Tropical Grasslands (2010) Volume 44, 192–201 192 The development and production of leaves and tillers by Marandu palisadegrass fertilised with nitrogen and sulphur F.D. DE BONA1 AND F.A. MONTEIRO up the canopy grow (Moore and Moser 1995; Escola Superior de Agricultura ‘Luiz de McMaster 2005). Therefore, alterations in the Queiroz’ (ESALQ), Universidade de São Paulo, rates of leaf and tiller appearance directly deter- Piracicaba, Brasil mine the quantity and seasonality of the dry matter production of grasses. Plant development is influenced by many Abstract environmental factors, most notably air temper- ature (McMaster 2005; Gramig and Stoltenberg The effects of combined nitrogen and sulphur 2007). From the relationship between air tem- fertilisation on the dynamics of leaf and tiller perature and plant development emerges the con- appearance in Marandu palisadegrass (Brachiaria cept of thermal time or degree-days that consist brizantha cv. Marandu) and its impact on dry of the accumulated values of mean daily air tem- matter production were evaluated in a greenhouse perature exceeding the base temperature (Tb), the study. Grass seedlings were grown in pots filled threshold below which plant development ceases with a soil classified as an Entisol and were har- or is negligible (Wilhelm and McMaster 1995). vested after 43 days, a further 35 days and finally According to this model, the production of leaves after 48 more days. Five rates of N (0, 100, 200, per plant is commonly represented by the phyl- 300 and 400 mg/dm3) and 5 rates of S (0, 10, lochron, which is defined as the thermal time 20, 30 and 40 mg/dm3) were tested in an incom- interval between the appearance of two succes- plete factorial design with 4 replications. Leaf sive leaves on the same stem and is represented and tiller development were monitored every by the unit degree-days per leaf (°C.day/leaf) 3 days by counting the appearance of recently (Wilhelm and McMaster 1995; Frank and Bauer expanded leaves and new basal tillers. The phyl- 1995; McMaster et al. 2003). Similarly, tillering lochron and thermal time between appearance rate can be calculated based on thermal time of tillers decreased as N and S fertiliser levels (Chauvel et al. 2000). increased to about 300 and 25 mg/dm3, respec- Other environmental factors such as water, tively, then tended to increase. In contrast, leaf CO2, light and nutrient availability can affect the and tiller appearance rates increased with the phyllochron and tillering of plants (Wilhelm and supply of these nutrients to similar levels, then McMaster 1995; McMaster et al. 2003; Martus- tended to decline. Leaf and tiller production and cello et al. 2005). Few studies have examined dry matter yields were affected by both N and S the effect of nutrient availability on the phyllo- levels, with the role of S increasing as the growth chron, and their results are equivocal. In the case phases increased. of nitrogen, some authors have found a reduction in phyllochron values with an increase in avail- able N (Longnecker et al. 1993; Martuscello et Introduction al. 2005), while others have found no change in this parameter with changing N levels (Cruz and The development of pasture grasses is character- Boval 2000; Stanford et al. 2005). ised by the emergence of tillers, which are basic Characteristics such as high productivity and production units from which the leaves that make rapid regeneration of the canopy after cutting are highly desirable in forage grasses and are major Correspondence: Fabiano Daniel De Bona, Department goals for the nutritional management of pasture of Soil Science, ESALQ-University of São Paulo, Av. Pádua Dias 11, PO Box 9, 13418-900, Piracicaba-SP, Brazil. E-mail: plants. Although several studies have demon- [email protected] strated the positive effects of N use in increased Leaf and tiller development in palisadegrass 193 production and N concentration in forage plant tions. Combinations of 5 rates of N (0, 100, 200, tissue (Lauriault et al. 2002; Reich et al. 2003; 300 and 400 mg/dm3) with 5 rates of S (0, 10, 20, Premazzi et al. 2003), few studies have evalu- 30 and 40 mg/dm3) were evaluated in a surface ated the influence of N availability on the rate of response study in an incomplete factorial with 13 leaf or tiller appearance in these plants (Martus- treatments according to Littell and Mott (1975). cello et al. 2005). In addition, we are unaware of The 13 combinations of N and S rates (in mg/ any previous study that has evaluated the com- dm3) were: 0–0, 0–20, 0–40, 100–10, 100–30, bined effects of N and sulphur (S) on the produc- 200–0, 200–20, 200–40, 300–10, 300–30, 400–0, tion dynamics of forage grasses, even though the 400–20 and 400–40. The N and S