Dry matter,nitrogen and phosphorus accumulation,partitioning and remobilization as affected by N and P fertilization and source–sink relations

Durum wheat (Triticum turgidum subsp. durum L.) is being increasingly grown in many areas of the world, but there is a lack of information about the physiological processes limiting grain yield. In this study, different rates of N and P fertilization were applied and the source:sink ratio was manipulated to examine the factor(s) limiting grain filling under rainfed conditions. Plants exposed to four fertilization treatments (control, 80 kg N ha^?1 (N), 50 kg P ha^?1 (P) and 80 kg N ha^?1 and 50 kg P ha^?1 (N–P)) and were artificially modified to obtain a range of different source:sink ratios. The treatments were (I) control; (II) half of the spike was removed; (III) all the spike was removed. The cultivar Cosmodur was used, which is widely grown in Greece and other Mediterranean countries and is quite productive especially under rainfed conditions. The distribution of dry matter, N and P among grains, stems and leaves was analyzed at anthesis and harvesting. Dry matter accumulation and partitioning into different plant parts was different between the fertilization treatments and the control. At anthesis, leaf + culm dry matter was higher than the chaff dry matter. Total aboveground biomass increased after anthesis in both years and at all fertilization treatments. N fertilization affected N concentration at the whole plant level at anthesis and at maturity. There was an average increase of 20% in N concentration with N application at anthesis in both years relative to the control. N content was affected by the fertilization treatments and it was increased by 33% over the 2 years of the study compared with the control. In addition, P fertilization affected P concentration both at anthesis and maturity in every plant organ, and there was also a significant effect of the change of P concentration at the two different growth stages. P accumulation was also affected by the fertilization regime and by the spike halving treatment. Dry matter translocation was an average of 22% higher at the fertilized treatments compared with the control, which indicates that fertilization led plants to translocate higher amount of dry matter. N and P translocation were affected by the fertilization treatment and in some treatments by the sink reduction. The spike reduction treatment increased the pre-anthesis contribution to seed indicating that the N and P remobilization from vegetative tissues were very important for grain development. The present study indicates that N and P fertilization and sink size can affect dry matter, N, and P accumulation, partitioning, and retranslocation of durum wheat which can affect seed yield.     

Quantifying the effect of nitrogen on productivity of cocksfoot (Dactylis glomerata L.) pastures

Inorganic nitrogen fertilisers are commonly applied to crops and pastures to increase or maintain productivity. The benefits of N application must be balanced with the potential for environmental damage. At Lincoln University, Canterbury, New Zealand a split plot experiment with two irrigation levels (irrigated and dryland) and two N fertiliser application rates (0 and 800 kg N/ha/y (2003/2004) or 1600 kg N/ha/y (2004/2005) was established on a 9-year-old cocksfoot (Dactylis glomerata L.) dominant pasture to validate the N dilution curve for temperate grass species. The extent of N deficiency of pastures which had suboptimal N was quantified by calculation of a ratio between measured N% of herbage and optimum N% from the N dilution curve. The N dilution curve had the form N% = 4.8 DM^?0.35 (R² = 0.65) and the NNI ranged from a maximum of 1.2, which indicated luxury uptake, to a minimum of 0.2, which has been proposed as the minimum NNI required to result in net growth. When moisture was adequate for growth, the main cause of yield differences between +N and ?N pastures was radiation use efficiency with ?N pastures producing 0.54 g DM/MJ PAR in spring or less than half that of +N pastures (1.16 g DM/MJ PAR). The intrinsic link between water availability and N uptake in dryland and irrigated pastures was explained (R² = 0.88) by the relationship between the water use efficiency and N uptake ratio. Periods of low N uptake (N deficiency) were associated with low water use efficiency.     

