield and water and nitrogen use efficiencies in rainfed Mediterranean conditions?

Tillage and N fertilization strategies including mineral and organic sources need to be studied in combination given their importance on the production cost that farmers face and their potential interaction on crop performance. A four-year (2010–2014) experiment based on barley monocropping was carried out in NE Spain in a typical rainfed Mediterranean area. Two tillage treatments (CT, conventional tillage; NT, no-tillage) and three rates of N fertilization (0; 75kgNha−1, applied at top-dressing; 150kgNha−1, applied at pre-sowing and at top-dressing at equal rate), with two types of fertilizers (ammonium-based mineral fertilizer and organic fertilizer with pig slurry), were compared in a randomized block design with three replications. Different soil (water and nitrate contents) and crop (above-ground biomass, grain yield, yield components and N concentration in biomass and grain) measurements were performed. Water- and nitrogen use efficiencies (WUE and NUE) as well as other N-related indexes (grain and above-ground biomass N uptake; NHI, nitrogen harvest index; NAR, apparent nitrogen recovery efficiency) were calculated. Barley above-ground biomass and grain yield were highly variable and depended on the rainfall received on each cropping season (ranging between 280mm and 537mm). Tillage and N fertilization treatments affected barley grain yields. No-tillage showed 1.0, 1.7 and 6.3 times greater grain yield than CT in three of the four cropping seasons as a result of the greater soil water storage until tillering. Water scarcity during the definition of the number of spikes per m2 under CT would have compromised the compensation mechanism of the other two yield components. Pig slurry application led to the same (3 of 4 years) or higher (1 of 4 years) grain yield than an equivalent rate of mineral N fertilizer. Regardless the N origin, barley yield did not respond to the application of 150kgNha−1 split between pre-sowing and top-dressing compared to the 75kgNha−1 rate applied as top-dressing. A significant nitrate accumulation in the soil over the experimental period was observed under CT. Greater barley water use efficiency for yield (WUEy), N uptake and grain N content were found under NT than CT in three of the four cropping seasons studied. Moreover, for a given N rate, the use of organic fertilization increased significantly the WUEy as an average of CT and NT. When CT was used, a greater NHI was observed when using pig slurry compared with mineral N as an average of the four years studied. However, the use of different N fertilization treatments (rates or types) under CT or NT did not increase the NUE compared with the control. Our study demonstrates that the use of NT and the application of agronomic rates of N as pig slurry leads to greater barley yield and water- and nitrogen-use efficiencies than the traditional management based on CT and mineral N fertilization.

Grain yield and nitrogen use efficiency of various modern rice cultivars grown at different nitrogen levels

ABSTRACTField trials were conducted to study the responses of grain yield and nitrogen (N) use efficiency at five input rates (N0, N82.5, N165, N247.5, and N330 kg ha−1) in a set of nine of the most representative rice cultivars. Grain yields of rice across the nine cultivars were increased significantly by N level. All the cultivars contained a significant linear plus plateau or quadratic relationship between N levels and grain yields.The minimum yields (means of 2 years) at N0, N82.5, N165, N247.5, and N330 level all occurred in No. 2 cultivar. Compared with the grain yield of No. 2 at different N levels, those of the maximum cultivars increased by 37.1 (No. 8), 39.1 (No. 7), 48.4 (No.3), 43.3 (No. 4), and 43.9% (No. 3), respectively. In 2011, the highest average apparent nitrogen recovery efficiency (ANRE) in grain of the 4 N levels occurred in No. 3 cultivar (45.9%), followed by No. 4, No. 6, and No. 1, and the highest average agronomic efficiency (AE) in grain of the 4 N levels occurred in No. 9 cultivar [29.0 kg (kg N)−1], followed by No. 3, No. 1, and No. 4. For the second-season planting, the highest average ANRE occurred in No. 4 cultivar (28.4%), followed by No. 3, No. 5, and No. 6, and the highest average AE occurred in No. 5 cultivar [18.1 kg (kg N)−1], followed by No. 4, No. 3, and No. 7. Overall, No. 3 and No. 4 cultivars were the ideal ones that not only increased the grain yield but also improved the N use efficiency.

