Thursday, October 3, 2019
Factors Impacting UK Winter Wheat Crops
Factors Impacting UK Winter Wheat Crops Summary Wheat is one of the main important cereal crops in the world. Also as one of the essential and important agricultural products. Wheat is considered as a strategic product due to its significant role in political and economic areas in the countries. Loss of wheat may harm the economy in several aspects, including reduced production rates, increased need for imports and waste the inputs required for the production (Fallah and Rasouliazar, 2016). In the UK average yields of winter wheat have increased progressively from the 1950s to the present a rate of approximately 100 kg ha-1 yr-1. Until the late 1980s, the increase was attributed about half to plant breeding and the half to husbandry. (Shearman et al., 2005) Any action was taken to improve the quantity and quality of the wheat would be of great importance. Many factors came together for increasing yield of a winter wheat crop in the UK. Including plant establishment, rotation management, nutrient management, disease, pest and weed control, and soil management. Each factor can affect or limit yield performance. In this research, we investigate factors that influence winter wheat crops and which will improve yield performance. Introduction Cereal crops are a major staple food worldwide, contributing more than 50% of total human calorie input directly. In the last twenty years, the annual increment in the average yields of UK wheat and oilseed rape increased slightly. In the second half of the 20th-century cereal yields for example wheat, in the worldwide from 1 to 3 t haà ¢Ãâ ââ¬â¢1and in the UK approximately less than three t haà ¢Ãâ ââ¬â¢1 increased (Fischer and Edmeades, 2010; Hawkesford et al., 2013. ) Wheat is one of the important cereal crops in the world. Wheat is special in several ways for instance in humans food, they are used to make flour for yeast bread, or are blended with soft spring wheat to make the all- purpose flour used in a wide variety of baked products and The highest grain yields are obtained with winter wheat. In this research, we investigate factors affecting winter wheat crops, and Evaluate of them can lead us to adjust management to achieve a greater yield. Crop Nutrition Each plant needs a different range of nutrients at every critical stage of its development. Cereal crops use nutrients for growth, progressively moving them from the roots and stems into the ear before the dying off and harvesting of the grain. For example, Phosphorus (P) is a vital component of adenosine triphosphate (ATP) which supplies the energy for many processes in the plant. Magnesium (Mg) is also a key component of leaf chlorophyll and the enzymes that support plant growth. Zinc and Boron directly influence the growth and yield of cereals and other crops, especially during flowering (Ghaffar et al., 2011). Wheat as an important source of minerals such as iron, zinc, copper and magnesium. The dietary intake of these nutrients have decreased significantly in recent years in the UK which corresponds with the introduction of semi-dwarf, high-yielding cultivars. (Ming-Sheng Fan et al., 2008) Semi-dwarf and high-yielding crop cultivars were responsible for increasing inputs of fertilisers and other agrochemicals which increased grain yield, however, increase in agronomic yield led to lower density of minerals in grain. The hypothesis of Davis et al indicated that decline in the nutrients in crops is because of changing in crops to varieties with improved yield. Ming-Sheng Fan et al, in the result of their experiments they also indicated that decreasing mineral concentrations in wheat grain are partly due to a dilution effect resulting from increased yield. It appears changing cultivars was affecting the mineral concentration. This change is further supported by (Flintham et al., 1997) that as a conclusion of the introduction of short-straw cultivars, HI (harvest index) increased, however mineral concentration significantly decreased in grain. The solution for helping minerals in grain is to add micronutrients. Supplementation, diversification of diet and bio-fortification of crops by agronomic or genetic methods such as plant breeding can increase the micronutrients; the genetic methods are considered to be the most efficient for resource-poor populations in developing countries (Graham et al., 1999; Bouis, 2002; Welch and Graham, 2004). In the germplasm of the main crops there is a sufficient genetic variation in micronutrient concentrations, which can be explored in breeding strategies to combine the high nutrient density with the high-yielding traits(Graham et al.,1999; Cakmak et al ., 2004) such as Triticum Oflococum, Triticum dicoccol, and Triticum dicoccoides (Cakmak et al.,1999a, 2000; Ortiz-Monasterio and Graham ,2000) Among wild wheat germplasm, the emmer wheat, Triticum dicoccoides, showed the largest variation and the highest concentration of micronutrients (Cakmak et al., 2000). Crop rotation One of the most effective management methods to prevent the development of the large population of plant diseases is crop rotation. Crop rotation means the planned order of specific crops planted on the same field (Huber et al., 1965), for example soil-borne pathogens which cause soil-borne diseases that lead to reducing crop yields can be