Split Application of Potassium Improves Yield and End-Use Quality of Winter Wheat

Many studies have investigated the effects of basal K fertilization on the yield and quality of wheat (Triticum aestivum L.). However, less is known about the influence of the split application of K on yield, size distribution of protein fractions, and quality of wheat. Field studies were conducted in two successive seasons (2010/2011 and 2011/2012) using four winter wheat cultivars, Jimai 20, Gaocheng 8901, Yannong 19, and Jinan 17, and three regimes of K fertilization (K0: no K fertilization; KB: basal K fertilization of 120 kg ha^–1; KS: basal K fertilization of 60 kg ha^–1 plus topdressing of 60 kg ha^–1 at jointing). The yield and its components, protein composition, dough-mixing properties, and bread-making quality were determined after harvesting. On average, the KS treatments had a yield advantage over KB treatments mainly resulting from higher kernel weight. The KS treatments improved wheat quality resulted in increased glutenin/gliadin ratio, higher polymerization index (the ratio of sodium dodecyl sulfate to insoluble glutenin in total glutenin), and larger glutenin macropolymer (GMP) particles compared to KB fertilization. No differences in the content of crude protein and wet gluten were found between the KS and KB treatments. Dough development time, stability time, and loaf volume were positively correlated with the glutenin/gliadin ratio, polymerization index, and average size of the GMP, respectively. These results suggest that KS can improve the yield and end-use quality of winter wheat.

Nutrient Management Decision Tool for Small-Scale Rice and Maize Farmers

Site-specific nutrient management (SSNM), as developed for rice (Oryza sativa L.) through partnerships of the International Rice Research Institute (IRRI) with organizations across Asia, provides scientific principles for determining field-specific fertilizer nitrogen (N), phosphorus (P), and potassium (K) requirements for cereal crops. These SSNM-based principles enable the determination of crop requirements for fertilizer N using a yield gain approach, the distribution of fertilizer N to match critical crop growth stages, and the determination of crop requirements for fertilizer P and K using a field-level nutrient balance approach. The uptake by farmers of improved nutrient management based on SSNM requires transforming the scientific principles into locally adapted tools that enable rapid development and implementation of nutrient management practices that match field-specific cropping conditions. We used recent advances in information and communication technology (ICT) and mobile phones to develop Web and mobile phone applications of "Nutrient Manager for Rice" (www.irri.org/nmrice), which transform the science of SSNM into guidelines matching the field-specific needs and conditions of a farmer. Nutrient management guidelines provided by "Nutrient Manager" are calculated by a `model' residing on a cloud-based server. Information obtained by the ‘model’ from answers of farmers to questions about their location-specific cropping conditions can be supplemented with Internet-based soils information to enhance the robustness of nutrient management guidelines provided to farmers. Field trials with rice reveal no relationship between soil analyses for soil N, P, or K status and field-measured rice response to the added nutrient. There is consequently an immediate need to identify soil information most indicative of crop requirements for supplemental nutrient in small landholding with large spatial and temporal variations in management, nutrient balances, and yield.

Soil Nutrient Management Based on Soil Information System in Korea

The Soil Information System (SIS) in Korea has been developed to manage the soil fertility and soil resources for sustaining agricultural production. To manage the fertilization, the fertilizer application rates were established considering soil nutrient contents and crop requirements. The fertilizer recommendation program in the soil information system is based on the fertilization equation by soil testing, and it provides the farmer with soil information such as soil physical and chemical properties, and fertilizer application rates. Through this system, the farmer can apply fertilizers economically, and the soil-testing database can be used to establish the fertilizer supply policy.

