eChapters

Organic carbon present in soil can be very labile, labile or non-labile. This procedure measures the extent of lability of soil organic carbon through relative degree of oxidation by K₂Cr₂O₇.

Labile fractions of soil carbon (C) refer to the fraction of soil carbon that are easily altered by microbial activities. These fractions serve as sensitive indicators to changes in management induced soil quality and are grouped under active soil C pool. The method described by Weil et al. (2003)estimates changes in biologically active soil C using a dilute KMnO . This is an improvement over the method used by Blair et al (1995), where a very high concentration (0.333 M) of KMnO₄ was used.

This is one of the commonly used method to estimate organic carbon content in soil. In this wet digestion method, soil organic matter is oxidised with a mixture of K₂Cr₂O₇ and concentrated H₂SO₄ utilizing the heat of dilution of H₂SO₄. The unused K₂Cr₂O₇ is back titrated with ferrous sulphate or ferrous ammonium sulphate.

In dry combustion technique, the combustion of soil sample (about 250 mg and mm sieved) is carried out at high temperature (about 1000 ºC) through feeding in an inert boat in the electric furnace. The CO₂ produced from the oxidation of carbon present in the soil sample at high temperature is carried towards non dispersive infrared detector (NDIR) by a carrier gas where it is quantified and total carbon content is determined.

Wet sieving procedure separates soil into different size aggregates. However, for comparing the aggregate size distribution among management treatments and soil types, it is convenient to use indices. Mean weight diameter (MWD) and water stable aggregate percentage are some of the common indices used in aggregate stability studies.

Mean Weight Diameter (MWD)

This index was proposed by Van Bavel (1949) and is being used widely. The entire soil sample is passed through an 8 mm sieve prior to analysis and is subjected to wet sieving procedure as described before. The parameter which Van Bavel (1949) called the MWD is equal to the sum of the product of (a) the mean diameter (d ) of each size fraction and (b) the proportion of the total sample weight (w ) occurring in the corresponding size fraction. The summation is carried out over all ‘n’ size fraction including the one that passes through the finest sieve.

Thisprocedure estimates aggregatestabilitytoimpact ofraindropsand water erosion. Wet sieving procedure was originally proposed by Yoder, 1936. Later, the procedure was modified byKemper and Rosenau, 1986.

Equipment

1. Yoder type sieve shaking electrically operated machine (3/4 inch stroke at 30 strokes per minute)
2. Concentric sieves of various sizes of pores to fit properly into the machine.
3. Weighing balance

Aggregation is one of the basic physical characteristics of soil. Under natural conditions, primary soil particles, particularly clays, tend to join together to form secondary units called aggregates. Size distribution of soil aggregates is important because the size of the aggregates determines their susceptibility to water and wind erosion. Also, their size is important in determining the pore size distribution and regulating pore space in cultivated soils.

There are a variety of procedures being in use to test the stability of aggregates and aggregate size distribution. However, choice of the method for analysis of aggregate size distribution is determined by the purpose of analysis. The developed measures are relative and purpose specific. This chapter discusses dry aggregate analysis.

Aggregation is a direct indicator of soil structure. Ahealthy soil is considered to have well aggregated structure. Though not routinely followed during soil testing and chemical analysis, aggregation is one of the major indicators of soil physical health. Wet sieve method (Yoder, 1936) is usually followed for soil aggregate analysis. This involves gently raising and lowering a nest of sieves in water to assess the stability of aggregates to rapid wetting. However, the Yoder’s wet sieving method has been modified to make it simpler and currently, the method of Kemper and Rosenau, 1986 is being commonly used in research laboratories. One of the pre-requisites in these methods is the availability of wet sieving apparatus and further, these methods are laborious and time consuming. On the other hand, the method described by Cambardella and Elliott (1993) is considered very ideal because of its simplicity and is being widely used for aggregate bound soil carbon fraction study. The soil sample is wet sieved with a series of three sieves (2000, 250 and 53 micron size).

Soil bulk density (BD) or apparent density is determined in -situ by core method. Stainless steel or metallic cores of cylindrical shape with known height and diameter are inserted into the soil till the rim of the core. The soil core is then excavated and the soil sample is oven dried to get the dry weight. The ratio of the oven dry weight to the total volume of the core gives the bulk density of the soil.

Soil texture refers to the relative distribution of sand, silt and clay on a sample of <2 mm size. It is an intrinsic soil property and basically refers to the particle size distribution in a soil. A number of physical characteristics and chemical properties of a soil are influenced by texture or particle size distribution. To estimate the content of sand, silt and clay particles, the soil samples are first brought into a dispersed state by mechanical and chemical treatments so that different binding agents are removed. In the dispersed soil samples, the soil particles settle down at a differential settling rate according to their size. In laboratory, the common methods for analysis for particle size distribution are : Buyoucos hydrometer method and International pipette method. In this chapter, the procedure of Buyoucos hydrometer method is described.

