The evolution of the nutrition index in relation to water regime

International audienceThe studies where carried out on two permanent grasslands located in France, in the Central Pyrenees (Ercé) and in the Massif-Central (Gramond). Our results show that there is an inverse relationship between the total biomass and a synthetic indicator of the water regime, namely, the number of decades with a reserve RFU=0 on the horizon 0-5 cm. easy to use. The results also revealed a marked reduction of the nitrogen nutrition index (IN) when the mineral balance becomes negative. This result suggests that the IN is able to account for the depletion of the level of reserves in nitrogen as a result of changing balances accumulated over time. However, the question arises to what extent this development does not depend on water conditions that have prevailed over the last 2 years (2003 and 2004)

The evolution of the nutrition index in relation to water regime

International audienceThe studies where carried out on two permanent grasslands located in France, in the Central Pyrenees (Ercé) and in the Massif-Central (Gramond). Our results show that there is an inverse relationship between the total biomass and a synthetic indicator of the water regime, namely, the number of decades with a reserve RFU=0 on the horizon 0-5 cm. easy to use. The results also revealed a marked reduction of the nitrogen nutrition index (IN) when the mineral balance becomes negative. This result suggests that the IN is able to account for the depletion of the level of reserves in nitrogen as a result of changing balances accumulated over time. However, the question arises to what extent this development does not depend on water conditions that have prevailed over the last 2 years (2003 and 2004)

Influence of leguminous fractions on in and ip index

The studies where carried out since 1999 on a permanent grassland placed on an alluvial soil from France, in the Central Pyrenees (Ercé). The experiment consisted from 2 annual doses of fertilization with N and P arranged in 4 randomised blocks. The analysis of IN and IP index using the cycle of growth method will provide the opportunity to analyze the effect of N and P levels on the nutrition of the grassland, and their impact on plants growth. The method for determining the nutritional index are based on plant analysis and show the concentration of mineral elements N and P depending on their accumulation in the plant biomass. The literature data have shown that considering the biomass of the legumes fraction in the calculation of IN and IP index, there are resulting errors in the estimation of nitrogen and phosphorus nutrition level, the index being overestimated in comparison with its real value. The data presented were collected only on the N0P0 and N0P1 fertilisation doses (where N0= 0 kg N ha-1 yr-1; P0= 0 kg P ha-1 yr-1; P1= 50 kg P ha-1yr-1), for cycles in that legumes percentage over 10% was registered in 2000 and 2002. IN and IP index of mixture fractions were calculated from N% and P% concentration of mixture fraction; IN and IP index of fractions without legumes (nonleg) were calculated from the levels of N% and P% of nonleg fractions. The difference between the index calculated from the mixture fraction and calculated for the nonleg fraction is even more important than the contribution of legumes harvested biomass. The results for the IN as well as for the IP confirm the need of doing tests on mineral-free forage legumes, if is necessary to eliminate the inaccuracies of the obtained results when the percentage of legumes in mixture biomass is higher then 10%

Multiannual evolution of the nutrition index in relationship with the annual balances

International audienceNutrition index are used on a wide scale for the diagnsosis of the mineral nutrition of the grasslands and to facilitate the decisions regarding their fertilisation mode.In literature are available few data regarding the inter-annual evolution of the nutrition indexes in relationship with the cumulated mineral balances. The problems that are coming from are to find out the measure in that those indexes are able to provide piece of information on the evolution of the N and P supplies level in the case that the mineral balance is positive or in the case in that the mineral balance is negative. The experimental fields were set by the Orphée team (INRA Toulouse) on two grassland types different from the pedological and climatic point of view, placed in Ercé in Central Pyrenees in 1999 (0° east, 43° north) and in Gramond in Massif Central in 1998 (2° east, 44° north). There were applied four treatments: N0P0, N0P1, N1P0 et N1P1; where 0 is correaponding to a treatment wihout N or P input; 1 is correasponding to a variable input depending by year and P correasponds to a unique annual dose of 50 kg ha– 1. On the ensemble of the plots was provided an input of 400 kg ha–1 year–1 of K as KCl applied in every year to provide a non-limited potassium level. The results are showing that IN are able to provide pieces of information regarding the finish the nitrogen supply level under the influence of the balance cumulated in time. When the available P level is low, the IP nutrition indexes measured for P0 treatments show that the level of the available P supplies are finishing when the cumulated balance I–O becomes negative. In some situations the cumulative effects haven’t diminished significantly the available P level from soil, the IP nutrition indexes being sensitive to the evolutions of P balance during time

Multiannual evolution of the nutrition index in relationship with the annual balances

International audienceNutrition index are used on a wide scale for the diagnsosis of the mineral nutrition of the grasslands and to facilitate the decisions regarding their fertilisation mode.In literature are available few data regarding the inter-annual evolution of the nutrition indexes in relationship with the cumulated mineral balances. The problems that are coming from are to find out the measure in that those indexes are able to provide piece of information on the evolution of the N and P supplies level in the case that the mineral balance is positive or in the case in that the mineral balance is negative. The experimental fields were set by the Orphée team (INRA Toulouse) on two grassland types different from the pedological and climatic point of view, placed in Ercé in Central Pyrenees in 1999 (0° east, 43° north) and in Gramond in Massif Central in 1998 (2° east, 44° north). There were applied four treatments: N0P0, N0P1, N1P0 et N1P1; where 0 is correaponding to a treatment wihout N or P input; 1 is correasponding to a variable input depending by year and P correasponds to a unique annual dose of 50 kg ha– 1. On the ensemble of the plots was provided an input of 400 kg ha–1 year–1 of K as KCl applied in every year to provide a non-limited potassium level. The results are showing that IN are able to provide pieces of information regarding the finish the nitrogen supply level under the influence of the balance cumulated in time. When the available P level is low, the IP nutrition indexes measured for P0 treatments show that the level of the available P supplies are finishing when the cumulated balance I–O becomes negative. In some situations the cumulative effects haven’t diminished significantly the available P level from soil, the IP nutrition indexes being sensitive to the evolutions of P balance during time