Phosphorus and Potassium Decision Support System: Bridging Soil Database and Fertilizer Application

This paper discusses the Phosphorus and Potassium Decision Support System (PKDSS) developed by ICALRD and its role in bridging soil database and fertilizer application. This system is a fertilizer recommendation model, as well as a computer program, used as a tool in determining fertilizer requirement for a given crop based on soil testing. In Indonesia, balanced fertilizer application approach is adopted to increase crop production while reducing negative impact on environment. This approach requires a better insight on soil characteristics and behaviour. The soil nutrient status determines fertilizer recommendation for a given crop. The PKDSS recommends fertilizer rate after correcting the standard rate by its correction factor. The correction factor indicates the effect of selected soil properties on soil nutrient dynamics. N-fertilizer is corrected by soil texture class and soil organic carbon content. P-fertilizer is corrected by soil texture class, soil pH, soil organic carbon content, and P-retention. K-fertilizer is corrected by soil texture class, soil organic carbon content, and cation exchange capacity of clay. PKDSS needs 14 soil properties as input, divided into two layers: first layer to select the standard recommendation and second layer to determine the correction factor. These soil properties can be provided by soil data stored in the soil database. These legacy data can be used to create quantitative soil property maps by using digital soil mapping techniques. These maps are inputted to PKDSS to come up with fertilizer recommendation area (FRA) for a given crop. The FRA assists the local government in planning fertilizer stock and distribution in each agricultural service. PKDSS plays an important role in bridging soil database and fertilizer application.

Significance of Potassium Use in Haryana Agriculture

Consumption of potassic fertilisers has increased in the state of Haryana. However, the quantity of fertilizer use is not only imbalanced but inadequate to meet the requirements of plant demand for optimum yield. The judicious fertilizer use takes into consideration the nutrient status of the soils as well as crop responses to fertilizer applications. The present paper outlines the results of a systematically GPS based recently conducted survey analysis for K status of Haryana soils. Overall, more than 73% soils falling under low to medium category in available K indicate an alarming situation of the depleting scenario of K status in the state and emphasizes the need for the application of potassic fertilisers for maintaining crop yields and nutrient status. The study also shows the growing responses of K application under different crops and cropping systems. Based on the results of different on site and farm field experiments, new recommendations for K in crops viz., pearl millet, cluster bean, mustard and sugarcane have been advocated and has been recently included in the package of practices for kharif and rabi crops in Haryana. It is suggested that readily available pools of potassium do not clearly synchronise with the K uptake/removal by crops and for a better picture on K supplying power of soils the non-exchangeable K pool of the soil should be periodically and simultaneously monitored.

Distribution of Forms of Potassium in Relation to Different Agroecological regions of North-Eastern India

Distribution of potassium (K) in soils is governed by the agroecological region (AERs), as the operational intensity of factors and processes of soil formation vary with AER. Therefore, we aimed at finding out the relationship between the forms of K (K forms) with AER and the association of K forms with soil properties in the North-Eastern region of India. For this, horizon-wise soil samples were collected from pedons, three each from three AERs (15 (hot sub-humid to humid), 16 (warm per-humid) and 17 (warm per-humid with less cool winter)) in the North-Eastern India. The water balance diagram for AER shows that precipitation (P) exceeds the potential evapo-transpiration (PET) from June to October, AER 16 shows almost no period when the PET is more than the P and AER 17 shows that the region experiences only a short water deficit of 100–150 mm during post-monsoon period. Soil samples were analysed for physical and chemical properties and K forms. The soils were acidic to neutral with low cation exchange capacity (CEC). The water-soluble K ranged between 0.006 and 0.144 cmol kg⁻¹, exchangeable K between 0.07 and 0.54 cmol kg⁻¹, fixed K from 16.7 to 61.3 cmol kg⁻¹ and total K from 17.4 to 63.6 cmol kg⁻¹ in soils of different horizons. Further, the results revealed that all the K forms followed the trend of AER 16 > AER 17 >AER 15. Exchangeable K showed higher correlation with clay (r = 0.519**), while fixed K with organic carbon (r = 0.390*).

