Nutrient use efficiency in different harvesting strategies of silage swards based on timothy and two fescue species

Transcription

1 Nutrient use efficiency in different harvesting strategies of silage swards based on timothy and two fescue species Kirsi Pakarinen, Maarit Hyrkäs, Raija Suomela, Perttu Virkajärvi MTT Agrifood Research Finland, Maaninka XVI International Silage Conference, Hämeenlinna, Finland 2 4 July 2012

2 Introduction Mineral nutrients in grassland In plants in the yield Uptake for growth and survival whole plant Removal in the yield harvested plant parts In animals - digestion of nutrients In manure - indigested nutrients In the soil and field level Nutrient dynamics in the soil Field gate budgets Environmental effects Economical effects Agricultural and environmental policy

3 Objectives Background and aim of this study Updated advisory guideline in Finland: From the point of animal performance and economical profitability, the combination of different cutting times and the number of cuts can be a farm-specific solution (a farm can have a rather large time window in cutting times) But: Changing the harvesting strategy, the dry matter (DM) yield, nutritive value and the content of mineral nutrients change What are the implications for nutrient use efficiency (NUE)?

4 Materials & Methods Experimental design Comparison of harvesting strategies in field experiments 3 cuts vs. 2 cuts in three combinations (during ) Experiment I (Maaninka): timothy (TIM) + meadow fescue (MF) Experiment II (Ruukki): pure TIM Timing of the second cut in 2 cut strategy Experiment III (Maaninka): TIM and tall fescue (TF) in pure stands, during Amounts of applied mineral nutrients N, P and K recorded DM yield and concentrations of N, P and K in the yield analyzed Nutrient yields for N, P and K calculated Annual NUE (nutrient yield divided by nutrients applied) for N, P and K were calculated a perfect balance, if NUE = ( red bar in result figures)

5 Results Effect of harvesting strategies on DM yield Strategy 1 st cut Regrowth (wks) Effect of 3 vs. 2 cuts harvesting strategies Experiment I (Maaninka): TIM + MF, Experiment II (Ruukki): pure TIM, Effect of timing of the 2nd cut (Experiment III, Maaninka) 2 cuts 2 cuts 2 cuts Booting Booting Booting Delaying the cutting time during 1 st cut in 2 cut strategies increased the yield, yield level of 3 cut strategies vary Delaying the cutting time during 2 nd cut increased the yield

6 Results Effect of 3-cut vs. 2-cut strategy, Maaninka (Experiment I) NOTE! Differing scales on X axes Strategy 1 st cut Regrowth (wks) NUE N NUE P NUE K 7 % higher NUE P with 3 cut strategy than with 2 cuts in average

7 Results Effect of 3-cut vs. 2-cut strategy, Ruukki (Experiment II) NOTE! Differing scales on X axes Strategy NUE N NUE P NUE K 1 st cut Regrowth (wks) Slight increase in NUE N inside 2 cut strategies 25 % higher NUE P with 3 cuts than with 2 cuts in average Moderate increase inside 2 cut strategies Moderate increase in NUE K inside 2 cut strategies

8 Results Differencies between nutrients and locations Strategy 1 st cut Regrowth (wks) Maaninka: mineral soil, Ruukki: high organic matter content in soil NUE N +6; NOW SAME scales on X axes! NUE P +6; Major differences between K availability of the soils and K fertilization levels! NUE K +6;

9 Results Effect of the timing of the 2nd cut 2.5 NUE N 2.5 NUE P 2.5 NUE K Strategy 2 cuts 2 cuts 2 cuts 2 cuts 2 cuts 2 cuts 2 cuts 2 cuts 2 cuts 1 st cut egrowth (wks) Booting Booting Booting Booting Booting Booting Booting Booting Booting All N was already uptaken before the first cut of regrowth ~ 90 % of P and K were already uptaken at 4 weeks of regrowth New uptake of K was unsignificant after 6 weeks of regrowth

10 Discussion Harvesting strategy affects more the DM yield than NUE DM yields increased as the cutting time was prolonged Mineral nutrients N, P and K seem to be uptaken at early developmental stages of the silage sward Later on, diluted into the DM Grasses have a great capacity of P and K uptake Concentration of P appr. 2,1 2,9 g kg -1 DM Concentration of K appr. 19,6 29,5 g kg -1 DM Near to luxury uptake?

11 Discussion So, where is the drama in NUE? What if NUE is constantly >>? May lead to reduced soil fertility Correlation with increasing yield levels? In some cases harvesting strategy can make a difference E.g. in Experiment II: changing from 2 to 3 cuts, the uptake of P increased by 6,0 7,5 kg P ha -1 year -1 At the moment, this can not be compensated by fertilization! During a 4-year cycle, effects to soil fertility may be significant Are current environmental practices and the maximum levels for fertilization up-to-date?

12 Conclusions Nutrient use efficiency in silage swards Grasses can easily have NUE values > NUE N not affected by the harvesting strategy Source of differences in NUE N : Soil N, yield level NUE P increased by 3 cut strategy (vs. 2 cuts) Source of differences in NUE P : Harvesting strategy, Soil P, yield level, fertilization level NUE K affected mostly by other factors than harvesting strategy Source of differences in NUE K : Soil K, yield level, fertilization level In most cases, choice of harvesting strategy does not bring out new environmental risks

13 Thank you for your attention!