Sorghum–Legume Mixtures to Improve Forage Yield and Nutritive Value in Semiarid Regions
1
Rex E. Kirksey Agricultural Science Center, New Mexico State University, Tucumcari, NM 88401, USA
2
Agricultural Science Center, New Mexico State University, Farmington, NM 87401, USA
*
Author to whom correspondence should be addressed.
Grasses 2024, 3(3), 163-173; https://doi.org/10.3390/grasses3030012
Submission received: 22 June 2024
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Revised: 1 August 2024
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Accepted: 9 August 2024
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Published: 14 August 2024
(This article belongs to the Special Issue The Role of Forage in Sustainable Agriculture)
Abstract
:In a continued search for legumes to grow with forage sorghum (FS) [Sorghum bicolor (L.) Moench] in semi-arid environments, studies in 2019 and 2022 at New Mexico State University Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA, evaluated FS mixed with cowpea [Vigna unguiculata (L.) Walp.], lablab (Lablab purpureus L.), both previously evaluated, and a native legume, big-pod sesbania (Sesbania macrocarpa), for yield and nutritive value in four randomized complete blocks each year. At harvest legume proportions of approximately 15% of the dry matter yield, there were no differences in the yield (mean = 15.97 Mg ha−1, p > 0.40) or land equivalency ratio between sole FS and any mixture or among mixtures; however, the crude protein of FS+Lablab was greater than sole FS, with FS+Cowpea and FS+Sesbania intermediate (67, 77, 87, and 79 g kg−1 for sole FS, FS+Cowpea, FS+Lablab, and FS+Sesbania, respectively; 5% LSD = 14). The neutral detergent fiber digestibility of FS+Sesbania was less than all other treatments (p = 0.0266). Although the sesbania did not improve forage yield or nutritive value when grown with FS and harvested near sesbania maturity, perhaps growing with a shorter season grass and harvesting earlier may show benefit, as sesbania’s nutritive value is known to be greater at earlier stages.
1. Introduction
The demand for forages with high nutritive value to sustain livestock enterprises continues to increase globally in semi-arid regions. Several legumes have been evaluated in a continuing search for candidate legumes to grow with forage sorghum (FS) [Sorghum bicolor (L.) Moench] in the semi-arid Southern High Plains of the USA (SHP) and similar environments to improve nutritive value and, potentially, dry matter (DM) yield [1,2,3,4,5]; however, only incremental improvements have been made, and several legumes have been discounted. In a previous work in this region [3], soybean (Glycine max) and tepary bean (Phaseolus acutifoliis A. Gray) were discounted, while cowpea [Vigna unguiculata (L.) Walp.] and lablab (Lablab purpureus L.) were found to be most suitable for mixing with sorghum forages. Additionally, Angadi et al. [1,4] discounted lima bean (P. lunatus) and pole bean (P. vulgaris) when compared to cowpea and lablab.
Several Sesbania species have been evaluated around the world for their performance as monocultures [6,7,8,9,10] or mixed with various summer cereal grasses [5,11,12]. Big-pod sesbania (S. herbacea (Mill.) McVaugh syn. S. exaltata (Raf.) Rydb. Ex A.W. Hill syn. S. macrocarpa Muhl), also known as hemp sesbania and coffee weed, is a North American native annual or perennial legume [6,13,14,15,16] that has been grown for cover crops, wildlife plantings, and to attract pollinator insects in various areas of the southwestern USA [17], but is also considered a weed in other areas [6,16]. Although big-pod sesbania has a fairly good nutritive value [16] when vegetative and, although possibly not as palatable for grazing, it may have value in increasing the nutritive value in hay or silage systems [6]. Farghaly et al. [8] reported that S. sesban could be used as an alternative to alfalfa (Medicago sativa) for livestock rations with beneficial effects on carcass quality. Khanum et al. [9] evaluated S. aculeata, reporting that it had good nutritive value and would likely mix well with FS; although, they did not directly evaluate the mixture. Kondo et al. [11] stated that because legumes, including S. cannabina, are low in fermentable carbohydrates, but high in crude protein (CP), and cereal grasses like maize (Zea mays) are low in CP but high in fermentable carbohydrates, mixtures of the two forages would complement each other for ensiling and feeding.
