Deficit irrigation for enhancing sustainable water use: Comparison of cotton nitrogen uptake and prediction of lint yield in a multivariate autoregressive state-space model

Deficit irrigation is an optimization strategy for achieving sustainability of irrigated crop production. A field-study of cotton (Gossypium hirsutum L.) response to a limited water supply was conducted in an Alfisol in the southern High Plains of Texas. The objectives were to investigate cotton N uptake, canopy temperature, plant spectral index and lint yield variation under deficit irrigation and to provide information for enhancing sustainability of the water resources and Alfisols in the semi-arid environment. The experimental treatments were two deficit-irrigation levels at 50% and 75% of cotton evapotranspiration (ET). Plant and soil variables were measured 15 m apart along the center-pivot irrigation circles. The results show that cotton plants under the 50%-ET deficit irrigation level were 21% more water stressed (P < 0.05) based on the reflectance water index ratio. The 50%-ET irrigation resulted in a 25% lint yield loss with a 33% water saving compared to the higher irrigation level (75%-ET). Plant reflectance, canopy temperature, total N uptake and lint yield were correlated with normalized difference vegetative index (NDVI), soil water content (SWC), soil NO₃-N concentrations and elevation (−0.69 < r < 0.72, P < 0.05, respectively). Future cotton lint yield is weighted on NDVI and water variation, quantified in a multivariate autoregressive state-space model. Increases in plant reflectance in the water band are signs of early plant water stress. Compared to the 12-year regional cotton lint yield obtained with full irrigation, the 75%-ET deficit irrigation would be agronomical, economical efficient in Alfisoils with only 7.8% of lint-yield loss from water stress but 25% of water saving for sustainable water use.     

Carbon, nitrogen, and hydrogen isotope ratios in creekside trees in western Kansas

Three species of creekside trees were monitored weekly during the 2007 and 2008 growing seasons. The 2007 growing season was wet early, but became drier as the season progressed. In contrast, the 2008 growing season was dry early, but became wetter as the season progressed. Creekside trees were measured to determine effects of changing water regimes on leaf-level processes. Lonicera tatarica plants were compared to Morus alba and Celtis occidentalis trees. Leaves were monitored for changes in stomatal conductance, transpiration, δ¹³C, δ¹⁵N, δD, leaf temperature, and heat losses via latent, sensible, and radiative pathways. δD of creek water was more similar to ground water than to rain water, but the creek was partially influenced by summer rains. δD of bulk leaf material was significantly higher in individuals of C. occidentalis compared to the other species, consistent with source water coming from shallower soil layers. Despite decreasing water levels, none of these tree species showed signs of water stress. There were no significant differences between species in stomatal conductance or transpiration. Leaf δ¹³C was significantly lower in individuals of L. tatarica compared to the other species. Differences in δ¹³C were attributed to a lower carboxylation capacity, consistent with lower leaf nitrogen content in L. tatarica plants. Leaf δ¹⁵N was significantly lower in individuals of L. tatarica compared to the other species, consistent with uptake of a different N source. Two of the three sites appeared to be affected by inorganic N from fertilizer run-off. Evidence is presented that these species acquired water and nitrogen from different sources, resulting from differences in root uptake patterns.     

Sources of Nitrogen in Combination with Systems of Irrigation Influence the Productivity of Modern Rice (<i>Oryza sativa</i> L.) Cultivars during Dry Season in Sub-Tropical Environment

In irrigated agricultural systems, nitrogen (N) and water are the vital resources for sustainability of the crop production in the modern era of climate change. The current study aimed to assess the impact of water and N management on the productivity of irrigated rice cultivars. In the context, a field observation was done at the research farm of Bangladesh Agricultural University, Mymensingh, during dry seasons in consecutive two years (2018–2019 and 2019–2020). The experiments were set up following split-plot design assigning water management in the main plots, nitrogen management in the sub-plots, and the cultivars were approved in the split-split plot with three replications. After two years observation, it was revealed that rice cultivar Binadhan-8 gave the maximum value of leaf area index, number effective tillers hill^-1 and grains panicle^-1 which lead to the higher grain yield (GY). Substantial relationships were observed among the concentration of N, growth, total dry matter (TDM) and N content, N uptake, N utilization effectiveness, and GY. However, with little exception, the Combined effect of water and N, cultivars and water management were varied significantly for all parameters. Finally, the results of the current study concluded that application of irrigation at 8 days after the disappearance of ponded water and source of 105 kg N ha^-1 from PU + Poultry manure are the best management approach for the excellent performance of rice cultivar Binadhan-8.     

