Agriculture Reference
In-Depth Information
The impact of cultivation practices or soil tillage practices on physical properties of the soil such
as structure, water retention, aggregate stability, aeration, bulk density, and biochemical processes
(mineralization, nitrification) is of considerable importance in the effective sustainable manage-
ment of soils and nutrient use efficiency including N. Adequate preparation of land may improve
soil aeration and drainage, improve root penetration, and influence the water retention properties
(Fageria, 2013). Lal (1991) reported that appropriate tillage operations are a powerful tool to over-
come problems associated with infiltration, surface crusting, poor drainage, soil compaction, burial
of weeds and surface debris, and pest management. All these changes in physical properties of the
soil may improve N use efficiency.
8.2.1 p
hYsICal
p
ropertIes
Physical properties of the soil that influence plant growth and development and consequently nitro-
gen use efficiency are soil temperature, soil water content, soil texture, soil structure, and soil bulk
density. These soil properties are responsible for the germination of seeds and consequently the
emergence of seedlings. In addition, root penetration, water-holding capacity, soil water infiltration
rate, soil aeration, soil microbial activities, and availability of nutrients are also determined by these
soil properties. Hence, if these soil properties are favorable or can be modified and/or improved in
favor of higher crop growth, nitrogen use efficiency will improve. However, some properties such as
soil texture are difficult to modify by normal soil management practices. Hence, the discussion in
this section will be on the remaining soil physical properties.
8.2.1.1 Favorable Soil Temperature
Soil temperature plays a role in many important functions and processes by regulating the biological
and chemical reaction rates (Paul and Clark, 1966; Soil Survey Staff, 1999). Oxidation-reduction
reactions, C storage, CO
2
efflux, nutrient availability, and bacterial mineral reduction rates have
all been correlated to soil temperature (Abdollahi and Nedwell, 1979; Koerselman et al., 1993;
Schimel et al., 1994; Fang and Moncrieff, 2001; Davidson and Janssens, 2006; Vaughan et al., 2009;
Salisbury and Stolt, 2011). As such, soil temperature plays an important role in soil formation, part
of the climate state factors described in Jenny's (Jenny, 1941) factors of soil formation. Soil tempera-
ture has been used in definitions of the biological zero and growing season in soil taxonomy and
wetland science (Soil Survey Staff, 1975; Salisbury and Stolt, 2011).
Favorable soil temperature influences the growth and development of crop plants and conse-
quently higher nitrogen use efficiency. On the other hand, a too high or too low temperature influ-
ences plant growth adversely and nitrogen use efficiency decreases. High and/or low temperatures
influence the photosynthetic rate, plant water relations, flowering, and fruit set in temperate and
tropical crops (Abrol and Ingram, 1996). Ali et al. (2009) reported that, in the winter season, in
crops such as wheat, an increase in the mean minimum and maximum temperatures during the
reproductive stage adversely affected grain yields in northern India. Baker and Allen (1993) reported
water requirements and decreased yields in rice, soybean, and citrus under higher maximum and
minimum temperatures. For every rise in the day/night temperature above 28/21°C, the rice yield
declined by 10%. Ali et al. (2009) in a review of the literature reported that due to the unprec-
edented heat wave in northern India in 2004, 4.4 million tons of loss in productivity was reported
in the wheat crop. These authors further reported that breeding for suitable varieties, improved crop
management, and changes in planting dates to some extent would help in overcoming the effects of
climatic change. However, evolving low-cost methods, which can be easily adopted by small farm-
ers, is a major challenge (Ali et al., 2009).
Available reports indicated that the adverse effect in plants by abiotic stresses such as drought,
salinity, and high and low temperature is alleviated by microbial inoculation (Timmusk and
Wagner, 1999; Redman et al., 2002; Han and Lee, 2005; Ait et al., 2006; Marquez et al., 2007; Ali
et al., 2009). Ali et al. (2009) reported that the
Pseudomonas
sp. strain AKM-P6 can enhance the