controlled with rotations with non-host crops. Also, rotation suppresses Take all disease, Cephaelosporium stripe, Cercosporella foot rot and Cercosporella herpotrichoides (Welch et al., 2004). However, this method is used for preventing and it cannot reduce the size of the population significantly, therefore it is better to view crop rotation as preventive rather than curative. Different crop rotations may have different effects on different pathogens, for instance Meloidogyne incognita were reduced by crops of crotalaria, marigold or bahiagrass while the population of Trichodorus christei were increased (Murphy et al.,1974), so it is vital to understand plant disease before planting crops. Crop Rotation benefits are = Maintains soil fertility. Reduces soil erosion. Controls pests, disease and weeds Reduces reliance on synthetic chemicals. There are two major limits for crop rotation, the first one is some pathogens have many host ranges so it may be difficult to identify them, for example Rhizoctonia solani .The second one is that non-host crops may have little monetary value, so the selection of crops to use for rotation may be small. (Battese and Fuller, 1972) and if crops rotation not chosen properly, have chances of competition between the crops for nutrients. Establishment management One of the most important factors that can provide the correct condition for both growing and crop establishment is tillage. Tillage is accomplished to optimise productivity by alleviating physical, chemical and biological constraints of soil (Gajri et al., 2002). Progressive tillage systems are developed to minimise cultivation costs and meet a range of variables such as soil or climate. It also improves the timeliness of planting which leads to an improved crop establishment. (Morris et al., 2010) In the UK, current tillage systems can be divided into two general categories; Inversion tillage, known as conventional plough tillage, and Conservation tillage, known as non-inversion tillage. Inversion tillage, inclusive of seed bed preparation by complete soil inversion, incorporates or buries most of the crop residue into the ground and consists of two processes: tillage and secondary tillage. Conservation tillage leaves the previous years crop residue (such as wheat) on fields before and after planting the next crop using the two processes of strip tillage and direct drilling to reduce soil degradation and achieve a sustainable balance between production (Carter et al., 2003a) (Davies and Finney,2002). No-till, known as direct drilling or zero tillage, is a conventional tillage system which sows directly in previous crops without any prior loosening of the soil cultivation. (Soane et al., 2012). Ploughing system is a farm implement used in farming for initial cultivation of soil in preparation for sowing seed or planting to loosen or turn the soil. Ploughing system can expose soil compacted at harvest, therefore when it is loosened by weather it increases mixing of nutrients which is beneficial. Ploughing reduces risk of crop disease, pests and weeds. In contrast, no-till increases area capability and reduces overall costs such as fuel and machinery (Soane et al., 2012). Other limited and benefit of ploughing and no-till present in table 1. Table1. Agronomic advantages and disadvantages of No-till and ploughing No-till Ploughing Advantages Disadvantages Advantages Disadvantages Reduce run-off, soil erosion and cost. Increase soil fertility. Increase area capability reduction of compaction below plough furrow Not suitable for controlling weeds, pest. Reduce grains yields. crop residue Remain on the soil surface Crop establishment problems during very wet and very dry. reduced nitrogen availability for yield Completely buries weeds and crop residue. Increase mixing of nutrients when loosened by weather Reduced weeds ,crop diseases and pest Suitable for preparing a seedbed after grass. High cost (fuel and machinery). Increased CO 2 emission. Extreme looseness to depth of ploughing. High sensitivity to re-compaction of topsoil. Pest management Crop plants are attacked by many pests that affect plant survival, growth, and reproduction and as a result influence crop yield. Approximately 22% of the total area of wheat in the UK is affected by slugs without pesticides, Calculated that total annual cost to the UK industry from not controlling slugs in oilseed rape and wheat is approximately à £43.5 million. (Nicholls, 2013). Pests can cause crop-damaging by reducing rates of germination, feeding on seeds, roots, stem and leaves which reduce yields. In crop growth stages, pests can reduce yield potential of the harvest and Reduces crops ability to compensate for damage caused later in development and cause harm to crops near their harvest by reduces yield and quality. (Oerke, 2006; Damalas and Eleftherohorinos, 2011) For example, two different aphid detriment in cereals crops in the UK because they transmit barley yellow dwarf luteovirus and Grain aphid Sitobion avenae. (Nicholls, 2013) Despite these commonly acknowledged risks, pesticides do improve agricultural productivity. Pesticides can be considered as an economic, labor-saving, and efficient tool for pest management and can do improve agricultural productivity (Campbell,1976), such as Acetamiprid , Azadirachtin , Bifenthrin , Carbaryl for controlling insects but these