水氮管理模式对不同氮效率水稻氮素利用特性及产量的影响

以高产氮高效品种(德香4103)和中产氮低效品种(宜香3724)为材料,通过“淹水灌溉+氮肥优化运筹(W1N1)”、“控制性交替灌溉+氮肥优化运筹(W2N1)”、“旱种+氮肥优化运筹(W3N2)” 3种水氮管理模式处理,研究其对氮素利用及产量的影响及其生理特性,并探讨氮素利用及产量与生理响应间的关系。结果表明,氮效率品种间的差异与水氮管理模式对水稻氮素利用特征、灌溉水生产效率、生理特性及产量均存在显著影响;不同氮效率品种间在氮肥利用效率方面的差异明显高于水氮管理模式的调控效应;而水氮管理模式对灌溉水生产效率、总吸氮量、氮素干物质生产效率及稻谷生产效率的调控作用显著。W2N1相对于W1N1及W3N2水氮管理模式能促进不同氮效率水稻拔节至抽穗期、抽穗至成熟期氮素的累积,提高功能叶谷氨酰胺合成酶(GS)活性、光合速率(P_n)及根系活力,进而提高稻谷产量及氮肥利用率,且对中产氮低效品种的调控效应显著高于对高产氮高效品种,为本试验最佳的水氮管理模式。高产氮高效品种的平均总颖花数、拔节至抽穗期稻株氮累积量、功能叶GS活性、P_n及根系活力均显著高于氮低效品种,尤其结实期高产氮高效品种更有利于维持叶片及根系的代谢同化能力,利于氮素转运、再分配到籽粒中提高稻谷生产效率及氮肥利用效率,是氮高效品种相对于氮低效品种高产、氮高效利用的重要原因。相关分析表明,水氮管理模式下不同氮效率水稻主要生育时期功能叶GS活性、P_n及根系活力与氮素利用及稻谷产量均存在显著或极显著的正相关;尤其以水稻抽穗期剑叶GS活性及根系活力与氮素利用及稻谷产量的正相关性最高。     

Nitrogen partitioning and utilization in corn cropping systems: Rotation,N source,and N timing

Nitrogen partitioning and utilization can partly control plant productivity. This study was conducted to estimate dry matter (DM) and N partitioning parameters in corn (Zea mays L.) as affected by N source, N timing, and crop rotation. We quantified yield by combine, aboveground DM accumulation [residues (stalk + cob) and grain], and C and N concentrations at growth stage R6 of corn continuously cropped (CC) or in rotation with soybean [Glycine max (L.) Merr.] (CS) and fertilized with side-dressed urea-ammonium nitrate (UAN) or with liquid swine manure applied in either spring (SM) or fall (FM). Of the assessed N partitioning parameters, N utilization showed the highest association with yield (r = 0.94***). Across treatment means, 72% of these increases in N utilization could be attributed to increases in N uptake. On the contrary, N harvest index (NHI) exhibited nearly constant values across experimental units, and therefore, NHI showed a minor relative contribution to variations in N utilization, thus supporting the basic premise of low NHI dependency on environment or management. Both N uptake and N utilization were driven by type of N addition (UAN > manure). Also, corn N utilization and yield were greater (10–13%) within the corn–soybean rotation, suggesting that a shift in land use from crop rotations into more continuous corn due to increasing demand for corn grain may impose additional challenges for enhancing plant N nutrition and sustaining yield.     

Nitrogen uptake and N-use efficiency of Mediterranean cotton under varied deficit irrigation and N fertilization

Efficient N management is essential to optimize yields and reduce degradation of the environment, but requires knowledge of deficit irrigation effects on crop yields and crop N outputs. This study assessed the N content and N-use efficiency of cotton over the 2008 and 2009 growing seasons in a single field site of the Thessaly Plain (central Greece). The experiment consisted of nine treatments with three fertilizer rates (60, 110 and 160 kg N ha⁻¹) split into three irrigation levels (approx. 1.0, 0.7 and 0.4 of the amount applied by the producer). Reduced water supply induced a shift in the distribution of N within the plant with seeds becoming an N sink under conditions of water stress. Total crop N increased linearly with irrigation level and reached a maximum average of 261 and 192 kg N ha⁻¹ in 2008 and 2009, respectively. Fertilizer application did not trigger a crop N or yield response and indicated that N inputs were in excess of crop needs. Variation in weather patterns appeared to explain annual differences of nitrate-N in the top soil and N uptake by the crop.The index of lint production efficiency (iNUE) detected crop responses caused by irrigation and annual effects, but failed to account for excessive N inputs due to mineral fertilizer applications. A maximum average iNUE of 9.6 was obtained under deficit irrigation, whereas an iNUE of 8.1 was obtained under 40 cm irrigation when crop N uptake was not excessive (192 kg ha⁻¹ in 2009). In contrast, NUE, as an estimator of N recovery efficiency, identified excessive fertilizer inputs as N losses to the environment and indicated that 60 kg N ha⁻¹ was a rate of high N removal efficiency and long-term N balance. However, NUE failed to account for crop N responses to irrigation and weather/management patterns. In this case study, neither index was able to detect all the factors influencing the N mass balance and both were required in order to provide a comprehensive evaluation of the environmental performance of our cropping system.     