Crop performance, nitrogen and water use in flooded and aerobic rice

Irrigated aerobic rice is a new system being developed for lowland areas with water shortage and for favorable upland areas with access to supplementary irrigation. It entails the cultivation of nutrient-responsive cultivars in nonsaturated soil with sufficient external inputs to reach yields of 70–80% of high-input flooded rice. To obtain insights into crop performance, water use, and N use of aerobic rice, a field experiment was conducted in the dry seasons of 2002 and 2003 in the Philippines. Cultivar Apo was grown under flooded and aerobic conditions at 0 and at 150 kg fertilizer N ha^–1. The aerobic fields were flush irrigated when the soil water potential at 15-cm depth reached –30 kPa. A ¹⁵N isotope study was carried out in microplots within the 150-N plots to determine the fate of applied N. The yield under aerobic conditions with 150 kg N ha^–1 was 6.3 t ha^–1 in 2002 and 4.2 t ha^–1 in 2003, and the irrigation water input was 778 mm in 2002 and 826 mm in 2003. Compared with flooded conditions, the yield was 15 and 39% lower, and the irrigation water use 36 and 41% lower in aerobic plots in 2002 and 2003, respectively. N content at 150 kg N ha^–1 in leaves and total plant was nearly the same for aerobic and flooded conditions, indicating that crop growth under aerobic conditions was limited by water deficit and not by N deficit. Under aerobic conditions, average fertilizer N recovery was 22% in both the main field and the microplot, whereas under flooded conditions, it was 49% in the main field and 36% in the microplot. Under both flooded and aerobic conditions, the fraction of ¹⁵N that was determined in the soil after the growing season was 23%. Since nitrate contents in leachate water were negligible, we hypothesized that the N unaccounted for were gaseous losses. The N unaccounted for was higher under aerobic conditions than under flooded conditions. For aerobic rice, trials are suggested for optimizing dose and timing of N fertilizer. Also further improvements in water regime should be made to reduce crop water stress.     

Biochar application to a fertile sandy clay loam in boreal conditions: effects on soil properties and yield formation of wheat, turnip rape and faba bean

Background and aims

We studied the effect of different biochar (BC) application rates on soil properties, crop growth dynamics and yield on a fertile sandy clay loam in boreal conditions.

Methods

In a three-year field experiment conducted in Finland, the field was divided into three sub-experiments with a split-plot experimental design, one for each crop: wheat (Triticum aestivum), turnip rape (Brassica rapa), and faba bean (Vicia faba). The main plot factor was BC rate (0, 5 and 10 t DM ha^?1) and the sub-plot factor was the N-P-K fertiliser rate. Soil physico-chemical properties as well as plant development, yield components and quality were investigated.

Results

BC addition did not significantly affect the soil chemical composition other than the increased C and initially increased K contents. Increased soil moisture content was associated with BC application, especially at the end of the growing seasons. BC decreased the N content of turnip rape and wheat biomass in 2010, thus possibly indicating an initial N immobilisation. In dry years, the seed number per plant was significantly higher in faba bean and turnip rape when grown with BC, possibly due to compensation for decreased plant density and relieved water deficit. However, the grain yields and N uptake with BC addition were not significantly different from the control in any year.

Conclusions

Even though BC application to a fertile sandy clay loam in a boreal climate might have relieved transient water deficit and thereby supported yield formation of crops, it did not improve the yield or N uptake.     

