Effect of nitrogen rates on yield and quality of fennel (Foeniculum vulgare Mill.) accessions

Nitrogen rates and plant genotypes effects yield and quality of medicinal plants therefore, this experiment was conducted in order to determine the effects of nitrogen rates on fennel accessions quality and quantity. The experimental design was a split plot with nitrogen rate (0, 40, 80, 120 and 160 Kg N ha⁻¹) as main and accession (Isfahan, Tehran, Yazd and EU11486) as sub plots and replicated four times. The experiment was conducted at the Isfahan University of Technology Experimental Station, Isfahan, Iran during 2008-2009. Plant height, number of umbel per plant, 1000seed weight, number of seeds per umbel, seed yield, seed essential oil yield, seed and foliage essential oil contents and seed ash, protein and fiber contents were measured. Nitrogen fertilization increased all measured traits, but reduced ash content. On average, the highest seed and foliage essential contents and seed essential yield were produced at 160 kg per N ha⁻¹ and EU11486 was a superior cultivar for these traits. However, there was an interaction between N rate and accession on all traits. Isfahan (11.65 kg ha⁻¹), EU11486 (38.26 kg ha⁻¹), Tehran (15.32 kg ha⁻¹) and Yazd (22.06 kg ha⁻¹) produced the highest seed essential oil yield under application of 160, 80, 160 and 120 kg N ha⁻¹, respectively. Foliage of the accessions contained 0.45-0.91% essential oil and seeds of accessions contained 17.6-18.2% protein and 8.9-9.4% ash suggesting that foliage of fennel also is a good source of essential oil and seeds of fennel are good sources of protein and minerals. The results showed that N fertilization and accession can affect yield and quality of fennel and accessions responded differently to N fertilization rates, thus selection among the accessions and N rates for better fennel production is possible.     

Phosphorus efficiency in long-term (15 years) wheat–maize cropping systems with various soil and climate conditions

Long-term (over 15 years) winter wheat (Triticum aestivum L.)–maize (Zea mays L.) crop rotation experiments were conducted to investigate phosphorus (P) fertilizer utilization efficiency, including the physiological efficiency, recovery efficiency and the mass (the input–output) balance, at five sites across different soil types and climate zones in China. The five treatments used were control, N, NP, NK and NPK, representing various combinations of N, P and K fertilizer applications. Phosphorus fertilization increased average crop yield over 15 years and the increases were greater with wheat (206%) than maize (85%) across all five sites. The wheat yield also significantly increased over time for the NPK treatments at two sites (Xinjiang and Shanxi), but decreased at one site (Hunan). The P content in wheat was less than 3.00 g kg⁻¹ (and 2.10 g kg⁻¹ for maize) for the N and NK treatments with higher values for the Control, NP and NPK treatments. To produce 1 t of grain, crops require 4.2 kg P for wheat and 3.1 kg P for maize. The P physiological use efficiency was 214 kg grain kg⁻¹ P for wheat and 240 kg grain kg⁻¹ P for maize with over 62% of the P from P fertilizer. Applying P fertilizer at 60–80 kg P ha⁻¹ year⁻¹ could maintain 3–4 t ha⁻¹ yields for wheat and 5–6 t ha⁻¹ yields for maize for the five study sites across China. The P recovery efficiency and fertilizer use efficiency averaged 47% and 29%, respectively. For every 100 kg P ha⁻¹ year⁻¹ P surplus (amount of fertilizer applied in excess of crop removal), Olsen-P in soil was increased by 3.4 mg P kg⁻¹. Our study suggests that in order to achieve higher crop yields, the long-term P input–output balance, soil P supplying capacity and yield targets should be considered when making P fertilizer recommendations and developing strategies for intensively managed wheat–maize cropping systems.     

Simulating water use and N response of winter wheat in the irrigated floodplains of Northwest Uzbekistan

The crop-soil simulation model CropSyst was used to simulate growth, water- and N-uptakes of irrigated winter wheat (Triticum aestivum L. cv. Kupava) in Khorezm, in the dry lands of northwest Uzbekistan, Central Asia. CropSyst was calibrated using the findings of field experiments of 2005/06 and 2006/07 and validated for the 2007/08 season. A relative root mean squared error of 11% proved the accuracy between simulated and observed aboveground biomass and grain yield in 2007/08. Scenario analyses showed that N-leaching was high and ranged from 63 to 106 kg ha⁻¹ when irrigated between 749 and 869 mm during the first two cropping seasons. The simulated N-leaching was lowest and ranged from 7 to 15 kg ha⁻¹ when irrigation was only 148–395 mm during 2007/08. The considerable N losses during leaching and high N-uptakes by wheat together resulted in a negative N-balance even during applications of 180 and 240 kg ha⁻¹ of N-fertilizer. N scarcity in the N-balance was reduced with increasing N-fertilizer amounts and ranged from −29 to −153 kg N ha⁻¹ in 2005/06 and 2006/07. Despite a common shallow groundwater table in the region during some time of the year, scenario analysis revealed that only full irrigation water (580 mm) and N supply according to crop demand (180 kg ha⁻¹) guaranteed high grain yields, unless the water table is permanently shallow to overcome irrigation deficits. Limited irrigation and N application (40% and 55% of ‘optimal’, respectively) in combination with a groundwater table below 3 m resulted in a 55% yield decline. The CropSyst wheat model proved a robust tool for assessing the influence of water and N dynamics under conditions of varying irrigation and shallow groundwater tables. It thus has potential as a decision support not only in northwest Uzbekistan, but also in comparable regions of Central Asia.     