Yield and nitrogen utilization efficiency of the pseudocereals amaranth,quinoa, and buckwheat under differing nitrogen fertilization

In recent years, the cultivation of the pseudocereal species amaranth, quinoa, and buckwheat has gained rising attention. This study was undertaken to explore nitrogen (N) fertility requirements and nitrogen use efficiency of these species. For this purpose, a 2-year field experiment with N rates of 0, 80, and 120 kg N ha⁻¹ for amaranth and quinoa and 0, 30, and 60 kg N ha⁻¹ for buckwheat and two cultivars of each species was conducted.Grain yield of amaranth responded to N and ranged between 1986 and 2767 kg ha⁻¹. Nitrogen utilization efficiency (NUtE) ranged from 13.9 to 15.4 kg grain yield per kg above-ground plant N and decreased with increasing N rate. Higher grain yields and NUtEs seemed to be mainly inhibited by the low harvest index (0.22–0.23) of the investigated amaranth cultivars.Quinoa yielded between 1790 and 3495 kg grain ha⁻¹ and responded strongly to N fertilization. NUtE averaged 22.2 kg kg⁻¹ and did not decrease with increasing N rates.The grain yield of buckwheat did not respond to N fertilization and averaged 1425 kg ha⁻¹. N uptake increased only slightly with N fertilization. NUtE ranged from 16.1 to 20.0 kg kg⁻¹. Main problems occurring with the application of N to buckwheat were grain scattering and lodging.     

The effect of tillage system and residue management on grain yield and nitrogen use efficiency in winter wheat in a cool Atlantic climate

The effects of soil tillage and straw management systems on the grain yield and nitrogen use efficiency of winter wheat (Triticum aestivum L. em. Thell.) were evaluated in a cool Atlantic climate, in central Ireland between 2009 and 2011. Two tillage systems, conventional tillage (CT) and reduced tillage (RT) each with and without incorporation of the straw of the preceding crop, were compared at five levels of fertiliser N (0, 140, 180, 220 and 260 kg N ha⁻¹).CT had a significantly higher mean grain yield over the three years but the effect of tillage varied between years. Yields did not differ in 2009 (Year 1), while CT produced significantly higher grain yields in 2010 (Year 2), while RT produced the highest yields in 2011 (Year 3). Straw incorporation had no significant effect in any year.Nitrogen application significantly increased the grain yields of all establishment treatment combinations. Nitrogen use efficiency (NUE) ranged from 14.6 to 62.4 kg grain (85% DM) kg N ha⁻¹ and decreased as N fertiliser rate was increased.The CT system had a significantly higher mean NUE over the three years but the effect of tillage varied with years. While there was no tillage effect in years 1 and 3, CT had a significantly higher NUE than RT in year 2. Straw management system had minimal effect on NUE in any year.The effect of tillage and N rate on soil mineral N content also varied between years. While there was no tillage effect in years 1 and 3, RT had significantly larger soil N contents than CT in the spring before N application, and post-harvest in year 2. N application rates had no effect on soil N in year 1, increased residual N content in year 2 and had an inconsistent effect in year 3. Straw management had no significant effect on soil mineral N content.These results indicate that RT establishment systems can be used to produce similar winter wheat yields to CT systems in a cool Atlantic climate, providing weather conditions at establishment are favourable. The response to nitrogen is similar with both tillage systems where the crop is successfully established. Straw management system has very little effect on crop performance or nitrogen uptake.     

Nitrogen and water-use efficiency of Australian wheat varieties released between 1958 and 2007

We used a collection of Australian wheats released between 1958 and 2007 to probe for time trends in evapotranspiration and nitrogen uptake, and the efficiencies in the use of water and nitrogen to produce grain yield. Yield increased linearly with year of cultivar release at a rate of 18 kg ha⁻¹ y⁻¹; this rate aligned with the relationship between rate of genetic gain and environmental yield from breeding programs worldwide. No time trend was apparent for seasonal evapotranspiration, hence the linear increase in yield per unit evapotranspiration with year of release which was fully accounted for by yield improvement. Under our experimental conditions, yield per unit transpiration of current varieties was ∼24 kg ha⁻¹ mm⁻¹, highlighting the need to update the 20 kg ha⁻¹ mm⁻¹ ratio commonly used in agronomic benchmarking.Yield per unit nitrogen uptake was largely unchanged as a consequence of increased nitrogen uptake that paralleled the increase in yield, and a secondary contribution of reduced grain protein concentration particularly under environmental conditions that favoured high protein. The nitrogen nutrition index, accounting for the effect of biomass on nitrogen uptake, increased linearly with year of cultivar release, hence supporting the conclusion that breeding for yield improved the nutrition status of wheat in association with an increased capacity to uptake nitrogen in equal-sized crops.     