Recovery of 15N-labeled urea and soil nitrogen dynamics as affected by irrigation management and nitrogen application rate in a double rice cropping system

A sophisticated soil microcosm system and ¹⁵N-labeled urea were used to investigate nitrogen (N) use efficiency and soil N dynamics in a rice monoculture system in two successive seasons. Topsoil (0 cm?C20 cm) and subsoil (20 cm?C50 cm) samples were collected from a traditional double rice cropping field in the Jiangxi Province, China, and these soil samples were derived from Quaternary red clay. Treatments were randomly assigned with two irrigation regimes and three N application rates (no application control, 80% traditional rate and 100% traditional rate noted as N0, N1 and N2, respectively). The levels of ¹⁵N recovery of plants, ¹⁵N and N remaining in soil were determined. Moreover, the N dynamic of soil solution from different layers of the soil profile was surveyed. The results showed that the effects of irrigation management and N application rate varied in different rice growing seasons. Irrigation regimes had remarkable effects on grain yield and chemical ¹⁵N fertilizers (CF-¹⁵N) uptake. When compared to flood irrigation (FI), the shallow water depth with wetting and drying (WD) increased grain yield up to 5.7%?C20%. Although the highest grain yield was obtained with reduced N application level, both N apparent recovery (NAR) and ¹⁵N use efficiency (the percentage of plant N uptake derived from applied N, %Ndfan) significantly decreased with increasing N inputs. However, the interaction between irrigation management and N application rate on grain yield and N use efficiency (NUE) of CF-¹⁵N were not significant. A survey of soil solutions every 5 days indicated that NH ₄ ⁺ -N was the main residual form of N, and high NH ₄ ⁺ -N leaching was observed. When compared to FI, WD decreased vertical NH ₄ ⁺ -N and TN leaching, especially at 10?C50 cm depths of soil profile in the second season. NH ₄ ⁺ -N was the main N residual form in the soil profile. Therefore, in this study, the WD irrigation regime and reduced rate (N1) was the optimal irrigation and fertilizer management strategy to increase the NUE of CF-N, increase the after effects of CF-¹⁵N, decrease leaching loss of CF-¹⁵N and minimize the shallow groundwater pollution risk, which were all beneficial for the ecological environment.     

不同水分和氮素处理对寒地水稻生育及产量的影响

为了探讨不同水分和氮素处理对寒地水稻生长发育及产量的影响,以水稻品种空育131、龙粳21为试验材料,于2010—2011年度在黑龙江建三江进行水分、氮素处理大田试验,水分为雨养、间歇灌溉、水层灌溉3个水平,氮素为不施氮、常规施氮(112—135 kg/hm2)、高氮(142—173 kg/hm2)3个水平。结果表明:与水层灌溉相比,雨养水稻生育期缩短1—5 d,生长指标明显降低,产量显著降低,间歇灌溉水稻生育期、生长指标与其相似,产量差异不显著。与常规施氮相比,不施氮生育期缩短2—5 d,高氮条件下延长2—4 d;施氮量增加,生长指标增大,产量显著增加;低氮条件下,水分不足的限制作用明显,高氮能一定程度弥补水分的限制,促进水稻生长。增加施氮量及灌溉水平可以显著地提高有效穗数、每穗粒数。在试验条件下,水氮互作效应不显著。间歇灌溉及高氮管理具有较好的增产效应及资源利用率,研究可为寒地水稻生产进行水氮科学管理、实现高产高效提供理论依据。     

Impact of drought on assimilates partitioning associated fruiting physiognomies and yield quality attributes of desert grown cotton

