Nutrient Use Efficiency In Crops Research Articles

Struvite as P Fertilizer on Yield, Nutrient Uptake and Soil Nutrient Status in the Rice–Wheat Rotation System: A Two-Year Field Observation

Long-term large inputs of phosphorus (P) fertilizer in China have caused serious soil P accumulation, low P use efficiency (PUE) and high risk of P loss. Controlling the amount of P fertilizer applied presents an inevitable choice for improving the PUE. Struvite recycled from agricultural wastewater rich in N and P concentrations are capable of slow nutrient release, improving nutrient uptake and enabling the reuse of nutrients from environmental sources when applied to agricultural land. A two-year field experiment was conducted to investigate the effects of struvite combined with P reduction under a rice–wheat rotation system in eastern China. A total of five treatments were set up, including conventional fertilization (FP), a struvite substitution of 100% P fertilizer (SP), a 50% P reduction with struvite substitution (RSP), no application of N fertilizer (N0) and no application of P fertilizer (P0). Grain yield, crop N and P uptake, N and P use efficiency (NUE and PUE) and soil nutrient status were assessed. Under the same P application rate, the yield and aboveground biomass of the SP treatment were slightly higher than those of FP treatment, but the crop P uptake, PUE and soil available P content were significantly increased. The RSP treatment did not reduce yield with 50% P reduction, and significantly improved the PUE and soil available P content. Crop N uptake and NUE were also found to be increased in SP and RSP treatments with struvite substitution. The P apparent balance showed that both the SP and FP treatments had a P surplus, but the RSP treatment had a P break-even, and the soil available P content remains stable compared with the initial value. The results indicate that struvite application could improve the soil P availability and crop nutrient uptake then promote the crop yield. To increase the nutrient use efficiency of crops while ensuring crop yield and soil fertility, appropriate P reduction combined with struvite as a P fertilizer could be sustainable in the rice–wheat rotation system in the long run.

Development and characterization of rice bran-gum Arabic based encapsulated biofertilizer for enhanced shelf life and controlled bacterial release.

Currently, microbe-based approaches are being tested to address nutrient deficiencies and enhance nutrient use efficiency in crops. However, these bioinoculants have been unsuccessful at the commercial level due to differences in field and in-vivo conditions. Thus, to enhance bacterial stability, microbial formulations are considered, which will provide an appropriate microenvironment and protection to the bacteria ensuring better rhizospheric-colonization. The present study aimed to develop a phosphobacterium-based encapsulated biofertilizer using the ion-chelation method, wherein a bacterial strain, Myroid gitamensis was mixed with a composite solution containing rice bran (RB), gum Arabic (GA), tricalcium phosphate, and alginate to develop low-cost and slow-release microbeads. The developed microbead was studied for encapsulation efficiency, shape, size, external morphology, shelf-life, soil release behavior, and biodegradability and characterized using SEM, FTIR, and XRD. Further, the wheat growth-promoting potential of microbeads was studied. The developed microbeads showed an encapsulation efficiency of 94.11%. The air-dried beads stored at 4°C were favorable for bacterial survival for upto 6 months. Microbeads showed 99.75% degradation within 110 days of incubation showing the bio-sustainable nature of the beads. The application of dried formulations to the pot-grown wheat seedlings resulted in a higher germination rate, shoot length, root length, fresh weight, dry weight of the seedlings, and higher potassium and phosphorus uptake in wheat. This study, for the first time, provides evidence that compared to liquid biofertilizers, the RB-GA encapsulated bacteria have better potential of enhancing wheat growth and can be foreseen as a future fertilizer option for wheat.

