Effect of Phosphate Fertilization on Flooding Pampa Grasslands (Argentina)

Abstract

We postulate that phosphorus (P) fertilization may increase above-ground net primary productivity (ANPP) of rotationally grazed rangelands without reducing the legume component, as does N fertilization. In doing so, we evaluated the effect of phosphate fertilization on the production and relative contribution of legumes and grasses of native and old tall fescue (Festuca arundinacea Schreb) grasslands; we recorded annual production, seasonal productivity, and biomass contribution of each component. The experiment was conducted in a commercial farm located in the Flooding Pampa and managed under rotational grazing. Treatments consisted of two fertilization programs (66 (P 66) and 29 (P 29) kg P ? ha 21 supplied as rock phosphate and/ or monoammonium phosphate from 1997 to 1999) and a nonfertilized control. A paddock dominated by native grassland and another dominated by old tall fescue grassland were selected. Nine 5-ha plots were established in each paddock, and treatments were randomly assigned. During the experimental period, from October 1998 to October 1999, total above-ground biomass was harvested from each plot before and after each grazing period and separated into components: tall fescue, other C 3 perennial grasses, legumes, C 3 annual grasses, C 4 grasses, forbs, and standing dead material. ANPP of each component was estimated during the warm (October 1998-February 1999) and the cool (March 1999-September 1999) season. In native grassland, phosphate fertilization increased ANPP of C 3 annual grasses and legumes during both the warm and the cool seasons; therefore annual ANPP of the grassland under P 66 was 40% higher than under P 29 and doubled ANPP of nonfertilized plots. Phosphate fertilization didn't increase total annual ANPP of old tall fescue grassland, but it did increase ANPP of legumes during both seasons. Resumen Postulamos que la fertilización fosforada permitiría incrementar la productividad primaria neta aérea (PPNA) de pastizales naturales y pasturas viejas dominadas por festuca sin afectar la contribución de las leguminosas, como ocurre cuando se fertiliza con nitrógeno. Para ello, se comparó la productividad estacional y anual así como la contribución de gramíneas y leguminosas en cada recurso, con distintos programas de fertilización: dos niveles de fósforo (66 y 29 kg de P ? ha 21 adicionados como roca fosfatada y/o fosfato monoamónico en sucesivas aplicaciones entre 1997 y 1999) y un control sin fertilización. El experimento se llevó a cabo en un establecimiento manejado con pastoreo rotativo ubicado en la Pampa Inundable, donde se seleccionaron dos potreros, uno de pastizal natural y otro de pastura dominada por festuca. En cada potrero se establecieron 9 parcelas de 5 ha a las que se asignaron al azar los tratamientos. Entre octubre de 1998 y octubre de 1999 se cosechó la biomasa de cada parcela antes y despue´s de cada pastoreo y se separó en: festuca, otras gramíneas C 3 perennes, leguminosas, gramíneas C 3 anuales, gramíneas C 4 , dicotiledóneas y material muerto de cada component...

Protection offered by leaf fungal endophytes to an invasive species against native herbivores depends on soil nutrients

“…This bottom-up control of herbivore populations should be evidenced by the enhancement of both plant productivity and insect abundance with high soil P availability. Although P has been proposed as one of the most important limiting factors for productivity of the Flooding Pampa grasslands due their chronic P shortage in soils, the evidence is not conclusive (Collantes, Stofella, Ginzo, & Kade, 1988;Ginzo, Collantes, & Caso, 1982;Rodríguez, Jacobo, Scardaoni, & Deregibus, 2007;Semmartin, Oyarzabal, Loretti, & Oesterheld, 2007). In particular, studies evaluating the addition of P in a natural grassland with very low cover of N-fixing legumes (Semmartin et al, 2007) and in an old pasture with tall fescue as main component (Rodríguez et al, 2007) found no significant response in terms of above-ground biomass production.…”

“…Although P has been proposed as one of the most important limiting factors for productivity of the Flooding Pampa grasslands due their chronic P shortage in soils, the evidence is not conclusive (Collantes, Stofella, Ginzo, & Kade, 1988;Ginzo, Collantes, & Caso, 1982;Rodríguez, Jacobo, Scardaoni, & Deregibus, 2007;Semmartin, Oyarzabal, Loretti, & Oesterheld, 2007). In particular, studies evaluating the addition of P in a natural grassland with very low cover of N-fixing legumes (Semmartin et al, 2007) and in an old pasture with tall fescue as main component (Rodríguez et al, 2007) found no significant response in terms of above-ground biomass production. Light availability is an important restriction for primary production in humid and subhumid grasslands such as the Flooding Pampa grasslands (Borer et al, 2014;Milchunas, Sala, & Lauenroth, 1988;Semmartin & Oesterheld, 2001;Semmartin et al, 2007).…”

Characterization of alkaline stress tolerance mechanisms inLotusforage species modulated byPantoea eucalypti

“…In the Salado River Basin, Argentina, the proportion of cropland has increased in areas historically used for raising cattle [25]. the Flooding Pampa [5,26]. Some of these strategies involve identifying and selecting was not certified by peer review) is the author/funder.…”

Glyphosate effects on seed bank and vegetation composition of temperate grasslands

“…), or rotational grazing with phosphate fertilization, which increases the production of C 3 annual grasses and legumes (Rodríguez et al. ). Both alternatives reduce the seasonal variability of plant production by increasing winter forage production and lead to an improvement in rangeland condition and carrying capacity (from 0.6 to 1.0 Animal Units ha −1 ).…”