The majority of agriculture in the dry and semi-arid regions remains to be rainfed. Small farmers with limited resources make up the majority of the farmers. Due to the scarcity of resources, only low-input subsistence farming with low and uncertain crop yields is possible. Agriculture’s low productivity in rainfed and dry farming regions is due to the cumulative effect of several crop production restrictions. Constraints can be divided into these categories:
• Climatic constraints
• Soil related constraints
• Traditional cultivation practices
• Heavy weed problem
• Lack of suitable varieties
• Socio economic constraints
1) Climatic constraints
– Rainfall characteristics: Rainfall is an essential factor impacting agricultural productivity in arid locations among the several climatic parameters.
• Variable rainfall: Rain fall varies both in time and space dimension. Annual rainfall varies greatly from year to year and naturally its coefficient of variation is very high. Generally, higher the rainfall less is the coefficient of variation. In other words, crop failures due to uncertain rains are more frequent in regions with lesser rainfall. The average annual rainfall of India is 1192 mm whereas in Andhra Pradesh it is 890 mm.
• Intensity and distribution: In general, more than 50 per cent of total rainfall is usually received in 3 to 5 rainy days. Such intensive rainfall results in substantial loss of water due to surface runoff. This process also accelerates soil erosion. Distribution of rainfall during the crop growing season is more important than total rainfall in dryland agriculture.
• Aberrations or variations in monsoon behavior: Late onset of monsoon: If the arrival of the monsoon is delayed, crops/varieties indicated for the region will be unable to be sown in time, resulting in low agricultural yields.
– Early withdrawal of monsoon: This condition is just as perilous as or even more dangerous than the monsoon’s late arrival. Crops grown during the rainy season will be subjected to terminal stress, resulting in low yields. Similarly, post-rainy season crops fail due to insufficient soil moisture, particularly during the reproductive and maturation stages.
Prolonged dry spells: Monsoon breaks of 7-10 days may not be a major issue. Breaks of more than 15 days, especially during crucial times of soil moisture stress, result in yield decrease. Drought caused by a monsoon break is more likely to harm crops in shallow soils than in deep soils.
– High atmospheric temperature: The demand for moisture in the atmosphere rises as the temperature rises, resulting in increased evapotranspiration losses and moisture stress.
– Low relative humidity: When moisture is scarce, low relative humidity causes substantial ET losses, resulting in moisture stress.
– Hot dry winds: Desiccation of leaves occurs as a result of hot, dry air, resulting in moisture stress. Dust storms and the loss of fertile soil are caused by high turbulent winds, especially during the summer months.
– High atmospheric water demand: Due to high atmospheric water demand the potential evapotranspiration exceed the precipitation during most part of the year.
– Inadequate soil moisture availability: Due to short depth, especially in alfisols (red soils), minimal rainfall, and low organic matter content, the moisture holding ability of soils in dry locations is limited.
– Poor organic matter content: Because of the high temperature and limited addition of organic manures, the organic matter content in most dry land soils is very low. Soil physical qualities related to moisture storage are negatively impacted by low organic matter concentration.
– Poor soil fertility: Dry land soils have a low fertility state due to low organic matter buildup and loss of fertile top soil due to soil erosion. The majority of dry land soils are nitrogen and zinc deficient. Erosion-induced soil degradation (wind, water). Nearly 175 million hectares of land in India are affected by various land degradations, the most common of which is soil erosion. Because of erosion, top fertile soil is lost, leaving a poor subsoil for agricultural growth.
– Soil crust problem: In red soils, the emergence of seedlings is hampered by the creation of hard surface soil layers, which has an impact on the plant population. Due to heavy runoff, crusting of the soil surface after rainfall inhibits infiltration and storage of rainfall.
– Presence of hard layers and deep cracks: The presence of hard layers in the soil and deep fractures has an impact on crop output, particularly in black soils.
Farmers’ current management approaches have evolved over time as a result of their long-term experience. The following are examples of classic management practices:
• Ploughing along the slope.
• Broadcasting seeds/ sowing behind the country plough leading to poor as well as uneven plant stand.
• Monsoon sowing.
• Choice of crops based on rainfall.
• Application FYM in limited quantity.
• Hand weeding.
• Mixed cropping.
• Use of conventional system of harvesting.
• Traditional storage system.