Enhance Nutrient Use Research Articles

Cloning and characterization of nutrient deficiency and salinity stress responsiveTaCBL4gene from bread wheat (Triticum aestivumL.)

Environmental stresses, such as drought, salinity, extreme temperatures and nutrient deficiencies affect plant productivity adversely. Calcineurin B-like proteins (CBLs) and CBL-interacting protein kinases (CIPKs) are components of calcium mediated stress response pathways in many plants. In the present study, TaCBL4 gene homologous to salt stress responsive Arabidopsis CBL4 (AtSOS3) was cloned from wheat and sequence characterized. The predicted protein of TaCBL4 showed 95, 83, 70 and 61% similarity with amino acid sequences of barley, rice, maize and Arabidopsis CBL4, respectively, demonstrating that CBL4 genes are conserved between dicots and monocots. TaCBL4 protein consists of three EF-hand calcium binding motifs, a characteristic feature of calcium sensor proteins. The modelled image of TaCBL4 protein was highly identical to the already resolved structure of the AtCBL4 protein. In addition to salinity stress, the expression of TaCBL4 gene was also up-regulated by deficiency of major nutrients, namely, nitrogen, phosphorus and potassium. This suggests that TaCBL4 may serve as node for signaling crosstalk between salinity and nutrient deficiency stress signaling pathways and nutrient homeostasis under salinity stress. The present study lays foundation for functional studies on role of TaCBL4 gene in nutrient use efficiency and for its further utilization in breeding new wheat varieties with enhanced nutrient use efficiency and salinity tolerance.

Fertiliser requirements for balanced nutrition of cassava across eight locations in West Africa

Abstracts Insufficient and unbalanced fertiliser use widens cassava yield gaps. We assessed the spatial variability of optimal fertiliser requirements of cassava for enhanced nutrient use efficiency and increased yield using the balanced nutrition approach of the QUEFTS model. Two datasets comprised of five fertiliser experiments conducted at eight locations across Southern Togo, Southern Ghana and Northern Ghana from 2007 to 2012 were used. The ratio of storage roots dry matter yield over the sum of available N, P and K expressed in crop nutrient equivalent from the soil and nutrient inputs was used as a proxy to estimate nutrient use efficiency. Nutrient use efficiencies of 20.5 and 31.7 kg storage roots dry matter per kilo crop nutrient equivalent were achieved at balanced nutrition at harvest index (HI) values of 0.50 and 0.65, respectively. N, P and K supplies of 16.2, 2.7 and 11.5 kg at an HI of 0.50, and 10.5, 1.9 and 8.4 kg at an HI of 0.65 were required to produce 1000 kg of storage roots dry matter. The corresponding optimal NPK supply ratios are 6.0–1.0–4.2 and 5.3–1.0–4.2. Nutrient use efficiencies decreased above yields of 77–93% of the maximum. Evaluation of the performance of blanket fertiliser rates recommended by national research services for cassava production resulted in average benefit:cost ratios of 2.4 ± 0.9, which will be unattractive to many farmers compared to 3.8 ± 1.1 for the balanced fertiliser rates. The indigenous soil supply of nutrients revealed that, at balanced nutrition, K was the most limiting nutrient to achieve storage roots yields up to 8 Mg dry matter ha−1 at most sites, whereas N and P were needed at greater yields. Dry weight of storage roots measured on the control plots in our researcher managed experiment ranged from 5.6 to 12.2 Mg ha−1, and were larger than the average weight in farmers’ fields in West Africa of 4 Mg ha−1. Substantial yield increase could be attained in the region with improved crop management and fertiliser requirements formulation on the basis of balanced nutrition.