Deficit irrigation has great significance for sustainable cultivation of cotton in water scarce arid regions, but this technique creates drought situation that induces stress adaptive changes in cotton plants due to indeterminate growth habit. In the present experiment, the impact of drought stress on assimilates partitioning associated vegetative and reproductive development, and yield quality attributes of cotton were examined under desert conditions. Four levels of drip irrigation including 100, 80, 60, and 40% replenishment of depleted water from field capacity were applied to develop drought stress regimes during two growing seasons (2015 and 2016). Results revealed that under limited water supplies, plant’s preference for allocation of photo-assimilates was roots?>?leaves?>?fruits that substantially increased root–shoot ratio and hampered reproductive growth. Consequently, boll density (m^?2), fresh boll weight and lint yield (kg ha^?1) were significantly reduced. An obvious change in partitioning of assimilates inside stressed bolls was observed that indicated relatively more accumulation in seeds than fiber, thus reducing the fiber quality. In addition, decreased starch, oil, and protein contents in seeds of stressed plants markedly reduced 100 seeds weight and also the vigor. Later, seed quality confirmatory tests of subsequent years (2016 and 2017) showed significant reduction in emergence counts (m^?2) and seedling biomasses of seeds harvested from deficit drip irrigated cotton. These results suggest that deficit irrigation could necessarily be an appropriate yield optimization and water saving technique for cotton in desert environment but, for the best quality fiber and cottonseeds, full irrigation should be preferred.     

Comparative performance of δ13C,ion accumulation and agronomic parameters for phenotyping durum wheat genotypes under various irrigation water salinities

The use of efficient selection traits for screening under contrasting irrigation water salinity is a challenge for breeders. To identify patterns, grain yield (GY) and yield components (kernels m^?2, thousand kernels weight), growth traits (plant height, biomass), flag leaf ion accumulation (Na⁺ and K⁺), carbon isotope composition (δ¹³C_grain) and nitrogen concentration (N_grain) of grains were assessed on 25 durum wheat genotypes (G) in two consecutive growing seasons (2010 and 2011), in three semi‐arid locations in Tunisia. Each location differed in their irrigation water salinity as measured by electrical conductivity: Echbika (S1, 6 dS m^?1), Barrouta (S2, 12 dS m^?1) and Sidi Bouzid (S3, 18 dS m^?1). GY was shown to be negatively correlated to N_grain as well as to δ¹³C_grain. This is confirmed by a multiple linear regression analysis that showed that both δ¹³C_grain and N_grain were the major determinant components for GY variability under S3. A high genotypic variability was observed and the improved genotype Maali exhibited the most stable GY under the three irrigation water salinities and the two cropping seasons. Maali showed the lowest δ¹³C_grain. This indicates that tolerance in durum wheat is likely to be correlated to the ability of maintaining a high stomatal conductance. According to our data suggests δ¹³C_grain can be used for an efficient screening of salt tolerant durum wheat. Under our experimental conditions, N_grain was shown to be highly correlated to δ¹³C_grain and can therefore be easier‐to‐use trait to assess the tolerance to salinity.     

Differential ecophysiological response of deciduous shrubs and a graminoid to long-term experimental snow reductions and additions in moist acidic tundra, Northern Alaska

Changes in winter precipitation that include both decreases and increases in winter snow are underway across the Arctic. In this study, we used a 14-year experiment that has increased and decreased winter snow in the moist acidic tussock tundra of northern Alaska to understand impacts of variation in winter snow depth on summer leaf-level ecophysiology of two deciduous shrubs and a graminoid species, including: instantaneous rates of leaf gas exchange, and δ¹³C, δ¹⁵N, and nitrogen (N) concentrations of Betula nana, Salix pulchra, and Eriophorum vaginatum. Leaf-level measurements were complemented by measurements of canopy leaf area index (LAI) and depth of thaw. Reductions in snow lowered summer leaf photosynthesis, conductance, and transpiration rates by up to 40 % compared to ambient and deep snow conditions for Eriophorum vaginatum, and reduced Salix pulchra conductance and transpiration by up to 49 %. In contrast, Betula nana exhibited no changes in leaf gas exchange in response to lower or deeper snow. Canopy LAI increased with added snow, while reduced winter snow resulted in lower growing season soil temperatures and reduced thaw depths. Our findings indicate that the spatial and temporal variability of future snow depth will have individualistic consequences for leaf-level C fixation and water flux by tundra species, and that these responses will be manifested over the longer term by changes in canopy traits, depth of thaw, soil C and N processes, and trace gas (CO₂ and H₂O) exchanges between the tundra and the atmosphere.     