The effects of nitrogen and iron fertilization on growth,yield and fertilizer use efficiency of soybean in a Mediterranean-type soil

Poor seed yield of soybean in Mediterranean-type environments may result from insufficient iron (Fe) uptake and poor biological nitrogen (N) fixation due to high bicarbonate and pH in soils. This study was conducted to evaluate the effects of N and Fe fertilization on growth and yield of double cropped soybean (cv. SA 88, MG III) in a Mediterranean-type environment in Turkey during 2003 and 2004. The soil of the experimental plots was a Vertisol with 176 g CaCO₃ kg⁻¹ and pH 7.7 and 17 g organic matter kg⁻¹ soil. Soybean seeds were inoculated prior to planting with commercial peat inoculants. N fertilizer rates were 0, 40, 80, and 120 kg N ha⁻¹ of which half was applied before planting and the other half at full blooming stage (R2). Fe fertilizer rates were 0, 200 and 400 g Fe EDTA (5.5% Fe and 2% EDTA) ha⁻¹. It was sprayed as two equal portions at two trifoliate (V2) and at five trifoliate stages (V5). Plants were sampled at flower initiation (R1), at full pod (R4) and at full seed (R6) stages. Application of starter N increased biomass and leaf area index at R1 stage whereas Fe fertilization did not affect early growth parameters. N application continued to have a positive effect on growth parameters at later stages and on seed yield. Fe fertilization increased growth parameters at R4 and R6 stages, and final seed yield in both years. This study demonstrated an interactive effect of N and Fe fertilization on growth and yield of soybean in the soil having high bicarbonate and pH. There was a positive interaction between N and Fe at the N rates up to 80 kg N ha⁻¹. However, further increase in N rate produced a negative interaction. Fertilization of soybean with 80 kg N ha⁻¹ and 400 g Fe ha⁻¹ resulted in the highest seed yield in both years. We concluded that application of starter and top dressed N in combination with two split FeEDTA fertilization can be beneficial to improve early growth and final yield of inoculated soybean in Mediterranean-type soils.     

Characteristics of canopy structure and contributions of non-leaf organs to yield in winter wheat under different irrigated conditions

Non-leaf green organs of wheat plants may have significant photosynthetic potential and contribute to grain yield when the plants are subjected to stress at late growth stages. Canopy structure, change of green non-leaf organ area (e.g., ear, peduncle, sheath), the proportion of green non-leaf organs area to total green area and the contribution proportion from different organs’ photosynthate to grain yield in winter wheat (Triticum aestivum L.) were studied at Wuqiao Experiment Station of China Agricultural University, Hebei, China, in 2001-2002 and 2002-2003 using two winter wheat cultivars, Shijiazhuang8 (SJZ-8) and Lumai21 (LM-21). Four irrigation treatments used were W0 (no water applied during spring), W1 (750 m³ ha⁻¹ water applied at elongation), W2 (1500 m³ ha⁻¹ applied 50% at elongation and 50% at anthesis) and W4 (3000 m³ ha⁻¹ applied 25% at upstanding, booting, anthesis and grain filling), respectively. Results showed that the area of top three leaf blades decreased and the proportion of green non-leaf organ area to the total green area at anthesis increased with the decreasing of water supply. Root weight increased in the 0-100 cm soil layer and decreased in the 100-200 cm layer when water supply increased, suggesting reducing irrigation enhanced root weight in deep soil layer. The photosynthetic contribution of non-leaf organs above flag leaf node to grain yield increased with decreasing water supply, and was significantly higher than that of the flag leaf blade contribution. Winter wheat grain yield increased, but water use efficiency (WUE) decreased, with increase in water supply. Higher light transmission ratio in the canopy after anthesis was achieved with smaller size and high quality top leaf blades, higher grain-leaf ratio and larger proportion of green non-leaf area, which lead to higher canopy photosynthetic rate and WUE after anthesis. Irrigation of 1500 m³ ha⁻¹ applied in two parts, 750 m³ ha⁻¹ applied at elongation and another 750 m³ ha⁻¹ applied at anthesis, was the best irrigation scheme for efficient water use and for high yield in winter wheat.     