Enhancing nutrient use and sugarcane (Saccharum officinarum) productivity with reduced cost through drip fertigation in western Maharashtra

A field experiment was conducted at Interfaculty Department of Irrigation Water Management, Mahatma Phule Krishi Vidyapeeth, Rahuri (Maharashtra) during three consecutive years 2007-2010 to study the yield, nutrient use and cost economics for sugarcane (Saccharum officinarum L.) cultivation under different fertigation schedules. The experiment comprised 100, 80 and 60 per cent water soluble fertilizers (WSF) applied through drip in two schedules and results were compared with three control treatments. The 100 per cent fertigation as per growth stages (schedule B) showed higher cane yield (187.85 tonnes/ha) and sugar yield (22.00 tonnes/ha); however, it was on par with 100% fertigation in uniform equal splits (schedule A) and 80% fertigation (schedule B). The study indicated that drip irrigation resulted into 25 % increase in sugarcane yield whereas drip with fertigation resulted into 42 % increase in yield as compared to conventional method. Application of water soluble fertilizers had positive effect on periodical availability of nutrients and uptake than conventional fertilizer. The higher net seasonal income (Rupees 226 195 per ha) and net extra income over conventional method (Rupees 66 246 per ha) were obtained in 100 % fertigation as per schedule B however, the economical parameters were on par with 100 % fertigation as per schedule A and 80% fertigation as per schedule B. The application of 80 % water soluble fertilizers as per schedule B through drip irrigation was found best practice to obtain better yield, improve nutrient and water use as well as cost economics among the practices studied.

Testing the use of an analytical and mechanistic C3 - biomass accumulation model for precision fertilization

A single and uniform fertilizer application may lead to ineffective crop nutrient uptake and use. In order to enhance nutrient use efficiency the application should be adjusted according to the need of the cultivated crop. This task is challenging because weather is unknown and unpredictable over the upcoming growing season. One solution is site-specific fertilizer application in several separate events throughout the season. Such a precision fertilization method requires information on the current crop state (e.g. the availability of water and nutrients in the soil) and a crop growth model that aims to assess current crop growth and near future needs. A field experiment with varying radiation, precipitation and nutrient conditions was established to test our crop growth model performance. Spring wheat (Triticum aestivum L.) was grown using three fertilization rates with three precipitation and two radiation treatments within each fertilization treatment. The observed crop biomass accumulation in the highest fertilization treatment was considered as the highest possible in the prevailing conditions. The simulated (maximal) biomass accumulation was in agreement with the highest observed biomass yield. The results were found promising for further use of the model in crop growth evaluation during the growing season.

Enhancing nutrient use efficiency of maize (Zea mays L.) from mixing urea with zeolite and peat soil water

The use of urea as N fertilizer has increased globally but lack of efficiency due to loss through ammonia volatilization has become a subject of considerable recent attention. In line with this, a pot experiment was conducted to determine the effect of mixing urea with zeolite and peat soil water on: (1) uptake and use efficiency of N, P and K in maize cultivation, and (2) soil exchangeable ammonium, available nitrate, pH, exchangeable K, and available P contents. The treatments evaluated were: No fertilizer (T0), 2.02 g urea (T1), 2.02 g urea + 30 g zeolite + 7 L peat soil water (T2), 2.02 g urea + 40 g zeolite + 7 L peat soil water (T3), and 2.02 g urea + 7 L peat soil water (T4). The fertilizers of TSP and MOP were applied twice that is 10 and 28 days after planting for all the treatments except T0. The application of peat soil water, and zeolite with urea had significant effect on dry matter, N, P, K uptake and N, P, K use efficiency compared with urea without additives. The soil exchangeable ammonium, K, Ca, Mg, available P, and nitrate contents were significantly increased compared with urea without additives. Formation of ammonium and nitrate over ammonia were reflected by the mixtures of peat soil water, and zeolite, with urea. Amending urea with zeolite and peat soil water can reduce ammonia loss by encouraging formation of ammonium and nitrate over ammonia. In addition, the mixtures ensure N, P, K uptake and their use efficiency while at the same time rendering soil ammonium, K, Ca, Mg, P, and nitrate available for plant use.