Big-pod sesbania is also more tolerant of pests than cowpea [17]. It has been grown in summer cover crop mixtures, with sorghum in orchards performing equally well with cowpea and lablab under full light conditions and better than six other legumes under reduced light intensity, typical of orchard understory crops [18]. Big-pod sesbania is rapidly growing [14] and tall [13,16], rather than a viny climbing or bushy legume, similar to other Sesbania spp. that will maintain growth at or above the canopy of companion species [4,9,16,19]; hence, it may compete well with FS, which is generally a taller-growing summer cereal forage than maize (Zea mays) and pearl millet (Pennisetum glaucum (L.) R. Br.) [20]. Big-pod sesbania also is moderately drought- and heat-tolerant, being native to the southeastern and southwestern USA [16]; although, it responds to irrigation [16] and is mainly found in wetter soils [13,14,21].
Therefore, the objectives of this study were to continue the search by evaluating big-pod sesbania (hereafter simply referred to as sesbania, while other Sesbania spp. will be identified by scientific name) as an alternative to cowpea and lablab for planting with FS and to improve forage yield and nutritive value under irrigation in global semi-arid environments, such as the Southern High Plains of the USA.
2. Materials and Methods
2.1. Site Description
Two identical studies were conducted over two years (2019, 2022) in separate fields at the New Mexico State University Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA (35°12′0.5″ N, 103°41′12.0″ W; elev. 1247 masl). There were four randomized complete blocks each year. Research was interrupted due to COVID-19 restrictions in 2020 and the unavailability of irrigation water in 2021. The soils were Canez (Fine–loamy, mixed, thermic Ustollic Haplargid) fine sandy loam in 2019 and Redona (Fine–loamy, mixed, superactive, thermic Ustic Calciargids) fine sandy loam in 2022. The climate in the region is Köppen–Geiger cold semi-arid (BSk; http://www.cec.org/north-americanenvironmental-atlas/climate-zones-of-north-america/, accessed on 22 May 2023), characterized by cool, dry winters and warm, moist summers. Approximately 83% of the precipitation occurs as intermittent, relatively intense rainfall events from April through October. Weather data were collected from a National Weather Service cooperative station located within 1 km of the study area (Table 1).
2.2. Study Layout and Management
Plots (1.5 × 6.1 m) were planted on 29 May 2019 and 9 June 2022 into a previously prepared conventionally tilled flat seedbed. Each plot had four rows spaced 38-cm apart when fully planted by making two passes in opposite directions with a disk drill fitted with a single cone arranged to plant two rows spaced 76 cm apart at a time, which were offset from the center of the planter by 19 cm. This led to four rows of each monoculture or two alternating rows of each component of mixtures. The seeding rates for sole FS, cowpea, lablab, and sesbania were 90,000, 98,000, 98,000, and 1,072,000 seeds ha−1, respectively, and the mixtures were sown at half that rate in alternate rows. The sesbania seeding rate was greater because low germination and high seedling death is a known trait of this species [14], as well as a decrease in germination due to two or more cycles of soil hydration and drying [16], which is common in irrigated semi-arid regions, particularly with sandy soils, such as those used in the present study. Irrigation water quality (treated municipal wastewater, Class 1B, which is a suitable level of treatment for application to animal feed and fiber crops, [22]) did not likely influence germination of the sesbania [21] and has not adversely affected the other crops used in this study when grown previously at this location.
A 1.5% solution of Glyphosate [isopropylamine salt of N-(phosphonomethyl)glycine] was applied on 31 May 2019, and 10 June 2022, to control weeds that had emerged since land preparation. On 30 June 2022, 31 kg N ha−1 were applied. No other pesticides or fertilizers were applied. The monthly irrigation amounts from May through October are reported in Table 1. The irrigations applied in May were for soil moisture to assist in land preparation. The treated municipal wastewater used for irrigation contained an average of 7.4 ppm NO3 throughout the 2019 study period, but averaged 22.5 ppm during the 2022 study period. Consequently, based on these values and the total annual irrigation amounts reported in Table 1, 15.3 kg N ha−1 were applied through the irrigation water in 2019, while 63.7 kg N ha−1 were applied in 2022. Thus, a total of 94.7 kg N ha−1 were applied throughout the growing season in 2022, but only 15.3 kg N ha−1 were applied in 2019, with a lesser amount of precipitation + irrigation (Table 1).
