On-farm nitrogen fixation is a driving force in organic agriculture. The efficiency with which this nitrogen is used can be increased by using alfalfa or grass-clover crops directly as fertilizer on other fields: cut-and-carry fertilizers. In two crops in two years, the use of several types of alfalfa and grass-clover as fertilizer is compared with the use of poultry manure and slurry. The nitrogen use efficiency at crop level is comparable or better for the cut-and-carry fertilizers as compared to the animal manures. The relative P and K content of these fertilizers comes closer to the crop demand than that of the poultry manure. Crop yields are comparable or better when using the alfalfa or grass-clover as fertilizer. It is concluded that the cut-and-carry fertilizers are a serious alternative for manure as part of an overall farm soil fertility strategy

Burgt, G.J.H.M., van der

Koopmans, C.J.

Scholberg, J.M.S.

English

Name not available

Developing novel farming systems: effective use of nutrients from cover crops in intensive organic farming

Wageningen Yield 

32 
 
Developing novel farming systems: effective use of nutrients 
from cover crops in intensive Organic Farming 
Van der Burgt, G.J.
1
, Scholberg, J.
2
 & Koopmans, C.J.
3
  
Key words: cover crops, organic farming, system development, alfalfa, ecosystem 
services. 
Abstract 
On-farm nitrogen fixation is a driving force in organic agriculture. The efficiency with 
which this nitrogen is used can be increased by using alfalfa or grass-clover crops 
directly as fertilizer on other fields: cut-and-carry fertilizers. In two crops in two years, 
the use of several types of alfalfa and grass-clover as fertilizer is compared with the 
use of poultry manure and slurry. The nitrogen use efficiency at crop level is 
comparable or better for the cut-and-carry fertilizers as compared to the animal 
manures. The relative P and K content of these fertilizers comes closer to the crop 
demand than that of the poultry manure. Crop yields are comparable or better when 
using the alfalfa or grass-clover as fertilizer. It is concluded that the cut-and-carry 
fertilizers are a serious alternative for manure as part of an overall farm soil fertility 
strategy. 
Introduction  
The objective of this study was to address the issue of developing intensive cropping 
systems that facilitate more effective use of on-farm N-fixation. This was achieved by 
developing innovative ―cut-and-carry‖ cropping systems based on perennial grass 
clover or alfalfa crops. Including these forage crops in arable cropping systems will 
enhance soil quality in general. In this manner nutrients accumulated by these deep-
rooted crops can be used as soil amendment rather than being sold and shipped off 
the farm as forage. This is very desirable because the revenues from these crops are 
rather limited whereas the on-farm nutrient use efficiency with these crops, that 
feature very high dry matter and nutrient accumulation, can be appreciable.      
Materials and methods  
The experiments were located on a organic farm in the centre of the Netherlands 
(52
o
39‘08 N ; 5
o
48‘07 E; 3 m below sea level) on a well drained clay soil with 2.6% of 
organic matter, 280 mg P kg
-1
 (P-Al) and 46 mg K kg
-1
. 
During 2009 the use of freshly (1
st
 cut of season) grass clover, alfalfa, and silaged 
alfalfa were compared with application of chicken manure as a nutrient source for fall-
grown spinach. Alfalfa was cut in pieces of about 3 cm. All materials were being 
                                                 
1
 Louis Bolk Institute LBI, Hoofdstraat 24, 3972 LA Driebergen, Netherlands, E-Mail 
g.vanderburgt@louisbolk.nl, Internet www.louisbolk.nl 
2
 Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen 
3
 Louis Bolk Institute LBI, Hoofdstraat 24, 3972 LA Driebergen, Netherlands, E-Mail 
c.koopmans@louisbolk.nl, Internet www.louisbolk.nl 
 
