1、Horticultural Science,YAO Qing 020-85286902(O),BILINGUAL COURSE,Contents,Introduction to Horticulture (2h)Classification of Horticultural Crops (4h)Anatomy of Horticultural Crops (6h)Growth Environment of Horticultural Crops (6h)Plant Physiology of Horticultural Crops (4h)Propagation of Horticultur
2、al Crops (2h)Mineral Nutrients and Fertilization of Horticultural Crops (4h)Organic Horticultural Practice (4h),Chapter 4,Growth Environment of Horticultural Crops,Glossary,Chemical Constitutes in Plants,Contents,Soil & Plant NutrientsSoil properties: Texture, Structure, pH, Oxy./Red., Aeration, Org
3、anicPlant nutrients: Essential elements, Nutrient deficiency, Fertilizer, Fertilizer application Mulches,Contents (conted.),Nutrient requirements of Horticultural CropsFruit Trees: Vegetable plants: Fertilization of Horticultural Crops,Soil properties,Soil space consists three phases: solid phase, l
4、iquid phase and gaseous phase.,Clay particles:d0.002mm Silt particles:d=0.002-0.02mm Sand particles:d=0.02-2mm,Soil properties,粘粒、粉粒、砂粒,Soil properties,砂土 壤土 粘土,Soil particles can be divided into three categories: clay particles, silt particles, and sand particles.,Soil texture is determined by the
5、relative amount of the different-size soil particles, e.g. the proportions of clay particles, silt particles, and sand particles.,Soil properties,Plant nutrients,Over 90% of a plants substance is made up from the hydrogen, carbon and oxygen it takes from the air and water. Plants need other elements
6、 in smaller quantities to sustain life. These it gets from the soil, taking them in via its roots. The plant can only absorb these elements from the soil when they can be dissolved in water, and that is almost always when they are in the form of simple salts such as nitrates and phosphates.,There ar
7、e 16 essential nutrients required for plant growth: carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), and chlorine (Cl). Of these 17, all except c
8、arbon, hydrogen, and oxygen are derived from the soil. When the soil cannot supply the level of nutrient required for adequate growth, supplemental fertilizer applications become necessary.,Plant nutrients,Plant nutrients,Plant nutrients,Standard adequacy ranges for foliar nutrient contents of some
9、essential elements for tree fruits (after Shear and Faust, 1980),Standard adequacy ranges for foliar nutrient contents of some essential elements for tree fruits (after Shear and Faust, 1980),Nutrient mobility in plant,Nutrient elements in stone fruit,Anatomy of Plant Roots,Roots take up nutrient el
10、ements mainly in the root hair zone.,Plants take up water and 13 mineral nutrients, in the form of soluble salts, via roots.,In soil, nitrogen can exist in a soil organic form, or as an ammonium ion (NH4+), nitrite ion (NO2-), or nitrate ion (NO3-). In most soils, more than 90 percent of the nitroge
11、n is in the soil in organic form, tied up in living organisms and decaying matter. Under natural conditions, this form breaks down slowly into ammonium ions.,N in Soil,degrades,The next step in the conversion of soil nitrogen, from the ammonium form to the nitrate form, occurs in two distinct steps
12、involving two groups of bacteria. The first step is from ammonium to nitrite and the second step from nitrite to nitrate.,nitrobacteria,Nitrogen exists in many different forms in fruit trees; each has a separate function and each exists in widely varying amounts. Most nitrogen in a growing plant is
13、found in proteins and nucleic acids. An estimated 10 percent exists as nucleic acids and 80 to 85 percent as proteins. Proteins function mainly as enzymes for such plant processes as nutrient uptake, photosynthesis, carbohydrate movement, and cell division. The nucleic acids, in RNA and DNA molecule
14、s, constitute the genetic material of plants.,N Forms in Tree,N is vital to growth, development, and reproduction of fruit tree.,Nitrogen is needed most where plant growth is actively occurring, especially in those processes involving cell division. Therefore, when various plant parts are analyzed,
15、nitrogen content tends to be high in growing shoot tips, growing leaves, young fruits, and seeds. It is also fairly high in mature leaves, since photosynthesis requires a large quantity of enzymes. It is important to note that nitrogen is NOT particularly high in woody tissues or in the flesh of fru
16、it tissues near harvest.,Where does N distribute in fruit tree?,Fruits can be expanding rapidly near harvest, but this is mostly a function of cell expansion from water uptake, which does not require as much enzymatic activity as the cell division stage of growth. Therefore, large quantities of nitr
17、ogen applied to trees near harvest would not be expected to directly affect fruit size.,P in Soil,(1) Phosphorus readily reacts with numerous elements in soil to form insoluble compounds. (2) These reactions are pH dependent.,Usually, a pH of 6 is considered optimum for phosphorus availability to pl
18、ants. Even at this level, only a small amount of the total phosphorus exists in a soluble form that is readily available to plants.,Three principal forms of phosphorus in plants are: in RNA and DNA molecules, in cell membranes (phosphorus lipid), and in ATP molecules. ATP is a molecule that stores t