Leaf gas exchange,source–sink relationship,and growth response of cotton to the interactive effects of nitrogen rate and planting density

Nitrogen (N) rate and plant density (PD) are important factors for sustainable cotton production. The objective of this study is to examine the effects of nitrogen rate and plant density on plant growth, source–sink relationship, and cotton yield. A split-plot arrangement was used in the field experiment with the main plots assigned to N rate (120 and 180 kg/ha), and the sub-plots assigned to plant density (8, 10, and 12 plants/m²). Results showed significant N and PD interaction on plant growth, leaf gas exchange, and yield. Higher plant growth and cotton yield were noted under low nitrogen rate and high planting density than other treatment combinations. Leaf photosynthesis, stomatal conductance, intercellular CO₂, transpiration rate, and water use efficiency were considerably influenced by planting density and nitrogen rate. Maximum values of these traits were obtained under low nitrogen rate with high planting density or high nitrogen rate with medium planting density, while the least values were under low nitrogen rate with low planting density. Correlation analysis revealed highly significant and positive relation between leaf gas exchange and cotton yield.     

Aerated subsurface irrigation water gives growth and yield benefits to zucchini, vegetable soybean and cotton in heavy clay soils

Inadequate oxygen concentration in the root zone is a constraint to plant performance particularly in heavy, compacted and/or saline soils. Sub-surface drip irrigation (SDI) offers a means of increasing oxygen to plant roots in such soils, provided irrigation water can be hyper-aerated or oxygenated. Hydrogen peroxide (HP) at the rate of 5 litre ha⁻¹ at the end of each irrigation cycle was injected through SDI tape to a field-grown zucchini (courgette) crop (Cucurbita pepo) on a saturated heavy clay soil in Queensland, Australia. Fruit yield, number and shoot weight increased by 25%, 29% and 24% respectively due to HP treatment compared to the control. Two pot experiments with vegetable soybean (Glycine max) and cotton (Gossypium hirsutum) compared the effectiveness of HP and air injection using a Mazzei air injector (a venturi), throughout the irrigation cycle in raising crop yield in a heavy clay soil kept at saturation or just under field capacity. Fresh pod yield of vegetable soybean increased by 82–96% in aeration treatments compared with the control. The yield increase was associated with more pods per plant and greater mean pod weight. Significantly higher above ground biomass and light interception were evident with aeration, irrespective of soil water treatment. Similarly cotton lint yield increased by 14–28% in aeration treatments compared with the control. The higher lint yield was associated with more squares and bolls per plant which accompanied greater above ground biomass and an increase in root mass, root length and soil respiration. Air injection and HP effected greater water use, but also brought about an enhancement of water use efficiency (WUE) for pod and lint yield, and increased leaf photosynthetic rate in both species but had no effect on transpiration rate and stomatal conductance per unit leaf area. Aeration-induced enhanced root function was arguably responsible for greater fruit set and yield in all three crops, while in vegetable soybean greater canopy cover, radiation interception and total vegetative biomass were responsible for additional yield benefit. Increased aeration of the root zone in heavy clay soils employing either air injection or HP proved beneficial to SDI irrigated crops, irrespective of the soil water conditions, and can add value to grower investments in SDI.     

Monitoring leaf nitrogen accumulation in wheat with hyper-spectral remote sensing

The water-retaining capacity, percolation and evaporation of stony soil in Liupan Mountains, China, were measured in order to understand the effect of rock fragments on soil hydrological processes. The results indicated that the effective water-retaining capacity of soil is positively related with the volumetric content of rock fragments, but there is no relation between saturated water-retaining capacity and rock fragment content. For the soil layers within 0–40 cm, the steady infiltration rate increases with increasing volumetric content of rock fragments until it reaches the range of 15%–20%, and then it decreases when the rock fragment content further increases. For the soil layers below 40 cm, the steady infiltration rate always increases with increasing rock fragment content. The soil evaporation rate decreases with increasing volumetric content of rock fragments when it varies in the range of 0–20%, while the soil evaporation rate keeps basically stable when the rock fragment content is higher than 20%. The soil evaporation rate shows a rising tendency with increasing size of rock fragments.     