Nitrogen applications modify seed and oil yields and fatty acid composition of winter mustard

Winter mustard (Brassica juncea L.) is not a common crop in the Southeastern United States. With increased interest in biodiesel production, there has been corresponding interest in mustard in this region. The objective of this study was to evaluate the effect of N fertilization (0, 50, 100, 150 kg N ha⁻¹) on productivity, oil content, and oil composition of winter mustard ‘Pacific Gold’ grown at three locations in Mississippi (Stoneville, and two locations at Verona, namely Verona silt loam (Verona-SL) and Verona clay (Verona-C)). Nitrogen did not affect oil content (percent oil). Seed and oil yields (kg ha⁻¹) increased with N application relative to the unfertilized control. At the Verona-C location, the concentration of oleic acid was higher in the 50 kg N ha⁻¹ treatment. At Stoneville, linolenic acid concentration was higher in the 150 kg N ha⁻¹ and lower in the 100 kg/N ha⁻¹ treatment, while it was not different in the other treatments. Overall, the yield of the fatty acids (FA) palmitic, palmitoleic, stearic, oleic, linoleic, linolenic, arachidic, eicosanoic, behenic, erucic, lignoceric, and nervonic acid increased with higher N rates (100 or 150 kg N/h). The highest yield of FA in the two Verona locations were achieved in the 100 kg N ha⁻¹, while greatest yield of FA at Stoneville was achieved in the highest N rate (150 kg N ha⁻¹). Means of mustard oil yields in our study in the higher fertility treatment ranged from 737 to 1094 kg ha⁻¹. This study demonstrated winter mustard production in Mississippi and possibly other areas in the Southeastern United States can be successful and could provide seed and oil yields comparable to yields from other production areas.     

Effect of tillage and nutrient management on wheat productivity and quality in Haryana, India

This article reports on field experiments with 4 different rotations that are commonly used throughout Haryana in NW India (rice-wheat, cotton-wheat, pearl millet-wheat, cluster bean-wheat), where we assess wheat yield and chapatti quality measures with different crop establishment methods and input of micronutrients. In a series of experiments conducted on farmers’ fields in 2007-2008 and 2008-2009 winter seasons, the addition of micronutrients and sulphur to wheat crops was used alongside the use of a common farmer practice, the use of farmyard manure (FM) and best practice inputs of N-fertilizer (150 kg N ha⁻¹), P-fertilizer (26 kg P ha⁻¹) and K-fertilizer (33 kg K ha⁻¹). The application of FM with the recommended NPK treatment produced 9-13% more grain yield in the rice-wheat rotation when compared with the recommended NPK only treatment. Given that the farm sites used here had low levels of soil P, this may suggest that the recommended rate of 26 kg P ha⁻¹ for the rice-wheat rotation is too low. The addition of FM did not improve any grain quality outcomes at any of the sites. There were no yield responses with S application with any of the rotations but the S input resulted in more wheat protein from all sites (average 8%). The addition of S also gave similar increases in grain hardness and the chapatti score. The inclusion of micronutrients (boron, copper, iron, zinc and manganese) with the recommended NPK treatment did not increase the grain yield at any of the sites when compared with the recommended NPK treatment, and sometimes, but not consistently, gave small responses with protein, grain hardness and chapatti score. In concurrent experiments wheat growth and chapatti quality were compared in zero till and conventionally sown systems, and with and without S fertilizer amendment. Here too there were no grain yield responses to S, and the protein, grain hardness and chapatti score were increased with S addition. Grain yields with zero till and conventional wheat were similar in the rice-wheat system and zero till sowing resulted in small increases in yield at all of the non-rice sites. The grain from the zero till treatments had higher protein (1-3%), grain hardness (3-10%) and chapatti score from all 4 rotations. Zero till has substantial adoption in the rice-wheat districts of Haryana but little farmer awareness and adoption in the areas where the other rotations are used. The data given here show that with zero tillage and an integrated practice of nutrient management farmers in Haryana can maintain grain yields of wheat whilst improving quality outcomes.     

Nitrogen efficiency in long-term wheat–maize cropping systems under diverse field sites in China