were provided close connection and interdependence of these as NH4NO3 and CaSO4.2H2O, respectively, and nutrients in plant metabolism is known (Craw- the quantity of calcium was balanced in the exper- ford et al. 2002). Physiological studies have imental units by the use of CaCl2. Basal fertili- shown that sulphur deficiency suppresses syn- sation with macronutrients for the establishment thesis of sulphur-containing amino acids (Niki- of Marandu palisadegrass was as follows: phos- forova et al. 2006), nitrate reductase activity phorus = 200 mg/dm3, potassium = 150 mg/dm3 (Migge et al. 2000) and nitrate and ammonium and magnesium = 50 mg/dm3, provided through uptake (Clarkson et al. 1989). Therefore, the CaH2PO4, KH2PO4, KCl and MgCl2.6H2O. After present study aimed to evaluate the effects of each harvest (see below), N, S and K fertilisa- combined N and S fertilisation on the dynamics tion was repeated as above, while only 20 mg/ of leaf and tiller appearance in Marandu palisade- dm3 of additional Mg was applied. No P was grass (Brachiaria brizantha cv. Marandu) and its applied after the first harvest, which reduced the impact on dry matter production. quantity of calcium to be balanced. Basal micro- nutrient fertilisation with boron, copper, zinc and molybdenum was performed, together with Materials and methods macronutrient fertilisation, using the following 3 sources and amounts: H3BO3 = 1.5 mg/dm ; 3 3 The study was carried out in a greenhouse in CuCl2.2H2O = 2.5 mg/dm ; ZnCl2 = 2.0 mg/dm ; 3 Piracicaba, São Paulo, Brazil (22° 43’S, 47° and Na2MoO4.2H2O = 0.25 mg/dm . 38’W), from January to May of 2006, using the During the experiment, soil moisture was forage grass Brachiaria brizantha cv. Marandu. maintained at 80% of field capacity by an auto- Pots with capacities of 3.6 L were filled with 5.6 matic subsurface irrigation system, as described kg of dry and sifted soil (mesh sieve = 4 mm) in Bonfim-Silva et al. (2007), which replaced the that had been collected from the 0–20 cm soil water according to the evapotranspiration of the layer of a pasture area. The soil was classified as soil-plant system. an Entisol. Five Brachiaria brizantha cv. Marandu seed- The chemical characteristics of the soil sample lings, grown in washed sand and deionised before treatments were applied included: pH water, were transplanted into each pot when (CaCl2) = 4.53; organic matter (OM) = 32.1 g/kg; they reached a height of approximately 5 cm (3 phosphorus extracted by resin (P-resin), S-sul- developed leaves). Every 3 days, the recently phate, total N, N-ammonium and N-nitrate = 5.8, expanded leaves (visible ligules) and new basal 7.4, 919.0, 21.8 and 14.3 mg/dm3, respectively; tillers produced by the plant were counted. Three potassium, calcium, magnesium, hydrogen plus harvests of the plants were performed at the fol- aluminium (H + Al), sum of bases (S) and cation lowing times: 43 days after transplantation, 35 exchange capacity (CEC) = 2.43, 13.0, 8.67, days after the first harvest and 48 days after the 3 40.0, 24.1 and 64.1 mmolc/dm , respectively; and second harvest (total growing time of 126 days). base saturation (V) and aluminium saturation (m) Each plant was cut at 4 cm above the soil surface, = 37.6 and 16.9%, respectively. Considering the and the plant material was dried in an oven with nutritional requirements of Brachiaria brizantha forced ventilation at 65°C until a constant mass cv. Marandu, lime was added to achieve 50% was reached. base saturation using 300 mg/dm3 and 230 mg/ Air temperatures inside the greenhouse were 3 dm of CaCO3 and MgCO3 salts, respectively. measured and registered by micro data loggers The experimental design consisted of a ran- (NOVUS® series Pingüim). Measurements were domised complete block design with 4 replica- performed every half hour for 24 hours each 194 F.D. De Bona and F.A. Monteiro day. The mean maximum, minimum and average where NNT is the number of new tillers produced daily air temperatures during the experiment are by the plant and TTa is the accumulated thermal presented in Figure 1. time for the assessment period (3 days). The daily thermal time (TTd, °C.day) was The phyllochron (°C.day/leaf) and the thermal determined according to Arnold (1960): time between appearances of tillers (TBAT, TTd = (Tave – Tb).1 day °C.day/tiller) were obtained from the inverses of the LAR (1/LAR) and TAR (1/TAR), respec- where Tave is the average air temperature tively. obtained from the arithmetic mean of the 48 The variables were evaluated by response air temperature readings performed during the surface analysis using the SAS software (SAS day and Tb (base temperature) is the tempera- ture threshold for the development of Brachi- Institute, Cary, NC, USA).