Plant Demand Adapted Fertilization in Organic and Precision …
141
Table 2 Influence of decomposition period (days) of Sesbania spp. green manure a on N availability
to flooded rice in alkaline soil in North India (from Ghai et al. [31])
Species
Decomp.
(days)
Fresh
biomass
turned in
(Mg ha −1 )
N turned in
(kg ha −1 )
Grain yield
(Mg ha −1 )
Total crop
N uptake
(kg ha −1 )
Fertilizer N
equivalence
(kg ha −1 )
S. cannabina 15
24.0
110 b
5.9
67 b
65
10
25.0
125
6.1
86
114
5
25.2
109 b
6.1
89
122
0
24.6
120
5.4 b
84
109
Sesbania sp.
PL-Se 17
15
20.9
98 b
5.2
61 b
50
10
20.6
81 b
5.1
73
81
5
21.4
108
5.0
74
83
0
20.1
103
5.4 b
72
78
a Green manure incorporated at 45d growth
b Significantly different from other treatments in same species (p = 0.05)
the mineralization and crop uptake reduces the yield losses. Incorporation of 45d old
Sesbania cannabina green manure containing 110 kg N could provide rice yields
equivalent to those obtained with 120 kg N/ha fertilizer application (Table 2, [31]).
Thus, the N of green manure can be utilized with the same or even greater efficiency
as urea.
Nitrogen fixation by legume cover crops like hairy vetch and field pea, can provide
up to 150 kg N/ha and can be especially useful for balancing the phosphorus and
potassium supplied through manure or compost applications. Dey and Jain [20] found
that N balance after rice in a rice-wheat cropping system was positively correlated
with the N content but negatively correlated with lignin content and C:N ratio of
the green manures. In agro-forestry, the catch crops are multi-purpose short duration
perennials whose green loppings are used as fodder or directly incorporated into the
soil as green manure.
Choice of catch crop has to be done carefully; if used indiscriminately, very deep
roots of catch crops can deplete the subsoil so effectively as to adversely affect the
deep-rooted main crop grown in rotation. The use of catch crops will usually benefit
weed control. Rotational benefits of legumes (e.g., soybean, beans, alfalfa or clover)
in the crop rotation can result in a nitrogen credit for subsequent crops due to biological nitrogen fixation and less depletion of soil nitrogen compared to a non-legume
as the preceding crop. The nitrogen credit for forage legumes is greater than for grain
or vegetable legumes because most of the nitrogen (whether scavenged from the soil
or biologically fixed) is removed during harvest of the grain. Deep-rooted crops like
alfalfa and Sesbania can scavenge immobile nutrient like phosphorus and leached
nutrient like nitrate-nitrogen from deep soil layers, which may be released near the
soil surface with decomposition of the crop residue for availability to subsequent
crops in rotation. In North India, at 100 days growth green stem and leaf production
141
Table 2 Influence of decomposition period (days) of Sesbania spp. green manure a on N availability
to flooded rice in alkaline soil in North India (from Ghai et al. [31])
Species
Decomp.
(days)
Fresh
biomass
turned in
(Mg ha −1 )
N turned in
(kg ha −1 )
Grain yield
(Mg ha −1 )
Total crop
N uptake
(kg ha −1 )
Fertilizer N
equivalence
(kg ha −1 )
S. cannabina 15
24.0
110 b
5.9
67 b
65
10
25.0
125
6.1
86
114
5
25.2
109 b
6.1
89
122
0
24.6
120
5.4 b
84
109
Sesbania sp.
PL-Se 17
15
20.9
98 b
5.2
61 b
50
10
20.6
81 b
5.1
73
81
5
21.4
108
5.0
74
83
0
20.1
103
5.4 b
72
78
a Green manure incorporated at 45d growth
b Significantly different from other treatments in same species (p = 0.05)
the mineralization and crop uptake reduces the yield losses. Incorporation of 45d old
Sesbania cannabina green manure containing 110 kg N could provide rice yields
equivalent to those obtained with 120 kg N/ha fertilizer application (Table 2, [31]).
Thus, the N of green manure can be utilized with the same or even greater efficiency
as urea.
Nitrogen fixation by legume cover crops like hairy vetch and field pea, can provide
up to 150 kg N/ha and can be especially useful for balancing the phosphorus and
potassium supplied through manure or compost applications. Dey and Jain [20] found
that N balance after rice in a rice-wheat cropping system was positively correlated
with the N content but negatively correlated with lignin content and C:N ratio of
the green manures. In agro-forestry, the catch crops are multi-purpose short duration
perennials whose green loppings are used as fodder or directly incorporated into the
soil as green manure.
Choice of catch crop has to be done carefully; if used indiscriminately, very deep
roots of catch crops can deplete the subsoil so effectively as to adversely affect the
deep-rooted main crop grown in rotation. The use of catch crops will usually benefit
weed control. Rotational benefits of legumes (e.g., soybean, beans, alfalfa or clover)
in the crop rotation can result in a nitrogen credit for subsequent crops due to biological nitrogen fixation and less depletion of soil nitrogen compared to a non-legume
as the preceding crop. The nitrogen credit for forage legumes is greater than for grain
or vegetable legumes because most of the nitrogen (whether scavenged from the soil
or biologically fixed) is removed during harvest of the grain. Deep-rooted crops like
alfalfa and Sesbania can scavenge immobile nutrient like phosphorus and leached
nutrient like nitrate-nitrogen from deep soil layers, which may be released near the
soil surface with decomposition of the crop residue for availability to subsequent
crops in rotation. In North India, at 100 days growth green stem and leaf production