Effect of organic and conventional farming systems on nitrogen use efficiency of potato,maize and vegetables in the Central highlands of Kenya

Increased per capita food production in the tropics is closely tied to soil organic matter and water management, timely nitrogen (N) supply and crop N use efficiency (NUE) which are influenced by farming systems. However, there is lack of data on the effect of organic farming systems on NUE and how this compares to conventional farming systems under tropical conditions. Therefore, the objectives of this study were to determine the effect of conventional and organic farming systems at low and high management intensities on N uptake and N use efficiency of potato (Solanum tuberosum L.), maize (Zea mays L.), cabbage (Brassica oleracea var. Capitata), kale (Brassica oleracea var. Acephala) and Swiss chard (Beta vulgaris sub sp. Cicla). The organic high input (Org-High) and conventional high input (Conv-High) farming systems are managed as recommended by research institutions while organic low input (Org-Low) and conventional low input (Conv-Low) farming systems are managed as practiced by small scale farmers in the Central highlands of Kenya. The study was conducted during three cropping seasons between October 2012 and March 2014 in an ongoing long-term trial established since 2007 at Chuka and at Thika, Kenya. Synthetic N-based fertilizer and cattle manure were applied at ∼225 kg N ha⁻¹ yr⁻¹ for Conv-High and at ∼50 kg N ha⁻¹ yr⁻¹ for the Conv-Low. Composts and other organic inputs were applied at similar N rates for Org-High and Org-Low. Nitrogen uptake efficiency (NUpE) of potato was highest in Conv-Low and Org-Low at Thika and lowest in Org-High and Org-Low at Chuka site where late blight disease affected potato performance. In contrast, the NUpE of maize was similar in all systems at Chuka site, but was significantly higher in Conv-High and Org-High compared to the low input systems at Thika site. The NUpE of cabbage was similar in Conv-High and Org-High while the NUpE of kale and Swiss chard were similar in the low input systems. Potato N utilization efficiencies (NUtE) and agronomic efficiencies of N use (AE_N) in Conv-Low and Conv-High were 11–21 % and 1.4–3.4 times higher than those from Org-Low and Org-High, respectively. The AE_N of maize was similar in all the systems at Chuka but was 3.2 times higher in the high input systems compared to the low input systems at the Thika site. The AE_N of vegetables under conventional systems were similar to those from organic systems. Nitrogen harvest index (NHI) of potato was similar between Conv-High and Org-High and between Conv-Low and Org-Low. N partitioned into maize grain was similar in all the system at Chuka, but significantly lower (P < 0.001) in Conv-low and Org-Low at Thika site. The NHI of cabbage in Org-High was 24 % higher than that of Conv-High. The study concluded that for maize and vegetables, conventional and organic farming systems had similar effects on NUpE, AE_N, NUtE and NHI, while for potato conventional systems improved NUE compared to organic systems. The study recommends that management practices for potato production in organic systems should be improved for a more efficient NUE.     

Response of giant reed (Arundo donax L.) to nitrogen fertilization and soil water availability in semi-arid Mediterranean environment

The aim of the present work was to evaluate the effect of soil water availability and nitrogen fertilization on yield, water use efficiency and agronomic nitrogen use efficiency of giant reed (Arundo donax L.) over four-year field experiment.After the year of establishment, three levels for each factor were studied in the following three years: I₀ (irrigation only during the year of establishment), I₁ (50% ETm restitution) and I₂ (100% ETm restitution); N₀ (0 kg N ha⁻¹), N₁ (60 kg N ha⁻¹) and N₂ (120 kg N ha⁻¹).Irrigation and nitrogen effects resulted significant for stem height and leaf area index (LAI) before senescence, while no differences were observed for stem density and LAI at harvest.Aboveground biomass dry matter (DM) yield increased following the year of establishment in all irrigation and N fertilization treatments. It was always the highest in I₂N₂ (18.3, 28.8 and 28.9 t DM ha⁻¹ at second, third and fourth year growing season, respectively). The lowest values were observed in I₀N₀ (11.0, 13.4 and 12.9 t DM ha⁻¹, respectively).Water use efficiency (WUE) was significantly higher in the most stressed irrigation treatment (I₀), decreasing in the intermediate (I₁) and further in the highest irrigation treatment (I₂). N fertilization lead to greater values of WUE in all irrigation treatment.The effect of N fertilization on agronomic nitrogen use efficiency (NUE) was significant only at the first and second growing season.Giant reed was able to uptake water at 160–180 cm soil depth when irrigation was applied, while up to 140–160 cm under water stress condition.Giant reed appeared to be particularly suited to semi-arid Mediterranean environments, showing high yields even in absence of agro-input supply.     