Nutrient Efficiency of Different Crop Species and Potato Varieties - in Retrospect and Prospect

Different plant species and potato cultivars differed in nutrient use efficiency. Earlier studies indicated that potato cv. Kufri Pukhraj was the most N, P and K efficient cultivar among released cultivars tested in the absence as well as presence of green manure. The efficient cultivars gave higher tuber yield under N, P and K stress (i.e. with less dose of N, P and K fertilizer) and had higher agronomic use efficiency (AUE) than less efficient cultivars. The main cause of higher nitrogen efficiency in the presence of green manure was the capacity of a genotype to use/ absorb more N per unit green manured soil. The variation in phosphorus and potassium efficiency of different potato cultivars was due to both their capability to use absorbed P and K to produce potato tubers (PUE) and to their capacity to take up more P and K per unit soil (NUE). Further comparison of nutrient (N, P & K) efficiency of promising potato hybrid JX 576, now released as Kufri Gaurav, with Kufri Pukhraj revealed that hybrid JX 576 is more N, P and K stress tolerant than Kufri Pukhraj. Its higher efficiency was mainly because of its better utilization of absorbed nutrients (N, P and K) for potato production than other cultivars. The higher expression of ammonium transporter, cytochrome oxidase and asparagine synthetase in leaves can be used as parameters to screen potato genotypes for high metabolism, utilization, transport and storage of N. This review brings out the need to establish linkage of nutrient efficiency with root and shoot parameters/DNA markers/genes.

Effect of Integrated Nutrient Management Practices on Yield of Potato

Potato is one of the leading commercial crops of Kashmir valley and is cultivated on an area of about 2500 ha with the production and productivity of 32.5 thousand t and 13 t/ha, respectively (Anonymous, 2009). Being a heavy feeder of nutrients, potato requires high amount of nitrogen, phosphorus and potassium. Chemical fertilizers are the main source of nutrients used for potato cropping. However, continuous dependence on chemical fertilizers causes nutritional imbalance and adverse effects on physico-chemical and biological properties of the soil. Integrated nutrient management (INM) is a better approach for supplying nutrition or food to the crop by including organic and inorganic sources of nutrients (Arora, 2008). Keeping the facts in view, the present investigation was planned to find out the appropriate combination of organic and inorganic sources of nutrients and bio-inoculants for improving yield of potato under temperate condition of Kashmir valley.

Spatial Distribution of Soil Available Nutrients in the Potato Growing Pockets of Hoshiarpur District of Punjab

Soil samples of potato growing pockets of Hoshiarpur district of Punjab were collected and analysed for pH, OC and available NPK. The soil analysis data was fed into GIS software and spatial maps generated. The soils of the district in general, were slightly acidic to slightly alkaline in reaction. The pH of collected soil samples varied from 5.0 to 8.2 with a mean value of 6.8. About 90 percent of the total area had pH less than 7.5, a situation considered much suitable for potato cultivation. The organic carbon ranged from low to medium (0.2 to 0.7%) with an average value of 0.4 percent. Available nitrogen ranged from 186.3 to 355.6 kg/ha with a mean value of 242.5 kg/ha and more than 88 percent of samples had available phosphorus greater than 20 ppm. None of the collected sample were deficient in available phosphorus, suggesting build-up of P fertilizers in these areas. In case of available soil potassium, 79, 19.2 and 2 percent samples were found to be low, medium and high, respectively. After kriging, results showed that 30.5 and 18.8% area had high and very high phosphorus, respectively, but were low in nitrogen and potassium. About 17.3 percent area was medium in available nitrogen, very high in phosphorus but low in available potassium, while 12.8% area was medium in both available N and K but very high in P.

Five Ideas that have Changed Research in the Cropping Sector

Innovation is now a prerequisite for institutions aiming to maintain their competitiveness in a more and more liberalized economy. This is also true for agricultural research. One of the objectives of ProfiCrops, the research program Agroscope, was to promote the innovation process leading to added value in the cropping sector. This article describes five ideas, their development into innovation and the scope for the innovation’s adoption. The sampling was done purposively, based on an innovations’ list for the cropping sector. The sample comprised: three process innovations: a portable Near-infrared spectroscopy (NIRS) tool, the sequence of the fire blight pathogen genome and the use of molecular markers, and two service innovations: Life Cycle Assessment (LCA) in agriculture and urban agriculture. The results show that the innovation process within research requires some scope that includes a clear research mission, sufficient financial resources, time and a risk-taking attitude.

