Potassium K is the most aboundant nutrient in the fruit where it affects positively the size, firmness, skin color, TSS, acidity, juiciness and aroma. Because pear trees generally show higher absorption and transport of Ca to the fruit than apple Marcelle, , the negative effect of K on quality of stored pear fruits is less frequent than in apple fruits. Potassium concentration in fruits is stable during the growing season ranging between 0. Due to little plant requirement, deficiency is unlikely to occur. Phosphorous concentration decreases toward the interior of the fruit Faust et al.
Deficiencies in plant tissues are common in acid soils, particularly where the soil is high in plant-available K. In pear fruits, Mg ranges between and mg kg dw -1 depending on fruit stage Table 2. The Mg accumulates linearly at a slow rate throughout the growing season Tagliavini et al.
Calcium differs from other nutrients because it is transferred to fleshy fruit in amounts much smaller than leaves Saure, Despite Ca sufficiency in most orchard soils, localized Cadeficiency- related disorders such as bitter pit in apple and pear fruit may become a serious problem. The dynamics and factors affecting Ca transfer to the fruit are still not fully understood Saure, Some authors reported that Ca uptake by the fruit occurs only during the first part of fruit growth Faust, or linearly until harvest Zavalloni et al.
Regardless the dynamics of fruit Ca-accumulation, Ca has a low vascular mobility. Consequentely, its uptake and partitioning to the fruits is most consistent in the first stage of fruit development. For this reason it is essential to promote Ca uptake early in the season, approximately within the first days after blooming Shear; Faust , ; Schlegel; Schoenherr, Calcium is involved in cell physiology, the integrity and stability of cell membranes, organization of the cell wall, and tolerance against fungal and bacterial infections Bateman ; Lumsden, , because Ca is associatedto polygalacturonic acid as exchangeable Ca pectate Marschner, The Ca pectate is considered to be the Ca fraction best associated with fruit suitability for storage.
On the other hand, high Ca concentration inhibits the activity of polygalacturonase and delays ripening of fruits Marschner, Optimum fruit Ca concentration promotes fruit firmness, increases disease tolerance and reduces storage related disorders. Fruit Ca accumulation is higher at the beginning of fruit development during fruit cytochinesis , reaches mg Ca kg dw - 1 , and decreases thereafter throughout the season until harvest, ranging from to mg Ca kg dw -1 with average values of mg Ca kg dw -1 Table 2.
Many physiological disorders and susceptibility to pre- and post-harvest fungal decay are related to the Ca status of pear fruits. Considering the low mobility of Ca and the little permeability of the fruit cuticle during most phenological stages, foliar and soil applications of Ca fertilizers often show a low effectiveness in promoting Ca accumulation in fruit in both controlled and field studies on calcareous soils in Northern Italy Toselli et al. Under such environmental conditions, largest effects were obtained with early bloom soil applications.
Foliar Ca applications have been reported to be effective in sandy, low in organic matter, soils of the US Pacific Northwest Sugar et al. Other variables may affect fruit Ca composition such as genotype and rootstock. On the other hand it was reported Sugar et al. Hence, where fruits occur to be sparse, the fruit N:Ca ratio is likely to be relatively high and the fruit to be more susceptible to defects Sugar et al.
In mature fruits, Ca concentration increases towards the core Saure, ; the peel is approximately 4 times higher in Ca than the pulp. This is why ammonium fertilizers should be applied at least 40 days after blooming Faust, , and split-applied at 3 occasions such as fruit set, fruit cell enlargement and end of summer immediately before havest or post-harvest.
The N can also be dissolved in fertigation water and applied at regular intervals from flower petal drop to harvest.
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Among micronutrients, boron B is one of the most critical in pear orchards. Indeed, it is believed that pear trees have a high B requirement Wojcik; Wojcik, Typical symptoms of B deficiency are the reduction of fruit set and yielding, as well as small, deformed, cracked and corked fruits Table 1. Optimum fruit B concentration at harvest may range between 16 and 20 mg B kg -1 dw -1 Raese, An adequate B concentration promotes Ca mobility, regulates flowering and fruit set, and contributes to a stable fruit production. Since B is mobile in the trees of the Rosacee family Brown et al.