Crop yields and N losses tradeoffs in a garlic–wheat rotation in southern Spain

The CropSyst model was parameterized and verified for garlic with data from six field experiments carried out in southern Spain from 2008 to 2011. The model simulated well crop dry matter production, N uptake, and yield from field plots with different N fertilization treatments. A garlic–wheat rotation was then simulated for a 30-year period to evaluate the role of wheat after garlic as a catch crop that utilizes and reduces the loss of residual soil N left at the time of garlic harvest. The scenarios studied were the combination of seven rates of mineral N fertilization in garlic (0, 50, 100, 150, 200, 250 and 300 kgN/ha) and three rates in wheat (30, 70 and 110 kgN/ha). Fertilization rates of 150 kgN/ha in garlic and 70 kgN/ha in wheat were found to provide the best tradeoff between N loss reductions (N leaching and N gas emissions) while attaining near-maximum yields. Increasing fertilization to 200 and 110 kgN/ha for garlic and wheat, respectively, rates not atypical in the region, had a minimum effect on yields but increased average N losses over the rotation by 19 kgN/ha/2-year (29%). Further reductions of N losses by decreasing N fertilization below the best tradeoff point are possible at the expense of crop yield.     

Effect of nitrogen fertilization on nitrate leaching in relation to grain yield response on loamy sand in Sweden

High rates of nitrogen (N) fertilizer may increase N leaching with drainage, especially when there is no further crop response. It is often discussed whether leaching is affected only at levels that no longer give an economic return, or whether reducing fertilization below the economic optimum could reduce leaching further. To study nitrate leaching with different fertilizer N rates (0–135 kg N ha⁻¹) and grain yield responses, field experiments in spring oats were conducted in 2007, 2008 and 2009 on loamy sand in south-west Sweden. Nitrate leaching was determined from nitrate concentrations in soil water sampled with ceramic suction cups and measured discharge at a nearby measuring station. The results showed that nitrate leaching per kg grain produced had its minimum around the economic optimum, here defined as the fertilization level where each extra kg of fertilizer N resulted in a 10 kg increase in grain yield (85% DM). There were no statistically significant differences in leaching between treatments fertilized below this level. However, N leaching was significantly elevated in some of the treatments with higher fertilization rates and the increase in nitrate leaching from increased N fertilization could be described with an exponential function. According to this function, the increase was <0.04 kg kg⁻¹ fertilizer N at and below the economic optimum. Above this fertilization level, the nitrate leaching response gradually increased as the yield response ceased and the increase amounted to 0.1 and 0.5 kg kg⁻¹ when the economic optimum was exceeded by 35 and 100 kg N ha⁻¹, respectively. The economic optimum fertilization level depends on the price relationship between grain and fertilizer, which in Sweden can vary between 5:1 and 15:1. In other words, precision fertilization that provides no more or no less than a 10 kg increase in grain yield per kg extra N fertilizer can be optimal for both crop profitability and the environment. To predict this level already at fertilization is a great challenge, and it could be argued that rates should be kept down further to ensure that they are not exceeded due to overestimation of the optimum rate. However, the development of precision agriculture with new tools for prediction may reduce this risk.     

Achieving legislation requirements with different nitrogen fertilization strategies: Results from a long term experiment

The Nitrates Directive (91/676/EEC, Anonymous, 1991) was developed in Europe to limit environmental threats from intensive livestock farming and N fertilizer applications to crops. It imposed several rules on farmers and public bodies, one of which was nutrient fertilization plan adoption. Here we use results from the Tetto Frati (Northern Italy) Long-Term Experiment to verify the terms and coefficients in the official Italian guidelines and evaluate the limitations imposed to organic fertilization amounts. For this purpose, we mined long-term experimental data of crop yield, N uptake, N use efficiency, and soil organic matter content from miscellanea cropping systems fertilized with farmyard manure (FYM) and bovine slurry (SLU), typical of a dairy farm in Northern Italy. N fertilization efficiency indicators (Removal to Fertilizer ratio, Apparent Recovery and Nitrogen Fertilizer Replacement Value) indicated that in the long run, FYM behaved similarly to urea, and better than SLU. Even N supply rates as high as 250 kg N ha⁻¹ were justified by high rates of crop removal. In fact, among the terms of the mass-balance equation, SOM mineralization was found to be most relevant, followed by meadow rotation residual effects. We conclude that a revised Nitrates Directives application scheme could be more relaxed in its application limit of manure-N, but should be more ambitious in setting efficiency coefficients for manure fertilization.     