Effects of Many Years of Organic Agriculture

More and more farmers consider to switch from conventional to organic production. What effect, then, does this have on yield and environmental performance? In particular, the question of how the duration of organic management affects plant yield, weed populations, biodiversity and soil fertility has rarely been investigated. To investigate this question, we compared 34 plots distributed over four farm categories – conventional, recently converted, and «new» and «old» organic farms. Our study shows that crop yield and soil fertility remain constant as length of time under organic management increases. Similarly, weed pressure has not increased along with duration of organic management. Weed abundance did, however, vary strongly among fields, with problematic weeds being highly abundant at specific field sites. This study demonstrates that duration of organic management does not have a negative impact on either plant yield or soil fertility on mixed-economy farms under Swiss conditions

Synergies and Trade-Offs with regard to Ensuring Food Security and the Efficient Use of Resources

In Switzerland, agriculture and the food industry are facing major challenges, as is society in general. The gap between desired and achievable levels of food production is growing wider, since ensuring sufficient food supplies for a growing population requires a constant increase in production while at the same time it is necessary to reduce the use of resources. By applying a dynamic simulation model to the situation in Switzerland it was possible to quantify the trade-offs and synergies between environmental and production outcomes with a time horizon of 2050. The aim of this project was to identify the key conditions for ensuring both long-term food provision and the efficient use of resources. The main finding arising from the application of the model was that Swiss agriculture has the potential to reconcile the aims of food provision and environmental protection; however, implementing the key conditions will depend inter alia upon technical and organisational progress that goes beyond the currently foreseeable possibilities.

Global Food Security - The Consequences for Switzerland

Society is facing major challenges in ensuring global food security. Global trends since the food-price crisis in 2008 have revealed significant new risks. In 2012, the Swiss Federal Office for Agriculture decided to identify, quantify and prioritise these risks and to derive potential areas of intervention. A literature review based on the analysis of key publications (Subproject 2) provides a global perspective on the global food security situation and future projections. The literature study identified seven drivers influencing the future of the global food security system: (i) population growth; (ii) climate change; (iii) environmental degradation and competition for land, water and energy resources; (iv) changing dietary patterns and consumer preferences; (v) rise in, and volatility of food prices; (vi) increasing vertical integration of value chains in food production and markets; (vii) technological progress. The report identifies six intervention areas for which conclusions and options for action are suggested: (i) agricultural production; (ii) environmental sustainability and resource efficiency; (iii) dietary patterns; (iv) trade policies and the role of multinational food companies; (v) research and innovation; and (vi) international cooperation.

Mechanisms and Physiological Roles of K⁺ Efflux from Root Cells

Potassium is the most abundant macronutrient, which is involved in a multitude of physiological processes. Potassium uptake in roots is crucial for plants; however, K⁺ efflux can also occur and has important functions. Potassium efflux from roots is mainly induced by stresses, such as pathogens, salinity, freezing, oxidants and heavy metals. Reactive oxygen species (ROS) and exogenous purines also cause this reaction. The depolarisation and activation of cation channels are required for K⁺ efflux from plant roots. Potassium channels and nonselective cation channels (NSCCs) are involved in this process. Some of them are ‘constitutive’, while the others require a chemical agent for activation. In Arabidopsis, there are 77 genes that can potentially encode K⁺-permeable channels. Potassium-selective channel genes include 9 Shaker and 6 Tandem-Pore K⁺ channels. Genes of NSCCs are more abundant and present by 20 cyclic nucleotide gated channels, 20 ionotropic glutamate receptors, 1 two-pore channel, 10 mechanosensitive-like channels, 2 mechanosensitive ‘Mid1-Complementing Activity’ channels, 1 mechanosensitive Piezo channel, and 8 annexins. Two Shakers (SKOR and GORK) and several NSCCs are expressed in root cell plasma membranes. SKOR mediates K⁺ efflux from xylem parenchyma cells to xylem vessels while GORK is expressed in the epidermis and functions in K⁺ release. Both these channels are activated by ROS. The GORK channel activity is stimulated by hydroxyl radicals that are generated in a Ca²⁺-dependent manner in stress conditions, such as salinity or pathogen attack, resulting in dramatic K⁺ efflux from root cells. Potassium loss simulates cytosolic proteases and endonucleases, leading to programmed cell death. Other physiological functions of K⁺ efflux channels include repolarisation of the plasma membrane during action potentials and the ‘hypothetical’ function of a metabolic switch, which provides inhibition of energy-consuming biosyntheses and releasing energy for defence and reparation needs.