Principle

This method is based on the principle of variable rate of settling of particles as per their size and as described by Stokes’Law. Large particles shall settle fast. The measurement of density of the suspension is done at different times using a hydrometer (ASTM 152H-Type hydrometer is preferred). The measurement in this hydrometer is based on a standard temperature of 20 _oC and a particle density of 2.65 Mg m_-3 and the units are expressed in grams of soil per liter.The principal source of error in this procedure is the incomplete dispersion of soil clays as the clay particles are cemented by agents such as organic matter, CaCO and iron oxides. Incomplete dispersion results in low values for clay and high values for silt and sand. Thus, soils with higher organic matter (>1.0%) should be first treated with 6% hydrogen peroxide (H₂O₂) for removal of organic carbon. The rate of sedimentation is also affected by temperature and the density of the dispersing solution.

Exchanges sodium (Na+) is animportantparameter forsalt affected soils. This is estimated by extraction with ammonium acetate and then measuring the extract inflamephotometer.

Reagents

1. Neutral normal ammonium acetate solution (1 N CH₃COONH₄ of pH 7): Dissolve 77.09 g of ammonium acetate in distilled water and make up the volume to one litre. Adjust the pH of the solution to 7 with ammonia solution or acetic acid.
2. Standard solution of Na (500 mg/L Na): Dissolve 1.271 g of NaCl in distilled water and make up the volume to one litre.
3. Working standard solution of Na (100 mg/L): Dilute 200 ml of 500 mg/L stock solution to 1000 ml.

Ion exchange is a reversible process by which a cation or anion held on the solid phase is exchanged with another cation or anion in the liquid phase. Soil mineral and organic colloidal particles have negative valence charges that hold dissociable cations. The power to retain cations at the surface of soil colloids is referred to as the cation exchange capacity (CEC). Cation exchange is a reversible reaction in soil solution, dependent upon negative charges of soil components arising from permanently charged or pH-dependent sites on organic matter and mineral colloid surfaces. The CEC is the sum of cations held by a kilogram of soil and is expressed in Cmol (p₊)/kg soil. In most agricultural soils, the cation-exchange capacity (CEC) is generally higher than the anion exchange capacity (AEC).

Electrical conductivity (EC) is a useful indicator of soil salinity. Relationships have been developed between EC and salinity classes for a 1:1 soil: water suspension. With increase in salt content in a soil, the EC increases. Thus, for salt affected soils, measurement of EC is vital as accumulation of salts in the root zone is detrimental to plant growth. EC is a measure of the ability of a soil solution to conduct electrical current.

Equipment and Reagents

1. Digital Conductivity meter
2. 0.01 M potassium chloride (KCl) solution: Dissolve 0.7456 g dry KCl in distilled water and make up the volume to 1.0 litre. This solution has an electrical conductivity of 1.413 dS m_-1 at 25ºC.

Soil pH is the measure of hydronium ion (H₃O⁺) or more commonly hydrogen ion (H⁺) activity in the soil suspension. Soil pH can be measured in soil-water suspension, saturation extract or in 0.01 M CaCl₂ solution. Saturation extract is used to identify specific soil problems such as salinity or sodicity. Measurement of pH using 0.01 M CaCl₂ solution gives more reproducible results than measured through soil-water suspension. It also provides a good approximation of field conditions as the electrolytic composition of 0.01 M CaCl₂ is considered similar to that of soil solution. However, among the three methods, soil-water suspension is most commonly used in research laboratories as well as for fertilizer recommendation as it is simpler and more convenient.

Soil sample collection is the first and most important step for soil quality analysis. A soil sample collected with due care and proper procedure is essential for getting reliable result of the analysis. The sample should represent the field and for practical purposes, an area of about 0.5 hectare is considered as one sampling unit. In case of conspicuous variation observed in the field in terms of texture, colour, slope etc, separate samples should be collected from areas differing in these attributes. In other words, sample should be collected from an area in the field with similar characteristics as seen through normal visual observation. Sampling should thus be avoided from areas like near trees, permanent vegetations, manure pits, manure piles or recently fertilized fields.

Soil Sampling procedure

1. For a particular field unit, one composite soil sample is prepared out of the samples collected from 7-8 spots distributed across the field unit. The entire field is covered by moving in a zig-zag manner from each sampling spot.
2. For each sampling point or spot, scrapping off the surface litter such as grasses or crop residues is done. Then, a “V” shaped pit of 15-20 cm length and of equal width is made. Depth of sampling depends upon the requirement and on the type of crop. For field crops like paddy, wheat etc, samples are collected from 15 cm depth. From the “V” shaped pits, take outslice of ½ inch thickness from both sides of the exposed pit surfaces from top to bottom.
3. The soil samples so collected from the 7-8 points are mixed thoroughly by hand and then is reduced to about 500 g by quartering process. The quartering process consists of a procedure in which the entire soil mass is divided into four quarters; the two opposite ones are discarded and the remaining two are remixed. This process is repeated till about 500g soil is obtained.

