Agriculture Reference
In-Depth Information
Table 12.1
Nutritional value of some common vegetables
Vegetables
Brinjal
Nutrient components (g/100 g)
Cabbage
Tomato
Potato
Energy (kcal)
25
25
18
77
Carbohydrate
5.88
5.80
3.9
17.47
Protein
0.98
1.28
0.9
2.00
Fat
0.18
0.10
0.2
0.10
Dietary fibre
3.00
2.50
1.2
2.20
Sugars
3.53
3.20
2.6
15.44
Source
: USDA Nutrient Database
growth until the maturity stage, an adequate supply of P is required by the plant
(Grant et al.
2001
). When sufficient concentration of P is taken up by potato, it
promotes rapid canopy development, root cell division, tuber set, and starch
synthesis in potato. An ample amount of P is therefore essential for optimizing
the tuber yield, nutritional quality, and resistance of potato to some diseases also.
Other studies have also demonstrated a significant increase in yield, number of
tubers, and tuber size distribution due to fertilizer P application (Jenkins and Ali
1999
; Maier et al.
2002
; Sanderson et al.
2003
). Even though an inverse relationship
between tuber number and tuber size is reported (Knowles and Knowles
2006
), an
increase in tuber number with P fertilization has shown both an increase and
decrease in tuber size (Freeman et al.
1998
; Jenkins and Ali
1999
). Also, P is an
important constituent of nucleoproteins and nucleic acids of other vegetables such
as brinjal (Parihar and Tripathi
2003
). Onion (
Allium cepa
L.) is yet another most
important commercial bulbous vegetable which requires sufficient amount of P
among other macro- and micronutrients, from very early stages of growth for
optimum production (Grant et al.
2001
).
12.3.1 Relevance of Phosphate-Solubilizing Bacteria
to Vegetable Crops
Vegetable crops require highest quantity of N, P, and K, while other nutrients,
including Fe, Cu, Mn, and Zn, are needed in much smaller amounts. Apart from N
and P, majority of these nutrients are most likely available in the soil in adequate or
even excessive amounts. When nutrients are not needed by vegetables yet they are
added to soil, may lead to deficiencies of other nutrients and can result into nutrient
imbalance within soils. For example, when P is applied, but not needed, it can kill
off the symbiotic mycorrhizal-forming fungi required by the plant and reduce the
ability of vegetables to absorb iron and other micronutrients. Similarly, excess soil
P also shuts down the plant's ability to produce phytochelates, organic molecules
produced by roots to increase its iron uptake. Considering the cost and some side
effects of excessive application in vegetable cultivation, there is an urgent need to