Is the Leaf Bundle Sheath a "Smart Flux Valve" for K⁺ Nutrition?

Evidence has started to accumulate that the bundle sheath regulates the passage of water, minerals and metabolites between the mesophyll and the conducting vessels of xylem and phloem within the leaf veins which it envelops. Although potassium (K⁺) nutrition has been studied for several decades, and much is known about the uptake and recirculation of K⁺ within the plant, the potential regulatory role of bundle sheath with regard to K⁺ fluxes has just begun to be addressed. Here we have collected some facts and ideas about these processes.

Cellular and Tissue Distribution of Potassium: Physiological Relevance, Mechanisms and Regulation

Potassium (K⁺) is the most important cationic nutrient for all living organisms. Its cellular levels are significant (typically around 100 mM) and are highly regulated. In plants K⁺ affects multiple aspects such as growth, tolerance to biotic and abiotic stress and movement of plant organs. These processes occur at the cell, organ and whole plant level and not surprisingly, plants have evolved sophisticated mechanisms for the uptake, efflux and distribution of K⁺ both within cells and between organs.

Great progress has been made in the last decades regarding the molecular mechanisms of K⁺ uptake and efflux, particularly at the cellular level. For long distance K⁺ transport our knowledge is less complete but the principles behind the overall processes are largely understood.

In this chapter we will discuss how both long distance transport between different organs and intracellular transport between organelles works in general and in particular for K⁺. Where possible, we will provide examples of specific genes and proteins that are responsible for these phenomena.

The Twins K⁺ and Na⁺ in Plants

In the earth's crust and in seawater, K⁺ and Na⁺ are by far the most available monovalent inorganic cations. Physico-chemically, K⁺ and Na⁺ are very similar, but K⁺ is widely used by plants whereas Na⁺ can easily reach toxic levels. Indeed, salinity is one of the major and growing threats to agricultural production. In this article, we outline the fundamental bases for the differences between Na⁺ and K⁺. We present the foundation of transporter selectivity and summarize findings on transporters of the HKT type, which are reported to transport Na⁺ and/or Na⁺ and K⁺, and may play a central role in Na⁺ utilization and detoxification in plants. Based on the structural differences in the hydration shells of K⁺ and Na⁺, and by comparison with sodium channels, we present an ad hoc mechanistic model that can account for ion permeation through HKTs.