Plant phosphorus nutrition indicators evaluated in agricultural grasslands managed at different intensities

A precise assessment of the phosphorus (P) nutrition status of plants is necessary for an efficient P management in agricultural grasslands. Plant mineral analysis is a tool to identify the nutrition status of grasslands and several P indicators derived thereof are available. However, the interpretation of plant P indicators in grassland samples is complex due to variation in botanical composition, changing nutrient concentrations during growth and interactions between nutrients. The aim of this study was to compare indicators on the P nutrition status of plants and eventually to improve their application in agricultural grasslands. We studied three agricultural grassland types in Switzerland that were managed at different intensity either for high biodiversity or high forage production. Each grassland type was for 5–25 years subjected to treatments of low, recommended or high rates of P, nitrogen (N) and potassium (K) fertilizer. The recommended P rates ranged from 15 to 48 kg P ha⁻¹ year⁻¹. We measured plant P, N and K concentrations in the aboveground biomass of grasses, legumes and forbs. The evaluated P indicators were: P concentration, N:P and K:P ratios and the P nutrition index (PNI). The PNI is calculated as P concentration divided by the linear relationship describing optimal sward P concentration as a function of N concentration (PNI = 100P/(0.06 × 5N + 1.5)). We observed significant yield reduction compared to the expected yield only when one or more nutrients were omitted from fertilization. Fertilizer P input higher than recommended did not significantly increase yields above the yield expected for the respective management and altitude. Under P limiting conditions, forbs and legumes had significantly higher P concentrations than grasses. Additionally, the proportion of legumes affected the P indicators integrating N. Therefore, we used the P indicators in the grass fraction, which was always the main botanical fraction. In grasses all P indicators differentiated between P fertilized and non-P-fertilized treatments. Concentrations of P from 2.1 to 3.0 mg g⁻¹ indicated sufficient P supply, while yield was reduced at lower and not increased at higher concentrations, suggesting luxurious P consumption. Our results for N:P and K:P suggested optimal ranges of 5.5–9.0 and 6.0–10.5, respectively. The PNI showed a clear differentiation between deficient, sufficient or surplus fertilizer inputs. For the precise and correct interpretation of the plant P nutrition status in agricultural grasslands under different management, we propose to use the PNI in the grass fraction. Finally, the interpretation of the indicators was valid for the agricultural grasslands managed at different intensities in spite that the grass fraction was composed by different species.     

Tillage,cover crops,and nitrogen fertilization effects on soil nitrogen and cotton and sorghum yields

Sustainable soil and crop management practices that reduce soil erosion and nitrogen (N) leaching, conserve soil organic matter, and optimize cotton and sorghum yields still remain a challenge. We examined the influence of three tillage practices (no-till, strip till and chisel till), four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secaele cereale L.)], vetch/rye biculture and winter weeds or no cover crop}, and three N fertilization rates (0, 60–65 and 120–130 kg N ha⁻¹) on soil inorganic N content at the 0–30 cm depth and yields and N uptake of cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench]. A field experiment was conducted on Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) from 1999 to 2002 in Georgia, USA. Nitrogen supplied by cover crops was greater with vetch and vetch/rye biculture than with rye and weeds. Soil inorganic N at the 0–10 and 10–30 cm depths increased with increasing N rate and were greater with vetch than with rye and weeds in April 2000 and 2002. Inorganic N at 0–10 cm was also greater with vetch than with rye in no-till, greater with vetch/rye than with rye and weeds in strip till, and greater with vetch than with rye and weeds in chisel till. In 2000, cotton lint yield and N uptake were greater in no-till with rye or 60 kg N ha⁻¹ than in other treatments, but biomass (stems + leaves) yield and N uptake were greater with vetch and vetch/rye than with rye or weeds, and greater with 60 and 120 than with 0 kg N ha⁻¹. In 2001, sorghum grain yield, biomass yield, and N uptake were greater in strip till and chisel till than in no-till, and greater in vetch and vetch/rye with or without N than in rye and weeds with 0 or 65 kg N ha⁻¹. In 2002, cotton lint yield and N uptake were greater in chisel till, rye and weeds with 0 or 60 kg N ha⁻¹ than in other treatments, but biomass N uptake was greater in vetch/rye with 60 kg N ha⁻¹ than in rye and weeds with 0 or 60 kg N ha⁻¹. Increased N supplied by hairy vetch or 120–130 kg N ha⁻¹ increased soil N availability, sorghum grain yield, cotton and sorghum biomass yields, and N uptake but decreased cotton lint yield and lint N uptake compared with rye, weeds or 0 kg N ha⁻¹. Cotton and sorghum yields and N uptake can be optimized and potentials for soil erosion and N leaching can be reduced by using conservation tillage, such as no-till or strip till, with vetch/rye biculture cover crop and 60–65 kg N ha⁻¹. The results can be applied in regions where cover crops can be grown in the winter to reduce soil erosion and N leaching and where tillage intensity and N fertilization rates can be minimized to reduce the costs of energy requirement for tillage and N fertilization while optimizing crop production.     

