Nutritional quality, nutrient uptake and biomass production of Pennisetum purpureum cv. King grass

Abstract

The research was conducted to determine the effects of cutting interval and fertilization on the nutritional quality, nutrient uptake, and biomass production of King grass. The experimental design was a randomized complete block, using 4 blocks and 8 treatments per block; treatments consisted of 4 ages of cutting (30, 45, 60, and 90 days), with fertilization and without fertilization. The results showed increases of up to 72,000 kg ha^-1 year^-1 of dry matter (DM) when fertilization was implemented. There was a significant reduction in with an increase in the cutting days (12.70-6.53% protein). Fiber increased (48.79-72.99% NDF) when fertilization treatments were included and cutting days increased. The elements that were included in fertilization (N, P, K) showed a higher foliar content and also presented a reduction in foliar content with growth of the plant. Treatments with fertilization showed a nutrient uptake increase for all the elements up to 60 days, where a reduction in uptake capacity was observed. King grass is a plant with a high nutrient uptake capacity and, therefore, with high biomass and nutrient production. This is an advantage since it can be used in multiple applications, such as animal feed, biofuel production, and as a substrate for biodigestion, among others.

Figure 1

Linear relationship between biomass production of King grass on different cutting days and in systems with and without fertilization. Plots were created in MATLAB R2021a. FM fresh matter, DM dry matter. Linear regression equation (C cutting day): Biomass FM with fertilization = 0.2269 C − 2.5525, r² = 0.9238, n = 63, P < 0.001. Biomass FM without fertilization = 0.0882 C − 1.352, r² = 0.9784, n = 63, P < 0.001. Biomass DM with fertilization = 0.03998C − 0.6448, r² = 0.9263, n = 63, P < 0.001. Biomass DM without fertilization = 0.01517 C − 0.2866, r² = 0.9747, n = 63, P < 0.001.

Figure 2

Linear relationship between biomass production of King grass on different cutting days and in systems with and without fertilization. Plots were created in MATLAB R2021a. FM fresh matter, DM dry matter. Lineal regression equations (C cutting day): Biomass FM with fertilization: − 199.4084 C² + 28,382.8977C − 240,005.9343. r² = 0.8113, n = 63, P < 0.001. Biomass FM without fertilization =  − 53.7566 C² + 8406.3371 C − 58,284.7854. r² = 0.9069, n = 63, P < 0.001. Biomass DM with fertilization =  − 32.0241 C² + 4824.9404 C − 58,229.4563. r² = 0.8290, n = 63, P < 0.001. Biomass DM without fertilization: =  − 8.2090 C² + 1374.6121C − 13,776.6985. r² = 0.8997, n = 63, P < 0.001.

Figure 3

Linear relationship between protein and leaf: stem ratio of King grass on different cutting days and in systems with and without fertilization. Plots were created in MATLAB R2021a. Lineal regression equations (C = Cutting day): Protein with fertilization =  − 0.0968C + 14.8642. r² = 0.8491, n = 63, P < 0.001. Protein without fertilization =  − 0.0519C + 11.7607. r² = 0.7271, n = 63, P < 0.001. Leaf: stem ratio with fertilization =  − 0.0162C + 1.8657. r² = 0.7986, n = 63, P < 0.001. Leaf: stem ratio without fertilization =  − 0.0220C + 2.5833. r² = 0.8399, n = 63, P < 0.001.

Figure 4

Linear relationship between neutral detergent fiber (NDF), acid detergent fiber (ADF) of King grass on different cutting days and in systems with and without fertilization. Plots were created in MATLAB R2021a. Lineal regression equations (C cutting day): Neutral detergent fiber with fertilization = 0.3922C + 40.2785. r² = 0.8228, n = 63, P < 0.005. Neutral detergent fiber without fertilization = 0.3937C + 33.2255. r² = 0.8383, n = 63, P < 0.005. Acid detergent fiber with fertilization = 0.1986C + 31.2225. r² = 0.7877, n = 63, P < 0.001. Acid detergent fiber without fertilization = 0.2138C + 27.1088. r² = 0.8436, n = 63, P < 0.001.

Figure 5

Cubic relationship between nutrient recovery efficiency and cutting day for (a) N (r² = 0.903, n = 42, P < 0.001), (b) P₂O₅ (r² = 0.6763, n = 43, P < 0.001), (c) K₂O (r² = 0.7803, n = 46, P < 0.001). Plots were created in MATLAB R2021a.