Despite the abundance of iron Fe in soils, Fe acquisition by fruit crops is often impaired, compromising fruit yield and quality. Iron concentration in pear fruits is low, ranging from 20 to 35 mg Fe kg dw -1 Table 2. Manganese Mn concentration in pear fruits is very low ranging from 2 to 4 mg Mn kg dw -1 Table 2. The Mn deficiency can severely reduce fruit yield and shows symptoms similar to Fe chlorosis; it may occur in alcaline and calcareous soils, but also in soils with a high content of organic matter Marschner, Pear is considered to be a Zn sensitive species Shear; Faust, At low level of soil Zn availability, plant growth is impaired, and fruit set and yields are limited.
Under such conditions, fruits are small, deformed and sour, and ripen early. Where Zn deficiency occurs, pre-bloom Zn sprays are successful to increase Zn concentration in flowers while post-bloom Zn sprays are effective in promoting leaf and fruit Zn levels. Copper concentration in pear fruits is low, ranging from 5 to 13 mg Cu kg dw -1 Table 2.
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Pear is one of the crops most subjected to Cu sprays for controlling diseases in low impact agricultural systems Toselli et al. As a result, soil Cu accumulation is frequent and may lead to Cu toxicity symptoms. Copper uptake by roots and plant susceptibility to Cu toxicity depend on soil texture, pH, hydrous oxide content, and clay mineralogy Brun et al.
High soil Cu concentration was found to reduce the photosynthetic activity of pear trees, indirectly by inhibiting the uptake of Mn and Zn -. Copper toxicity is common in sandy, low pH soils; in loam to silt loam soils high in organic matter, the toxicity threshold exceeds mg Cu kg -1 Toselli et al.
All other factors but N being equal, the higher the N availability in the soil and the higher the N uptake, the higher will be the vegetative growth of apple trees. Shoot growth responds more to enhanced soil N availability than root growth and crop productivity. Annual N uptake data based on estimates of tree growth crop productivity and mineral nutrient concentration of tree organs suggest that N removals from soil are in the range of 60 to 75 kg N ha -1 yr -1 , depending on yields Tagliavini ; Scandellari, The N allocation to fruits for yields from 40 to 60 t FW ha -1 are often in the range 20 to 30 kg N ha -1 Table 4.
From growth resumption in spring and until two weeks from full bloom, apple trees use mainly N derived from remobilization, while root N uptake becomes the main N source thereafter. As recently indicated in Zanotelli et al. Foliar-applied N is absorbed rapidly with higher efficiency and therefore represents an interesting mean to supplement soil N supply Toselli et al.
Apple nutrient concentration depends on cultivars and years, being often in the range of ppm. Excessive soil N availability causes luxury consumption and depresses apple fruit color in redcolored varieties mainly because of increased shading caused by excessive shoot growth; it can moreover depress shoot hardening lignification , making them more susceptible to winter frost damages.
Because N is highly mobile in the soil, the higher is the N supply the higher the risks of N losses by leaching or by volatilization. In mature and highly productive apple orchards, K is often the nutrient absorbed at highest rates. Apple fruit, in fact, is a strong sink for K and it normally contains significant amounts of K, with concentration ranging from 0. Zavalloni et al. Therefore annual K uptake strongly depends on fruit yields and can range from 80 to kg K ha -1 with yields ranging from 40 to 60 Mg fruit f.
Optimum sugar to acid ratio and fruit size are often reported in soils well endowed with K. Similarly to N, the highest rate of K uptake by apple trees occurs after cell division and lasts for at least 5 weeks Table 5 ; K uptake rates remain relatively high until fruit harvest. Due to its high phloem mobility, K allocation to fruit remains relatively stable from fruit set to fruit maturity Zavalloni et al. Main issues related with Ca uptake and partitioning as well as the physiological role of Ca in fruits have been discussed in details in the preceding section.