2.3. Measurements
On 30 September 2019 and 13 October 2022 (124 and 126 days after planting (DAP), respectively), a 0.37 m2 area within each plot, including all 4 planted rows, was hand-clipped to near ground level to estimate the forage yield. The harvest timing was scheduled to coincide with the FS soft dough stage [1,3,20] and mid-fruiting of the legumes [6,10,15,18], although the sesbania life cycle is flexible based on stresses [15]. The species in mixtures were bagged separately. Harvested biomass was weighed, dried for 48 h at 65 °C, and reweighed to determine the dry matter (DM) yield of each species, legume DM proportion, and LER, where LER of mixtures = (mixture FS yield/monoculture FS yield in the replicate) + (mixture legume yield/monoculture legume yield in the replicate), and LER of monocultures = 1. Dried samples were ground to pass a 1 mm screen and delivered to Ward Laboratory (Kearney, NE, USA) for CP, neutral detergent fiber (NDF), 48 h NDF digestibility (NDFD), and in vitro true dry matter digestibility (IVTDMD) analyses via near-infrared spectroscopy. Universal equations developed for sorghum forages and warm-season annual legumes by the NIRS Consortium (https://www.nirsconsortium.com/; accessed 15 July 2024) were used by the laboratory to estimate nutritive value. The nutritive value of the mixtures was calculated as the weighted mean of the component species, such that, mixture CP = ((FS CP × FS yield) + (legume CP × legume yield))/mixture yield, for example, where CP = g kg−1/1000, and yield is Mg ha−1.
2.4. Statistical Description
Data were combined across the years, DM yield, and nutritive value of each species, and the DM yield, legume proportion, LER, and nutritive value of the total forage harvested were analyzed using the mixed procedure of SAS [23] to determine if differences existed among years and treatments (TRTs), as well as the year × TRT interaction. Replicates were identified as unique within the years and considered random. When differences among the TRTs or interactions were significant (p ≤ 0.05) or the interactions indicated a biologically important trend (0.05 ≤ p ≤ 0.10 [24]), LS-means were separated by least significant difference using the PDMIX800 macro [25].
3. Results
3.1. Sorghum Yield and Nutritive Value
The main effect of TRT was significant only for yield because all mixtures had a lesser yield than the sole FS (Table 2). Additionally, there was a trend toward a year × TRT interaction (0.05 ≤ p ≤ 0.10 [24]) because of a change in rank from greatest yielding to least yielding across the years by FS+Sesbania, while sole FS increased in rank from second to having significantly greater yield than the mixtures (Table 3). Although these were minor, mostly non-significant changes across the years, it was likely the contributing factor to the main effect of TRT difference shown in Table 2 and was related to the difference in management and moisture availability across the years (Table 1). The year effect was significant for CP, NDFD, and IVTDMD, with greater nutritive value observed in 2022 compared to 2019 (Table 2), which was likely associated with the N application and greater precipitation + irrigation (Table 1). No differences existed for the nutritive value of FS.
3.2. Legume Yield and Nutritive Value
The year effect was significant only for legume NDFD and IVTDMD, while all variables were influenced by TRT, and a year × TRT interaction existed for all nutritive value variables (Table 4). For the TRTs, all sole legumes had numerically greater yield than their mixture with FS, but only sole lablab was significantly greater than its mixture counterpart. Contrary to the year effect for FS NDFD and IVTDMD (Table 2), legume NDFD and IVTDMD were less in 2022 than in 2019 (Table 4).
The significant year × TRT interactions for the legume nutritive value components (Table 4) were fairly consistent in nature and occurred because there was no difference across the years for any TRT except sole cowpea for all variables, sole lablab for CP, and sole sesbania for NDF, NDFD, and IVTDMD (Table 5). Another factor of the interaction was that in 2019, sole lablab had a greater CP than its mixture counterpart, and sole sesbania had a lesser NDF, but a greater NDFD and IVTDMD than its mixture counterpart.
3.3. Mixture Yield and Nutritive Value
There were no significant differences for total forage yield, LER, or NDF; however, TRT influenced CP and NDFD and the year × TRT interaction was significant for legume proportion, while there was a trend (0.05 ≤ p ≤ 0.10 [24]) toward an interaction for CP (Table 6).
The year × TRT interaction for legume proportion occurred due to a lack of difference in FS+Cowpea across the years, while the other two mixtures had a greater legume proportion in 2022 than in 2019 (Table 7). The lack of difference across the years for FS+Cowpea and the greater legume proportion in 2022 for FS+Lablab likely had no influence on the trend across the years previously described for FS yield (Table 3); however, the greater legume proportion for FS+Sesbania in 2022 may have been a factor in the change in rank for that TRT regarding FS yield (Table 3).
The trend (0.05 ≤ p ≤ 0.10 [24]) toward a year × TRT interaction for total CP (Table 6) was an trend of magnitude because all TRTs had a greater CP in 2022 than in 2019, but the difference was greater for Sole FS and FS+Lablab than for FS+Cowpea or FS+Sesbania (Table 8). The significant increase across the years would be expected due to increased availability of applied N from the 2022 application, along with the increased NO3 levels in the irrigation water, which also was applied at a greater amount in 2022 (Table 1).
