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<strong>AGRONOMIJAS</strong> VĒSTIS (Latvian Journal of Agronomy), No.10, LLU, 2008%1008060402001 2 3 4 5 6 7 8 9 101112131415161718R05%30201001 2 3 4 5 6 7 8 9 101112131415161718R05TreatmentTreatmentFigure 1. Impact of fertilization on development of grasses and legumes in natural swardAccording to the data of the research fertilization background had greater effect on the legumesthan on grasses in the natural sward (Fig. 1). Forage should be composed at least 40 % of legumesfor full providing of proteins. The share of legumes determined 13 % (2004) and 17 % (2005) inthe treatment without fertilizers. A small N60 rate increased the share of legumes by 2% in the 2ndand did not have any impact in the 3rd yr. A double N120 rate had a negative effect on legumes inthe natural sward. This is demonstrated by both yrs’ data. A N180 fertilizing backgrounddecreased the share of legumes by 5 % only in the 3rd yr and did not have any influence in the 2ndyr. The greatest N240 kg ha-1 rate applied during the experiment decreased the share of legumesby 1 % in the 2nd and by 10 % in the 3rd yr. Applying nitrogen fertilizers together with phosphorusincreased the rate of legumes by 2 % in the 2nd and decreased their quantity by 2 % in the 3rd yr.A background of nitrogen and potassium (N180K150) had a similar influence, only in 2005legumes decreased by 3 % in compared to the control treatment. Treatments treated withphosphorus fertilizers showed a positive influence on the legumes of the natural sward. As the ratesof phosphorus fertilizers increased, legumes showed increase tendencies both in the 2nd and the3rd yr. However, the same number of legumes was found after separate treatments had beenfertilized with rates of P120 and P160 in 2005. A background of P120K150 statisticallysignificantly increased the quantities of legumes in 2004. Significant increase of legumes was alsodetermined in the treatments fertilized with K100, K150 and K200. The share of legumes increasedby 3, 2 and 1 % respectively K rates in 2005. Share of legumes determined closer to the controltreatment and fluctuated less at NPK treatments.Forbs are an inevitable part of every natural sward. Forbs ranged from 14 % in the 2nd yrand 16 % of in the 3rd yr in a control treatment of natural sward (Fig. 2).The share of forbs decreased by 1 % in a treatment treated with N60 in compare to thecontrol both in 2004 and 2005. The tendencies of forbs decreasing remained with increased N rateto 120 kg ha-1. Share of forbs decreased by 4 % and by 2 % in the treatment N180 kg during 2004-2005. With applying the greatest rate (N240) the share of forbs decreased also. The greatest P ratesin this investigation significantly increased the quantity of forbs especially in the second yr.Accordingly to the obtained data the quantity of forbs decreased both in the 2nd and the 3rd yr inthe PK treatments.Impact of fertilization background on the botanical composition of a natural sward.According to the data of botanical composition of the sowed sward in 2004, a ratio betweengrasses and legumes changed by 5-10% in compare to the composition of the sowed mixture (Fig.2 and 3). Increase of grasses share was observed in treatments 4 and 5, 12, 17 and 18. Thesetreatments had been treated with N fertilizers. Legumes made 29-40 % of the total composition ofthe sward in 2004. It was observed in the 2nd yr already that legumes reacted negatively to thebackground of N. The share of legumes was by 6 % less than in the control treatment (N0P0K0). Inthe treatment fertilized with a 240kg ha-1 rate of N, The background of P (from 120 kg ha-1) and Kinfluenced legumes in a positive way and their share grew up. Legumes rate increased by 5 % inthe treatments fertilized with K100 and K200 at the 2nd yr after sowing than in a control treatment.In all treatments 1-5 % of forbs were found.130
<strong>AGRONOMIJAS</strong> VĒSTIS (Latvian Journal of Agronomy), No.10, LLU, 2008%30201001 2 3 4 5 6 7 8 9 101112131415161718R05Treatment100806040200%1 2 3 4 5 6 7 8 9 101112131415161718R05TreatmentFigure 2. Impact of fertilization on development of forbs in natural sward and grasses in sowedswardBotanical composition of the sowed sward varied more during 2005 in compare with 2004. Theshare of grasses increased from 4 to 14 % in all treatments. Increase in the share of legumes wasnot observed in the 3rd yr after sowing an in any treatment irrespectively from the fertilizingbackground. Increase in the share of grasses was determined in the treatments with greater rate ofN (treatment No.5), as well as NP and NPK. The share of legumes decreased from 4 to 18% indifferent fertilizing backgrounds. Share of legumes remained by 4 to 12 % higher in the treatmentswith P and K backgrounds than in other treatments in 2005. Share of legumes determined by 18 %less in the treatment fertilized with the greatest rate of N than in the treatment without fertilizers(Control) in 2005. DM accumulated more in sowed sward than in a natural one, except for thetreatment fertilized with the greatest rate of N in 2005. The highest concentration of DM wereobserved in the treatments fertilized with the biggest rate of N240, in N180+P120 as well as in thetreatment fertilized with NPK both in case of the sowed and natural swards.Share of forbs was accounted for 1-10 % of the swards in 2004 (Fig. 3). The largestamounts of them were found in treatments fertilized with K50 and K100. That is by 3 % more thanin a control treatment. Fertilizing with phosphorus and potassium only did not have any significantinfluence on forbs in 2004. Share of forbs decreased by 6 % in treatments fertilized with NK, NPand NPK, than in the control sward. Forbs composition was found increased in five treatmentsthan control in 2005. Treatments N180, N60 and N60P40K50 especially distinguished themselves,due to the increased amount of forbs compared both to the control treatment and investigations ofthe 1st and the 2nd yr.%504030201001 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 R05Treatment%141210864201 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 R05Treatment2004 20052004 2005Figure 3. Impact of fertilization on development of legumes and forbes in sowed sward131
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AGRONOMIJAS VÄSTIS - Latvijas LauksaimniecÄ«bas universitÄte