The impact of legumes incorporation on the yield formation in organic crop rotation

Zydre Kadziuliene and Lina Sarunaite

Abstract – A whole range factors and their influence the potential of legumes as nitrogen suppliers to subsequent crops. The experiments were aimed to assess the impact of several legumes  to crop yield in organic crop rotation. Diferent field studies were conducted on a loamy Endocalcari-Epihypogleyic Cambisol in Dotnuva (55o 24' N). The effect of different legume/grass swards on the subsequent winter wheat crop depended on sward composition, and highest grain yield was obtained after ploughed-in lucerne. Spring wheat following lucerne/grass swards produced a higher grain yield than that red clover swards. Pre-crop of white clover and conventional drilling significantly affected winter wheat grain yield and the yield of triticale was higher following wheat after pre-crops that included white clover.  The highest winter wheat and following barley grain yield was achieved on the ploughed-in legumes plots using conventional sowing method.

Introduction
There is a general view that organic farming is leading a development towards a more integrative view on agriculture, food production and environment. It is often suggest that organic farming solves many of the problems observed in conventional intensive agriculture (Jensen,2003). Unlike conventional farming, organic farming has to rely on efficient nutrient circulation within the farm to maintain soil fertility and high production. Organic farming is affected by many factors, such as management, climate and soils, all of which interact over time and space (Olesen, 1999). Unfortunately, in Lithuania many organic farms are involved solely in crop production, farming without livestock. Hence, there is a need for alternative strategies for nutrient management. Introduction of ley/arable rotations could be an effective tool for a significant further reduction of the use of external mineral N-input and an increase of the N use efficiency (Nevens et al., 2004). Therefore legumes are of great importance in organic plant production as valuable preceding crop, as catch crop in general and because of their biological nitrogen fixation (Younie, 2000). A whole range of factors and their interactions influence the potential of legumes, which is greatly dependent on legume species and successful management (Bergkvist, 2003; Kadziulis, 2001; Maiksteniene and Arlauskiene, 2004). The aim of the studies was to asssess the potential of several forage legumes as nitrogen suppliers to subsequent crops.

Materials and methods
Different field experiments were conducted on a loamy Endocalcari-Epihypogleyic Cambisol in Dotnuva (55o 24' N). Soil pH varied between 6.5 - 7.0, humus content - 2.5-4.0 %, available P 50-80 and K 100-150 mg kg-1. Experiment 1. Legume/grass swards (Table 1) of 3rd year use in summer were ploughed-in and winter wheat for grain was sown in autumn. Experiment 2. Different legume/grass mixtures (Table 2) in 2nd year of swards age in autumn were ploughed-in and spring wheat for grain was sown in spring. Experiment 3. Winter wheat was no-till or conventionally drilled into pre-crop barley  for grain,  white clover with barley cover crop, white clover for forage, and white clover for green manure was harvested for grain (Table 3). In autumn triticale was conventionally drilled. Experiment 4. In the autumn 2003, winter wheat was no-till or conventionally drilled into pre-crops as peas, white clover, red clover, barley, and perennial  ryegrass (Table 4). In 2005, spring barley was  no-till or conventionally drilled.
The yield data were statistically processed using analysis of variance.

Results 
Experiment 1.
The DM yield of swards was depended on legume species (Table 1). The lucerne based swards were the highest yielding before swards ploughed-in. Winter wheat grain yield was low.
  
Table 1. Effect of ploughed-in different legume and legume/grass swards (2002) on winter wheat yield (2003)  
Swards	DM  t ha-1	Wheat grain yield t ha-1	
White clover 	1.64	2.54	
Red clover 	1.58	2.70	
Lucerne 	4.78	3.43	
W. clover/grasses	1.53	2.53	
W. clover, r. clover/grasses	1.58	2.33	
W.clover, lucerne/grasses	4.83	3.58	
Grasses/N0	0.77	1.71	
LSD05	0.645	0.424	

This was resulted from growing conditions and the N-release to the succeeding crop. The highest yield was obtained when it had been grown after ploughed-in lucerne-based swards.

Experiment 2.
The lucerne based swards were more productive in the second year of age and the highest forage yield was obtained from lucerne/grass sward grown without cover crop, therefore spring wheat following lucerne/grass swards produced a higher grain yield (Table 2). 