benefits often go unnoticed by the general public. Pesticides are widely used in the agricultural production hence, increasing amounts of pesticides must be applied at rising costs to maintain sufficient control. This increasing has led to integrated pest management (IPM) programs which reduce pest numbers to an acceptable threshold (Jain and Bhargava, 2007). Push-pull strategies were conceived as a strategy for insect pest management (IPM) by Pyke et al. The push-pull technology is a strategy for controlling agricultural pests by using propulsive (push) while luring them toward an attractive source (pull) plants and trap them. This method can maximise the efficacy of behavior-manipulating stimuli through the additive and synergistic effects of integrating their use. Also can reduce pesticide input (Cook et al., 2006). The other method that can effect on pests is no-till. It seems pest under no-till method decreases dramatically because of increased numbers of predators. For example, it reduces springtails (Onychiurus spp.) that cause damage in shoot and root of the sugar beet (Soane et al., 2012).However, the preservation of crop residues in wet conditions tends to increase slug population, and this can lead to damage to young seedlings in winter-sown Wheat and barley (Jordan et al., 1997).Using molluscicides may control slug population, but it will still increase production costs and affect beneficial soil biota (abid.) Soil management Soil is the product of a complex set of interacting processes and cycles (Fitzpatrick, 1991) Plants need a network of pore spaces to assistance gas exchange such as oxygen and carbon dioxide. Also water movement and nutrient uptake. Over time if the soil environment under intensive agricultural production was disturbed, the ability of the soil to maintain these conditions is compromised (Gerrard, 2000). So Preservation and improvement of soil quality are important in agricultural productivity and environmental quality. Soil management practice which consideration all operations practices, and treatments used to protect the soil organic matter, soil structure, and the maintenance of a thriving soil microbial population. (Johnston and Fellow, 2005) In central Great Plains, soil erosion and drought are the main problems associated with grain production. No- till is a good system for reducing soil erosion and maximise soil water conservation. (Fenster and Peterson, 1979) In the UK using no-till after ploughing led to lower yields because of imperfect drainage and weak structure of soils during wet winter however all over the UK, good internal drainage was considered a pre-requisite for reliable success with no-till as discovered in the Germany (Ehlers and Claupein, 1994). No-till, can also increase biological activity such as earthworms and improve stable root channels this can develop greater water permeability (Soane et al., 2012). Under no-till, it seems, soil nutrients such as P and K increased dramatically near soil surface because of this microbiological activity. (Ehlers and Claupein, 1994). Also no-till it seems not suitable for sandy or drained soils. In Netherland, under the sandy soil, no-till decreased root penetration and yield such as root crop (Soane et al., 2012). Weeds Management Weeds have many attributes undesirable to crop producers and cause the adverse effect on their yield. There are limited reports on the inhibitory effects of weeds on crop plants (Bhowmik Doll, 1992).Wheat (Triticum aestivum L.) is the most important cereal in the world. It has been estimated that globally yield reduction in wheat due to weeds is 13.1% (Oerke et al., 1994). Weeds compete with the crop plants for sunlight, water, mineral nutrients and occupying a space, which would reduce the plant growth and this led to reducing crop yields, quality and harvesting efficiency. (Wright et al., 2001) Water requirement for the growth of weeds is primarily of interest from the standpoint of competition with the crop plant for the available moisture (Gibson, 2000). Weeds provide a host for insects, nematodes and certain plant pathogens such as fungi. For instance Fusarium species pathogenic to winter wheat have been isolated from common broad-leaved weeds. (Jenkinson Parry, 1994). Weed management strategies attempt to eliminate or limit the deleterious effects of weeds when growing with crop plants and decrease weeds ability to reduce yield. (Hager et al., 2003) The basic of all Weed control methods is prevention. In few years the concept of prevention is not relevant anymore because of the availability of effective herbicides and mechanical control measures. These controlling tools have led to control weeds even after they have become established. (Walker 1995). Herbicides may influence disease development via direct effects on the pathogens (Rodriguez-Kabana et al. 1966) or by altering plant resistance to pathogens (Dann et al. 1999; Levene et al. 1998) for example Broad-leaved weeds in winter wheat can be controlled by herbicides applied before or after wheat emergence in autumn or in spring. In Table 2 we mentioned a few Common herbicides used to control weeds In recent years using Herbicides for controlling weed decreased because using herbicides may damage the crop. Also can get mixed with air, water and soil and kill other unwanted plant pests.So we must use other methods for