19、he energy from photosynthesis and the breakdown of sugars. It is very mobile and can therefore be trans-ported to sites requiring a great deal of energy such as expanding shoots, leaves, and fruits. When phosphorus is deficient, this last form is particularly depleted, so developing shoots and fruit
20、s are especially sensitive.,P Forms in Tree,Only a small proportion of these potassium ions is actually in solution at any given time; the remainder is adsorbed on negatively charged clay or humus particles. These different forms are in equilibrium with each other. Therefore, as potassium ions in so
21、lution are depleted by plant uptake, they are quickly replaced by adsorbed ions, which are then gradually replaced by weathering of more unavailable forms. This provides a tremendous storage of potassium so that trees can usually be amply and continuously supplied without adding any fertilizer.,K in
22、 Soil,Potassium exists in large quantities in both leaf and fruit tissues. Although one of its functions is to activate enzymes, most potassium ions are not tied up in complex molecules, but are used in the ionic form by cells as a solute to help maintain turgor. Potassium accumulates substantially
23、in fruit tissues and appears to have a role there in fruit growth, since potassium-deficient trees have been shown to have greatly reduced fruit sizes. On low potassium soils, a heavy crop load can induce deficiency symptoms.,K in Tree,Clay particles: Silt particles: Sand particles: Soil aggregates:
24、 Nitrogen: Phosphorus: Potassium: Calcium: Magnesium: Sulfur:,Soil structure: Soil profile: Soil texture: Macro-element: Trace element: Soil erosion: Minor element: Deficient symptom: Nutrient deficiency: Water holding capacity:,Fruit growers have three main tools to use in evaluating the mineral nu
25、trition status of their plantings. These are:Examine visual symptoms exhibited by leaves, stems, and fruit;Analyzing leaf tissue and;Testing the soil.Used together properly these are powerful tools that can be used to prevent nutrient deficiencies or toxicities as well as to assess current fertility
26、 management practices.,Diagnosing the mineral nutrition status of fruit crops,N-deficient apple flowers,Nitrogen deficiency,N deficiency in peach, showing characteristic reddening of stem and leaf midrib.,N-deficient apple leaf,Nitrogen deficiency,Severe nitrogen deficiency in peach. Leaves are very
27、 chlorotic and have developed typical brown spots.,N-deficient citrus leaf,Nitrogen deficiency,N content increases.,N & Mg deficient apple trees,Nitrogen & Magnesium deficiency,K deficient,Potassium deficiency,Potassium deficiency (right) compared with normal peach shoots (left). Note pale color and
28、 leaf-rolling symptoms.,Calcium deficiency,Ca deficient apple fruit,Mg deficient leaves,Magnesium deficiency,Magnesium deficiency,Mg deficient leaves,Magnesium deficiency in peach leaves, showing the typical, inverted, green “V“ around the midrib. Healthy leaf is far right.,Magnesium deficiency,S de
29、ficient,Sulfur deficiency,Fe deficient leaf& trees,Iron deficiency,Iron deficiency in peach. Veins remain green while the rest of the leaf turns chlorotic.,Iron deficiency,Increasing iron deficiency (right to left) in peach. With severe deficiency the leaf turns almost white.,Cu deficient leaf & tre
30、e,Copper deficiency,Midsummer copper deficiency symptoms in plum showing small, chlorotic, and malformed young leaves. Older leaves are more normal in size and color.,Copper deficiency,Zinc deficiency,Zn deficient citrus leaf,Zinc deficiency,Zn deficient apple leaf,Zinc deficiency (left) compared to
31、 healthy plum shoot (right). The most typical symptom: small, pointed leaves.,Zinc deficiency in a plum tree. Rosetting on shoots occurs due to shortened internodes and small, pointed leaves.,Zinc deficiency,Zinc deficiency (right) compared with healthy peach shoot (left).,Boron deficiency,B deficie
32、nt citrus fruit & leaf,B-deficient damage of fruit & bark,Boron deficiency,B toxicity on citrus leaf,Boron toxicity,Molybdenum deficiency,Mo-deficient citrus leaf,Manganese deficiency symptoms in peach leaves, showing characteristic “herringbone“ pattern. Healthy leaf is upper left.,Manganese defici
33、ency,Proper fruit plant sampling for diagnostic plant analysis,Fertility status of apples in relation to nutrient content in leaves,Fertility status of strawberry in relation to nutrient content in leaves,1. Collect leaf samples during mid-July through August. 2. A single sample should not represent
34、 an area larger than 2 hectares (about 5 acres). 3. Include only one cultivar or strain in a sample and preferably only one rootstock type. 4. Mark or map each plant or area sampled for future resampling. 5. Select leaves from the periphery of trees at shoulder height or higher from the middle of th
35、e current seasons terminal shoots of about average vigor.,Leaf Sampling: Sampling ProcedureSamples should only be collected from plantings old enough to bear a commercial crop or where a nutritional problem is suspected.,6. Collect 10 leaves per tree from shoots randomly selected from all sides of t