Efficiency of fertilizer N is becoming increasingly important in modern agricultural production owing to increasing food requirement and growing concern about environments. However, there is almost no study regarding its long-term efficiency in wheat and maize cropping systems. Long-term (15 years) experiments involving wheat (Triticum aestivum L.) and maize (Zea mays L.) rotations at five field sites with various soil and climate characteristics in China were used to determine the nitrogen (N) efficiency, including the physiological efficiency, recovery efficiency and N mass balance of soil–plant systems in response to different fertilization treatments. The present study consisted of nine treatments: unfertilized, N, phosphorus, potassium, straw and manure or their combinations. The contribution of N fertilizers to wheat yield was higher than to maize and suggested that wheat could be given priority over maize when determining N application rates. Uptake of 1 kg N produced 35.6 kg of wheat grain and 39.5 kg of maize grain. The deficit of N in soils without applied N ranged from 40 to 103 kg N ha⁻¹ year⁻¹, while N surpluses in soils with applied N fertilizers ranged from 35 to 350 kg N ha⁻¹ year⁻¹. The apparent accumulated N recovery efficiency (NRE_ac) varied widely from 4% to 90%: unbalanced fertilization and other soil limiting factors (such as aluminium toxicity) were associated with low NRE_ac. In the treatments of combination of N, phosphorus and potassium with normal application rates, the average of NRE_ac in four out of five sites reached 80%, which suggested that best management of N fertilizers could recover most of N fertilizers applied to soils. The results will be helpful to understand the long-term fate of N fertilizers and to optimize the N fertilization for agricultural practices and environment protection.     

Clover cover crops under-sown in winter wheat increase yield of subsequent spring barley—Effect of N dose and companion grass

Four two-year field trials, arranged in randomised split-plots, were carried out in southern Sweden with the aim of determining whether reduced N fertiliser dose in winter wheat production with spring under-sown clover cover crops, with or without perennial ryegrass in the seed mixture, would increase the clover biomass and hence the benefits of the cover crops in terms of the effect on the wheat crop, on a subsequent barley crop and on the risk of N leaching. Four doses of nitrogen (0, 60, 120 or 180 kg N ha⁻¹) constituted the main plots and six cover crop treatments the sub-plots. The cover crop treatments were red clover (Trifolium pratense L.), white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) in pure stands and in mixtures. The winter wheat (Triticum aestivum L.) was harvested in August and the cover crops were ploughed under in November. The risk of N leaching was assessed in November by measuring the content of mineral N in the soil profile (0–30, 30–90 cm). In the following year, the residual effects of the cover crops were investigated in spring barley (Hordeum distichon L.) without additional N. Under-sowing of cover crops did not influence wheat yield, while reduced N fertiliser dose decreased yield and increased the clover content of the cover crops. When N was applied, the mixed cover crops were as effective in depleting soil mineral nitrogen as a pure ryegrass cover crop, while pure clover was less efficient. The clover content at wheat harvest as well as the amount of N incorporated with the cover crops had a positive correlation with barley yield. Spring barley in the unfertilised treatments yielded, on average, 1.9–2.4 Mg DM ha⁻¹ more in treatments with clover cover crops than in the treatment without cover crops. However, this positive effect decreased as the N dose to the preceding wheat crop increased, particularly when the clover was mixed with grass.     

Irrigation and nitrogen scheduling as a requirement for optimising wheat yield and quality in Haryana, India

Wheat in Haryana (NW India) is grown as a winter crop in an annual sequence with rice, cotton, pearl millet or cluster bean as the main monsoon crops. Higher wheat yields in Haryana are associated with the use of modern varieties, increase in fertiliser use, improved irrigation practice and conservation tillage, and the recommendation to farmers for N fertiliser rates and timing and irrigation practice have an emphasis on optimising yield and input efficiencies. In India the importance to consumers of product quality does exist and, although the market place presently does not actively reward farmers for better quality wheat, the need for creating suitable and targeted marketing opportunities is now recognised. This paper examines aspects of input efficiencies and focuses on combinations of N-fertiliser and irrigation input in wheat crops grown with these four rotations (rice-wheat, cotton-wheat, pearl millet-wheat and cluster bean-wheat). Management practices that optimise grain production as well targeting grain that achieves best chapatti (Indian flat bread) quality are evaluated within a split-plot experiment where 4 irrigation schedule treatments were split with nitrogen management treatments involving a 2-way or 3-way split of N fertiliser. With the rice-wheat system, there were no differences between different split timings of N with grain yield, however with the 3 other wheat systems the 3 way split of N-fertiliser application, with N applied equally at N-fertiliser applied at seeding, early tillering and first node stage, always gave the highest yield. With all 4 rotations the highest protein level was achieved (range 11.8-12.5%) with this 3-way N application split. Grain yield increased in a step-wise manner as additional irrigation was implemented with all rotations and the highest protein outcomes were achieved with the least irrigations. The apparent recovery of N fertiliser applied was similar and highest with the 3-way split, and the 2-way split that did not include a basal N fertiliser application. Different rates of N fertiliser were included in separate experiments using the 3-way split of N application, and with the rice-wheat rotation the GreenSeeker instrument was used to establish the rate for the third application of N. The application of extra N-fertiliser with the non rice-wheat rotations produced no additional grain yield with an increase in the N-fertiliser input beyond 150 kg N ha⁻¹, although protein and N-content increased incrementally. Grain hardness and chapatti score trended higher with increases in N-fertiliser input but the increases were relatively small. The use of the GreenSeeker instrument with the rice-wheat rotation resulted in N saving of 21-25 kg N ha⁻¹ with similar grain yield, protein and grain hardness to that provided by using the recommended 150 kg N ha⁻¹. Where the GreenSeeker was used the apparent recovery was 70-75% compared with 60% with the wheat receiving the recommended 150 kg N ha⁻¹, suggesting farmers are likely to be over-fertilising their wheat crop. The best yields obtained in these experiments were about 5.5-6.0 t ha⁻¹ and these yields are consistent with a decade-long attainable yield identified for wheat in rice-wheat rotation for Haryana. If farmers can achieve market recognition for chapatti quality, and with the use of appropriate varieties, then farmers can assume that the best practice outlined here for optimising grain yield with integrated nutrient and soil management will be the same practice that optimises chapatti quality.     