controlling weeds without much dependence on chemicals like fertilisers and herbicides which have unpredictable harmful effects on the environment and human health. ( Varshney et al., 2012) Crop rotation is often identified as a valuable component of weed management for example Downy brome (Bromus tectorum L.) density remained relatively constant when winter wheat (Triticum aestivum L.) was rotated with oilseed rape (Blackshaw 1994a). (Abid.) A cover crop is another method for managing weeds. They contribute organic matter to the soil, improve soil structure, and they can suppress weeds. Cover crops could permit reduction of herbicide inputs and a shift toward entire post-emergence herbicide programs for many crops. The early weed suppression provided by cover crop residue allow plants to become established before weed emergence. (Upadhyaya, and Blackshaw 2007) Table 2. Common herbicides used to control weeds. Herbicide Mode of action Weeds controlled Versatil Simazine Buster Terbuthylazine Absorbed by leaves, stems and roots. Absorbed only through roots of germinating plants Systemic contact herbicide (via the leaf) Absorbed through roots and leaves Controls thistles, yarrow, clovers and many difficult flat weeds Prevents the emergence of a wide range of grasses and weeds. Broadleaved weeds and clovers. Provides short-term weed control Controls a wide range of annual and perennial grasses and weeds Disease management Wheat, its an important food resource which approximately contains 40% of the worlds population (Bockus, et al., 2010) annually global yield losses because of wheat diseases are estimated to be 20% in the field or the storage. (Abid.) The disease can terminate entire trees in orchards or plantations Such as Phytophthora root or collar rot, and some can destroy before or after harvested product. For instance, the smuts, which destroy before or after the harvesting the cereal grains (all postharvest rots of fruits and vegetables) (James, 1974) Each year in the UK the percentage of yield decreases because of disease diverse. The highest yield loss was between 1991, 1993 and 1998, and lowest was in 1995.Eyespot compared to other diseases caused greater yield losses. The second most significant disease was Powdery mildew in seven of the ten years but in 1990 demonstrate the greater losses than any other illness. The national economic impact of these yield losses varied depending on annual production figures and the price per tonne. (Hardwick et al., 2001) Each of these can infect wheat and cause disease throughout the growing season. It is important to deliver consistently, high yields of high-quality grain thus controlling of cereal diseases is an important component of successful crop management. Recognition of the disease and an understanding of the pathogens purpose are the first step for a successful disease control. Therefore disease management is necessary. Many strategies, tactics and techniques in disease management used in advanced (prevention) which applied before infection for protecting plant from disease and after infection controlled by heat or chemical treatment as bulbs, corms and fungicide (OC Maloy ,2005) Plant disease management is a factor that has positive and negative externalities on the yield. The adverse effect includes environmental pollution; toxin remains in the soil, ecological damage, resource depletion, reduced disease management efficiency and costs associated with meeting minimum chemical residues on crop harvest. And positive effects can benefits to disease management in neighbouring farms, can reduce evolutionary potential of pathogens, and ensure social stability and safety (HE et al., 2016) Farmers only pay the direct costs associated with plant disease management; they strongly select strategies that generate the best immediate economic returns while largely discounting potential negative impacts on the environment. To date, some highly effective disease management strategies have been used without sufficient regard to their long-term ecological effects such as Fungicide. Fungicide was used on more than 93% of crops throughout the word for about ten years. In 1996 and 1998, fungicide usage reached 98%.it seems farmers do not value disease resistance but apply fungicides widely. Disease-induced losses are still substantial, despite the heavy reliance on fungicides (Stevens et al., 1997). During the 10-year using Fungicide has increased but so have septoria leaf blotch and eyespot. It has been suggested that national disease levels and yield losses were influenced more by season than fungicide usage. (Hardwick et al. 2000). Priestley Bayles (1980)found, from a postal survey of NIAB Fellows, that disease was seen more frequently in fungicide-treated (such as benomyl, carbendazim) than in untreated fields. Cook King (1984) indicated that final disease levels were often similar in treated and untreated crops. For improving yield, it would be better for plant disease management to focus on increasing crop productivity, using fewer fungicides, reducing food contamination by microbial toxins, Change the philosophy of plant disease management to focus on pathogens (or insect vectors) to managing host plants for achieving high productivity yield and Considerations in agricultural productivity and crop health. 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