Identifying drivers of leaf water and cellulose stable isotope enrichment in <Emphasis Type="Italic">Eucalyptus</Emphasis> in northern Australia

Several previous studies have investigated the use of the stable hydrogen and oxygen isotope compositions in plant materials as indicators of palaeoclimate. However, accurate interpretation relies on a detailed understanding of both physiological and environmental drivers of the variations in isotopic enrichments that occur in leaf water and associated organic compounds. To progress this aim we measured δ¹⁸O and δ²H values in eucalypt leaf and stem water and δ¹⁸O values in leaf cellulose, along with the isotopic compositions of water vapour, across a north-eastern Australian aridity gradient. Here we compare observed leaf water enrichment, along with previously published enrichment data from a similar north Australian transect, to Craig–Gordon-modelled predictions of leaf water isotopic enrichment. Our investigation of model parameters shows that observed ¹⁸O enrichment across the aridity gradients is dominated by the relationship between atmospheric and internal leaf water vapour pressure while ²H enrichment is driven mainly by variation in the water vapour—source water isotopic disequilibrium. During exceptionally dry and hot conditions (RH < 21%, T > 37 °C) we observed strong deviations from Craig–Gordon predicted isotope enrichments caused by partial stomatal closure. The atmospheric–leaf vapour pressure relationship is also a strong predictor of the observed leaf cellulose δ¹⁸O values across one aridity gradient. Our finding supports a wider applicability of leaf cellulose δ¹⁸O composition as a climate proxy for atmospheric humidity conditions during the leaf growing season than previously documented.     

Variation in leaf and soil δ<Superscript>15</Superscript>N in diverse tree species in a lowland dipterocarp rainforest,Malaysia

Key message

Large variations in leaf δ ¹⁵ N in Bornean tropical rainforest trees may indicate that various tropical species have species-specific strategy for nitrogen uptake under low soil nutrient conditions, including root symbiotic microorganisms such as ectomycorrhiza.

Abstract

Lowland tropical rainforests in Southeast Asia are characterized by high species diversity despite limited soil nutrient conditions. The plant nitrogen isotope ratio (δ¹⁵N) reflects plant uptake of soil nitrogen. We analyzed δ¹⁵N values and nitrogen content (N %) in leaves and roots of 108 woody species with different types of symbiotic microorganisms, of different life forms (emergent, canopy, sub-canopy, understory, and canopy gap species), and from different families in a Bornean lowland dipterocarp forest to gain more insight into the diversity of nitrogen uptake strategy in the rhizosphere. Leaf δ¹⁵N values in the species studied varied largely from ?7.2 to 5.0 ‰, which is comparable to the values of known Asian trees including temperate, sub-tropical, and tropical mountain forests. Leaf δ¹⁵N also varied significantly among both life forms and families, though the phylogenetically independent contrast (PIC) relationships were not statistically significant among life form, family, and symbiotic types. Some families showed specific leaf δ¹⁵N values; Dipterocarpaceae, the dominant family in the canopy layer with symbiotic ectomycorrhiza in Southeast Asia, had small intraspecific variation and higher leaf δ¹⁵N values (0.03 ‰) compared with species exhibiting arbuscular mycorrhiza, whereas several families such as Burseraceae, Euphorbiaceae, and Myrtaceae showed large interspecific variation in leaf δ¹⁵N (e.g., from ?7.2 to 5.0 ‰ in Euphorbiaceae). These variations suggest that tropical species may have family- or species-specific strategy, such as root symbiotic microorganisms, for nitrogen uptake under low-nutrient conditions in tropical rainforests in Southeast Asia.

