3.2 Propuestas de solución al problema establecido
3.2.1 Desarrollo del Procedimiento de Mejora Continua y Establecimiento
Nutrient balances
Nitrogen balances
The nitrogen balance for arable farming showed a nitrogen surplus of 40 kg ha-1 per
year (table 1). The main nitrogen inputs were by inorganic fertilizers (66% of the total in- puts), whereas manure and compost played a minor role (9% and 6% of total inputs, re- spectively). Atmospheric deposition ac- counted for 13% of the total inputs.
Table 1 Nitrogen balance of arable farming, field growing of vegetables, and viticul-
ture in Vienna (kg N ha-1 yr-1)
Arable farming
(kg N ha-1 yr-1) vegetables (kg N haField growing of -1 yr-1) (kg N haViticulture -1 yr-1)
Inputs 137.6 176.4 60.4
Inorganic fertilizers 90.7 142.2 32.8
Manure 11.7 11.7 5.6
Organic products (compost) 8.3 - -
Atmospheric deposition 18.0 18.0 18.0
Biological nitrogen fixation 6.1 4.5 4.0
Seeds and planting material 2.8 - -
Outputs 97.4 105.7 8.9
Total harvested crops and forage 97.4 105.7 8.9
Balance (inputs minus outputs) 40.2 70.7 51.5
The nitrogen surplus of 40 kg ha-1 appears to
be relatively low. The low value is explained by the fact that most of the agriculture in Vienna is stockless arable farming and arable farming always has a much higher nutrient efficiency and therefore lower nutrient surpluses than animal production (Isermann, 1994). The Vi- ennese people, however, are mostly not vege-
tarians and the nutrient surpluses induced by the corresponding livestock occur outside Vienna.
For field growing of vegetables, the nitrogen balance showed a surplus of 71 kg ha-1 due to
the higher intensity of cultivation. The main nitrogen inputs were inorganic fertilizers
(81% of the total inputs). Manure provided a minor input (7% of total inputs). Compost is usually not used in field cropping of vegeta- bles. Atmospheric deposition made up 10% of the nitrogen inputs.
For viticulture, the nitrogen balance showed a surplus of 52 kg ha-1, although it was assumed
that newly established vineyards were not fertilized with nitrogen. The major input was through inorganic fertilizers (54% of total inputs). Compost is usually not used in viticul- ture. The nitrogen removal with the grapes is very low (25 - 30 kg N for a yield of 100 hl ha-1; KTBL, 1986).
Due to the calculation method for fertilizer input based on the "guidelines for proper fer- tilization" (BMLF, 2000) and on soil nutrient contents of phosphate and potassium, the balance results of all three nutrients must be regarded as minimum values, because this calculation assumes that all farmers follow the "guidelines for proper fertilization".
All three branches of Vienna's agriculture showed higher nitrogen surpluses than the nitrogen balance for Austrian agriculture according to OECD criteria, which yielded a surplus of 30 kg N ha-1 (Götz, 1998). This
balance, however, is calculated using the total agricultural area of Austria, including areas which are not fertilized at all, such as alpine meadows and pastures. Furthermore, 15% of the nitrogen present in manure is subtracted as "destruction and evaporation of manure", so that these N-losses do not show up in the balance. The Austrian nitrogen balance calcu-
lated without these assumptions gave an aver- age annual nitrogen surplus of 46 kg ha-1
(Götz, 1998). Agricultural nitrogen balances for other European countries, calculated by the soil surface balance method, revealed N surpluses ranging from 99 to 367 kg N ha-1
(Isermann, 1994). The nitrogen balances are typical for each type of farming: arable farms typically show nitrogen surpluses of 30 - 40 kg ha-1, whereas animal producing farms have
nitrogen surpluses between 55 and 320 kg ha- 1, depending on the stocking density (data
based on representative supply/withdrawal balances; Isermann, 1994). Organic farms, also organic farms keeping livestock, usually show negative to slightly positive nitrogen balances at farmgate level (Kaffka and Koepf, 1989; Hege and Weigelt, 1991; Wieser et al., 1996).
Phosphorus balances
The phosphorus balance for arable farming was slightly negative with -8 kg ha-1 P2O5 (ta-
ble 2). This results from the calculation of the nutrient input according to the guidelines for proper fertilization (BMLF, 2000). As the plant-available soil P2O5 content (measured
using the calcium-acetate-lactate method) in arable farming in Vienna was between 110 and 400 mg kg-1 on average (Anonymous,
1994), the guidelines propose a very low level of phosphate fertilization. Half the P2O5 in-
puts were through inorganic fertilizers, one third through manure. Compost accounted for 12% of the input.
