Pasture Science and other Crops

Strategic fertilization in Cenchrus purpureus varieties tolerant to drought in the western region of Cuba

0000-0003-1424-6311R. S. Herrera^{1  *} 

¹Instituto de Ciencia Animal. C. Central km 47 ½, San José de las Lajas, Mayabeque, Apdo 24, San José de las Lajas, Mayabeque, Cuba

ABSTRACT

The influence of strategic fertilization with nitrogen (150 kgN/ha) applied in the rainy season in Cenchrus purpureus varieties tolerant to drought (CT-600, CT-601, CT-602, CT-603, CT-604, CT-605, CT-608 y CT-609) compared with CT-115 as control was studied. A random block design with five replications was used. In the dry season only CT-604 had the highest (P<0.001) dry matter percentage of leaf, stem and the hole plant. The highest (P<0.001) leaves content was showed by CT-605 (60.07 and 60.17 % in the rainy and dry season, respectively). The varieties CT-605, CT-608 and CT-609 (5.0, 5.6 and 5.2 tDM/ha, respectively) exceeded (P<0.001) the yield of CT-115 (3.4 tDM/ha) in the dry season. The leaf area varied (P<0.001) between varieties, while CT-604 showed the lower population (P<0.001) in both climatic seasons (7.2 and 4.6 tillers/5min the dry and rainy season, respectively). The varieties CT-605, CT-608 and CT-609 increased their yield in the dry season with adequate leaves contents and adequate population. It is suggest expanding this information with the chemical composition and extending these varieties in the western region, always you had the nitrogenous fertilizer.

Key words: Cenchrus; yields; leaves; population

Due to the extension reached by Cenchrus purpureus in the tropical world, several are the countries, universities and research centers that study the varieties from this genus, including those obtaining through genetic improvement programs using different methods (^{Herrera and Martínez 2015}, ^{Guimaraes de Favare et al. 2019}, ^{Sinche et al. 2021}, ^{Vander Pereira et al. 2021} and ^{Lire Wachamo 2022}).

At the Instituto de Ciencia Animal were obtained, by in vitro tissue culture, new C. purpureus varieties tolerant to drought and salinity (^{Herrera et al. 2003}) and were evaluated in the western region of the country (Granma), those tolerant to drought (^{Díaz 2007}, ^{Ray et al. 2016} and ^{Arias et al. 2018}, ^{2019a b}) and to medium soil salinity (^{Ledea et al. 2017}, ^{Álvarez et al. 2019} and ^{Álvarez 2021}) showed promising results.

However, in the western region of the country with a rainfall pattern up to 1400 mm annual (^{Herrera et al. 2018}), the drought tolerant varieties did not show an effective response, due to the high rainfall volume during the dry season (^{Herrera 2022}). These evaluations were made without irrigation and fertilization as same in Granma province.

These elements determined the questioning about of what could be their performance if during the rainy season, strategic nitrogen fertilization were applied and irrigation were not used in the dry season, which was the objective of this research.

Materials and Methods

Location. The experiment was carried out at the Miguel Sistachs Naya pasture station belonging to Instituto de Ciencia Animal, San José de las Lajas, Mayabeque, Cuba. The rainfalls and temperature during the experimental stage are shown in table 1.

Table 1 Some climate indicators during the experimental stage 

Indicator	Months
	J	F	M	A	M	J	J	A	S	O	N	D
Min.t, °C	10.0	19.4	20.2	20.0	21.1	22.5	20.7	20.6	20.5	20.1	16.8	17.5
Max.t, °C	24.3	26.0	29.2	27.3	30.9	27.9	27.3	31.9	31.3	30.5	26.0	25.0
A.t, °C	18.7	22.1	25.2	25.0	25.0	25.3	25.8	24.7	25.5	24.8	21.5	22.9
Rain, mm	12.0	46.0	37.0	62.0	234.0	151.0	180.0	383.0	152.0	44.0	51.0	55.0

Min.t: minimum temperature Max.t: maximum temperature A.t: average temperature

Experimental design and treatments. A random block design with five replications was used. A total of eight Cenchrus purpureus varieties (CT-600, CT-601, CT-602, CT-603, CT-604, CT-605, CT-608 and CT-609) drought tolerant obtained by in vitro tissue culture (^{Herrera et al. 2003}) were evaluated and compared with C. purpureus CT-115 which was its parent. During the dry season was fertilized with 150 kgN/ha fractionated in three times (50 kgN/ha/application) and phosphoric and potassium fertilizer was not used. The soil was Typical Red Ferralitic (^{Hernández et al. 2015}) and its composition appears in table 2.