Innovations in agronomy for food legumes. A review

Although there is increasing awareness of the importance of food legumes in human, animal and soil health, adoption of improved production technologies for food legume crops is not proceeding at the same pace as for cereal crops. Over the previous decade, the only food legumes to have shown significant production increases have been chickpea, lentil and faba bean in North America, chickpea in Australia, and faba bean in Europe. In smallholder farming in developing countries, production trends have mostly been static or have declined over the past decade despite the existence of technology that should permit higher and more stable yields. Ability to reverse negative trends is jeopardized by climate change as food legumes are mostly grown rainfed and are being exposed to increasingly variable and extreme weather. This review examines recent innovations in cultivation technology for the major food legumes—chickpea, lentil, dry pea, faba bean, lupin, common bean, mung bean, black gram, cowpea, and pigeonpea—and explores constraints to their adoption, particularly by resource-poor smallholder farmers. Conservation agriculture, involving minimum soil disturbance, maximum soil cover, and diverse rotations, has contributed to sustainable cropping system production in large-scale commercial farming systems in the Americas, Europe, Australia, and Turkey. Temperate food legumes have been incorporated into such systems. Adoption of conservation agriculture is only just beginning for smallholder farming in Asia and Africa, catalyzed by the development of low-cost implements suitable for minimum tillage. Water use efficiency improves with conservation agriculture as it allows for earlier planting, reduced soil evaporation, better weed management, and increased access to nutrients. Ecosystem-based approaches to plant nutrition are evolving which place more reliance on accessing organic and mineral reservoirs than in replenishing the immediately available pool with chemical fertilizers, leading to enhanced nutrient use efficiency of cropping systems. Ecosystem-based approaches are also being applied to management of weeds, diseases, and insect pests of food legumes, again with decreased reliance on synthetic chemicals. In achieving sustainable agricultural production systems, there is increasing realization of the need to move towards the tenets of organic agriculture, as exemplified in conservation agriculture and ecosystem-based approaches to plant nutrition and pest management. This does not necessarily imply a desire to qualify for organic product certification but more a realization of the need for sustainable agriculture. The movement towards conservation and organic agriculture encourages greater inclusion of food legumes, and legumes generally, in cropping systems. Unfortunately, however, technology transfer to resource-poor farming situations, where most food legumes are produced, remains a major bottleneck to meeting global demand. More participatory approaches to technology development, testing, and dissemination are required than hitherto practiced. It is suggested that this process could be enhanced by better focusing on major constraints within the value addition chain for food legumes.

Increased plant uptake of nitrogen from 15N-depleted fertilizer using plant growth-promoting rhizobacteria

Harmful environmental effects resulting from fertilizer use have spurred research into integrated nutrient management strategies which can include the use of specific micro-organisms to enhance nutrient use efficiency by plants. Some strains of plant growth-promoting rhizobacteria (PGPR) have been reported to enhance nutrient uptake by plants, but no studies with PGPR have used 15N isotope techniques to prove that the increased N in plant tissues came from the N applied as fertilizer. The current study was conducted to demonstrate that a model PGPR system can enhance plant uptake of fertilizer N applied to the soil using different rates of 15N-depleted ammonium sulfate. The experiments were conducted in the greenhouse with tomato using a mixture of PGPR strains Bacillus amyloliquefaciens IN937a and Bacillus pumilus T4. Results showed that PGPR together with reduced amounts of fertilizer promoted tomato growth compared to fertilizer without PGPR. In addition, atom% 15N per gram of plant tissue decreased as the amount of fertilizer increased, and PGPR inoculation resulted in a further decrease of the atom% 15N values. The atom% 15N abundance in plants that received 80% fertilizer plus PGPR was 0.1146, which was significantly lower than 0.1441 for plants that received 80% fertilizer without PGPR and statistically equivalent to 0.1184 for plants that received 100% fertilizer without PGPR. The results demonstrate that increased plant uptake of N applied in fertilizer could be achieved with PGPR as indicated by the differences in 15N uptake. Strains of PGPR that lead to increased nutrient uptake by plants should be evaluated further as components in integrated nutrient management systems.