Pig slurry fertilization in a double-annual cropping forage system under sub-humid Mediterranean conditions

In areas of Southern Europe with very intensive pig production, most of the pig slurry (PS) is applied as fertilizer. However, in the European Union, no more than 170 kg N ha⁻¹ year⁻¹ can be applied in nitrate vulnerable zones (NVZs) from livestock manures. In this context, a six-year trial was conducted for a maize-triticale double-annual forage cropping rotation under rainfed conditions. Four different N rates were applied (0, 170, 250 and 330 kg N ha⁻¹ year⁻¹), to evaluate their effect on crop yield, N uptake, unrecovered N and soil nitrate content. The corresponding PS rates were defined as zero (PS 0), low (PSL) medium (PSM) and high (PSH). The annual average dry matter (DM) yields (maize + triticale) for the PS fertilization treatments PS0, PSL, PSM and PSH were 12.6, 17.7, 20.2 and 22.0 Mg DM ha⁻¹, respectively. Maize DM yield was influenced mainly by weather conditions, and triticale DM yield was clearly influenced by initial soil NO₃⁻-N and PS fertilization rates. Unrecovered N was affected by PS fertilization rate and initial soil NO₃⁻-N content. A residual effect of the PS when applied to maize had an important effect on soil NO₃⁻-N and subsequent triticale DM yield. Moreover, total annual average unrecovered N, considering the sum of both crops (maize + triticale), were 91, 144, and 222 kg N ha⁻¹ in PSL, PSM and PSH, respectively. In order to avoid part of this unrecovered N, mainly by lixiviation of nitrates, PS fertilization in triticale should be applied as side dressing at tillering. The application of N, in the form of PS, at rates higher than the legally permitted maximum of 170 kg N ha⁻¹ year⁻¹, may result in better yields. However, high rates of PS fertilization may originate in significantly lower N use efficiency and a higher potential environmental impact in double-cropping systems, practiced in rainfed sub-humid Mediterranean conditions.     

Application of pig slurry—First year and residual effects on yield and N balance

Crops generally utilize nitrogen (N) from slurries less efficiently than from mineral fertilizers. In order to compare the effects of slurry and mineral N application on yield and residual fertilization effects, a long-term field trial was established in autumn 1994, where pig slurry was applied to oilseed rape (OSR), winter wheat and winter barley at the same application dates as mineral N fertilizer. N amounts ranged from 0 to 240 kg total N ha⁻¹. The same treatment regimes were applied to the same plots in each year. Starting in 2010 (2011), wheat (barley) received no N fertilization in order to allow for testing residual fertilizer effects. Every year seed yield and N offtake by the seeds were determined.Accounting only for ammonia N of pig slurry, similar seed yields in OSR and slightly higher grain yields in wheat and barley compared to mineral N fertilizer were achieved. This indicates that mineralization of organically bounded slurry N compensated gaseous ammonia losses. In plots without N fertilization, OSR showed no yield trends during the experimental period, whereas wheat (barley) yield started to decrease after 10 (13) years without N fertilization. In the highly fertilized treatments, no significant trend in seed yield or N amount required for maximum yield could be detected. In the subsequent unfertilized wheat crop, accumulated slurry effects increased grain yield more than those of mineral N fertilizer. Barley grown in the second year without N supply remained unaffected by the previous slurry N application.     

Winter cereal yields as affected by animal manure and green manure in organic arable farming