36、he tree. Select leaves free of disease or damage (unless diagnosing a trouble spot). 7. 50 leaves per sample are sufficient unless leaves are small. Remove leaves with the petiole (use a downward pull). 8. For trouble spots, take a composite sample from five affected trees and five non-affected tree
37、s and label bags accordingly. 9. Contaminated samples (by soil, spray, or other residues that would interfere with analysis) should be cleaned with a nonionic detergent solution and rinsed with soft water (not tap water). Wash leaves ASAP and quickly (for one minute or less).,10. Dry leaves at 80oC
38、or air dry. Samples should not be stored in a location that is moist where mold or damage may occur. 11. Submit the dried sample to laboratory for analysis along with the following information: orchard name and location, date of sampling, soil type, cultivar, fertilizer practice, and special problem
39、s. Make sure the samples are labeled in a fashion that the corresponding location in orchard can be found easily.,Recommendations for fertilizing fruit and vegetable crops are based in part on soil test results. Soil testing provides information on lime and fertilizer needs prior to planting and is
40、particularly well calibrated for nutrients such as phosphorus, potassium, magnesium, calcium, sulfur, zinc, and boron. Soil testing prior to planting leads to more efficient nutrient management.,Soil Test for Horticultural Crops,Soil samples can be collected through much of the year, although fall (
41、September to December) or spring (February to April) are the best times. Fall sampling will often result in a faster return of results and recommendations.,Common soil sampling equipments,Soil core depth,Current soil-test interpretationsused for environmental horticulture crops,1. For established la
42、wns, sample the top 2 inches of soil only. 2. For areas to be tilled up for a new lawn, sample the top 4 inches of soil. 3. Sample problem areas and areas within shrubs or flowerbeds separate from other turf of lawn areas. 4. Sample front and back yards separately. 5. For lawn samples, do not sample
43、 under the dripline of trees. 6. Do not take samples close to driveways or streets, unless this is treated as a “problem area“, which would require a separate sample.,Lawns and Turfgrasses,1. Sample the top 8 or 12 inches of soil. 2. Take separate samples for each block or different flower variety.
44、3. For large fields, up to 30 soil core samples may be needed per sample.,Commercial Production of Field-Grown Flowers,Commercial Vegetable Fields,1. Sample the top 8 to 12 inches of soil.,1. Sample the top 12 to 18 inches of soil. 2. Take samples from dripline area under branch tips (or closer to t
45、runk for newly planted trees).,Tree Fruits,After all cores from one crop area are collected and placed in the bucket, crush the materials and mix the sample thoroughly. Allow the sample to air dry in an open space free from contamination. Spread the soil out to dry on newspapers. Do not dry the samp
46、le in an oven or at an abnormally high temperature.,Sample Preparation,Soil Organic Matter (SOM),This pie chart represents organic matter in soil before cultivation. After land has been cultivated for one or two decades, much of the active fraction is lost and stabilized organic matter makes up more
47、 than half of the soil organic matter.,Distribution of SOM in USA,1. Additions. When roots and leaves die, they become part of the soil organic matter. 2. Transformations. Soil organisms continually change organic compounds from one form to another. They consume plant residue and other organic matte
48、r, and then create by-products, wastes, and cell tissue. 3. Microbes feed plants. Some of the wastes released by soil organisms are nutrients that can be used by plants. Organisms release other compounds that affect plant growth. 4. Stabilization of organic matter. Eventually, soil organic compounds
49、 become stabilized and resistant to further changes.,The Changing Forms of SOM,What Does SOM Do? Nutrient cycling Increases the nutrient holding capacity of soil (CEC). Is a pool of nutrients for plants. Chelates (binds) nutrients, preventing them from becoming permanently unavailable to plants. Is
50、food for soil organisms from bacteria to worms. These organisms hold on to nutrients and release them in forms available to plants. Water dynamics Improves water infiltration. Decreases evaporation. Increases water holding capacity, especially in sandy soils. Soil structure Reduces crusting, especia
51、lly in fine-textured soils. Encourages root development. Improves aggregation, preventing erosion. Prevents compaction. Other effects of SOM Pesticides break down more quickly and can be “tied-up“ by organic matter (and clays). Dark, bare soil may warm more quickly than light-colored soils. Many of the effects of SOM are related to the activity of soil organisms as they use SOM. Plant residues and other organic material may support some diseases and pests, as well as predators and other beneficial organisms.,