Table 2 Chemical composition of the soil in the experimental area 

pH		mg/100g		OM, %	Total salts, %
KCl	H2O	P2O5	K2O
4.9	6.7	2.9	7.8	3.0	0.39

Procedure. During the dry season, conventional soil preparation was performed and the plantation was carried out in the rainy season at a distance of 1m between rows. Plots of 25 m2 were delimited for each varieties and in each of them the same number of buds were distributed to guarantied the population homogeneity. The seed had five months and belongs to the germplasm bank from the Station. After one hundred and fifty days of sowing the establishment cut was made. From that moment cuts every 60 and 90 days were carried out in the rainy and dry season, respectively at a height of 10cm above soil level. The fertilizer was applied after each cut in the rainy season. Irrigation was not used during the dry season. The experiment lasted a year.

Sampling were carried out in the central rows leaving free the two of the plots side as border effect, for 15 m2 of harvestable area. In this area a total of five tillers were taken as sampling units and in each of them were measured: height, dry matter percentage of leaves, stems and whole plant, percentage of leaves and stems, length and wide of the fourth leaf completely open, number of green leaves per stem, foliar area, dry matter yield and population. All was performed according to the methodology described by ^{Herrera (2006)}.

Statistical analysis. The database was created and analysis of variance was performed (^{Di Rienzo et al. 2012}) according to the experimental design and the mean values were compared according to ^{Duncan (1955)}. The theoretical assumptions of the analysis of variance were verified for all the variables, based on the ^{Shapiro and Wilk (1965)} tests for the normality of errors and ^{Levene (1960)} for the variance homogeneity and there was only the need to transform the variables number of leaves per stem and population using √x.

Results

The plants height differs (P <0.001) between varieties in both climatic seasons and CT-603 showed the lower value in both seasonal periods. However, drew the attention that the height of varieties was numerically higher, in general, in the rainy season (table3).

Table 3 Height (cm) of varieties in both seasonal periods 

Variety	Dry season	Rainy season
CT-115	86.3^de	60.8^ab
CT-600	68.3^ab	58.5^ab
CT-601	80.0^bcd	66.8^ab
CT-602	73.0^abc	88.8^d
CT-603	66.5ª	56.0^a
CT-604	104.5^f	73.7^bcd
CT-605	66.5^c	81.2^cd
CT-608	97.5^ef	80.2^cd
CT-609	82.7^d	71.4^abc
EE±	4.1***	5.3***

^abcdef Values with uncommon letters differ to P<0.05 ^{Duncan (1955)} *** P<0.001

There were differences (P <0.05) in the dry matter percentage of leaf, stem and the whole plant between the varieties in both seasonal periods and the highest value, in general, was recorded by CT-604 (table 4). It is of highlighted, that plants had lower dry matter content in the dry season.

Table 4 Dry matter percentage of leaves, stem and whole plant of the varieties in both climatic seasons 

Variety	Dry season			Rainy season
	Leaf	Stem	Plant	Leaf	Stem	Plant
CT-115	21.50^a	11.78^ab	15.66^ab	19.82^a	12.58^a	16.01^a
CT-600	22.00^a	12.13^b	14.54^a	20.45^a	14.46^bc	17.29^a
CT-601	22.48^a	11.98^b	15.85^ab	20.16^a	13.80^ab	16.82^a
CT-602	22.65^a	12.54^b	16.56^bc	22.74^c	18.57^c	19.07^b
CT-603	21.62^a	11.39^ab	16.42^bc	20.99^ab	13.98^ab	17.11^a
CT-604	32.00^b	31.64^d	30.69^d	21.96^bc	13.41^ab	16.07^a
CT-605	21.31^a	10.74^a	14.97^a	20.94^ab	13.10^ab	16.73^a
CT-608	22.43^a	13.74^c	17.61^c	20.88^ab	13.72^ab	16.77^a
CT-609	23.96^a	14.62^c	17.60^c	21.16^ab	14.44^bc	17.14^a
EE±	0.98***	0.39***	0.50***	0.43***	0.29**	0.50**

^abcd Values with uncommon letters differ to P<0.05 ^{Duncan (1955)}

In the rainy season the amount of leaves did not varied between varieties, but in the dry season the highest value (P<0.01) was recorded by CT-605 and did not differ of CT-601, CT-602 and CT-603, while CT-115 only reached 50.7 %. For the stem content there were differences between varieties in both seasonal periods and the performance was variable, but, in general, during the rainy season recorded the highest values (table 5).