Rain ratio variation in the Tropical Ocean: Tests with surface sediments in the eastern equatorial Pacific

The organic carbon to calcite flux ratio (rain ratio) has a profound effect on the preservation of carbonates in the deep sea and may influence atmospheric pCO2 over millennia. Unfortunately, the degree to which the rain ratio varies in the more productive regions of the oceans is not well determined with sediment trap data. The rain ratio in the upper ocean appears dominantly linked to diatom productivity, which is not necessarily directly linked to total production and may be regionally variable. However, ballasting and protection of organic carbon by calcareous particles in the deeps may limit ratio variability at the seafloor. Sediment trap data do not exist for the regional determination of rain ratios in key highly productive areas like the eastern equatorial Pacific (EEP). To overcome this, we turn to surface sediment composition and accumulation rates as a representation of modern ratio variation. We present 230 Thorium ( 230 Th)-normalized carbonate, opal, organic carbon and detrital matter accumulation rates from core top samples in the EEP. We demonstrate a novel approach for estimating modern rain ratios from sedimentary proxies by (1) calculating vertical calcite flux from 230 Th-normalized carbonate accumulation rates (CARs) with correction for preservation and (2) calculating organic carbon fluxes with multiple algorithms that depend in varying degrees on ballasting. We find that organic carbon flux estimates from algorithms with and without a ballasting function produce results different from one another. Sediment accumulation rates for opal reflect the likely pattern of diatom production. By contrast, the organic carbon accumulation rate does not correlate well with surface ocean productivity or any of our algorithm-based organic carbon flux estimates. Instead, it correlates with the detrital component of the sediments suggesting an allochthonous input to sedimentary organic carbon accumulation in the EEP, which reduces its value as a productivity tracer. However, our calcite and multiple, satellite-based organic carbon fluxes allow estimation of the rain ratio and demonstrate a common regional pattern with moderate to strong variability in the rain ratio across the EEP. This variability is significant and is transmitted into the deeps leaving a sedimentary record regardless of the algorithm chosen to calculate organic carbon fluxes. Furthermore, we provide evidence suggesting that the rain ratio in the EEP may be driven by wind-supplied iron availability, which would regionally enhance nutrient use and promote diatom growth. r 2007 Elsevier Ltd. All rights reserved.

Nitrogen Management Affects Carbon Sequestration in North American Cropland Soils

Agricultural soils in North America can be a sink for rising atmospheric CO2 concentrations through the formation of soil organic matter (SOM) or humus. Humification is limited by the availability of nutrients such as nitrogen (N). Recommended management practices (RMPs) that optimize N availability foster humus formation. This review examines the management practices that contribute to maximizing N availability for optimizing sequestration of atmospheric CO2 into soil humus. Farming practices that enhance nutrient use, reduce or eliminate tillage, and increase crop intensity, together, affect N availability and, therefore, C sequestration. N additions, from especially, livestock manure and leguminous cover crops are necessary for increasing grain and biomass yields and returning crop residues to the soil thereby increasing soil organic carbon (SOC) concentration. Conservation tillage practices enhance also the availability of N and increase SOC concentration. Increase in cropping intensity and/or crop rotations produce higher quantity and quality of residues, increase availability of N, and therefore foster increase in C sequestration. The benefit of C sequestration from N additions may be negated by CO2 and N2O emissions associated with production and application of N fertilizers. More studies need to be conducted to ascertain the benefits of adding N via manuring versus N fertilizer additions. Furthermore, site specific adaptive research is needed to identify RMPs that optimize soil N use efficiency while improving crop yield and C sequestration thereby curbing greenhouse gas (GHG) emissions. Due to the wide range of climate in North America, there is a large range of C sequestration potential in agricultural soils through N management. Humid croplands may have the potential to sequester 8–298 Tg C yr−1 while dry croplands may sequester 1–35 Tg C yr−1. These estimates, however, are highly uncertain and wide-ranging. Clearly, more research is needed to quantify, more precisely, the C sequestration potential across different N management scenarios especially in Mexico and Canada.