A global meta-analysis on surface and drip fertigation for annual crops under different fertilization levels

So far, many studies have examined the effects of surface (FF) and drip (DF) fertigation compared to surface (FC) and drip (DC) irrigation along with fertilization at different levels of fertilizer on crop yield indices, nutrient use efficiency (NUE), and irrigation water productivity (WP); however, each of them have been conducted under different conditions. Because of the scattered results and the lack of a general conclusion from the published results, conducting a meta-analysis as a structured method for arriving at an overall conclusion regarding the effects of different fertigation methods on different indices is essential. This study was conducted to examine the effects of surface and drip fertigation methods and different fertilizer application levels on crop yield, NUE, and WP. To this end, eight global databases of publications (e.g., Scopus and Web of Science) were reviewed. A total of 5494 studies were extracted, of which 32 studies met the entry criteria for the meta-analysis. To assess the effects of fertigation, each study was used to extract the effect sizes for each index. A total of 119 effect sizes were obtained for crop yield, 85 for NUE, and 84 for WP. The meta-analysis results showed that surface and drip fertigation methods increased the average yield by 20%. NUE and WP on an average increased by 26% and 51%, respectively. Based on the reported results, the optimal fertilizer application level is 75% of the recommended dose, which can reduce fertilizer use by 25% without significantly reducing the yield. In general, fertigation can be recommended as an effective operation for improving the proposed indices examined in both surface and drip fertigation methods.

Precision Nutrient Rates and Placement in Conservation Maize-Wheat System: Effects on Crop Productivity, Profitability, Nutrient-Use Efficiency, and Environmental Footprints

Intensive tillage-based production systems coupled with inefficient fertilizer management practices have led to increased production costs, sub-optimal productivity, and significant environmental externalities. Conservation agriculture (CA) is being increasingly advocated as a management strategy to overcome these issues but precision nutrient management under the CA-based maize-wheat system is rarely studied. Two year’s (2014–2015 and 2015–2016) research was conducted at the research farm of BISA, Pusa, Bihar, India to develop precision nutrient management practices for CA-based management in the maize-wheat system. Seven treatment combinations involving (i) tillage (conventional tillage; CT & permanent beds; PB) and (ii) nutrient management rates, application methods (farmers’ fertilizer practices; FFP, state recommended dose of fertilizer; SR and precision nutrient management using Nutrient Expert tool; NE and GreenSeeker; (GS), applied using two methods; broadcasting (B) and drilling (D)) were investigated for multiple parameters. The results showed that NE, NE+GS, and SR-based nutrient management tactics with drilling improved crop yields, nutrient-use efficiency (NUE), and economic profitability relative to NE-broadcasting, SR broadcasting, and FFP broadcasting methods. Maize-wheat system productivity and net returns under NE+GS-drilling on PB were significantly higher by 31.2%, 49.7% compared to FFP-broadcasting method, respectively. Total global warming potential (GWP) was lower in the PB-based maize-wheat system coupled with precision nutrient management compared to CT-based maize-wheat system with FFP. Higher (15.2%) carbon sustainability index (CSI) was recorded with NE-drilling compared to FFP-broadcasting method. Results suggests that PB-based maize-wheat system together with precision nutrient management approaches (NE+GS+drilling) can significantly increase crop yields, NUE, and profitability while reducing the emission of greenhouse gases (GHGs) from maize-wheat systems in eastern Indo Gangetic Plains (IGP).

Connecting Bio-Priming Approach with Integrated Nutrient Management for Improved Nutrient Use Efficiency in Crop Species

The increasing demand for qualitative and varietal foods by the consumer society is a big concern for energy production, and utilization of that energy in a judicious manner for sustainable management of resources is a big challenge in the eminent future. Existing resources (land, water, fertilizer, etc.) and their socioeconomic aspects warrant the farming community to adopt alternative strategies aimed at enhancing the use efficiency of inputs and improve the environmental quality. The adaptability of microbes to thrive in different environments has prompted scientists to introduce microbial intervention in the agricultural processes. Bio-priming has the potential to fulfill many objectives of the modern production system with the use of beneficial microorganisms in an eco-friendly manner. Interestingly, it also plays a crucial role in enhancing the nutrient use efficiency of crops. There is rising evidence of a paradigm shift from the use of a single microbe to a consortium approach for efficient rhizosphere engineering in the context of sustainable agriculture. Our understanding of different signaling cascades, rhizosphere chemistry, and other mechanisms of plant–microbial interactions will frame suitable strategies to harness the best ecosystem services including improved resource use efficiency.