Organelle-Localized Potassium Transport Systems in Plants

Some intracellular organelles found in eukaryotes such as plants have arisen through the endocytotic engulfment of prokaryotic cells. This accounts for the presence of plant membrane intrinsic proteins that have homologs in prokaryotic cells. Other organelles, such as those of the endomembrane system, are thought to have evolved through infolding of the plasma membrane. Acquisition of intracellular components (organelles) in the cells supplied additional functions for survival in various natural environments. The organelles are surrounded by biological membranes, which contain membrane-embedded K⁺ transport systems allowing K⁺ to move across the membrane. K⁺ transport systems in plant organelles act coordinately with the plasma membrane intrinsic K⁺ transport systems to maintain cytosolic K⁺ concentrations. Since it is sometimes difficult to perform direct studies of organellar membrane proteins in plant cells, heterologous expression in yeast and Escherichia coli has been used to elucidate the function of plant vacuole K⁺ channels and other membrane transporters. The vacuole is the largest organelle in plant cells; it has an important task in the K⁺ homeostasis of the cytoplasm. The initial electrophysiological measurements of K⁺ transport have categorized three classes of plant vacuolar cation channels, and since then molecular cloning approaches have led to the isolation of genes for a number of K⁺ transport systems. Plants contain chloroplasts, derived from photoautotrophic cyanobacteria. A novel K⁺ transport system has been isolated from cyanobacteria, which may add to our understanding of K⁺ flux across the thylakoid membrane and the inner membrane of the chloroplast. This chapter will provide an overview of recent findings regarding plant organellar K⁺ transport proteins.

K⁺ Uptake in Plant Roots. The Systems Involved, their Regulation and Parallels in other Organisms

Potassium (K⁺) is an essential macronutrient for plants. It is taken into the plant by the transport systems present in the plasma membranes of root epidermal and cortical cells. The identity of these systems and their regulation is beginning to be understood and the systems of K⁺ transport in the model species Arabidopsis thaliana remain far better characterized than in any other plant species. Roots can activate different K⁺ uptake systems to adapt to their environment, important to a sessile organism that needs to cope with a highly variable environment. The mechanisms of K⁺ acquisition in the model species A. thaliana are the best characterized at the molecular level so far. According to the current model, non-selective channels are probably the main pathways for K⁺ uptake at high concentrations (>10 mM), while at intermediate concentrations (1 mM), the inward rectifying channel AKT1 dominates K⁺ uptake. Under lower concentrations of external K⁺ (100 μM), AKT1 channels, together with the high-affinity K⁺ uptake system HAK5 contribute to K⁺ acquisition, and at extremely low concentrations (<10 μM) the only system capable of taking up K⁺ is HAK5. Depending on the species the high-affinity system has been named HAK5 or HAK1, but in all cases it fulfills the same functions. The activation of these systems as a function of the K⁺ availability is achieved by different mechanisms that include phosphorylation of AKT1 or induction of HAK5 transcription. Some of the characteristics of the systems for root K⁺ uptake are shared by other organisms, whilst others are specific to plants. This indicates that some crucial properties of the ancestral of K⁺ transport systems have been conserved through evolution while others have diverged among different kingdoms.

Going Beyond Nutrition: Regulation of Potassium Homoeostasis as a Common Denominator of Plant Adaptive Responses to Environment

Partially and fully completed plant genome sequencing projects in both lower and higher plants allow drawing a comprehensive picture of the molecular and structural diversities of plant potassium transporter genes and their encoded proteins. While the early focus of the research in this field was aimed on the structure?function studies and understanding of the molecular mechanisms underlying K⁺ transport, availability of Arabidopsis thaliana mutant collections in combination with micro-array techniques have significantly advanced our understanding of K⁺ channel physiology, providing novel insights into the transcriptional regulation of potassium homeostasis in plants. More recently, posttranslational regulation of potassium transport systems has moved into the center stage of potassium transport research. The current review is focused on the most exciting developments in this field. By summarizing recent work on potassium transporter regulation we show that potassium transport in general, and potassium channels in particular, represent important targets and are mediators of the cellular responses during different developmental stages in a plant's life cycle. We show that regulation of intracellular K⁺ homeostasis is essential to mediate plant adaptive responses to a broad range of abiotic and biotic stresses including drought, salinity, and oxidative stress. We further link post-translational regulation of K⁺ channels with programmed cell death and show that K⁺ plays a critical role in controlling the latter process. Thus, is appears that K⁺ is not just the essential nutrient required to support optimal plant growth and yield but is also an important signaling agent mediating a wide range of plant adaptive responses to environment.