Phytoplankton nutrient competition under dynamic light regimes

Many physiological processes in phytoplankton, including nutrient uptake, vary on a number of temporal scales. Experiments show that the daily cycle in irradiance affects nutrient uptake rates. We used a Droop‐based model of resource competition to investigate how diel variability in nutrient uptake influences phytoplankton competition and community structure. The analytical approximation we derive shows that if nutrient uptake is light dependent, the minimum nutrient requirements and, hence, nutrient competitive abilities depend on light regime in a species‐specific way. Consequently, daily variations in irradiance may slow rates of competitive exclusion or reverse the identity of the superior competitor but not allow stable coexistence. Irradiance‐induced fluctuations in the maximum nutrient uptake rate of the superior competitor can lead to fluctuations in ambient nutrient concentration and an increase in the average nutrient concentration compared to constant light conditions. This can enhance nutrient use by inferior competitors. These results may be applicable to bacteria‐phytoplankton nutrient competition as well. Depending on the costs and benefits of maintaining nutrient uptake in the dark, different strategies of nutrient use are optimal under different light regimes. Our results suggest that by mediating limiting nutrient use, fluctuations in irradiance may alter the structure of phytoplankton communities.

Endophytic establishment of Azorhizobium caulinodans in wheat

Nitrogen fixing nodules are formed on the roots and stems of the tropical legume Sesbania rostrata by Azorhizobium caulinodans as a result of crack entry invasion of emerging lateral roots. Advantage was taken of this invasion capability of A. caulinodans to determine whether inoculation of the non–legume wheat with A. caulinodans would result in the endophytic establishment of azorhizobia within wheat roots. Advantage was also taken of the oxygen tolerance of the nitrogenase of free–living azorhizobia to assess the extent to which the endophytic establishment of azorhizobia in wheat roots would provide a niche for nitrogen fixation of benefit to the plant. Wheat was inoculated with A. caulinodans and grown in pots under controlled conditions, without added growth reglators and without addition of fixed nitrogen. Microscopic examination of the short lateral roots of inocluated wheat showed invasion of azorhizobia between cells of the cortex, within the xylem and the root meristem Acetylene reduction assays combined with analysis of tissue nitrogen levels indicated the likelihood that colonization led to nitrogenase activity. Inoculated wheat showed significant increases in dry weight and nitrogen content as compared with uninoculated controls. We discuss the extent to which this nitrogen fixation is likely to involve symbiotic nitrogen fixation, and we indicate the need for field trials to determine the extent to which inolculation of wheat with A. caulinodans will reduce the requirement for inputs of nitrogenous fertilizers.

The Nutritional Dynamics of Tillandsia circinnata in Southern Florida and the Origin of the "Air Plant" Strategy

The kinetics of mineral absorption by adult specimens of Tillandsia circinnata were determined in the laboratory. The rates at which 11 essential elements were accumulated in proportion to concentrations in the organism at time zero varied considerably, being greatest for certain metallic micronutrients The significance of these observations for the nutrient budget and life history of this air plant is considered with reference to the nutrient composition of canopy fluids in forests inhabited by vascular epiphytes in general and, in particular, to the rainfall in southern Florida. In addition to its many adaptations designed to enhance nutrient use efficiency for regenerative purposes, T. circinnata is a very effective scavenger of certain mineral elements. An evolutionary scheme describing the origin of the oligotrophic competence obliged by the atmospheric way of life is offered.