Table 5 Values (%) of leaves and stems of varieties in both seasonal periods 

Variety	Dry season		Raint season
	Leaf	Stem	Leaf	Stem
CT-115	50.7^ab	41.4ª	32.02	54.61ª
CT-600	44.1ª	40.7ª	30.84	55.14ª
CT-601	52.9^abc	47.0^ab	31.30	55.19ª
CT-602	56.1^bc	43.9^ab	30.30	61.28^ab
CT-603	53.5^abc	43.5^ab	31.24	62.22^ab
CT-604	47.3^ab	52.6^b	30.84	57.70^ab
CT-605	60.2^c	39.8ª	30.53	57.30^ab
CT-608	45.7ª	49.1^ab	30.61	60.21^ab
CT-609	48.3^ab	45.9^ab	31.21	63.79^b
EE ±	2.9**	3.2*	0.49 NS	1.99**

^abcValues with uncommon letters differ to P<0.05 ^{Duncan (1955)}

* P<0.05 ** P<0.01 NS: Not significant

In the dry season the length leaves of CT-604 only differ (P<0.001) of all variables with the lower value (48.75 cm) while, in the rainy season the highest values were obtained in CT-605, CT-608 and CT-609 (82.33, 82.50 and 83.17 cm, respectively). In both seasonal periods the varieties CT-605, CT-608 and CT-609 recorded the higher (P<0.001) leaves width (table 6).

Table 6 Leaves characteristics in both seasonal periods 

Variety	Dry season		Raint season
	Leaf	Stem	Leaf	Stem
CT-115	94.75^b	70.50^a	2.73^bc	1.82^a
CT-600	94.50^b	71.67^ab	3.08^cde	1.93^a
CT-601	95.25^b	79.50^abc	2.88^cd	2.04^ab
CT-602	93.75^b	76.67^abc	2.78^bc	1.99^a
CT-603	96.75^b	73.33^abc	2.48^b	1.94^a
CT-604	48.75^a	81.67^bc	1.50^a	3.28^d
CT-605	97.25^b	82.33^bc	3.50f	2.52^c
CT-608	96.75^b	82.50^c	3.73e	2.49^c
CT-609	95.75^b	83.17^c	3.23^def	2.41^bc
EE ±	2.77***	3.36*	0.11***	0.13***

^abcdef Values with uncommon letters differ to P<0.05 ^{Duncan (1955})

* P<0.05 *** P<0.001

The number of leaves per stem did not differ between varieties in both seasonal periods with a range of values between 4.97 and 6.02 in the dry season and between 6.25 and 7.23 in the rainy season.

There were differences (P<0.001) between varieties in leaf area/stem. In the dry season CT-604 variety showed the lower value, while in the rainy season recorded the higher area (table 7).

Table 7 Leaf area/stem (cm²) of varieties in both seasonal periods 

Variety	Dry season	Rainy season
CT-115	1841.48^c	923.09ª
CT-600	1403.37^b	978.68ª
CT-601	1459.88^bc	1143.62^abc
CT-602	1419.91^b	961.48ª
CT-603	1686.96^bc	1015.92^ab
CT-604	486.28ª	1839.63^d
CT-605	1523.72^bc	1475.12^c
CT-608	1654.04^bc	1374.86^bc
CT-609	1523.72^bc	1278.90^abc
EE±	124.64***	126.08***

^abcdValues with uncommon letters differ to P<0.05 ^{Duncan (1955)}

*** P<0.001

The dry matter yield in both seasonal periods and in the annual total differed (P<0.001) between varieties. In the dry season the higher values were reached by the varieties CT-605, CT-608 and CT-609 and the lower value was to CT-115. In the rainy season the lower value was to CT-605. In the annual total CT-608 reached the highest (P<0.001) yield with 19.06 t DM/ha (table 8).

Table 8 Yields (DM t/ha) of varieties 

Variety	Dry season	Rainy season	Anual total
CT-115	3.42ª	11.26^ab	14.68^de
CT-600	3.47ª	10.53^ab	14.00^ef
CT-601	4.70^bc	11.93^b	16.63^bc
CT-602	4.43^abc	12.70^b	17.13^b
CT-603	3.66^ab	11.64^b	15.30^cd
CT-604	4.53^abc	12.89^b	17.42^b
CT-605	5.01^c	8.55ª	13.56^f
CT-608	5.64^c	13.42^b	19.06ª
CT-609	5.25^c	11.11^ab	16.36^bc
EE ±	0.40***	0.68***	0.50***

^abcdef Values with uncommon letters differ to P<0.05 ^{Duncan (1955)}

***P<0.001

The population at the beginning of the experi-ment varied between varieties in a close range (7.3-10.2 tillers/5 m) and the lower value (P<0.001) was to CT-604. When finish the experimental stage, there were not differences between varieties (table 9).