Identification of traits to improve the nitrogen-use efficiency of wheat genotypes

Nitrogen (N) fertilizer represents a significant cost for the grower and may also have environmental impacts through nitrate leaching and N₂O (a greenhouse gas) emissions associated with denitrification. The objectives of this study were to analyze the genetic variability in N-use efficiency (grain dry matter (DM) yield per unit N available from soil and fertilizer; NUE) in winter wheat and identify traits for improved NUE for application in breeding. Fourteen UK and French cultivars and two French advanced breeding lines were tested in a 2 year/four site network comprising different locations in France and in the UK. Detailed growth analysis was conducted at anthesis and harvest in experiments including DM and N partitioning. Senescence of either the flag leaf or the whole leaf canopy was assessed from a visual score every 3-4 days from anthesis to complete canopy senescence. The senescence score was fitted against thermal time using a five parameters monomolecular-logistic equation allowing the estimation of the timing of the onset and the rate of post-anthesis senescence. In each experiment, grain yield was reduced under low N (LN), with an average reduction of 2.2 t ha⁻¹ (29%). Significant N × genotype level interaction was observed for NUE. Crop N uptake at harvest on average was reduced from 227 kg N ha⁻¹ under high N (HN) to 109 kg N ha⁻¹ under LN conditions while N-utilization efficiency (grain DM yield per unit crop N uptake at harvest; NUtE) increased from 34.0 to 52.1 kg DM kg⁻¹ N. Overall genetic variability in NUE under LN related mainly to differences in NUtE rather than N-uptake efficiency (crop N uptake at harvest per unit N available from soil and fertilizer; NUpE). However, at one site there was also a positive correlation between NUpE and NUE at LN in both years. Moreover, across the 2 year/four site network, the N × genotype effect for NUpE partly explained the N × genotype effect for grain yield and NUE. Averaging across the 16 genotypes, the timing of onset of senescence explained 86% of the variation in NUtE amongst site-season-N treatment combinations. The linear regression of onset of senescence on NutE amongst genoytpes was not significant under HN, but at three of the four sites was significant under LN explaining 32-70% of the phenotypic variation amongst genotypes in NutE. Onset of senescence amongst genotypes was negatively correlated with the efficiency with which above-ground N at anthesis was remobilized to the grain under LN. It is concluded that delaying the onset of post-anthesis senescence may be an important trait for increasing grain yield of wheat grown under low N supply.     

Determinants of ruminant nutritional quality of pearl millet [Pennisetum glaucum (L.) R. Br.] stover: I. Effects of management alternatives on stover quality and productivity

The paper investigates management and cultivar type effects on pearl millet stover yield and fodder quality. Sixteen pearl millet cultivars available to farmers in India were selected to represent three cultivar types: (1) traditional landrace germplasm from the arid/semi-arid millet production zones, (2) improved dual-purpose (grain and stover) open-pollinated varieties incorporating differing amounts of traditional landrace germplasm and (3) commercial, grain-type F1 hybrids, bred for use in the arid/semi-arid zone. The cultivars were grown for 2 years (2000 and 2001) at high fertility (HF: 65 kg N ha⁻¹ and 18 kg P ha⁻¹) and low fertility (LF: 21 kg N ha⁻¹ and 9 kg P ha⁻¹). Within each fertility level high (HP) and low (LP) plant population densities were established by varying sowing rate and then thinning to the target populations (HP: 11 plants m⁻² and LP: 5 plants m⁻²). Stover fodder quality traits (nitrogen concentration, sugar content, in vitro digestibility and metabolizable energy content) were analyzed using a combination of conventional laboratory analysis and near infrared spectroscopy. In general, fertility level and cultivar type had strong effects on grain and stover yields, and on a range of stover nutritional quality traits, but with significant year interactions. In contrast, the effect of population density on these variables was largely insignificant. Higher fertilizer application significantly increased grain and stover yields and stover nitrogen concentration, in vitro digestibility and metabolizable energy content. As a result, fertilization resulted in significant increases in the yields of both digestible and metabolizable stover. Landrace cultivars as a group produced higher quality fodder than modern hybrids, but at a significant cost in grain yield. Dual-purpose, open-pollinated cultivars were generally intermediate between the landraces and hybrids, in terms of both stover quality and grain yield, but produced the highest yields of both digestible and metabolizable stover. The paper discusses the implications of these findings for Indian pearl millet farmers with various resource levels and farming objectives.     