Table 2. The impact of legumes on spring wheat grain yield (2005)
Swards+cover crop	DM yield
 t ha-1	Wheat grain yield
t ha-1	
	2004	2005	
R. clover, p. ryegrass 	6.05	2.98	
R. clover,  p. ryegrass+Bgr	5.60	3.09	
R. clover, p.ryegrass+Bwc	5.87	3.20	
R. clover, p.ryegrass+Pwc	5.71	3.27	
Lucerne, p. ryegrass 	9.19	3.85	
Lucerne, p. ryegrass+Bwc	7.46	3.78	
Lucerne, p. ryegrass+Pwc	9.08	3.81	
Perennial ryegrass	2.85	2.09	
LSD05	0.919	0.212	
Bgr–barley for grain, Bwc-barley for whole crop, Pwc-peas for whole crop

Experiment 3.
Both pre-crop and sowing method affected the winter wheat grain yield (Table 3). A significantly higher wheat grain yield was obtained having used conventional sowing compared with no-till sowing. Wheat after white clover ploughed-in and with conventional sowing was higher yielding than after conventionally sown barley. The yield of triticale was also higher following wheat after pre-crops that included white clover.

Table 3. The impact of pre-crop and sowing method on wheat (2003) and triticale (2004) grain yield 
Wheat pre-crops + sowing method	W. clover (DM) or barley grain1) 
(t ha-1)	Wheat 
(t ha-1)	Triticale
(t ha-1) 	
Barley, CD	3.211)	4.59	2.99	
White clover, NT 	1.41	3.01	3.79	
W. clover, barley cover crop, NT	2.861)	2.45	3.46	
W. clover, green manure, CD	1.23	4.89	3.78	
White clover, CD	1.27	5.07	3.18	
LSD05		0.641	0.493	
CD- conventional drilling; NT- no-till drilling

Experiment 4.
The wheat grain yield was determined by different growth conditions: sowing method, amount of biological nitrogen accumulated by different pre-crops, and climatic conditions. The highest wheat grain yield was achieved on the ploughed-in legumes plots using conventional sowing method (Table 4). Grain yield after ploughed-in peas and conventional drilling was 15 per cent higher compared to direct drilling after pre-crop peas. Grain yields with application of conventional drilling after white clover and after red clover were respectively 3.7 and 7.9 times higher compared to no-till drilling application after the same pre-crop. Barley grain yield was obtained also higher having used conventional drilling. Barley competed weakly with white clover and red clover, and even with weeds in no-till peas, therefore grain yield in no-till drilling was very low.

Table 4. The impact of legumes and sowing method on wheat (2004) and barley (2005) grain yield 
Wheat pre-crops + sowing method	Forage DM or grain1) 
(t ha-1)	Wheat (t ha-1)
	Barley
(t ha-1)	
Barley, CD	  3.30-1)	2.68	2.29	
Peas, CD	5.00	3.70	1.89	
Peas, NT	5.06	3.22	0.27	
White clover, CD	1.63	3.77	2.02	
W.clover, NT 	3.03	1.02	0.11 	
Red clover, CD	2.11	3.80	2.23	
R. clover, NT	3.00	0.48	0.26 	
P.ryegrass, NT	1.04	2.91	2.01	
LSD05	0.429	0.306	0.199	
CD- conventional drilling; NT- no-till drilling

Conclusions
Lucerne-based swards showed the highest effect on subsequent crops. More comprehensive investigations are necessary to draw clearer conclusions about the influence of legumes on subsequent crop in different crop rotations and using no-till drilling method. 

Acknowledgement
This study was partly funded by the Lithuanian State Foundation of Science and Studies.

References
Bergkvist, G. (2003). Acta Agric.Scand., SectB, Soil and Plant Sci. 53: 97-109. 

Jensen, E.S. (2003). In “Nordic Agriculture in Global Perspective”, pp.190-193. (NJF: Turku, Finland).

Kadziulis, L. (2001). Grassland Science in Europe 6:51-54.

Maiksteniene, S. and Arlauskiene, A. (2004). Agronomy Research 2(1): 87-97.

Nevens, F., Bommele, L.M., Reheul, D., Verbruggen, I. and De Cauwer, B. (2004). Grassland Science in Europe 9:532-534.

Olesen, J.E. (1999). In “Designing and Testing Crop Rotations for Organic Farming” pp.11-19, eds. J.E. Olesen et al. (DARCOF Report, Denmark). 

Younie, D. (2000). In “Grass:its Production and  Utilization” pp.365-393, ed. A. Hopkins. (British Grassland Society: Blackwell Publishing Ltd).