     

水氮供应对夏棉产量、水氮利用及土壤硝态氮累积的影响

通过田间试验,研究了黄淮地区水氮供应对夏棉生长、产量及水氮利用效率的影响,探索在保证产量的同时提高水氮利用效率、减少农田水氮排放的管理模式.试验设置5个氮素水平(0、60、120、180、240 kg·hm^-2,分别记为N₀、N₁、N₂、N₃、N₄)和3个灌水水平(滴灌,灌水定额30、22.5、15 mm,分别记为I₁、I₂、I₃),使用裂区设计,主区为氮用量,裂区为灌水水平,共15个处理,3次重复.结果表明: 氮素和水分施用对夏棉生长和产量都有明显促进作用,但氮素影响更显著,是该地区调控夏棉生长和籽棉产量的主要因素.随着施氮量和灌水量的增加,花铃期生殖器官积累量、地上部干物质积累量和籽棉产量在开始阶段都逐步增加,当施氮量超过180 kg·hm^-2时,进一步增施氮肥会导致生殖器官积累量、地上部干物质积累量和籽棉产量减小.籽棉产量在N₃I₁处理达到最大,为4016 kg·hm^-2.增加施氮量能显著提高地上部总吸氮量和茎叶含氮量,但会降低氮肥偏生产力.灌溉水利用效率和田间水分利用效率分别在N₃I₃和N₃I₁处理最大,分别为5.40和1.24 kg·m^-3.随着施氮量的增加,土壤硝态氮含量明显增加,且硝态氮累积区域有下移趋势.综合考虑对地上部干物质积累、产量、水氮吸收利用及土壤硝态氮累积等的影响,N₃I₁处理可作为试验区夏季棉花生产的最优水氮管理方案.     

Use of mycorrhizal fungi and phosphorus fertilization to improve the yield of onion (Allium cepa L.) plant

Improving the economical yield of commonly cultivated crops is one of the most pressing social and scientific issues in modern agriculture. This paper was conducted to investigate the bio-efficacy of arbuscular mycorrhizal fungi (AMF) in improving phosphorous (P) utilization and increasing the yield of onion plant grown in sandy soil under a drip irrigation system. The obtained results showed that AMF inoculation of onion and application of 120 kg P fertilizer ha⁻¹ significantly increased the fresh and dry weights, chlorophyll content of onion as well as P concentration in the root, shoot, and bulb during two growing seasons. Moreover, AMF increased the bioavailability of P in the rhizosphere and significantly enhanced the N-utilization by the inoculated plant. The economic yield of the onion plant inoculated by AMF and fertilized by different doses of P fertilizer was much higher than that obtained by the control (without AMF). These findings indicated that inoculating the onion plant in the field with AMF could be very effective in increasing the yield of the onion plant. Additionally, this study suggests AMF as a low-cost and promising candidate for the sustainable production of the onion crop using reclaimed sandy soils and a drip irrigation system.Keyword: Onion, Mycorrhizal Fungi, Economic yield, P fertilization, N utilization, ¹⁵N     

Nitrogen-induced variations in leaf gas exchange of spring triticale under field conditions

Nitrogen (N) is the key factor limiting photosynthetic processes and crop yield. Little is known about the response of leaf gas exchange of spring triticale (Triticosecale Wittm.) to N supply. The effect of N fertilizers on different gas exchange variables, i.e., photosynthetic rate (A), transpiration rate (E), stomatal conductance (g _s), instantaneous water use efficiency (WUE) and maximum quantum yield of photosystem II (PSII) (F _v/F _m), chlorophyll index (SPAD, soil–plant analysis development), and the relationship of these variables with yield were studied in spring triticale grown under field conditions. Six treatments of N—0, 90, 180, 90 + 30, 90 + 30 + 30 kg ha^?1 (applied as ammonium nitrate, AN) and one treatment of N 90 + 30 + 30 kg ha^?1 (applied as urea ammonium nitrate solution, UAN) were compared. The analysis of variance showed that throughout the triticale growing season, N fertilization had significant effects on A, WUE, g _s and SPAD. On average, N fertilizer application increased A values by 14–70%. E and F _v/F _m values were not influenced by N fertilization levels. The effect of growth stage and year on gas exchange variables and F _v/F _m and SPAD was found to be significant. At different growth stages, A values varied and maximum ones were reached at BBCH 31–33 (decimal code system of growth stages) and BBCH 59. With aging, values of A decreased independently of N fertilization level. The gas exchange variables were equally affected by both fertilizer forms. The interplay among grain yield, leaf gas exchange variables, F _v/F _m and SPAD of spring triticale was estimated. The statistical analysis showed that grain yield positively and significantly correlated with A and SPAD values throughout the growing season.     

