Triticale genotype evaluated

The genotype evaluated was Triticale 118 from the College of Postgraduates. The sowing of cycle 1 was carried out on December 05, 2012 and that of cycle 02 on December 04, 2013, the sowing density used was 100 kg ha^-1. The experimental plots were 2 m wide by 10 m long, and three replications were established. Fertilization was 40-40-00 NPK at planting and 40 nitrogen units at the beginning of the tillering process. The experimental plots were watered nine times, at fifteen-day intervals at field capacity.

Average height of the evaluated varieties

The height of 20 plants chosen at random in each experimental unit was measured with a ruler of 1.5 m in length, registering the height data that indicated the movable mica of the ruler at the first contact with the plant.

Intercepted radiation (IR)

Before cutting the plants in the sampling units, 5 readings were taken at random, of the amount of solar radiation intercepted by the plants within each sampling unit with the Model LP-80 Ceptometer (Decagon Devices, Inc.), at 12:00 a day.

Forage accumulation

From 43 days after sowing, forage samples were harvested every 7 days, until Triticale 118 reached physiological maturity. The sampling unit was a 0.45 m² table, within which all the Triticale 118 plants were cut at a height of 12 cm above ground level. The harvested forage was dried to constant weight, in a forced air oven at 55 °C. With the dry weight, the forage yield per hectare was calculated. The main stages of development were identified, using the scale of ^{Zadoks et al. (1974)}.

Morphological composition of harvested forage

To estimate the morphological components, a subsample of 100 g of harvested forage was taken. The subsample was separated into leaves, stems, ears and dead material. Each component was placed in identified industrial paper bags and dried in a forced air stove at 55 °C to constant weight and weighed with a digital scale (Gramera Brand Model hh). The dry weight in kg ha^-1 of each component was estimated.

Leaf area index (LAI)

Before drying the leaves obtained from the subsample (100 g), their leaf area was determined with an integrator model LI-3100 (LI-COR, inc.). The LAI was estimated with the data obtained from the leaf area and the area of the sampling unit.

Statistical analysis

The experimental design used was in repeated measures over time with three repetitions. The data of the measurements made were analyzed with the SAS GLM (Statistical Analysis System Version 9.0 for Windows) procedure. Tukey’s test was used to compare means (α= 0.05).

Dry matter yield

In cycle 1, the maximum recorded forage accumulation was found at 84 dds, with a yield of 1 852 kg ha^-1 when it was in ear (52, Zadoks). This was the last sampling date due to the premature death of the plants caused by a frost, which was the most intense throughout the cycle (Figure 1).

Figure 1 DM accumulation, morphological composition, LAI, IR and height of Triticale 118 in winter. 

In the case of cycle 2 the highest dry matter accumulation value was 8 733 kg of DM ha^-1, this was found at 119 dds, since at 126 dds the dry matter value decreased to 7 653 kg of DM ha^-1 (Figure 2). Comparing the production cycles, from sowing to 84 days, the best performance was observed in cycle 2, since as indicated in cycle 1, the maximum accumulation of dry matter was 1 852 kg of DM ha^-1, while for the same date in cycle 2 it was 2 85 kg of DM^-1, a situation that was due to the greater presence of frost in cycle 1 with a total of 79, while in cycle two there were only 72 (Table 1). It is worth mentioning that this type of crops are resistant to low temperatures and require accumulation of cold hours to complete their development cycle, low temperatures also affect their development and very intense frosts can cause plant death (^{Llera and Cruz, 2014}).

Figure 2 DM accumulation, morphological composition, LAI, IR and height of Triticale 118 in winter. 

In the second cycle, it is in which the highest DM yield is reached at 119 dds, which is why it is considered a late genotype, for this reason ^{Morant et al. (2007)}, mention that the most important characteristics that forage wheat and triticales should possess are having a longer biological cycle and being adapted to early sowing, which would allow having a longer vegetative phase for a greater number of cuts.

Morphological composition

In cycle 1, the best leaf yields in combination with the highest leaf/stem ratio were found between 63 and 77 dds with average leaf and stem yields of 784 and 273 kg ha^-1, since, for the following sampling, the percentage of leaf in relation to the stem was equalized, which detracts from the quality of the forage. In cycle 2, the greatest contribution of leaves to total yield and the best leaf/stem ratio was also found between 77 and 91 dds in the enchanting state (35, Zadoks) with leaf and stem of 1 111 and 661 kg ha^-1, in the case of 77 dds.

Similar data is reported by ^{Keles et al. (2013)}, that when evaluating the yield of triticale in the tillering and mowing stages, reported that winter cereals can be grazed until the mowing stage, without causing large reductions in the yield of regrowth and total forage.