Dryland maize yields and water use efficiency in response to tillage/crop stubble and nutrient management practices in China

Rainfed crop production in northern China is constrained by low and variable rainfall. This study explored the effects of tillage/crop residue and nutrient management practices on maize (Zea mays L.) yield, water use efficiency (WUE), and N agronomic use efficiency (NAE) at Shouyang Dryland Farming Experimental Station in northern China during 2003–2008. The experiment was set-up using a split-plot design with 3 tillage/crop residue methods as main treatments: conventional, reduced (till with crop residue incorporated in fall but no-till in spring), and no-till (with crop residue mulching in fall). Sub-treatments were 3 NP fertilizer rates: 105–46, 179–78 and 210–92 kg N and P ha⁻¹. Maize grain yields were greatly influenced by the growing season rainfall and soil water contents at sowing. Mean grain yields over the 6-year period in response to tillage/crop residue treatments were 5604, 5347 and 5185 kg ha⁻¹, under reduced, no-till and conventional tillage, respectively. Grain yields under no-till, were generally higher (+19%) in dry years but lower (−7%) in wet years. Mean WUE was 13.7, 13.6 and 12.6 kg ha⁻¹ mm⁻¹ under reduced, no-till, and conventional tillage, respectively. The no-till treatment had 8–12% more water in the soil profiles than the conventional and reduced tillage treatments at sowing and harvest time. Grain yields, WUE and NAE were highest with the lowest NP fertilizer application rates (at 105 kg N and 46 kg P ha⁻¹) under reduced tillage, while yields and WUE tended to be higher with additional NP fertilizer rates under conventional tillage, however, there was no significant yield increase above the optimum fertilizer rate. In conclusion, maize grain yields, WUE and NAE were highest under reduced tillage at modest NP fertilizer application rates of 105 kg N and 46 kg P ha⁻¹. No-till increased soil water storage by 8–12% and improved WUE compared to conventional tillage, thus showing potentials for drought mitigation and economic use of fertilizers in drought-prone rainfed conditions in northern China.     

Are seeding densities an opportunity to increase grain yield of winter wheat in a living mulch of white clover?

Optimum plant densities are a key to maximise yields in most crops. However, such information is often lacking for more environmentally sound cropping systems, such as living mulches (LM) for small grains. In 2004 and 2005, three trials were conducted in the Swiss Midlands on fields managed in accordance with the Swiss organic farming guidelines. The objective of the study was to determine whether seeding density of winter wheat (Triticum aestivum L.) is a relevant factor for determining grain yield in a white clover (Trifolium repens L.) living mulch. The winter wheat cv. Titlis was directly sown in wide spaced rows (0.375 m) at densities of 300 (LM300), 450 (LM450) or 600 (LM600) viable grains m⁻² in a white clover living mulch established at a seeding rate of 15 kg ha⁻¹. A bare soil control treatment with a wheat density of 450 viable grains m⁻² (BS450) was also included in the trials. Mean grain yields of LM300, LM450, and LM600 never reached the values observed in BS450. This was mainly due to a lower ear density, which, nevertheless, increased linearly with the seeding density within the living mulch in all trials, but the rate of increase depended on the environment. The decrease of the grain weight brought about by the increasing seeding density had only a marginal impact on the grain yield, which was increased from 1.31, 1.98, and 4.09 Mg ha⁻¹ (LM300) to 1.97, 2.64, and 4.75 Mg ha⁻¹ (LM600) for each of the three trials in the study. Significantly higher protein contents were observed for LM300 compared to the higher densities in the living mulch and to BS450. Our research showed that an increase of the seeding density is an effective mean to increase the grain yield in living mulch systems with white clover. However, it is likely that the control of the living mulch to reduce competition with the main crop is a more relevant factor.     

Tiller traits of spring cereals under tiller-depressing long day conditions

Long days partially depress tiller growth of spring cereals. In this study we characterised and quantified growing conditions and cultivar-induced variation in tiller traits and contribution of tillers to grain yield. Experiments were done at two locations in southern Finland, incorporating two nitrogen fertiliser application rates (80 and 120 kg N ha⁻¹) and 12 two-row barley (Hordeum vulgare L.), 10 six-row barley, ten oat (Avena sativa L.) and 11 wheat (Triticum aestivum L.) cultivars. Spring cereal species differed significantly in their tillering: two-row barley was superior compared with other spring cereals, with the highest number and growth capacity of tillers and head-bearing tillers. Grain yield produced by tillers was, however, always modest compared with that of main shoots, ranging from 13% and 15% in oat and wheat to 20% in six-row barley and 64% in two-row barley. Cultivar and growing condition-induced differences were marked in tiller traits, but tillers were never able to out-yield the main shoot. This is likely to be emphasised by standard use of high seeding rates. Tillers are dominated by the main shoot under long day conditions at high latitudes, and tiller yield potential remains clearly underutilised even under conditions favouring growth.     