Soil mineral nitrogen benefits derived from legumes and comparisons of the apparent recovery of legume or fertiliser nitrogen by wheat

Nitrogen (N) contributed by legumes is an important component of N supply to subsequent cereal crops, yet few Australian grain-growers routinely monitor soil mineral N before applying N fertiliser. Soil and crop N data from 16 dryland experiments conducted in eastern Australia from 1989–2016 were examined to explore the possibility of developing simple predictive relationships to assist farmer decision-making. In each experiment, legume crops were harvested for grain or brown-manured (BM, terminated before maturity with herbicide), and wheat, barley or canola were grown. Soil mineral N measured immediately before sowing wheat in the following year was significantly higher (P &lt; 0.05) after 31 of the 33 legume pre-cropping treatments than adjacent non-legume controls. The average improvements in soil mineral N were greater for legume BM (60 ± 16 kg N/ha; n = 5) than grain crops (35 ± 20 kg N/ha; n = 26), but soil N benefits were similar when expressed on the basis of summer fallow rainfall (0.15 ± 0.09 kg N/ha per mm), residual legume shoot dry matter (9 ± 5 kg N/ha per t/ha), or total legume residue N (28 ± 11%). Legume grain crops increased soil mineral N by 18 ± 9 kg N/ha per t/ha grain harvested. Apparent recovery of legume residue N by wheat averaged 30 ± 10% for 20 legume treatments in a subset of eight experiments. Apparent recovery of fertiliser N in the absence of legumes in two of these experiments was 64 ± 16% of the 51–75 kg fertiliser-N/ha supplied. The 25 year dataset provided new insights into the expected availability of soil mineral N after legumes and the relative value of legume N to a following wheat crop, which can guide farmer decisions regarding N fertiliser use.

Corn Yield and Grain Nutrient Uptake from 50 Years of Nitrogen and Phosphorus Fertilization

Core Ideas Initiated in 1961, a 50‐yr field study quantified continuous irrigated corn response to annual N and P rates. Positive N–P interactions on grain yield and grain N/P concentrations were documented. Economic optimum N rate varied greatly over years, but averaged ∼175 kg N ha−1 (1992‐2010). Significantly greater apparent fertilizer N recovery in grain (∼45%) occurred with P fertilization compared to no P (∼20%). Long‐term field studies can be used to improve nutrient effects on productivity. Long‐term agricultural field experiments provide valuable information regarding the effects of nutrient inputs on crop productivity. The objectives of this study were to quantify the effects of 50 yr of annual N and P application on irrigated continuous corn (Zea mays L.) grain yield, grain nutrient uptake, and economic optimum N rates. Six N (0, 45, 90, 134, 179, and 224 kg N ha−1) and three P rates (0, 20, and 40 kg P ha−1) in a factorial arrangement were applied annually from 1992 to 2010 to a Ulysses silt loam near Tribune, KS. From 1961 to 1991, only two P rates (0 and 20 kg P ha−1) were applied with the six N rates. During the last 19 yr, grain yield increased 20% with P alone and 103% with N alone; however, N and P applied together increased grain yields up to 225% compared to the unfertilized control. The N rate required for maximum profit at 20 and 40 kg P ha−1 averaged 172 and 180 kg N ha−1, respectively. At the economic optimum N rate of 172 kg N ha−1, apparent fertilizer nitrogen recovery in grain (AFNRg) was 44% and apparent fertilizer phosphorus recovery (AFPRg) was 63 and 44% with 20 and 40 kg P ha−1, respectively. Fifty years of irrigated corn response to N and P fertilization demonstrated a strong positive interaction between N and P on grain yield, apparent N and P recovery, and profitability.