Table 2 Phosphorus balance of arable farming, field growing of vegetables, and viti-
culture in Vienna (kg P2O5 ha-1)
Arable farming
(kg P2O5 ha-1 yr-1)
Field growing of vege- tables (kg P2O5 ha-1 yr-1) Viticulture (kg P2O5 ha-1 yr-1) Input 33.5 30.3 11.4 Inorganic fertilizers 16.7 18.9 - Manure 11.4 11.4 11.4
Organic products (compost) 4.2 - -
Atmospheric deposition - - -
Seeds and planting material 1.2 - -
Outputs 41.4 42.7 3.8
Total harvested crops and forage 41.4 42.7 3.8
Balance (input minus output) -7.9 -12.4 7.6
For field growing of vegetables, the phos- phate balance showed a negative value of -12 kg ha-1, again due to the high level of plant-
available phosphate in the soil (260-400 mg kg-1 P2O5; Labor Pottmann, 2001). The main
phosphate inputs were inorganic fertilizers (63% of total inputs) and manure (37% of total inputs).
The phosphorus balance in viticulture showed a small surplus of +8 kg ha-1. The average
available soil phosphate contents of vineyards ranged between 110 and >400 mg kg-1 (Wr.
LWK, 2001), so that, following the guidelines (BMLF, 2000), it was assumed that no phos- phate fertilization was given. The high levels of phosphate and also potassium in Vienna’s agricultural soils come from ample fertiliza- tion in the last decades, a practice, which is now followed by a more moderate fertilization regime.
For other European countries, agricultural phosphorus balances, calculated by the soil surface balance method, yielded surpluses between 20 and 88 kg P2O5 ha-1 (Isermann,
1994). Arable farms typically show phosphate balances of around 20 kg ha-1, whereas the
annual surpluses of animal producing farms
range from 29 to 95 kg ha-1 (data based on
representative supply/withdrawal balances; Isermann, 1994). The phosphorus balances of organic farms range from -13 to +8.5 kg P2O5
ha-1 at farmgate level (Kaffka & Koepf, 1989;
Hege & Weigelt, 1991; Wieser et al., 1996).
Potassium balances
In arable farming, the K2O balance showed a
small surplus of +5 kg ha-1 (table 3). As the
available K2O content in soils (measured us-
ing the calcium-acetate-lactate method) of all three farming types in Vienna was between 140 and 400 mg kg-1 on average (Anonymous,
1994; Labor Pottmann, 2001; Wr. LWK, 2001), the level of potassium fertilization ac- cording to the guidelines was low. The main potassium inputs were by inorganic fertilizers (55% of the total inputs) and manure (34% of total inputs), whereas compost played a minor role (8% of total inputs). Atmospheric deposition accounted for 1.6% of the total inputs.
For field cropping of vegetables, the K2O
balance showed a surplus of +27 kg ha-1. 89%
Table 3 Potassium balance of arable farming, field growing of vegetables, and viti-
culture in Vienna (kg K2O ha-1)
Arable farming
(kg K2O ha-1 yr-1)
Field growing of vege- tables (kg K2O ha-1 yr-1) Viticulture (kg K2O ha-1 yr-1) Inputs 62.4 195.3 23.2 Inorganic fertilizers 34.4 173.5 1.4 Manure 21.1 21.1 21.1
Organic products (compost) 5.4 - -
Atmospheric deposition 0.7 0.7 0.7
Seeds and planting material 0.8 - -
Outputs 57.6 168.1 16.5
Total harvested crops and forage 57.6 168.1 16.5
Balance (inputs minus outputs) 4.8 27.2 6.7
The potassium balance in viticulture showed a small surplus of +7 kg ha-1.
The potassium balances of arable farms typi- cally show surpluses of 50 kg ha-1. Animal
producing farms usually have potassium sur- pluses of 68 to 124 kg ha-1, depending on
livestock density (data based on representative supply/withdrawal balances; Isermann, 1994). For organic farms, including farms with live- stock, potassium balances at farmgate level ranging from –6 kg ha-1 to +19 kg ha-1 were
recorded (Kaffka & Koepf, 1989; Hege & Weigelt, 1991; Wieser et al., 1996).
Isermann and Isermann (1994) calculated maximum tolerable nutrient budget surpluses for a sustainable agriculture. For arable farm- ing they called for a maximum nitrogen sur- plus of 30 kg ha-1, for a phosphorus balance
of ± 0 and for a potassium balance ≥ 0.