Systematic recording is vital for smooth running of any artificial insemination enterprise. All the information in the center should be so arranged so that it can be readily be traced out and used for analysis of performance of the center. The records should be critically analyzed for selecting better animals / personnel and for improving reproductive management. The objective of record keeping is as follows.

1. Introduction

Persian walnut is of great importance across worldwide where nuts are harvested from wild stands, backyard gardens and rarely from commercial orchards that vary considerably in their size due to degree of management. The walnut is an old tree cultivated before the Greek age and appreciated for centuries for its fruits, wood and other parts utilized in several ways. Before the discovery of the phenomena of allelopathy, someone considered the walnut an un-healthful tree, since peasants used to wake up with migraine or fever after they had slept under a walnut tree. Some others considered the walnut a cursed tree, and in fact in Italy an old walnut tree growing in Benevento, has long been considered the place where the witches used to dance during the night of Saint John and, therefore, that tree was named “Tree of the Witches” (Avanzato, 2010).

Nuts are collected for home consumption, sale at local roadside stands and markets and for shipping to cities. Walnut trees are further utilized for their high quality timber to make a wide array of products. The leaves, bark and other plant parts are used for medicinal remedies and trees are grown and maintained for soil conservation purposes (Mamadjanov, 2006b). A diverse mix of seedlings, local selections, and advanced cultivars are grown for nut production, many with unknown origins, including some of which are the direct result of selection from the wild.

1. Introduction

The modern cultivated strawberry (Fragaria x ananassa Duch.) is one of the most delicious, refreshing and soft fruits of the world. Worldwide it is also the most widely distributed fruit-crop due to its genotypic diversity, highly heterozygous nature and broad range of environmental adaptation. The plant is cherished in gardens and in commercial fields for its beautiful red fruit that has a tentalizing aroma (Sharma, 2002; Sharma and Sharma, 2004). Being a rich source of vitamins and minerals coupled with delicate flavour, strawberry has now become an important table-fruit of millions of people around the globe. It is amongst the few fruit crops, which gives quicker and very high returns per unit area on capital investment, as the crop is ready for harvesting within 6 months of planting. However, due to several technological advances in its cultivation like, introduction of day-neutral cultivars, and protected cultivation, strawberries remain available as fresh fruit throughout the year.

At present, strawberry is grown in wide climatic zones, extending to temperate, Mediterranean, sub-tropical and taiga zones (Sharma, 2002; Sharma and Sharma, 2004). Its cultivation is influenced by the specific regional adaptations due to critical photoperiods and temperature requirements and thus its cultural systems are highly variable. Due to the constant efforts of strawberry breeders, the world-wide interest for strawberry cultivation has boosted its production tremendously, which has resulted in widespread popularity of strawberry in the last 50 years.

1. Introduction

Quince is a highly nutritious underutilized fruit of sub-Himalayan region which has great economics and medicinal potential and it belongs to the group of the oldest cultural plants. Quince is known with different names, Urdu name ‘Bahee Dana’, Farsi name ‘Beh’, Greek name ‘Strythion’, Kashmiri name ‘Bamchunth’ and Hindi name ‘Bihi’ (Torkelson, 1995, Khoubnasabjafari and Jouyban, 2011). Quince is very much like pear in shape and gets a golden yellowish outer layer when mature. Quince fruit is a valuable dietary product and even then it less suitable for the direct consumption (Hricovsky et al., 2003) and for that reason they are mostly used either cooked (Alvarenga et al., 2008) or preserved (Kyzlink, 1990). However, as compared with other species, this fruit tree species is less popular throughout the world. Its predisposition to turning brown and decay is a limiting factor in the long-term storage of this fruit (Gunes, 2008). The nutritional value of the fruit is high (Bucsek et al., 1996; Kopec and Balik 2008). It is well known that quince fruit shows antioxidant effects (Silva et al., 2002) which result from the presence of a number of polyphenolic substances (Fattouch et al., 2007), e.g. flavonoids quercetin, rutin, kaemp ferol etc. (Silva et al., 2005), and also from increased levels of vitamin C (Tetera, 2006). Quince has the important nutritional and flavor composition more than many fruits. Vitamin C content of quince is nearly two times higher than in apple (Biro and Lindner, 1999).

1. Introduction

Plum is one of the important stone fruit crops of temperate region throughout the world. The Japanese group of plum is native to China but was domesticated in Japan and subsequently was introduced to different parts of the world. In India, Japanese plums were introduced by European settlers and missionaries around 1870. Plum grows well in areas ranging from 900 m to 1600 m above mean sea level.

1.1. Uses

Among deciduous fruits, plum is widely distributed in the world, because of wider adaptability among different species and cultivars of plum to varied agro-climates and soil conditions. Plum is consumed as dessert, dried and processed products. Plum fruit is considered best to overcome the jaundice. Its fruit use for a preparation of juice and squash. It ranks next to peach in commercial production. It is widely cultivated in several countries in Europe, Asia and in the America.