Ecophysiological determinants of biomass and grain yield of wheat under P deficiency

Grain yield of crops can be expressed as a function of the intercepted radiation, the radiation use efficiency and the partitioning of above-ground biomass to grain yield (harvest index). When a wheat crop is grown under P deficiency the grain yield is reduced but it is not clear how these three components are affected. Our aim was (i) to identify which of these components were affected in spring bread wheat under P deficiency at field conditions and (ii) to relate the grain yield responses to processes of grain yield formation during the spike growth period. Three field experiments were conducted in the potentially high wheat yielding environment of southern Chile. All experiments had two levels of P availability: with (155 kg P ha⁻¹) or without P fertilization (average soil P-Olsen concentration of 10 ppm, a medium level of P availability). High wheat grain yields were obtained varying between 815 and 1222 g m⁻² with P applications. Experiments showed a grain yield reduction caused by P deficiencies of 35, 16 and 18% in experiments 1, 2 and 3, respectively. This was related (R² = 0.99, P < 0.01) to a reduction in the total above-ground biomass at harvest and not to the harvest index. Reductions in above-ground biomass were due to a reduction in radiation intercepted under P deficiency without effecting radiation use efficiency. Grain number per square meter was the main yield component (R² = 0.99, P < 0.01) that explained the grain yield reduction caused by the P deficiency which was due to low spike biomass at anthesis (R² = 0.96, P < 0.05). The reduction in spike biomass at anthesis was related (R² = 0.86, P < 0.01) to reductions in crop growth rate during the spike growth period as a consequence of a lower radiation intercepted during this period. This study showed that under high wheat yield conditions the main effect of a P deficiency on grain yield reduction was a negative impact on the total above-ground biomass due to the negative impact on intercepted radiation, particularly during the spike growth period, affecting negatively spike biomass at anthesis and consequently grain number and yield.     

Effect of winter cover crop species and planting methods on maize yield and N availability under irrigated Mediterranean conditions

Under semiarid Mediterranean conditions irrigated maize has been associated to diffuse nitrate pollution of surface and groundwater. Cover crops grown during winter combined with reduced N fertilization to maize could reduce N leaching risks while maintaining maize productivity. A field experiment was conducted testing two different cover crop planting methods (direct seeding versus seeding after conventional tillage operations) and four different cover crops species (barley, oilseed rape, winter rape, and common vetch), and a control (bare soil). The experiment started in November 2006 after a maize crop fertilized with 300 kg N ha⁻¹ and included two complete cover crop-maize rotations. Maize was fertilized with 300 kg N ha⁻¹ at the control treatment, and this amount was reduced to 250 kg N ha⁻¹ in maize after a cover crop. Direct seeding of the cover crops allowed earlier planting dates than seeding after conventional tillage, producing greater cover crop biomass and N uptake of all species in the first year. In the following year, direct seeding did not increase cover crop biomass due to a poorer plant establishment. Barley produced more biomass than the other species but its N concentration was much lower than in the other cover crops, resulting in higher C:N ratio (>26). Cover crops reduced the N leaching risks as soil N content in spring and at maize harvest was reduced compared to the control treatment. Maize yield was reduced by 4 Mg ha⁻¹ after barley in 2007 and by 1 Mg ha⁻¹ after barley and oilseed rape in 2008. The maize yield reduction was due to an N deficiency caused by insufficient N mineralization from the cover crops due to a high C:N ratio (barley) or low biomass N content (oilseed rape) and/or lack of synchronization with maize N uptake. Indirect chlorophyll measurements in maize leaves were useful to detect N deficiency in maize after cover crops. The use of vetch, winter rape and oilseed rape cover crops combined with a reduced N fertilization to maize was efficient for reducing N leaching risks while maintaining maize productivity. However, the reduction of maize yield after barley makes difficult its use as cover crop.     