4. Discussion
4.1. Sorghum Yield and Nutritive Value
The yield of the sole FS was similar to slightly greater than that reported by others [4,9]; about half that reported by Bhattarai et al. [20], and two to three times that reported by Contreras-Govea et al. [3], who found no difference between sole FS and FS mixed with four legumes as binary mixtures at the same location as the present study. The yields of sole FS at a location to the south of the present study were very similar to those of the present study [3]. Angadi et al. [1] also reported lesser FS yield than sole FS of FS+Lablab, but, contrary to the present study (Table 2), they reported an equal FS yield between sole FS and FS+Cowpea, while Contreras-Govea et al. [3] only reported reduced FS yield when grown with tepary bean. Iqbal et al. [26] reported yields for sole FS and FS in FS+Cowpea similar to the present study (Table 2). Some of the differences between FS yields in the present study and those reported from elsewhere are due to differences in the length of the growing period, but not always. The trend in the present study toward a year × TRT interaction for FS DM yield as related to the difference in magnitude over the years for FS in FS+Sesbania compared to the other mixtures indicates the potential for considerable variability in FS yield when grown with sesbania compared to cowpea and lablab (Table 3).
The nutritive value of sole FS, in regard to CP (Table 2), was less than that reported by Bhattarai et al. [20]. Otherwise, IVTDMD in the present study was greater than that measured by Bhattarai et al. [20]. Contreras-Govea et al. [3] reported 111 and 512 g kg−1 CP and NDF, respectively, for sole FS in one study and, in another test, CP similar to the present study (Table 2), as did Khanum et al. [9].
4.2. Legume Yield and Nutritive Value
The sole legume DM yields of cowpea and lablab were slightly less than those reported by Contreras-Govea et al. [27], but at about the same ratio of lablab having about twice the yield of cowpea (Table 4). The legume DM yields in the present study were greater than those reported by others [1] in this region when grown with FS. The yield differences between the legumes may be associated with plant height and growth habit. Bybee-Finley et al. [2] described ‘Iron Clay’ cowpea, the same cultivar used in the present study, as a short bushy species that could be viny [4], but would remain short, only attaining about 1 m in height. That said, the sole and mixture cowpea yields in the present study (Table 4) were generally greater than those measured by Bybee-Finley et al. [2], who also reported reduced yields in mixtures with sorghum forages. The present study’s sole cowpea yields were about half of those reported by Iqbal et al. [26], while the cowpea in our FS+Cowpea mixture was about one-third of what they reported. Khanum et al. [9] reported sole S. aculeata yields measured at 80 DAP that were about half those of sole sesbania in the present study (Table 4), but Kondo et al. [11] reported yields of S. cannabina when harvested 77 DAP that were similar to the corresponding sole sesbania and FS+sesbania of the present study, which were measured about 125 DAP.
Contreras-Govea et al. [27] reported greater CP and NDFD (220 and 591 g kg−1, respectively) and lesser NDF (289 g kg−1) than the sole cowpea and lablab in the present study (Table 4), with cowpea having greater nutritive value, but they [27] harvested less mature forage, based on the number of DAP (82 and 73 for their study vs. 125 DAP for the present study). For fruiting sesbania, Bosworth et al. [6] reported 112 and 520 g kg−1 for CP and IVDMD, respectively, which is consistent with the maturity and levels measured in the present study (Table 4), while Dan and Brix [7] reported 12.57 mg N g−1 (=88 g CP kg−1 using standard calculations [6,11]) for 79-day-old S. sesban grown under greenhouse conditions in sandy soil, but up to 156 g CP kg−1 in other soils, all well-drained. Bosworth et al. [6] reported that less mature sesbania had greater CP, up to 312 and 139 g kg−1 during the vegetative and fruiting stages, respectively, and Khanum et al. [9] reported a decline in S. aculeata’s CP from 126 to 111 g kg−1 when harvested 50 and 80 DAP, respectively. Kondo et al. [11] also reported from the literature [28] that S. cannabina CP declined with maturity, and they reported a CP of 158 g kg−1 at 77 DAP for that species, which is fairly consistent with that reported by Bosworth et al. [6] for less mature sesbania.
Sesbania is a taller-growing, stemmy legume [13,16] compared to both cowpea [2,4] and lablab [4], which would typically lead to greater NDF and reduced digestibility (e.g., NDFD and IVTDMD; Table 5) compared to cowpea and lablab, which are vinier [4] and would use the FS for support in mixtures [19] rather than increase stem NDF (not measured in the present study). That the difference only occurred in 2019 could be associated with lesser N applied and less precipitation + irrigation (Table 1).