The effects of dairy cattle manure and mineral N fertilizer on irrigated maize and soil N and organic C

This work was aimed at providing a sustainable approach in the use of manure in irrigated maize crop under Mediterranean climatic conditions. To this end, the effect of continuous annual applications of dairy cattle manure, combined or not with mineral N fertilizer, on the following parameters was studied: grain yield, grain and plant N concentration, N uptake by plant, N use efficiency, and soil N and organic carbon. The experiment was conducted in a furrow-irrigated sandy soil under dry Mediterranean conditions during seven years. Three different rates of cattle manure (CM): 0, 30 and 60 Mg ha−1, were applied each year before sowing. These CM rates were combined with four mineral N rates (0, 100, 200 and 300 kg N ha−1) applied at sidedress. On average, the highest grain yields during the 7 years were obtained with the combination of CM at 30 Mg ha−1 and mineral fertilizer and with CM at 60 Mg ha−1 without mineral fertilizer. With CM at 30 Mg ha−1, mineral fertilizer increased yields during most of the growing seasons, meanwhile with CM at 60 Mg ha−1, there was not any significant effect of the joint application of mineral fertilizer on yields. Overall, best results were obtained exceeding maximum rates according to present legislation. The mean apparent nitrogen recovery (ANR) fraction during the 7 seasons was 29% for N exclusively applied as CM. Overall, increased N rates applied as CM resulted in decreased ANRs. However, ANR with CM at 30 and 60 Mg ha−1 increased during the first two seasons. This increased ANR ascribed to mineralization of residual organic N applied in previous seasons explained the increasing yields observed in the treatments along the study. The application of CM during 7 years increased the soil organic carbon in the first 30 cm by 5.7 and 9.9 Mg ha−1 with CM at 30 and 60 Mg ha−1, respectively, when compared to the initial stock. Thus, manure-based fertilization could be an alternative to mineral fertilizer in order to achieve high maize yields while improving soil quality under dry Mediterranean conditions.

Accounting for the nitrogen in solid manures incorporated immediately after application in order to reduce emissions of ammonia

In four replicated field experiments the impacts of immediate incorporation of solid manures on ammonia (NH3) and direct nitrous oxide (N2O) emissions and apparent nitrogen recovery (ANR) of manure-N were measured. The impacts of immediate incorporation on nitrate (NO3−) leaching were modelled. Four manures: cattle farmyard manure (FYM); pig FYM; layer manure and broiler manure were applied to the soil surface or immediately incorporated by mouldboard plough, disc or tine. Two of the experiments were carried out on a clay soil and two on a sandy soil. There was, on average, no significant effect of application technique on ANR but there were significant increases in ANR following immediate incorporation in three experiments. Recovery of N by the succeeding crop was c. 8 % for cattle FYM, c. 13 % for pig FYM and c. 20 % for the poultry manures. Only c. 30 % of the applied N could be accounted for from measurements of NH3, N2O and ANR and modelling of NO3−. While immediate incorporation by plough increased direct N2O emissions from the sandy soil and all methods of immediate incorporation in autumn increased modelled estimates of NO3− leaching, these increases were only a small proportion of the NH3–N conserved which was probably either recovered by the crop or remained in the soil. Therefore concerns over so-called ‘pollution swapping’ should not be a barrier to the immediate incorporation of solid livestock manures in order to reduce emissions of NH3 and increase crop recovery of manure-N.