The effect of nitrogen (N) supply through animal and green manures on grain yield of winter wheat and winter rye was investigated from 1997 to 2004 in an organic farming crop rotation experiment in Denmark on three different soil types varying from coarse sand to sandy loam. Two experimental factors were included in the experiment in a factorial design: (1) catch crop (with and without), and (2) manure (with and without). The four-course crop rotation was spring barley undersown with grass/clover – grass/clover – winter wheat or wheat rye – pulse crop. All cuttings of the grass–clover were left on the soil as mulch. Animal manure was applied as slurry to the cereal crops in the rotation in rates corresponding to 40% of the N demand of the cereal crops.Application of 50 kg NH₄–N ha^?1 in manure increased average wheat grain yield by 0.4–0.9 Mg DM ha^?1, whereas the use of catch crops did not significantly affect yield. The use of catch crops interacts with other management factors, including row spacing and weed control, and this may have contributed to the negligible effects of catch crops. There was considerable variation in the amount of N (100–600 kg N ha^?1 year^?1) accumulated in the mulched grass–clover cuttings prior to ploughing and sowing of the winter wheat. This was reflected in grain yield and grain N uptake. Manure application to the cereals in the rotation reduced N accumulation in grass–clover at two of the locations, and this was estimated to have reduced grain yields by 0.1–0.2 Mg DM ha^?1 depending on site. Model estimations showed that the average yield reduction from weeds varied from 0.1 to 0.2 Mg DM ha^?1. The weed infestation was larger in the manure treatments, and this was estimated to have reduced the yield benefit of manure application by up to 0.1 Mg DM ha^?1. Adjusting for these model-estimated side-effects resulted in wheat grain yields gains from manure application of 0.7–1.1 Mg DM ha^?1.The apparent recovery efficiency of N in grains (N use efficiency, NUE) from NH₄–N in applied manure varied from 23% to 44%. The NUE in the winter cereals of N accumulated in grass–clover cuttings varied from 14% to 39% with the lowest value on the coarse sandy soil, most likely due to high rates of N leaching at this location. Both NUE and grain yield benefit in the winter cereals declined with increasing amounts of N accumulated in the grass–clover cuttings. The model-estimated benefit of increasing N input in grass–clover from 100 to 500 kg N ha^?1 varied from 0.8 to 2.0 Mg DM ha^?1 between locations. This is a considerably smaller yield increase than obtained for manure application, and it suggests that the productivity in this system may be improved by removing the cuttings and applying the material to the cereals in the rotation, possibly after digestion in a biogas reactor.Cereal grain protein content was increased more by the N in the grass–clover than from manure application, probably due to different timing of N availability. Green-manure crops or manures with a relatively wide C:N ratio may therefore be critical for ensuring sufficiently high protein contents in high yielding winter wheat for bread making.     

Influence of sulfur on apparent N-use efficiency,yield and quality of oilseed rape (Brassica napus L.) grown on a calcareous soil

In the Lorraine region, major soils used for winter oilseed rape are calcareous. Across two pot and two field experiments, we studied the influence of sulfur applied at different levels on apparent N-use efficiency (ANU), yield, glucosinolate (GLS) and oil content of seeds. The soil received a constant dose of 200 kg N ha⁻¹ as ammonium nitrate, urea or cow slurry and three levels of S: 0, 30 and 75 kg ha⁻¹ as ammonium thiosulfate (ATS), MgSO₄ or ATS plus MgSO₄. Apparently, oilseed rape is a N-inefficient crop as revealed by low ANU values which varied within 36 and 53% from field experiment versus 25 and 61% under controlled conditions. In both cases, S additions improved N-use efficiency only at the highest dose of 75 kg S ha⁻¹, which is not attained by ATS with 35 kg S ha⁻¹ (10% v/v). S fertilization increased the GLS contents that were found to be negatively correlated with plant N/S uptake ratios observed at maturity. The most important increase in GLS content by 52% was noted with cow slurry in the pot experiment. But, as a whole, the GLS levels remain below the European norm of 18 μmol g seed⁻¹. Moreover, the oil content (% DM) of seeds decreased (but the total production increased) when the soil was fertilized with N and with or without S. The results showed that N and S nutrition during the growth were tightly linked. Their interactions, as reflected by plant uptake, are synergistic at optimum rates and antagonistic at excessive levels of one of the both. Collectively, the results indicate that S fertilization is required to improve N-use efficiency and thereby maintaining a sufficient oil level and fatty acid quality.     

An evaluation of the combined usage of separated liquid pig manure and inorganic fertiliser in nutrient programmes for winter wheat production

The effect of spring application of separated liquid pig manure (LPM) in combination with medium to high levels of inorganic nitrogen (N) to winter wheat was investigated in a field trial study at two sites in two successive growing seasons (2007–2008). The key crop parameters examined were crop N uptake (CNU), N use efficiency and grain yield. The LPM product (3.5–4.0 g/kg total N) was applied at three application rates: 15, 30 and 45 m³/ha using a band spread application technique. The LPM was used in combination with reduced and recommended inorganic N levels; a zero N control was also included. Weather conditions in both seasons were similar with below average rainfall levels in spring followed by above average summer rainfall levels. The zero N control gave lowest CNU levels in both growing seasons (70–88 kg N/ha). Inorganic N application at the reduced and recommended N rates increased CNU levels by approximately 100 kgN/ha and 112 kgN/ha, respectively compared to the untreated control. Liquid pig manure application resulted in an additional crop uptake of 58 kgN/ha. Nitrogen use efficiencies for LPM ranged from 23 to 56% while inorganic N use efficiency levels were higher ranging from 58 to 73%. Lowest grain yield levels were measured from the zero N control (range 3.95–5.01 t/ha). The application of inorganic N increased grain yield levels by a minimum of 4.05 t/ha with LPM usage increasing grain yield levels by an additional 0.2–1.09 t/ha. This study showed that LPM could be successfully used in combination with inorganic fertilisers for the improved N nutrition of winter wheat in spring as part of an integrated nutrient programme.