4.3. Mixture Yield and Nutritive Value
Similarly to the present study (Table 6), others [1,4] also reported little or no differences in yield among FS and its mixtures with cowpea, lablab, lima bean, or pole bean, as did Bybee-Finley et al. [2] for mixtures of cowpea and sunn hemp (Crotalaria juncea) with sorghum forage. Nadeem et al. [5] reported an increase in maize+S. sesban yield compared to sole maize and maize+cowpea or maize+clusterbean (Cyamopsis tetragonoloba), but their yields were less than ours (Table 6); although, they harvested 60-day-old forage compared to ours at 125 DAP, and the associated cereal was a different species.
A lack of difference has also been reported by others for CP [1,3], NDF [1,3], NDFD [1], and IVTDMD [1] values between sole FS and its mixture with either cowpea or lablab at lesser [1] or greater [3] legume proportions than in the present study (Table 6). On the other hand, in comparison to the present study (Table 3 and Table 5), Kondo et al. [11] reported that maize+S. cannabina CP was greater than sole maize, but less than sole S. cannabina.
Darapuneni et al. [4] reported that even small legume proportions that do not seem to contribute to total yield can lead to FS yield adjustments to increase the total mixture yield and, as in the case of the present study, cowpea and lablab also contributed to increased nutritive value, but sesbania did not (Table 6). They [4] stated that the legume proportion was greater at early stages when they had a significant role in light capture, which may also have allowed them to contribute to FS biomass production and mixture nutritive value during the later stages. Angadi et al. [1] proposed that increasing the seeding rate of the legume may increase the legume proportion in the mixture and lead to significant differences in nutritive value. Iqbal et al. [26] reported greater LER for FS+cowpea, FS+clusterbean, and FS+soybean (Glycine max) than measured in the present study (Table 6), but no difference among their mixtures. They [26] attributed the better performance of FS+cowpea compared to FS+clusterbean and FS+soybean to greater shade tolerance of cowpea, which was also more complementary to the extensive root system of FS.
5. Conclusions
Although the sesbania in the present study did not improve in forage yield or nutritive value when grown with FS and harvested at 125 DAP (Table 6), perhaps an earlier harvest with an earlier-maturing cereal grass or during the grass vegetative stage at 50–80 DAP may show some benefit, as sesbania’s nutritive value is known to be greater at that time [6,9,10,11]. This said, Mengistu et al. [10] reported that numerous Sesbania spp. did not have good regrowth after being harvested 65 DAP, and, thus, it would not likely be suitable for multiple harvest systems, except for the first cutting. Additionally, Rasool et al. [12] increased forage yield and nutritive value with pearl millet+S. sesban compared to sole pearl millet by alternating two rows of pearl millet with one row of S. sesban on 22.5-cm row spacing. In a previous study at this location, we [29] demonstrated the greatest success for increasing the pearl millet+cowpea yield and nutritive value by alternating two 15-cm rows of each species. Perhaps such planting arrangements also would benefit sorghum+legume forages. Additional studies are needed to evaluate planting arrangements and harvest timing to determine if big-pod sesbania could have value for improving sorghum-based forages.
Author Contributions
Conceptualization, L.M.L. and M.K.D.; methodology, L.M.L. and G.K.M.; validation, L.M.L.; formal analysis, L.M.L.; investigation, L.M.L. and G.K.M.; resources, L.M.L.; data curation, L.M.L.; writing—original draft preparation, L.M.L.; writing—review and editing, L.M.L., M.K.D. and G.K.M.; visualization, L.M.L.; supervision, L.M.L.; project administration, L.M.L.; funding acquisition, L.M.L. All authors have read and agreed to the published version of the manuscript.
Funding
Salaries and research support were provided by state and federal funds appropriated to the New Mexico Agricultural Experiment Station. This research was also partially supported by Hatch Project NM-LAURIAULT-19H (accession 1021538).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Data are available upon reasonable request from the authors.
Acknowledgments
The authors gratefully acknowledge technical and field assistance by Jason Box, Jared Jennings, and Shane Jennings and secretarial assistance by Patty Cooksey, all at Tucumcari; and the staffs with the NMSU Library Document Delivery Service; NMSU College of Agricultural, Consumer and Environmental Sciences Information Technology; and other University support services.
Conflicts of Interest
The authors declare no conflicts of interest, and the funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
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Table 1.
Monthly and annual mean air temperatures, total precipitation, and total irrigation at Tucumcari, NM USA, during 2019 and 2022 and the long-term (1905–2022) means.