Forage soybean yield and quality response to water use

Forages could be used to diversify reduced and no-till dryland cropping systems from the traditional wheat (Triticum aestivum L.)-fallow system in the semiarid central Great Plains. Forages present an attractive alternative to grain and seed crops because of greater water use efficiency and less susceptibility to potentially devastating yield reductions due to severe water stress during critical growth stages. However, farmers need a simple tool to evaluate forage productivity under widely varying precipitation conditions. The objectives of this study were to (1) quantify the relationship between crop water use and dry matter (DM) yield for soybean (Glycine max L. Merrill), (2) evaluate changes in forage quality that occur as harvest date is delayed, and (3) determine the range and distribution of expected DM yields in the central Great Plains based on historical precipitation records. Forage soybean was grown under a line-source gradient irrigation system to impose a range of water availability conditions at Akron, CO. Dry matter production was linearly correlated with water use resulting in a production function slope of 21.2 kg ha⁻¹ mm⁻¹. The slope was much lower than previously reported for forage production functions for triticale (X Triticosecale Wittmack) and millet (Setaria italic L. Beauv.), and only slightly lower than slopes previously reported for corn (Zea mays L.) and pea (Pisum sativa L.) forage. Forage quality was relatively stable during the last four weeks of growth, with small declines in crude protein (CP) concentration. Values of CP concentration and relative feed value indicated that forage soybean was of sufficient quality to be used for dairy feed. A standard seed variety of maturity group VII was found to be similar (in both productivity and quality) to a variety designated as a forage type. The probability of obtaining a break-even yield of at least 4256 kg ha⁻¹ was 90% as determined from long-term precipitation records used with the production function. The average estimated DM yield was 5890 kg ha⁻¹ and ranged from 2437 to 9432 kg ha⁻¹. Regional estimates of mean forage soybean DM yield ranged from 4770 kg ha⁻¹ at Fort Morgan, CO to 6911 kg ha⁻¹ at Colby, KS. Forage soybean should be considered a viable alternative crop for dryland cropping systems in the central Great Plains.     

Optimum nitrogen fertilization rates for second-year corn succeeding alfalfa under irrigation

The N contribution of alfalfa (Medicago sativa L.) to the succeeding corn (Zea mays L.) crop (FYC) is widely recognized. However, there is less information regarding the optimum N fertilization rates (ONR) for a second-year corn (SYC) following alfalfa. Thus, the objective of this study was to evaluate the response of SYC after alfalfa to N fertilization under irrigated semiarid conditions. Three field experiments of SYC following alfalfa were conducted between 2007 and 2009 in Northeast Spain. Treatments included the combination of six N rates applied to FYC (0, 50, 100, 150, 200, and 300 kg N ha⁻¹) with four N rates applied to SYC (0, 100, 200, and 300 kg N ha⁻¹). In one of the three fields, high SYC yields (16.8 Mg ha⁻¹) were obtained in plots that remained unfertilized during two consecutive years after alfalfa. On the other two fields, 81-100% of the maximum corn yields were obtained with application of 200 kg N ha⁻¹ to SYC. Results suggest that the typical N fertilizer rates applied to SYC after alfalfa in irrigated semiarid areas (300 kg N ha⁻¹) could be reduced by at least 100 kg N ha⁻¹, with small or no economic penalties and important reductions in N losses.     

Effects of transition season management on soil N dynamics and system N balances in rice–wheat rotations of Nepal

In the low-input rice–wheat production systems of Nepal, the N nutrition of both crops is largely based on the supply from soil pools. Declining yield trends call for management interventions aiming at the avoidance of native soil N losses. A field study was conducted at two sites in the lowland and the upper mid-hills of Nepal with contrasting temperature regimes and durations of the dry-to-wet season transition period between the harvest of wheat and the transplanting of lowland rice. Technical options included the return of the straw of the preceding wheat crop, the cultivation of short-cycled crops during the transition season, and combinations of both. Dynamics of soil N_min, nitrate leaching, nitrous oxide emissions, and crop N uptake were studied throughout the year between 2004 and 2005 and partial N balances of the cropping systems were established. In the traditional system (bare fallow between wheat and rice) a large accumulation of soil nitrate N and its subsequent disappearance upon soil saturation occurred during the transition season. This nitrate loss was associated with nitrate leaching (6.3 and 12.8 kg ha⁻¹ at the low and high altitude sites, respectively) and peaks of nitrous oxide emissions (120 and 480 mg m⁻² h⁻¹ at the low and high altitude sites, respectively). Incorporation of wheat straw at 3 Mg ha⁻¹ and/or cultivation of a nitrate catch crop during the transition season significantly reduced the build up of soil nitrate and subsequent N losses at the low altitude site. At the high altitude site, cumulative grain yields increased from 2.35 Mg ha⁻¹ with bare fallow during the transition season to 3.44 Mg ha⁻¹ when wheat straw was incorporated. At the low altitude site, the cumulative yield significantly increased from 2.85 Mg ha⁻¹ (bare fallow) to between 3.63 and 6.63 Mg ha⁻¹, depending on the transition season option applied. Irrespective of the site and the land use option applied during the transition season, systems N balances remained largely negative, ranging from −37 to −84 kg N ha⁻¹. We conclude that despite reduced N losses and increased grain yields the proposed options need to be complemented with additional N inputs to sustain long-term productivity.