In apple, Ca is involved in the development of physiological fruit disorders such as bitter pit especially in post-harvest. On the other hand, increased fruit Ca content by pre-harvest Ca spray applications reduced the infection by Gloeosporium, an internal breakdown and softening of apples. Post-harvest CaCl 2 applications are also known to reduce the decay caused by Penicillium and other fungal diseases. Soils in the main apple districts worldwide are often well endowed with Ca and Ca-related disorders are the consequence of internal problems of proper fruit Ca allocation rather than in Ca uptake.
Total Ca uptake by apple trees can be comparable N; for instance, Scandellari et al. Several susceptible apple varieties e. When fruits reach large sizes e. Thus, grapevine berries, must and wine quality are affected by the addition of nutrients, principally by N, that regulate the synthesis of some important compounds, such as anthocyanins, which are responsible for coloring of the must and the wine. Nitrogen excess may increase the pulp to peel ratio, diluting the concentration of anthocyanins and promoting the migration of anthocyanins from berries to the growing plant organs.
In apple and pear fruit, Ca and K are important for fruit quality and storage. Nitrogen availability should be monitored to avoid excessive N uptake that may decrease fruit skin color and storability. Data are per single bourse shoot and are the average of Golden del.
Foliar fertilization to control iron chlorosis in pear Pyrus communis L. Plant and Soil , Dordrecht, v.
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Relation between calcium content and nature of pectic substances in bean hypocotyls of different ages to susceptibility to an isolate of rhizoctonia solani. BELL, S. Implications of nitrogen nutrition for grapes, fermentation and wine. Effect of nitrogen fertilization on growth, canopy density, and yield of Vitis vinifera L. Cabernet Sauvignon. American Journal of Enology and Viticulture , Davis, v. Effects of nitrogen fertilization and graftiong on the composition of must and wine from Merlot grapes,particularly on the presence of ethyl carbamate. Influence of nitrogen on yeast and fermentation of grapes.
Effects of nitrogen, potassium fertilizer, and clusters per vine on yield and anthocyanin content in Cabernet Sauvignon grape, Suranaree. Journal of Science and Technology , Peshawar, v. Occurrence of sugar alcohols determines boron toxicity symptoms of ornamental species. BRUN, L. Evaluation of copperavailability to plants in copper-contaminated vineyard soils.
Environmental Pollution , Barking, v. Application of nitrogen sources on grapevines and effect on yield and must composition. Revista Brasileira de Fruticultura , Jaboticabal, v. Contribution of nitrogen from agricultural residues of rye to Niagara Rosada grape nutrition.
Scientia Horticulturae , Amsterdam, v. Concentrazione di potassio nelle bacche e valori di pH e zuccheri nel mosto della cv Cabernet Sauvignon innestata su diversi portinnesti nel Sud del Brasile. Acta-Italus Hortus , Sardegna,v. Mobility of copper and zinc fractions in fungicide-amended vineyard sandy soils.
Archives of Agronomy and Soil Science , Berlin, v. Nutrients release during the decomposition of mowed perennial ryegrass and white clover and its contribution to nitrogen nutrition of grapevine. As rice crop will remove 0. These recommendations take into account the said removal factor. These recommendations are based on the assumption that the straw will be recycled into the soil after the harvest.
However, if the straw is removed from the field, K 2 O requirements for a yield of 6. K fertilizer added at this time probably has little benefit for the current rice crop, but will remain in the soil for the future crops. Silt and sandy loam soils have a very low buffering capacity and soil test K can decline rapidly if K fertilizer is omitted for several consecutive crops.