Table 1.
Monthly and annual mean air temperatures, total precipitation, and total irrigation at Tucumcari, NM USA, during 2019 and 2022 and the long-term (1905–2022) means.
| Year | Jan. | Feb. | Mar. | Apr. | May | June | July | Aug. | Sep. | Oct. | Nov. | Dec. | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Temperature, °C | |||||||||||||
| 2019 | 3.4 | 2.7 | 9.1 | 15.7 | 21.4 | 26.0 | 29.0 | 25.9 | 23.9 | 15.4 | 7.6 | 4.7 | 15.4 |
| 2022 | 3.8 | 5.7 | 8.6 | 14.3 | 17.4 | 23.9 | 27.8 | 27.6 | 25.0 | 12.3 | 3.2 | 5.7 | 14.6 |
| Long-term | 3.5 | 5.6 | 9.5 | 14.2 | 19.1 | 24.3 | 26.2 | 25.2 | 21.6 | 15.2 | 8.6 | 4.0 | 14.7 |
| Precipitation/irrigation, mm | |||||||||||||
| 2019 | 4 | 5 | 19 | 0 | 3/25 | 54/140 | 48/165 | 86/57 | 1/127 | 50/0 | 7 | 0 | 278/514 |
| 2022 | 4 | 1 | 6 | 24 | 47/102 | 31/133 | 51/203 | 34/159 | 43/74 | 35/32 | 25 | 15 | 316/703 |
| Long-term | 10 | 12 | 19 | 28 | 47 | 47/--- | 67/--- | 68/--- | 39 | 34 | 17 | 16 | 398/--- |
Table 2.
The dry matter (DM) yield and nutritive value of forage sorghum (FS) as a monoculture grown in 38-cm rows or with various annual legumes in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of two years and four replicates.
Table 2.
The dry matter (DM) yield and nutritive value of forage sorghum (FS) as a monoculture grown in 38-cm rows or with various annual legumes in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of two years and four replicates.
| Effect | Yield | CP | NDF | NDFD | IVTDMD |
|---|---|---|---|---|---|
| Year | Mg DM ha−1 | g kg−1 | g kg−1 | g kg−1 | g kg−1 |
| 2019 | 14.68 | 49.9 | 622.6 | 478.1 | 689.1 |
| 2022 | 13.77 | 95.3 | 635.0 | 545.9 | 733.9 |
| Treatment (TRT) | |||||
| Sole FS | 17.89 A | 68.6 | 645.4 | 516.3 | 711.9 |
| FS+Cowpea | 14.13 B | 69.9 | 625.3 | 509.6 | 708.6 |
| FS+Lablab | 12.48 B | 76.8 | 622.5 | 510.0 | 712.4 |
| FS+Sesbania | 12.40 B | 75.3 | 621.9 | 512.2 | 713.1 |
| LSD, 0.05 | 3.76 | NS | NS | NS | NS |
| p-Values | |||||
| Year | 0.6715 | <0.0001 | 0.4537 | <0.0001 | <0.0001 |
| TRT | 0.0272 | 0.3788 | 0.5532 | 0.9545 | 0.9793 |
| Year × TRT | 0.0971 | 0.2919 | 0.5019 | 0.8410 | 0.8595 |
CP, NDF, NDFD, IVTDMD, and NS signify crude protein, neutral detergent fiber, NDF digestibility, and in vitro true dry matter digestibility, respectively. The treatment values within a column followed by similar letters are not significantly different at p < 0.05. The differences between the years are indicated by the p-value for the year effect.
Table 3.
The trend (0.05 ≤ p ≤ 0.10) toward year × treatment interaction for dry matter (DM) yield (Mg ha−1) of forage sorghum (FS) as a monoculture (sole FS) grown in 38-cm rows or with various annual legumes in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of four replicates.
Table 3.
The trend (0.05 ≤ p ≤ 0.10) toward year × treatment interaction for dry matter (DM) yield (Mg ha−1) of forage sorghum (FS) as a monoculture (sole FS) grown in 38-cm rows or with various annual legumes in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of four replicates.
| Treatment | Year | |
|---|---|---|
| 2019 | 2022 | |
| Sole FS | 16 AB | 20 A |
| FS+Cowpea | 14 B | 14 B |
| FS+Lablab | 13 B | 12 B |
| FS+Sesbania | 17 AB | 8 B |
Treatment values within an interaction followed by similar letters are not significantly different at p ≤ 0.05.
Table 4.