Genome-wide association analysis unveils novel QTLs for seminal root system architecture traits in Ethiopian durum wheat

BackgroundGenetic improvement of root system architecture is essential to improve water and nutrient use efficiency of crops or to boost their productivity under stress or non-optimal soil conditions. One hundred ninety-two Ethiopian durum wheat accessions comprising 167 historical landraces and 25 modern cultivars were assembled for GWAS analysis to identify QTLs for root system architecture (RSA) traits and genotyped with a high-density 90 K wheat SNP array by Illumina.ResultsUsing a non-roll, paper-based root phenotyping platform, a total of 2880 seedlings and 14,947 seminal roots were measured at the three-leaf stage to collect data for total root length (TRL), total root number (TRN), root growth angle (RGA), average root length (ARL), bulk root dry weight (RDW), individual root dry weight (IRW), bulk shoot dry weight (SDW), presence of six seminal roots per seedling (RT6) and root shoot ratio (RSR). Analysis of variance revealed highly significant differences between accessions for all RSA traits. Four major (− log10P ≥ 4) and 34 nominal (− log10P ≥ 3) QTLs were identified and grouped in 16 RSA QTL clusters across chromosomes. A higher number of significant RSA QTL were identified on chromosome 4B particularly for root vigor traits (root length, number and/or weight).ConclusionsAfter projecting the identified QTLs on to a high-density tetraploid consensus map along with previously reported RSA QTL in both durum and bread wheat, fourteen nominal QTLs were found to be novel and could potentially be used to tailor RSA in elite lines. The major RGA QTLs on chromosome 6AL detected in the current study and reported in previous studies is a good candidate for cloning the causative underlining sequence and identifying the beneficial haplotypes able to positively affect yield under water- or nutrient-limited conditions.

Biochar and its importance on nutrient dynamics in soil and plant

Biochar, an environmentally friendly soil conditioner, is produced using several thermochemical processes. It has unique characteristics like high surface area, porosity, and surface charges. This paper reviews the fertilizer value of biochar, and its effects on soil properties, and nutrient use efficiency of crops. Biochar serves as an important source of plant nutrients, especially nitrogen in biochar produced from manures and wastes at low temperature (≤ 400 °C). The phosphorus, potassium, and other nutrient contents are higher in manure/waste biochars than those in crop residues and woody biochars. The nutrient contents and pH of biochar are positively correlated with pyrolysis temperature, except for nitrogen content. Biochar improves the nutrient retention capacity of soil, which depends on porosity and surface charge of biochar. Biochar increases nitrogen retention in soil by reducing leaching and gaseous loss, and also increases phosphorus availability by decreasing the leaching process in soil. However, for potassium and other nutrients, biochar shows inconsistent (positive and negative) impacts on soil. After addition of biochar, porosity, aggregate stability, and amount of water held in soil increase and bulk density decreases. Mostly, biochar increases soil pH and, thus, influences nutrient availability for plants. Biochar also alters soil biological properties by increasing microbial populations, enzyme activity, soil respiration, and microbial biomass. Finally, nutrient use efficiency and nutrient uptake improve with the application of biochar to soil. Thus, biochar can be a potential nutrient reservoir for plants and a good amendment to improve soil properties.