It is recommended to apply all potassium rates by broadcasting and incorporating before planting in both water-seeded and dry-seeded rice. If potassium fertilizers could not be applied pre-plant, they can be applied before establishing the permanent flood. Split application is also common in some areas. It gradually releases available nitrogen to the rice plant. This controlled release procedure, prevents nitrogen loses and increases the uptake efficiency by the plant. Precision-timed foliar sprays are a fast-acting and effective method for treating nutrient deficiencies.
Haifa Bonus , a high-K foliar fertilizer contains a special adjuvant, which improves the adhesion of the fertilizer to the leaf surface and creates fertilizer clusters that release nutrients over a prolonged period of time. The fully water soluble high K and chloride-free fertilizer, is suitable for rice crop wherever it is grown. Add this solution to the spray tank when it is half full with water. When tank-mixing with crop-protection agents, addition of wetting agents is not necessary.
To ensure inter-compatibility of the two or more tank-mix components, a small-scale spray test should be performed on few rice plans several days prior to the commercial application. The exact number of sprays and their concentrations should be decided according to local balance between the prices of the rice, wages and fertilizers.
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The three optimal spray timings are:. As shown in chapter 2. In the dry-seeded system, soil-applied zinc should be broadcast and shallow incorporated no more than 2. It can be tank-mixed with propanil, if the propanil is needed, for weed control or with any other pesticide. All plants require 17 elements to complete their life cycle, and an additional four elements have been identified as essential for some plants Havlin et al. The bulk of the soil solid fraction is constituted by soil minerals, which exert significant direct and indirect influences on the supply and availability of most nutrient elements.
The main processes involved in the release and fixation of nutrient elements in soils include dissolution-precipitation and adsorption-desorption. We will discuss these processes and how they impact macronutrients and micronutrients. Soil parent material has a significant direct influence on the nutrient element contents of the soil; this influence is more pronounced in young soils and diminishes somewhat with increasing soil age and soil weathering.
In order to better understand the effect of soil parent materials on the soil elemental composition, it is useful to review the mineralogical composition of common rocks that make up the soil parent material Table 1. Primary minerals form at elevated temperatures from cooling magma during the original solidification of rock or during metamorphism, and they are usually derived from igneous and metamorphic rocks in soil Lapidus In most soils, feldspars, micas, and quartz are the main primary mineral constituents, and pyroxenes and hornblendes are present in smaller amounts.
Primary minerals — including K-feldspars orthoclase, sanidine, and microcline , micas muscovite, biotite, and phlogopite , and clay-size micas illite — are widely distributed in most soil types, except in highly weathered and sandy soils.
Significant amounts of Ca, Na, and Si and smaller amounts of Cu and Mn are also present in the feldspars. Micas and illite are the most important source of K in many soils, and they also contain Mg, Fe, Ca, Na, Si, and a number of micronutrients. Amphiboles and pyroxenes are vital reservoirs of Mg, Fe, Ca, Si, and most of the micronutrients.
Carbonate minerals, including those derived from soil parent material and those formed in soil through pedogenic processes, serve as both a source and a sink for Ca and Mg in soils. The physical, chemical, and biological weathering of primary minerals releases a number of nutrient elements into the soil solution.
Weathering rates and pathways of primary minerals are highly variable and depend on several factors, including mineral properties and climatic conditions. Although the weathering rates of primary minerals for certain elements may not be fast enough to meet plant nutrient requirements on a short-term basis, particularly in managed cropping systems, mineral weathering is an important and long-term source of several geochemically derived nutrients.
The nutrient supply capacity of a soil through weathering of primary minerals diminishes as the extent of soil weathering increases. Adsorption reactions involving minerals are often more important in controlling plant nutrient element availability than the release of nutrient elements by mineral weathering. Phyllosilicates with a permanent charge e. On the other hand, variable charge minerals e. Important reactions relevant to specific nutrient elements are discussed below. All rights reserved. In soils, N applied through fertilizers and mineralized N from organic matter mostly ends up in the NO 3 - form.
