Agriculture Reference
In-Depth Information
to apply lower amounts of both N and P instead of a large amount of N alone. These authors also
concluded that the N × P interaction varied among crop species and also within genotypes of the
same species.
In a field study conducted for 5 years in a loamy sand soil in the state of Punjab in India, the
interaction effect of N and P on the yield and protein content of field peas was significant (Pasricha
et al., 1987) for harnessing the optimum yield potential, where the interaction impact was 23%. In
dry beans (
Phaseolus vulgaris
L.), while N alone was beneficial only up to 30 kg N ha
−1
, the crop
made effective use of 60 kg N ha
−1
when this was combined with 100 kg P
2
O
5
ha
−1
(Srinivas and
Rao, 1984). Compared to the control plots, dry bean yields could be increased by more than five
times by a judicious N + P combination, of which 59% was due to the interaction effect. Phosphorus
application can create a more favorable environment for biological nitrogen fixation in legumes
compared to N application alone. A balanced application of N and P maintains nitrogenase activ-
ity at high levels in field peas (Pasricha et al., 1987). Hence, the N × P interaction is favorable for
biological nitrogen fixation in legumes enhancing N fixation as was also observed by Muller et al.
(1993) and Amanuel et al. (2000) in faba beans (
Vicia faba
L.).
In a field study in Argentina, Zubillaga et al. (2002) reported that the yield of sunflower
(
Helianthus annuus
L.) can be increased by 20% with the application of N and P together as com-
pared to N alone. They concluded that P fertilizer provides a more efficient use of N by produc-
ing greater and consistent effects on crop performance most likely due to early root development.
Available data on other oilseeds revealed that the interaction was positive in sesame (
Sesamum
indicum
L.) (Daulay and Singh, 1982). Application of P to rapeseed (
Brassica napus
L.) and mus-
tard (
Brassica juncea
L.) was more effective when combined with N, and, as a general guideline, N
and P are recommended in a 2:1 ratio (Pasricha et al., 1991). The application of excessive N could
increase aphid infestation in rapeseed, whereas a combined application of N + P suppresses its
attack and increases the yield significantly (Khattak et al., 1996). In cotton (
Gossypium hirsutum
L.), the interaction between N and P was synergistic and accounted for 15% of the response to N + P
in the first year and 29% in the second year (Raghuvanshi et al., 1989). Aulakh and Malhi (2005)
concluded that the positive N × P interaction in cereals, legumes and nonlegume oilseeds, and other
crops is responsible for improved N and P use efficiencies. However, the magnitude of this interac-
tion can be modified by the climatic condition, crop species and genotypes within species, and level
of available soil P and N.
Nonspecific N × P interactions are commonly observed if for no other reason that they are
typically the two most limiting nutrients in crop production and therefore demonstrate additive
or synergistic yield effects in bringing both nutrients to sufficiency levels of availability (Pan,
2012). Mechanisms of N × P interactions have been ascribed to all stages of the soil-plant con-
tinuum (Miller, 1974). Brennan and Bolland (2009) demonstrated classic Liebig-type responses
to P at varying levels of N, suggesting that P was critically more limiting than N in these soils
(Pan, 2012).
6.2.2 n
ItroGen
versus
p
otassIum
These two nutrients are required in large amounts by crop plants. Hence, their sufficiency as well as
deficiency has significant effects on the growth and development of plants. In addition, interactions
having economic significance occur when one of these two nutrients is present at near deficiency lev-
els, and the other at high or toxic levels (Wilkinson et al., 2000). Aulakh and Malhi (2005) reported
that after N × P interactions, N × K interactions are the second most important interaction in crop
production. The significance of the N × K interaction and its optimum management is increasing due
to the increasing cropping intensity, higher crop yield, and greater depletion of soil K. Crops with
a high requirement of K, such as corn and rice, often show strong N × K interaction (Loue, 1979;
Singh, 1992; Fageria, 2014). Application of K was having a significant positive influence on the
uptake of N in soybean (Abbasi et al., 2012).