Site-specific Nutrient Management for Enhancing Crop Productivity

Nutrient management plays a crucial role in achieving self-sufficiency in food grain production. High price index of chemical fertilizers coupled with mount pollution problem gave rise to interest in precision nutrient management tools. Site specific nutrient management (SSNM) increases and maintains the yield by optimizing the balance between supply and demand of nutrients. Nutrient application as per SSNM concept resulted in significantly higher grain yields of maize, rice, wheat and other important crop over recommended dose of fertilizers (RDF) and farmer’s fertilizers practices. The SSNM is real time feeding of crops with nutrients while recognizing the inherent spatial variability which enhances crop productivity, nutrient use efficiency (NUE) and avoids nutrient wastage. For effective SSNM, utilization of different sensing devices of soil and plant nutrient status, decision support systems, GIS, remote sensing, simulation models and nenoparticles play an important role. Traditional techniques like balanced fertilization, use of nitrification inhibitors and slow-release nitrogenous fertilizers (SRNF) are also used to attain higher productivity and reduce environmental pollution. This paper deals with the SSNM approaches which are able to enhance crop productivity, NUE and sustainability.

Targeting Root Ion Uptake Kinetics to Increase Plant Productivity and Nutrient Use Efficiency.

Root system architecture has received increased attention in recent years; however, significant knowledge gaps remain for physiological phenes, or units of phenotype, that have been relatively less studied. Ion uptake kinetics studies have been invaluable in uncovering distinct nutrient uptake systems in plants with the use of Michaelis-Menten kinetic modeling. This review outlines the theoretical framework behind ion uptake kinetics, provides a meta-analysis for macronutrient uptake parameters, and proposes new strategies for using uptake kinetics parameters as selection criteria for breeding crops with improved resource acquisition capability. Presumably, variation in uptake kinetics is caused by variation in type and number of transporters, assimilation machinery, and anatomical features that can vary greatly within and among species. Critically, little is known about what determines transporter properties at the molecular level or how transporter properties scale to the entire root system. A meta-analysis of literature containing measures of crop nutrient uptake kinetics provides insights about the need for standardization of reporting, the differences among crop species, and the relationships among various uptake parameters and experimental conditions. Therefore, uptake kinetics parameters are proposed as promising target phenes that integrate several processes for functional phenomics and genetic analysis, which will lead to a greater understanding of this fundamental plant process. Exploiting this genetic and phenotypic variation has the potential to greatly advance breeding efforts for improved nutrient use efficiency in crops.

Biochar, poultry manure and NPK fertilizer: sole and combine application effects on soil properties and ginger (Zingiber officinale Roscoe) performance in a tropical Alfisol

Abstract Biochar has a low chemical composition and is recalcitrant to degradation. For good soil fertility and nutrient use efficiency of crops it becomes imperative that addition of a fast releasing nutrient source to biochar be sought. Therefore, studies were conducted in 2017 and 2018 to evaluate the effects of biochar with poultry manure (PM) and NPK fertilizer on soil properties, growth and yield of ginger. Treatments evaluated were: biochar applied alone at 15 t ha-1 , PM applied alone at 15 t ha-1, NPK fertilizer applied alone at 200 kg ha-1, biochar applied at 15 t ha-1 with poultry manure applied at 15 t ha-1 (B+PM), biochar applied at 15 t ha-1 with NPK fertilizer applied at 200 kg ha-1 (B+NPK) and a control with no amendment whatsoever. The experimental design was a randomized complete block design with three replications. Biochar, PM, NPK fertilizer alone or B+PM and B+NPK improved soil physical and chemical properties, growth and yield of ginger compared to no amendment (control). NPK fertilizer did not improve soil physical properties nor increased pH, OM, Ca and Mg significantly. B+PM and B+NPK improved soil physical and chemical properties, growth and ginger yield compared to their sole forms. Although B+PM had better soil physical properties, B+NPK increased yield and growth of ginger compared to B+PM. B+NPK increased the yield of ginger by 12.2% and 10.6% in 2017 and 2018, respectively compared with B+PM. B+NPK also increased the yield of ginger by 49.2% and 50.3% in 2017 and 2018, respectively compared to biochar alone. This was related to high presence of nutrients in B+NPK especially N and K which are important for ginger rhizome formation.