Regarding the ear, the data indicates that from 91 dds it appears, with a yield of 550 kg of DM ha^-1, and later up to 126 dds with a yield of 3 843 kg of DM ha^-1, situation that the quality of forage decreases when the proportion of this morphological component is higher; similar results have been reported in the literature (^{Pérez-Amaro et al., 2004}).

The quality of a forage is generally related to the age of the plants, since, in advanced stages of development, senescent leaves tend to fall, which was reflected in the latest samplings; likewise, a shadow effect is produced on the lower leaves by those of the upper stratum, causing their death, in cycle 2 for the 122 dds a quantity of 147 kg ha^-1 of dead matter was observed, mainly senescent leaves (^{Chapman and Lemaire, 1993}).

In the case of the ears, these also form in advanced stages of development, initiating a process of translocation of photosynthates from the stems and the leaves for the filling of grain, with the consequent death of the leaves that are those that provide the highest quality to the harvested forage (^{Juskiw et al., 2000}).

Foliar area index

In the cycle 1 experiment, the LAI variable reached its highest value on the 77 dds, which was 1.4, which coincides with the largest amount of leaf in relation to the stem; however, due to the black frost that affected this cycle, it was not possible to see if the LAI value could have increased. The opposite case occurred in cycle 2, in which it was observed that the highest amount of LAI was at 91 dds with 3.2, which coincides with a crop that still had a significant percentage of leaf in relation to the stem, since according the proportion of stem and spike in the crop increased, the LAI gradually decreased to 1.9 at 119 dds.

The LAI is a very important variable if it is considered to have the maximum dry matter yield, since ^{Parsons and Penning (1988)} mention that when 95% of incident light is intercepted by the canopy and the average forage accumulation rate reaches its maximum, there is a balance between the processes of maximum growth and senescence that allows a greater accumulation and quality of forage, due to the greater amount of leaf present. Therefore, in a practical way, the IR and the LAI have been related to height, allowing to define optimal dates for cutting forage, with good nutritional quality, in addition to allowing the regrowth of plants.

Intercepted radiation

There is no information on the optimum harvest point in relation to the radiation intercepted in small grain cereals for forage production, but in works carried out in tropical and temperate pastures, ^{Da Silva and Hernández (2010)} observed that the optimal harvest point is when the plants reach 95% light interception and it is related to the greater contribution of leaves to the yield, in this case no cycle reached 95% IR, for the case of cycle 1 the maximum value was 75%, at 84 dds.

In the case of cycle 2, the maximum IR was 86%, a value that was obtained at 91 dds, later this variable possibly decreased due to the lower production of leaves in relation to the stems and the spikes, also, the low temperatures they were also a negative factor for the development of the leaves and that the crop could reach 95 of light interception (^{Juskiw et al., 2000}). Likewise, it would be important in future studies to evaluate different planting densities to determine if this variable is related to IR.

Height

In the case of height, the maximum reached during cycle 1 was 52 cm at 84 days. For cycle 2 it was 98 days with a height of 86 cm, since in the following samplings there was senescence and death of foliage, which apparently affects the height when there is leaf fall from the upper part. In this case, height is the most practical tool if you want to easily recommend an ideal cut point to producers, however, this variable depends on environmental conditions, since for example in cycle 1 at 77 days the crop reached an average height of 39 cm; while for the same date in cycle 2 the height registered was 49 cm, which is due to the greater presence of frost in the first growing cycle, which affects its development, so it is important to assess radiation intercepted.

A variable that influences the height of a forage is the planting time, since some authors such as ^{Mendoza et al. (2011)}, evaluated three winter planting dates (November 09 and 23 and December 07), finding heights of 104 and 102 cm on the first two dates respectively, and a height of just 68 cm on that of December 07 . For this experiment, the planting date was December 5; however, plant heights of 86 cm were reached.

With the DM accumulation data it can be seen that triticale is a good option as feed for cutting or grazing, similar results were found by ^{Zamora et al. (2002)}, who compared triticales with oats, barley and ryegrass, obtaining the same yields as oats; as well as winter triticales were compared in two cuts, in which they maintained quality and performance even in the second cut.

Conclusions

Triticale 118 is a material that can be used as green forage during winter, as it is a long-cycle genotype and has good forage aptitude in terms of dry matter yield and leaf quantity. The optimum cutting moment for forage in cycle 2 was found in encañe (35 Zadoks-77 to 91 dds), since in this state of development is when the highest leaf and LAI yields were found and there was coincidence with the most high light intercepts. Intercepted radiation, LAI and height can be criteria used to determine the optimum cutting moment for forage in triticale plants.