Agriculture Reference
In-Depth Information
fertilization influenced crop yields similarly, only systems involving liberal applica-
tions of organic manure could sustain the SOM level. However, the liberal use of
organic manures is not a practical reality in Moldova.
9.3.5 i irrigation.
In the long-term experiment with irrigation in crop rotation, the yield of winter
wheat responded more than that of sugar beet (Table 9.9). With a deep root system,
sugar beet can absorb water from deeper soil layers during periods of peak demand.
In comparison, winter wheat has a shallow root system and responds strongly to
supplementary irrigation in the autumn, before or after sowing. Thus, changing the
structure of land area and seeding wheat after early harvesting of the preceding crop
offers an opportunity to reduce expenditures on irrigation.
Surprisingly, even in a six-field rotation with 50% of alfalfa, 13.3 Mg/ha/year manure
over the rotation together with recommended rates of mineral fertilizers, there are
losses of SOM from the 0-20 cm layer amounting to 0.09-0.18 Mg C/ha/year (Table
9.10), and losses are much greater for the whole soil profile (0-100 cm), especially on
irrigated, fertilized plots (0.45 Mg C/ha/year) relative to rainfed, fertilized plots.
9.3.6 i integration oF C rop r otation , t illage , and
F fertilization into a F arming s Ystem
A multifactorial long-term field experiment was initiated in 1996 to study the action and
interaction between crops, systems of soil tillage, and fertilization within the framework
of crop rotation (Boincean et al. 2013b). The experiment includes two crop rotations
(with and without perennial legumes and grasses), two systems of soil tillage (mini-
mum tillage and combination of minimum tillage and plowing), and three fertilization
systems (without fertilization, manure, and manure + NPK). The data show residual
effects of the alfalfa and ryegrass on the yields of the following crops in the rotation:
winter wheat, sugar beet, and maize ( Table 9.11 ). The data support the conclusion that
including alfalfa and ryegrass in the third year after the first cut is a good preceding
crop for winter wheat, compared with maize silage in the other crop rotation.
Soil tillage hardly changed crop yields; at least, minimum tillage showed no improve-
ment compared with the combination of minimum tillage and plowing. The open ques-
tion is whether the saving of fuel from minimum tillage compensates for the extra
expenditure on chemicals for weed control. Mineral fertilization is not efficient for winter
wheat after alfalfa and grasses harvested as fodder (for feeding animals), which offers
real opportunities to reduce mineral nitrogen use. Nonetheless, fertilizer is very effective
on winter wheat after maize silage. The extra yield of wheat from application of organo-
mineral fertilizers is equivalent to 1.31 Mg/ha on a plot with a combination of minimum
soil tillage with selective moldboard plowing and 1.67 Mg/ha on a plot with minimum
tillage alone. The extra yield from fertilization is more for sugar beet sown after
winter wheat following maize silage compared with winter wheat sown after alfalfa
and grasses in the third year after the first cut: −11.2-8.9 Mg/ha and 5.2-6.2 Mg/ha,
respectively. The same trend appears for maize for grain, in particular on a plot with
a combination of minimum tillage and moldboard plowing.
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