Microbial Consortia versus Single-Strain Inoculants: An Advantage in PGPM-Assisted Tomato Production?

The use of biostimulants with plant growth-promoting properties, but without significant input of nutrients, is discussed as a strategy to increase stress resistance and nutrient use efficiency of crops. However, limited reproducibility under real production conditions remains a major challenge. The use of combination products based on microbial and non-microbial biostimulants or microbial consortia, with the aim to exploit complementary or synergistic interactions and increase the flexibility of responses under different environmental conditions, is discussed as a potential strategy to overcome this problem. This study aimed at comparing the efficiency of selected microbial single-strain inoculants with proven plant-growth promoting potential versus consortium products under real production conditions in large-scale tomato cultivation systems, exposed to different environmental challenges. In a protected greenhouse production system at Timisoara, Romania, with composted cow manure, guano, hair-, and feather-meals as major fertilizers, different fungal and bacterial single-strain inoculants, as well as microbial consortium products, showed very similar beneficial responses. Nursery performance, fruit setting, fruit size distribution, seasonal yield share, and cumulative yield (39–84% as compared to the control) were significantly improved over two growing periods. By contrast, superior performance of the microbial consortia products (MCPs) was recorded under more challenging environmental conditions in an open-field drip-fertigated tomato production system in the Negev desert, Israel with mineral fertilization on a high pH (7.9), low fertility, and sandy soil. This was reflected by improved phosphate (P) acquisition, a stimulation of vegetative shoot biomass production and increased final fruit yield under conditions of limited P supply. Moreover, MCP inoculation was associated with selective changes of the rhizosphere-bacterial community structure particularly with respect to Sphingobacteriia and Flavobacteria, reported as salinity indicators and drought stress protectants. Phosphate limitation reduced the diversity of bacterial populations at the root surface (rhizoplane) and this effect was reverted by MCP inoculation, reflecting the improved P status of the plants. The results support the hypothesis that the use of microbial consortia can increase the efficiency and reproducibility of BS-assisted strategies for crop production, particularly under challenging environmental conditions.

Nutrients accumulation in black oat (Avena strigosa) and pearl millet (Pennicetum glaucum) after application of herbicides glyphosate or glufosinate-ammonium

Cover crops used in conservative cropping systems can accumulate large amounts of nutrients, reducing nutrient losses from the soil-plant system and improving the nutrient use efficiency in crops. However, recent researches demonstrated that herbicides used to kill cover crop could decrease N status in the straw, reducing the nutrient availability to the cash crop. In this context, the aim of this work was to investigate the effect of glyphosate or glufosinate-ammonium application in K, P, Ca, Mg, S and C status in plant´s tissues of black oat (Avena strigosa) and peal millet (Pennicetum glaucum) desiccated with herbicides. An experiment was carried out under greenhouse conditions using a factorial design 2x3. The evaluated factors were cover crop (black oat or peal millet) and cover crop management (1-Control- mechanical cut, without herbicide application; 2-Glyphosate- cover crop desiccation with glyphosate; 3-Glufosinate- cover crop dessication with ammonium-glufosinate). Dry mass production, nutrients accumulation in plants part and entire plants and the nutrient´s utilization efficiencies were determined. The nutrients accumulation in plants was not reduced by herbicides; however, a lower dry matter and C accumulation was observed after herbicides application. Glyphosate increased K, P, S and C remobilization from leaves to stalks, but glufosinate did not affect it, suggestion a lower effect of this herbicide in nutrients availability to cash crop. Herbicides did not affect K, P, Ca, Mg and S losses from plants, thus the total amount of these nutrients in the system should be not affected by glyphosate or ammonium glufosinate utilization. However, since glyphosate changes these nutrients distribution among plant´s parts, increasing nutrients in the stalks and reducing nutrients in the leaves of pearl millet, it may affect nutrient availability to cash crops, since leaves mineralization is faster than stalks mineralization on soil. In this sense, the herbicide application is a practice that should be considered for prediction of nutrients availability in soil-plant systems, aiming improve the nutrient´s use efficiency.