The dry matter (DM) yield and nutritive value of various legumes grown as monocultures (sole legume) in 38-cm rows or with forage sorghum (FS) in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of two years and four replicates.
Table 4.
The dry matter (DM) yield and nutritive value of various legumes grown as monocultures (sole legume) in 38-cm rows or with forage sorghum (FS) in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of two years and four replicates.
| Effect | Yield | CP | NDF | NDFD | IVTDMD |
|---|---|---|---|---|---|
| Year | Mg DM ha−1 | g kg−1 | g kg−1 | g kg−1 | g kg−1 |
| 2019 | 3.48 | 126.4 | 493.9 | 438.2 | 726.9 |
| 2022 | 4.97 | 129.0 | 520.7 | 390.0 | 693.4 |
| Treatment (TRT) | |||||
| Sole Cowpea | 4.79 AB | 145.1 A | 464.9 B | 477.5 A | 776.1 A |
| FS+Cowpea | 1.95 B | 128.5 AB | 477.4 B | 454.6 A | 758.3 A |
| Sole Lablab | 8.15 A | 147.4 A | 459.6 B | 477.5 A | 779.5 A |
| FS+Lablab | 2.42 B | 136.0 A | 453.9 B | 477.5 A | 782.0 A |
| Sole Sesbania | 5.66 AB | 112.7 BC | 574.2 A | 314.2 B | 599.5 B |
| FS+Sesbania | 2.40 B | 96.5 C | 613.8 A | 283.3 B | 565.3 B |
| LSD, 0.05 | 4.77 | 28.6 | 70.4 | 40.2 | 50.2 |
| p-Values | |||||
| Year | 0.1982 | 0.6942 | 0.1158 | <0.0001 | 0.0085 |
| TRT | 0.0138 | 0.0031 | <0.0001 | <0.0001 | <0.0001 |
| Year × TRT | 0.3101 | 0.0042 | 0.0346 | 0.0097 | 0.0266 |
CP, NDF, NDFD, and IVTDMD signify crude protein, neutral detergent fiber, NDF digestibility, and in vitro true dry matter digestibility, respectively. The treatment values within a column followed by similar letters are not significantly different at p ≤ 0.05. The differences between the years are indicated by the p-value for the year effect.
Table 5.
The significant (p ≤ 0.05) year × treatment interactions for the nutritive value of various legumes grown as monocultures (sole legumes) in 38-cm rows or with forage sorghum (FS) in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. Values are the means of four replicates.
Table 5.
The significant (p ≤ 0.05) year × treatment interactions for the nutritive value of various legumes grown as monocultures (sole legumes) in 38-cm rows or with forage sorghum (FS) in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. Values are the means of four replicates.
| Variable/Treatment | Year | |
|---|---|---|
| 2019 | 2022 | |
| Legume CP (g kg−1) | ||
| Sole Cowpea | 166 A | 124 BC |
| FS+Cowpea | 139 ABC | 118 BC |
| Sole Lablab | 145 AB | 150 AB |
| FS+Lablab | 112 CD | 160 A |
| Sole Sesbania | 112 CD | 114 CD |
| FS+Sesbania | 84 D | 109 BCD |
| Legume NDF (g kg−1) | ||
| Sole Cowpea | 398 F | 532 BCD |
| FS+Cowpea | 468 DEF | 487 CDE |
| Sole Lablab | 427 EF | 492 CDE |
| FS+Lablab | 466 DEF | 442 EF |
| Sole Sesbania | 562 BC | 587 AB |
| FS+Sesbania | 643 A | 585 ABC |
| Legume NDFD (g kg−1) | ||
| Sole Cowpea | 503 A | 453 C |
| FS+Cowpea | 463 ABC | 447 C |
| Sole Lablab | 495 AB | 460 BC |
| FS+Lablab | 478 ABC | 478 ABC |
| Sole Sesbania | 375 D | 253 F |
| FS+Sesbania | 317 E | 250 EF |
| Legume IVTDMD (g kg−1) | ||
| Sole Cowpea | 823 A | 730 C |
| FS+Cowpea | 771 ABC | 745 BC |
| Sole Lablab | 794 AB | 766 BC |
| FS+Lablab | 767 BC | 798 AB |
| Sole Sesbania | 638 D | 561 E |
| FS+Sesbania | 570 E | 561 DE |
CP, NDF, NDFD, and IVTDMD signify crude protein, neutral detergent fiber, NDF digestibility, and in vitro true dry matter digestibility, respectively. The treatment values within an interaction followed by similar letters are not significantly different at p ≤ 0.05.
Table 6.