Corn Era Hybrid Response to Nitrogen Fertilization

Corn (Zea mays L.) N use is of continued interest due to agronomic performance and environmental issues. This 2‐yr study evaluated era hybrid response to fertilizer nitrogen (FN) rate in a factorial arrangement of one popular hybrid per five decades (1960–2000 eras) and five N rates (0–224 kg N ha−1). An additional hybrid per era was grown at 168 kg N ha−1. Hybrid productivity and nitrogen use efficiency (NUE) increased across the eras, but not between the 1980 and 1990 eras. Grain yield (GY) increased 65% and total plant biomass 43%, however, total plant nitrogen uptake (PNU) increased only 19% and across N rates was only higher for the 2000 era. At the agronomic optimum nitrogen rate (AONR), there was a linear GY increase of 0.13 Mg ha−1 yr−1 and GY N response of 0.091 Mg ha−1 yr−1, indicating considerable genetic gain. There was no trend in AONR across eras. For plant N status measures, SPAD readings decreased and canopy index values increased across eras. All NUE measures indicated significant improvement in NUE. The apparent nitrogen recovery efficiency (NRE) at N rates near the AONR of each era, however, was not highest for the most recent eras. Harvest index (HI), grain nitrogen harvest index (GNHI), and fraction of total PNU accumulated by R1 were the same among eras. The grain nitrogen concentration (GNC), however, was 24% lower for the 2000 compared to the 1960 era. Corn hybrid development across the 50‐yr period improved productivity and NUE, but not the AONR.

Fertilizers with coated urea in upland rice production and nitrogen apparent recovery

Urea is the most used N fertilizer for upland rice, however, a great percentage of N loss can occur with the use of this fertilizer. The use of products that provide reduction of N loss for urea fertilizers can contribute to increase N use efficiency. The objective of this study was to determine the effect of N rates applied in the form of coated urea in the content and accumulation of N in dry biomass, apparent recovery of nitrogen and grain yield of upland rice. The experimental design was a randomized complete blocks arranged in a 4 x 3 + 1 factorial scheme. The treatments consisted of four sources of N fertilizer [1. Common urea; 2. Polymer-coated urea for slow release of N (PCU); 3. urea with the urease inhibitor N-(n-Butyl) thiophosphoric triamide (NBPT); and 4. urea coated with copper sulfate and boric acid as urease inhibitors (UCCB)], with three fertilization rates (30, 60 and 90 kg ha -1 of N). In addition, we included a control treatment without N application. Coated urea did not provide increases in rice grain yield in relation to common urea. The increasing amount of N resulted in significant increases in rice grain yield (from 3217 to 5548 kg ha -1 , 2010/11, and from 3392 to 4560 kg ha -1 , 2011/12). The apparent nitrogen recovery rate decreased with the increase in N applied doses.

Determination of optimum nitrogen application rates in Zhejiang Province, China, based on rice yields and ecological security

Excessive nitrogen (N) fertilization in intensive agricultural areas such as the plain region of South China has resulted in low nitrogen use efficiency and serious environmental problems. To determine the optimum N application rate, grain yield, apparent nitrogen recovery efficiency (ANRE), apparent N loss, and ammonium (NH3) volatilization under different N application rates in the three years from 2012 to 2014 were studied. The results showed that the relationship between grain yields and N application rate in the three years were well fitted by quadratic equations. When N application rate reached 197 kg ha−1 in 2012, 199 kg ha−1 in 2013 and 196 kg ha−1 in 2014, the plateau of the grain yields appeared. With the increase of N application rate, the ANRE for rice decreased which could be expressed with sigmoidal equation; when N application rate was 305 kg ha−1 in 2012, 275 kg ha−1 in 2013 and 312 kg ha−1 in 2014, the curves of ANRE appeared turing points. Besides, the relationship between soil Nresidual and N application rate was fitted by the quadratic equation and the maximums of soil Nresidual were reached in the three years with the N application rate of 206, 244 and 170 kg ha−1, respectively. Statistical analysis indicated that NH3 volatilization and apparent N loss in three years all increased with the increasing N application rate. When the amount of NH3 volatilization increased to 11.6 kg N ha−1 in 2012, 40.5 kg N ha−1 in 2013 and 57.0 kg N ha−1 in 2014, the apparent N loss in the three years had obvious increase. To determine the optimum N application rate, the average N application on the plateau of the grain yield was considered as the lower limit while the average N application rate at the turning points of ANRE, the residual N in soil and apparent N loss was taken as the upper limit. According to the results in three years, the optimum N application rate for rice in Zhejiang was 197–255 kg ha−1.