Cover Caption: Nutrient use efficiency in crops

Improving nutrient efficiency is important for agricultural sustainability. In the invited review article written by Chen and Liao (pp. 710‐735), it is proposed that integrations of nutrient acquisition, translocation, remobilization and metabolic efficiency may help crops to achieve a higher nutrient use efficiency, and the strategies that can be used.

Root type is not an important driver of mycorrhizal colonisation in Brachypodium distachyon

Breeding for favourable root traits in food and energy crops should be considered in the context of interactions with soil biota, notably those that can increase the nutrient use efficiency of crops. Arbuscular mycorrhizal (AM) fungi can provide services to plants but a better understanding of the interactions between root traits and AM fungi is required to maximise these benefits.One source of intraspecific variation in root architecture is the allocation of resources to different root types. We hypothesized that different root types would have different traits and be colonised differently by AM fungi, either in the amount of colonisation or identity of colonisers. We studied communities colonising the seminal, coleoptile nodal and leaf nodal roots of seven Brachypodium distachyon accessions grown in three crop or pasture soils.Leaf nodal roots had low specific root length compared to coleoptile nodal and seminal roots, yet all three root types harboured similar AM fungal communities and levels of colonisation. Most of the variation in the AM fungal communities was explained by soil; significant proportions were explained by plant accession and root type but these effects were weak.Differential allocation of resources between root types is not a trait that could be selected to maximise beneficial interactions with AM fungi and we found no link between a root phenotypic trait (specific root length) and AM fungal colonisation. Accessions did vary in extent of colonisation by arbuscules, meaning B. distachyon may be a useful model to study mechanisms underlying the symbiotic interface and mycorrhizal growth response of cereals.

Thermal post-treatment alters nutrient release from a controlled-release fertilizer coated with a waterborne polymer.

Controlled-release fertilizers (CRF) use a controlled-release technology to enhance the nutrient use efficiency of crops. Many factors affect the release of nutrients from the waterborne polymer-coated CRF, but the effects of thermal post-treatments remain unclear. In this study, a waterborne polyacrylate-coated CRF was post-treated at different temperatures (30 °C, 60 °C, and 80 °C) and durations (2, 4, 8, 12, and 24 h) after being developed in the Wurster fluidized bed. To characterize the polyacrylate membrane, and hence to analyze the mechanism of nutrient release, Fourier transform mid-infrared spectroscopy, scanning electron microscopy, and atomic force microscopy were employed. The nutrient-release model of CRF post-treated at 30 °C was the inverse “L” curve, but an increased duration of the post-treatment had no effect. The nutrient-release model was “S” curve and nutrient-release period was enhanced at higher post-treatment temperatures, and increased post-treatment duration lengthened slowed nutrient release due to a more compact membrane and a smoother membrane surface as well as a promoted crosslinking action. CRF equipped with specified nutrient-release behaviors can be achieved by optimizing the thermal post-treatment parameters, which can contribute to the development and application of waterborne polymer-coated CRF and controlled-release technologies.

Improvements in nutrient uptake and nutrient use-efficiency in cotton cultivars released between 1973 and 2006