Prof. Dr. H. C. Władysław Węgorek 16 February 1918-16 July 2001

Abstract

In 2004, two field trials with cotton were conducted at two locations in Tajikistan to estimate the effectiveness of FZB 24® Bacillus subtilis (ABiTEP GmbH Berlin) as a biofertilizer for increasing the cotton yield in comparison to the utilization of the conventional fertilizer containing nitrogen (N), phosphorus (P) and potassium (K), with an application rate per ha 180 kg N, 120 kg P, 60 kg K. The following treatments of cotton cultivated as test variants each on 1 ha field under the same conditions were carried out and the effect on the plant growth, the development of number of bolls/plant and mainly the cotton fibre yield were calculated: (i) Seed treatment with water and only crop application of the NPK fertilizer; (ii) Only seed treatment with spore suspension of FZB 24 WG Bacillus subtilis, without application of the NPK fertilizer; (iii) Seed treatment with spore suspension of FZB 24 WG Bacillus subtilis plus crop application of the NPK fertilizer; and (iv) Only seed treatment with the comparable plant-growth-promoting rhizobacteria product Extrasol 55 (ARRIAM St Petersburg), without application of the fertilizer. Comparing cotton growth and yield of the variants in both field tests, there appeared a remarkable yield and growth increase (up to 30%) by the use of FZB 24 alone compared to the application of the NPK fertilizer. The additional application of the NPK fertilizer (Variant: FZB 24 + NPK) could not enlarge this plant productivity-promoting effect. Apparently under the test conditions the increase of the root system in size and capacity as well as the additional enzymatic mobilizing of organic bound phosphorus for the plant as activities from the Bacillus subtilis introduction was more important for the plant system than the limited direct input with N, P and K. The plant treatment alone with Extrasol 55 resulted in similar promotion of cotton growth and yield as FZB 24 when compared with the NPK plant fertilizing, showing that the activity of FZB 24 was not very specific. However the cotton field tests generally demonstrate for FZB 24 Bacillus subtilis a high ability to improve plant growth and yield based on increasing the capacity of roots to mobilize and take up nutrients and substances for overall reproductive plant fitness. The use and value for part-substitutions of some environmentally problematical mineral fertilizers in other and intensive plant production systems is discussed.     

Dual Δ¹³C/δ¹⁸O response to water and nitrogen availability and its relationship with yield in field-grown durum wheat

The combined use of stable carbon and oxygen isotopes in plant matter is a tool of growing interest in cereal crop management and breeding, owing to its relevance for assessing the photosynthetic and transpirative performance under different growing conditions including water and N regimes. However, this method has not been applied to wheat grown under real field conditions. Here, plant growth, grain yield (GY) and the associated agronomic components, carbon isotope discrimination (Δ¹³C) plus oxygen isotope composition (δ¹⁸O) as well as leaf and canopy gas exchange were measured in field‐grown wheat subjected to different water and N availabilities. Water limitation was the main factor affecting yield, leaf and canopy gas exchange and Δ¹³C and δ¹⁸O, whereas N had a smaller effect on such traits. The combination of Δ¹³C and δ¹⁸O gave a clear advantage compared with gas exchange measurements, as it provides information on the instantaneous and the long‐term plant photosynthetic and transpirative performance and are less labour intensive than gas exchange measurements. In addition, the combination of plant Δ¹³C and δ¹⁸O predicted differences in GY and related agronomical parameters, providing agronomists and breeders with integrative traits for selecting crop management practices and/or genotypes with better performance under water‐limiting and N‐limiting conditions.