Soil And Climatic Studies In Rainfed Agriculture
i) Soils: – Out of total cultivable land in M.S. 87 per cent area comes ur rained. Soils of drought prone areas of M.S. area derived from the be igneous rock Basalt commonly known as Deccan trap. The colours of soil vary from reddish brown to dark gray black and are called verti. The soils exhibit a definite to posegence of ridge medium dear 122 – 90 cm depth) soils on sloped land deep soils (more than 90 cm meen) end of watershed. The distribution of very shallow, shallow, medium deep and deep soils in drought prone areas of M.S. is about 10,20,45 and 25% respectively. They usually under lined partially decomposed rock locally known as murrum which overlies parent material. On account of more or less complete absence of leaching the soils are base saturated. The exchangeable calcium is predominant cation. The free lime is reserve is fairly high (3 to 10%) and at places excessive quantities of time nodules accumulate. The problematic soils viz. saline, saline sodic land sodic soils do occur in patches in low lying areas.
As regards the fertility status, the soils are generally low in organic carbon (0.35 to 0.5%) total nitrogen (0.03 to 0.05%) low to medium available phosphate (10 to 30 kg p2O5/ha) and high available potash (300 to 750 kg K2O/ha). Usually micro-nutrient deficiencies are not observed in dry land crops. However in eroded soils, crop like groundnut have shown some response to boron application. Cereal crops give fairly good response to nitrogenous fertilizers while oilseeds and legumes give good response to phosphatic fertilizers.
Soils exhibit adverse physical characters because of high clay content (35 to 65%) of type clay mineral. The soils exhibit high volume expansion when moist and shrink when dry. The infiltration rate of soils is moderately slow (0.5 to 0.9 cm/ha). During the process of shrinkage, wide land deep cracks are developed even up to Murrum strata in medium deep soils. The crack development accelerates the soil moisture loss from the deeper layers (phases). Further soils exhibit varying degree of erosion depending on the slope, tillage operations and cropping season. The soils classed as moderate to high erodible. Hence soil and water conservation is a pre – requisite for successful cropping. Limited soil depth puts limitations on availability of water and nutrients for cropping intensity. Usually soils having less than 45 cm depth are useful for Kharif crops as they are unretentive of soil moisture. Inter mittant wetting due to frequent rainfall during June to Aug helps to mature crops on such soils. Soils having depth more than 45 cm have high moisture storage and retentive capacity. Under dry land to bring the soil moisture in the available range (i.e. above PWP) the rainfall required is quite high since the precipitation in the early part of monsoon is quite inadequate the medium deep soils (beyond 45 cm deep) usually do not have adequate moisture for sowing. It is only due to receipt of about 200 mm of rains during September the medium deep and deep soils are adequately moistened for Rabi cropping. Hence Rabi cropping is predominant and medium deep and despoils one grown with Rabi crops.
The moisture storage capacity of soil mainly depends on clay content and soil depth. However, city content is generally above 45 percent in medium deep and deep soil the moisture deptetion of soil depends on the moisture held in the soil at different tensions. The soil moisture is always below the moisture at 15 bar (PWD) which ultimately results in faiture of crops in dry land agriculture.
ii) Climate: Wether, which is part of climate, plays an important role in crop planning in dry farming area. Out of the several elements of weather, rainfall has key position in success of dryfarming.
In dry land areas, South West Monsoon brings the bulk of rainfall. The South West Monsoon is followed by North East Monsoon which supplements to South West Monsoon are the main source of rainfall. There are four types of rainfall characterized by the nature in different parts of India. Generally, the rainfall is scanty, erratic and ill distributed. The draught prone area in Maharashtra State Covers about 1/3 of the total area of the state. The climate in this is usually hot and PE (Potential Evaporation) is for in excess of the precipitation is classified as semiarid e.g. Annual precipitation at Solapur is about 7/22 mm. but PE is about 1300 mm annually resulting in deficient 60%.
iii) Rainfall features :- The annual Average rainfall varies from 400 mm to 700 mm. Year to year fluctuations are so much that there is no guaranteed of fixed quantity of rainfall. Uncertain and ill distributions of rainfall are two qualities which makes the Rainfed farming difficult. Rainfall starts in lated June to Early July.
There is depression during late July and early August Again there is good rainfall in late August and September. The rainfall totally recedes but mid October. The probability of rainfall is more than half of the normal fairly good (P = 0.58) during September.
iv) Dry spells: – It is another rainfall feature. Breaks in monsoon a normally experienced (observed) during rate July and August. They month extend by 2 week to 13 weeks at a stretch. A break is defined as period receiving less than 15 mm rainfall in consecutive weeks. The normal rainfall during the week being more than 50 mm. A duration of break month than 4 week and frequently more than 3 times usually results in fatures than 4 weeks and frequently more than 3 times usually results in faitures crops.
Variation in the rainfall with in the district is also observed. In Solapur, particularly variation in annual precipitation is noticed from 500 mm in western part to about 700 mm in eastern parts.
v) Water availability period: – Water availability depends on rainfall and PE. Humid (when rainfall exceeds PE) and moist (when rainfall is less than PE but exceeds PET) period together provides congenial weather for active crop growth.
vi) Wind velocity: – Wind velocity is generally hitch during July and August. If wind velocity exceeds 18 – 20 km./hr. Such period coincided with dry spell. Hence Evapotranspiration is at high degree. If velocity is low the lowest evaporation rates are observed during November and December.
vi) Bright sunshine hours: – Bright sunshine is usually experienced during months of Jan. and Feb. At Solapur it is about 8 to 9 hours. During April and May the sky is usually have with more dust particles, lowest bright sunshine is noticed during Aug. (4 to 5 hours). This indicates the cloudy weather but no rainfall.
vii) Humidity: – Humidity is high during July and Sept. During Feb. to May it is low. During dry spell, less relative humidity is noticed. Evaporation demands are also accelerated with high temperature and low humidity.
viii) Temperature: – a Maximum temperature exceeds 410 C during late April and early May. Minimum temp. is noticed during December. Lowest weekly minimum temperature is about 14 to 150C. Generally climate is semi and with mild winter and hot summer. Crop like wheat and gram requiring longer cool period hence do poor while prolonged cold weather however, Jowar suffers considerably.
1. Inadequate and uneven distribution of rainfall.
2. Late on set and early cessation of rainfall.
3. Prolonged dry spells during the crop growth period.
4. Low moistone retension capacity of soils.
5. Low fertility of soils, low humidity, higher temperatures, higher wind velocity.