Table 9 Population (tillers/5 m) at the beginning and end of the experimen-tal stage 

Variety	Biginning	End
CT-115	3.2^c (10.2)	3.22 (10.73)
CT-600	3.0^bc (9.0)	2.99 (8.52)
CT-601	3.0^bc (9.0)	3.16 (9.85)
CT-602	3.2^c (10.2)	2.99 (9.36)
CT-603	3.1^bc (9.6)	2.99 (8.78)
CT-604	2.7ª (7.3)	3.10 (9.40)
CT-605	3.0^bc (9.0)	3.07 (9.53)
CT-608	3.1^bc (9.6)	3.10 (9.60)
CT-609	2.9^b(8.4)	4.21(10.43)
SE ±	0.07***	0.06 NS

^abcValues with uncommon letters differ to P<0.05 ^{Duncan (1955)} ***P<0.001 ( ) Real values NS: Not significant

Discussion

Height is an indicator of development degree and physiological state of the plant and depends on variables as fertilization, irrigation, soil, climate and varieties, among other factors. This is an indicator useful in improvement programs for varieties selection (^{Jabessa et al. 2022}).

In the western region of Cuba, ^{Arias et al. (2019a b)} reported that in both seasonal periods the height showed significant differences between Cenchrus purpureus varieties tolerant to drought. Similar performance shows ^{Herrera (2022)} when evaluating the same varieties in the western region of Cuba. In both researchers was clearly showed the genotype-environmental effect, since numerical values were different in both regions and this was fulfilled in the results of this experiment.

On the other hand, it is important to highlight that the plants height was superior in the dry season regard to the rainy season. This is logical and can be attributing to two main elements: the residual effect of nitrogen fertilization in the rainy season and the differences of regrowth age between both seasonal periods.

The values of dry matter percentage of the whole plant were in the range of the reported by ^{Díaz (2007)} and ^{Herrera (2013)} in the evaluation of these varieties in the eastern and western region, respectively. However, the CT-604 showed high value which is probable that indicate certain sensitive to maintain the adequate water balance under stress conditions, aspect that should be depth study in future researchers. On the other hand, ^{Maleko et al. (2019)} when evaluating these indicators found values variability between Napier varieties. These indicators depend on different factors which are climatic elements, specially relative humidity and rainfalls. These elements made the plant to be forced to maintain their water balance and therefore, they give variability to the dry matter content of the leaf, stem and the whole plant.

^{Alves et al. (2022)} reported that Napier leaves content varied with the regrowth age and the fertilization, while ^{Herrera (2020)} when evaluating Cenchrus varieties tolerant to drought found differences between them in leaves value and the highest values were recorded, in general, during the rainy season and showed their decrease with the production time. On the other hand, it was encouraging that CT-605 showed the highest leaves content in the dry season. This could be a positive aspect of this variety since, despite the high value of leaves content, the dry matter percentage is relatively low, which show the existence of an adequate mechanism to maintain water balance in the plant and to avoid high transpiration.

^{Guimarães de Favare et al. (2019)}, ^{Jabessa et al. (2022)} and ^{Tesfaye Atumo et al. (2022)} reported the high variability of length and width of leaves as a result of Napier variety effect, location and season of the year. In addition, these indicators are considered essentials in the evaluation of new varieties. This same performance was obtained in this research and it is important to add that, these leaves indicators are basics in the physiology and metabolism of the plant because it is the place where photosynthesis is performed.

These varieties yields are in the range of values obtained by ^{Herrera et al. (2012)} and ^{Álvarez et al. (2013)} when evaluating, without irrigation and fertilization, Cenchrus purpureus varieties obtaining by tissue culture from CT-115 and were characterized by having better agronomic indicators than it partners, although three of the studied varieties (CT-605, CT-608 and CT-609) achieved higher yields, especially during the dry season. The above is determined by fertilization effect on the rainy season, because when previously evaluating (^{Herrera 2022}) these same varieties without fertilization there was not the mentioned response.

On the other hand, ^{Ray et al. (2016)} evaluated under drought conditions (800 mm annual rainfall) a group of Cenchrus varieties drought tolerant and among the ones that showed the best results are studied in this research. This means that, when the plant nutrition increase through strategic fertilization, the plant nutritional profile favorable changes to the best adaptation to water stress.

The previous was showed by ^{Herrera et al. (2016)} when performing a study of relation between climatic factors and the yield of Pennisetum varieties. These authors point out that the Pearson correlation coefficients between yield and rain or their distributions are specific for each climatic season and this showed that the plant has the particular ability of adapting to volume and rain distribution.

On the other hand, population varied in a closely range and these varieties, above all the promising, maintained the same population during the experimental period and strengthens the previous.

The previous show the need to carry out the economic valuation of the obtained results in this study, since it is possible to produce forage during the dry season with the varieties CT-605, CT-608 and CT-609 with productivity superior to the species currently used.

Acknowledgments

Thanks to the technicians M. García and Ana M. Cruz for their attention to the experiment, the sampling, the processing of samples and the analysis of the results.

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Received: May 28, 2022; Accepted: July 29, 2022

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There are no conflicts of interest between the authors

Authors contribution: R. S. Herrera: Conceptualization, Research, Formal Analysis, Writing - original draft