Due to the limited anion exchange capacity of most soils, leaching of applied N in the form of NO 3 - ions is a common water quality problem, particularly in agricultural regions. It also represents an important economic inefficiency, because producers apply excessive amounts of fertilizer to compensate for the leaching. Highly weathered soils, such as oxisols and ultisols , are the exception. The mineralogy of oxisols and ultisols is dominated by minerals with variable surface charge, mainly kaolinite and Fe and Al oxides, which provide these soils with the capacity to retain large amounts of NO 3 -N, particularly in the subsoil horizons.
For example, Lehmann et al. The anion exchange capacity of the Australian oxisols was large, with values as high as 41 mmol c kg The adsorbed nitrate is too deep and is likely inaccessible to most field crops, nevertheless, it does not leach into groundwater. In contrast to highly weathered oxisols and ultisols with variable charge minerals, soils in temperate regions generally have permanent charge minerals e.
Indeed, a large proportion of the NH 4 -N is retained in the interlayers of phyllosilicates and is not readily exchangeable, causing it to be referred to as fixed NH 4. The process of NH 4 -fixation is similar to that of K-fixation, which is demonstrated in Figure 3. NH 4 -fixation generally increases with the increasing amount of layer charge in the phyllosilicates, and the fixation is greater in minerals with charge originating in the tetrahedral sheet than in minerals with charge originating in the octahedral sheet.
The reverse reaction results in release of the fixed cations. The concentration of P in soil water is generally very low Adsorption reactions of phosphate ions on mineral surfaces predominantly involve the formation of inner-sphere complexes on the variable charge surfaces of Fe and Al oxides and kaolinite. An example is provided in Figure 2, where phosphate ions are adsorbed on goethite surfaces by forming monodentate and bidentate bonds. Phosphate ions adsorbed by such processes are only slowly available to plants.
Phosphate is also known to be sorbed by calcite in calcareous soils, with the sorption occurring via the replacement of CO 3 2- on the calcite surfaces. In strongly acidic soils, the precipitation reactions involving soluble phosphate from fertilizer results in the formation of insoluble Al, Fe, or Mn phosphates. In contrast, in calcareous soils, insoluble Ca phosphates are formed, which are gradually converted to insoluble carbonated hydroxyapatite.
General chemical reactions of phosphate in acidic and calcareous soils are shown below:. Potassium: Among the essential elements, K is usually the most abundant in soils. Total K in soils varies from 0. Potassium is released following the weathering or dissolution of K minerals in soils, as shown in the following examples:. Of these two reactions, K release by the weathering of mica is generally more important in supplying K to plants in unfertilized soils. Phyllosilicates retain and release K for plants from non-exchangeable or fixed i. Potassium ions present on the exchange sites are adsorbed by outer-sphere complexation and are readily available for plant uptake Figure 1.
On the other hand, illite, vermiculite, and interstratified clay minerals release fixed or non-exchangeable K from interlayer sites through cation exchange and diffusion processes at slower rates than the exchangeable K Figure 3. The non-exchangeable or fixed K can be potentially released back into soil solution if the solution K concentration falls below a certain threshold value.
Sulfur is taken up by plants as sulfate SO 4 2- , and this is the most common inorganic S form in soils. Fe and Al oxides and kaolinite provide adsorption sites for SO 4 2- in most soils, even if these minerals are present in small amounts. Sulfate ions are believed to be adsorbed by these minerals by forming both inner- and outer-sphere complexes. Sulfide S - , S 2- minerals form under reducing environments e. Copper, Zn, and Ni are adsorbed by Fe and Al oxides by forming inner-sphere complexes at low solution concentrations. In alkaline soils, adsorption of Zn on calcite and co-precipitation of Cu in calcite may also occur.
Limited evidence suggests that B species i. Similarly, MoO 4 2- is strongly adsorbed by metal oxides.
In certain soil environments, such as those with restricted leaching or those with low-lying areas in arid climates, Cl may exist in precipitated mineral forms, such as NaCl, CaCl 2 , and MgCl 2. Brady, N. The Nature and Properties of Soil, 14th ed.
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