33 
 
applied manually five weeks before the sowing of spinach and shallow (8 cm) 
incorporated. An additional treatment was included to evaluate the effect of applying 
materials later by incorporating alfalfa at ten days before sowing as well. Actual N 
application rates amounted to 0, 165, 200, 202, 267 and 271 kg N /ha for the control, 
late application of alfalfa, silaged alfalfa, chicken manure, grass clover, and alfalfa, 
respectively. There were four replicates of each treatment in a randomized field lay-
out. 
In 2010 the experiment was repeated in a potato crop using slightly adapted 
treatments. The treatments, again in four replicates, were zero application, freshly cut 
alfalfa, alfalfa silage early application, alfalfa silage late application, poultry manure 
and a mixture of cattle slurry with vinasse. Poultry and cattle slurry originated from 
organic sources, vinasse from sugar beet production. Alfalfa early application was 
realized when planting the potato seeds; the other applications took place three weeks 
later when the ridges were build.  The N application rates were 125 kg for the alfalfa 
treatments and the poultry manure treatment, and 93 kg for the mixture of cattle slurry 
and vinasse. 
Results  
Regarding N-availability, it was observed that after soil incorporation the subsequent 
mineralization of plant material was very rapid and within 5 weeks between 27% 
(silaged alfalfa) and 38% (fresh partly-dried alfalfa) was readily available while for 
chicken manure this number staggered at 17%.   
Fresh yield of spinach was the highest with the use of fresh cut grass clover and 
alfalfa, applied 5 weeks before sowing of the spinach (Fig. 1). Yield increased with soil 
mineral-N values at sowing time with maximum yields occurring at around 175 kg 
N/ha. Compared with chicken manure, use of alfalfa and grass clover applied 5 weeks 
before sowing increased N production efficiency by 32-44%. However, delaying 
application to 10 days before sowing did not result in an appreciable improvement of  
N production efficiency. Mineral removal rates amounted to 67-126 kg N, 13-17 kg P 
and 122-233 kg K per hectare.  
0
10
20
30
40
50
Control Alfalfa fresh
10-days
Poultry
manure
Alfalfa silage Alfalfa fresh GrassClover
fresh
Fertilizer treatment
F
re
s
h
 y
ie
ld
 (
t.
/h
a
)
 
Figure 1: Fresh yield of spinach in different fertilizer treatments 
The P and K content of the forage crops closely matched actual crop demands of 
spinach resulting in only relatively slightly positive nutrient balances (Table 1).  
34 
 
The P surplus of the poultry manure is very high. To assess the effects of treatments 
on crop performance we also calculated the apparent nitrogen recovery (ANR). This 
index calculates the additional nitrogen yield in comparison with the non-fertilized 
control per unit nitrogen present in the nutrient source. 
Tab. 1: Mineral balance of phosphate and potassium and ANR for spinach in 
2009.  
 P*  K*  ANR*  
Spinach (kg ha-1)  (kg ha-1)  (%)  
Control -7 e -31 c -  
Alfalfa fresh 10 days 36 b 70 a 21 ab 
Alfalfa silage 21 c 36 bc 23 a 
Poultry manure 141 a 61 ab 15 b 
Grass clover fresh 20 c 89 a 22 ab 
Alfalfa 36 days 14 d 59 b 22 ab 
*Significant for P < 5% after ANOVA 
When the ridges were build in the 2010 potato experiment, soil Nmin in the early alfalfa 
silage plots was on average 38 kg ha
-1
 higher than on the other plots. The marketable 
yield of the potatoes was in all treatments higher than in the control and the alfalfa 
treatments had the highest yields, but differences between the fertilized treatments 
were statistically insignificant. Nitrogen removal rates varied from 64 to 92 kg ha
-1
 . 
The P content of forage crops closely matched actual crop demands of potatoes 
resulting in only relatively slightly positive nutrient balances (Table 2). For K all 
treatments except the Slurry/Vinasse show negative balances. The ANR is lower for 
the poultry manure. 
Tab. 2   Mineral balance of phosphate and potassium and ANR for potato in 
2010.  
 P* K* ANR**  
Potato (kg ha-1) (kg ha-1) (%)  
Control -16 -139 -  
Alfalfa fresh 11 -83 20 b 
Alfalfa silage early 2 -68 22 b 
Alfalfa silage 3 -58 20 b 
Poultry manure 132 -28 11 a 
Slurry/vinasse -10 26 18 b 
* P and K based on measured input and default P and K content. 
**Significant for P < 5% after ANOVA 
Discussion and conclusions 
The nitrogen out of alfalfa and grass-clover has a comparable or better ANR then 
nitrogen out of poultry manure or slurry/vinasse. At crop level the P balance was much 
better using alfalfa or grass-clover in both crops. Use of chicken manure resulted in a 
hyper-accumulation of phosphorus of 132 - 141 kg P ha
-1
. The K balances are more 
ambivalent. This shows that cut-and-carry fertilizers such as fresh or silage alfalfa and 
grass-clover have a high potential as nitrogen fertilizer, meanwhile substantially 
reducing the risk of unbalanced P and K applications. 
35 
 