We examined twelve cotton (Gossypium hirsutum L.) cultivars that were released in Australia between 1973 and 2006, in three field experiments, harvested in 2009, 2010 and 2012. Crop biomass and nutrient uptake were measured at 160 days after sowing and lint yield at crop maturity. Crop nutrient use-efficiency was determined by dividing lint yield by nutrient uptake. Lint yield increased by 40% (P<0.001) for cultivars released between 1973 and 2006; crop biomass increased by 25%; N, S uptake increased by 20%, and 26% respectively; 33% for Ca, Mg and Na; and 22% for trace elements Fe, Mn, B, Zn and Cu (all P<0.001). With the release of improved cultivars, the use-efficiency increased for N (20%, P<0.001), P (23%, P<0.001) and K (24%, P<0.01). Similar increases were found for trace elements Fe, Cu and Zn (P<0.05–0.001). Newer cultivars also had substantial improvements in lint fraction, fibre strength and fibre length. We conclude that crop nutrient use-efficiency has increased relatively slowly, crop nutrient uptake has increased faster but neither has increased as quickly as lint yield. Improved use-efficiencies of N, P, K, Fe, Zn and Cu have occurred through selective breeding for lint yield over the past three decades. Based on nutrient demand, it is calculated that further increases in yield will require improved nutrient use-efficiency, and probably with better internal redistribution of nutrients. Such research should be done using a soil type and growing system capable of producing high-yielding cotton.

Agriculture Intensification and Ecologically Sustainable Land Use Systems in Niger: Transition from Traditional to Technologically Sound Practices

ABSTRACT Increasing population pressure in Niger has increased demand for arable land leading to expansion of cropping into marginal land resulting in soil erosion and diminishing pasture, woodland and forest area which threatens ecosystem sustainability. Highly variable rainfall adds risk to crop production. Intensification of agriculture with adoption of sustainable, yield enhancing technologies is critical to the future development of all agroecological regions in Niger. Farm constraints analysis of crop productivity conducted in rainfed areas of the Niger by farmer surveys and on-farm experiments revealed that the major limitations to increased productivity were (1) low soil fertility and lack of fertilizer use, (2) limited organic manure availability, (3) low mineral nutrient use efficiency of crops when fertilizers were applied during soil moisture stress, (4) lack of high yielding varieties resistant to biotic and abiotic stresses, (5) practice of using low plant densities, (6) limited access to farm inputs, (7) lack of a marketing strategy, and (8) lack of adequate extension service to farmers. The use of improved technologies, such as fertilizer, improved varieties or hybrids, optimum plant density and water conservation technologies were shown to increase yields more than two-fold at the farm level. Key elements in a strategy to increase total crop production in Niger must include support from both the private and public sectors to promote more rapid acceptance of improved production technologies. This will require institutional modifications that enhance technology transfer, development of input delivery systems, improved policies of land tenure, availability of fertilizer, and improved policies that affect the input and output pricing structure.

Genotype-environment interaction and correlation between vegetative and grain production measures of potassium use-efficiency in wheat (T. aestivum L.) grown under potassium stress

Nutrient use-efficiency (NUE) is commonly measured in relation to vegetative growth without regard for economic productivity of crops whose valued product is reproductive. Although vegetative measures can be useful, particularly in forage crops, their validity in the quantification of NUE in grain crops is questionable. This study was undertaken primarily to examine the relationship between vegetative and economic potassium use-efficiency (KUE) in several wheat (T. aestivum) genotypes under conditions of potassium stress. Genotype environment interaction for vegetative KUE was also examined. Vegetative KUE was assessed as shoot fresh weight, efficiency ratio (VKER) and utilization index (VKUI) whereas economic KUE was evaluated as grain weight, total weight and economic efficiency ratio (EKER). Significant genotype-environment interactions for shoot weight, VKER and VKUI were observed. In some instances interaction was associated with crossovers between genotypes indicating that it can affect selection. Correlations between vegetative and economic measures of KUE were generally nonsignificant, but negative and significant for shoot weight of three-week-old plants and grain weight. It appears that if genotypes differ considerably for harvest index and it is not positively correlated with total biomass, vegetative measures of KUE are unreliable as indicators of economic KUE. Therefore, economic rather than vegetative measures should be used to evaluate KUE in crops whose valued product is reproductive. ei]{gnH}{fnMarschner} ei]{gnH.}{fnLambers}