At farm level, the use of cut-and-carry fertilizers has consequences for the mineral 
balance. If a manure input from outside the farm is replaced by a farm-grown fertilizer, 
less phosphorous and potassium are brought into the farm to compensate the output 
of minerals by sold products. On the other hand, by selling a forage crop a lot of 
nutrients are sold and normally this will be compensated by purchasing manure. The 
overall effect on the mineral balance of introducing cut-and-carry fertilizers in a 
farming system will strongly depend on the starting situation and the choices made by 
the farmer. An economic evaluation study indicated that the cut-and-carry fertilizers 
are of interest with prices above 12 € per ton of cattle slurry (€3.50 kgN
-1
). 
Conclusions  
It is concluded that a cut-and-carry fertilizer system facilitates an effective use of 
perennial leguminous forage crops for sustaining inherent soil fertility. Based on 
studies in spinach and potato it appears that use of freshly cut or silage materials from 
such crops will result in comparable yields while reducing the dependence of arable 
farms on external animal manures by more effectively closing nutrient cycles. It is 
expected that, with pending and more restrictive regulations for the use of animal 
manures and phosphates in the Netherlands, the cost of organic nutrient sources such 
as cattle slurry will increase. This will render the use of cut-and-carry fertilizer crops  
more cost-effective. Using this strategy will further reduce the fertilization cost of 
forage-based systems while minimizing the potential risk of nutrient depletion 
associated with exclusive use of green manure crops or hyper-accumulation of 
phosphate due to excessive use of chicken manure.             
Acknowledgments 
We thank the organic farmer Joost van Strien and Coen ter Berg for their help with the 
trial. The authors gratefully acknowledge funding from the Dutch Ministry of 
Agriculture, Nature and Food Quality. 
References  
Antichi, D., Mazzoncini, M., Barberi, P., Bigongiali, F., Carpi, G. (2008): Leguminous cover crops: 
an important tool for improving resource use efficiency in organic arable cropping systems. 
Cultivating the Future Based on Science: 2nd Conference of ISOFAR, Modena, Italy, June 
18-20, 2008. 
Burgt, G.J.H.M. van der, G.J.M Oomen, A.S.J. Habets and W.A.H. Rossing (2006): The NDICEA 
model, a tool to improve nitrogen use efficiency in cropping systems. Nutrient Cycling in 
Agroecosystems 74: 275-294 
Burgt, G.J.H.M. van der, Timmermans, B, and Berg, C. ter (2010): Luzerne als meststof. 
Onderzoeksresultaat van Strien 2010.  Louis Bolk Instituut, Driebergen, 37 pp. 
Scholberg, J., Berg, C. ter, Staps, S., Strien, J. van (2010): Minder en Anders Bemesten. 
Voordelen van maaimeststoffen voor de teelt van najaarsspinazie. Resultaten veldproef bij 
Joost van Strien in Ens, 2009. Louis Bolk Instituut, Driebergen, order no. 2010-007 LbP, 44 
pp. 
 
 


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