The dry matter yield, legume proportion, land equivalency ratio, and nutritive value of forage sorghum as a monoculture (sole FS) grown in 38-cm rows or with various annual legumes in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of two years and four replicates.
Table 6.
The dry matter yield, legume proportion, land equivalency ratio, and nutritive value of forage sorghum as a monoculture (sole FS) grown in 38-cm rows or with various annual legumes in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of two years and four replicates.
| Effect | Yield | Legume Proportion | LER | CP | NDF | NDFD | IVTDMD |
|---|---|---|---|---|---|---|---|
| Year | Mg DM ha−1 | % | g kg−1 | g kg−1 | g kg−1 | g kg−1 | |
| 2019 | 15.83 | 9.5 | 1.2 | 54.6 | 616.1 | 475.1 | 691.3 |
| 2022 | 16.10 | 22.0 | 1.1 | 101.0 | 614.7 | 515.4 | 724.9 |
| Treatment (TRT) | |||||||
| Sole FS | 17.89 | ---- | 1.0 | 68.6 B | 645.4 | 516.3 A | 711.9 |
| FS+Cowpea | 16.10 | 12.1 | 1.3 | 77.4 AB | 607.1 | 503.4 A | 715.1 |
| FS+Lablab | 14.90 | 16.3 | 1.1 | 86.1 A | 594.4 | 501.4 A | 722.6 |
| FS+Sesbania | 14.97 | 18.8 | 1.1 | 79.1 AB | 614.8 | 460.0 B | 682.8 |
| LSD, 0.05 | NS | NS | NS | 14.1 | NS | 29.9 | NS |
| p-Values | |||||||
| Year | 0.9156 | 0.0016 | 0.7150 | <0.0001 | 0.9339 | 0.0044 | 0.0010 |
| TRT | 0.4042 | 0.0813 | 0.2469 | 0.0224 | 0.0613 | 0.0266 | 0.0522 |
| Year × TRT | 0.2592 | 0.0045 | 0.3316 | 0.0971 | 0.9197 | 0.1987 | 0.1290 |
LER, CP, NDF, NDFD, IVTDMD, and NS signify land equivalency ratio, crude protein, neutral detergent fiber, NDF digestibility, in vitro true dry matter digestibility, and not significant, respectively. The treatment values within a column followed by similar letters are not significantly different at p ≤ 0.05. The differences between years are indicated by the p-value for the year effect.
Table 7.
The significant (p ≤ 0.05) year × treatment interaction for the legume proportion (%) of various legumes grown with forage sorghum (FS) in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of four replicates.
Table 7.
The significant (p ≤ 0.05) year × treatment interaction for the legume proportion (%) of various legumes grown with forage sorghum (FS) in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of four replicates.
| Treatment | Year | |
|---|---|---|
| 2019 | 2022 | |
| FS+Cowpea | 12.4 B | 11.7 B |
| FS+Lablab | 8.9 B | 23.7 A |
| FS+Sesbania | 7.1 B | 30.6 A |
Treatment values within the interaction followed by similar letters are not significantly different at p ≤ 0.05.
Table 8.
The trend (0.05 ≤ p ≤ 0.10) toward a year × treatment interaction for the crude protein (g kg−1) of forage sorghum (FS) as a monoculture (Sole FS) grown in 38-cm rows or with various annual legumes in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of four replicates.
Table 8.
The trend (0.05 ≤ p ≤ 0.10) toward a year × treatment interaction for the crude protein (g kg−1) of forage sorghum (FS) as a monoculture (Sole FS) grown in 38-cm rows or with various annual legumes in alternate 38-cm rows in 2019 and 2022 at the Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA. The values are the means of four replicates.
| Treatment | Year | |
|---|---|---|
| 2019 | 2022 | |
| Sole FS | 39.8 D | 97.5 B |
| FS+Cowpea | 60.0 C | 94.8 B |
| FS+Lablab | 58.0 C | 114.3 A |
| FS+Sesbania | 60.8 C | 97.5 B |
Treatment values within the interaction followed by similar letters are not significantly different at p ≤ 0.05.
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MDPI and ACS Style
Lauriault, L.M.; Darapuneni, M.K.; Martinez, G.K. Sorghum–Legume Mixtures to Improve Forage Yield and Nutritive Value in Semiarid Regions. Grasses 2024, 3, 163-173. https://doi.org/10.3390/grasses3030012
AMA Style
Lauriault LM, Darapuneni MK, Martinez GK. Sorghum–Legume Mixtures to Improve Forage Yield and Nutritive Value in Semiarid Regions. Grasses. 2024; 3(3):163-173. https://doi.org/10.3390/grasses3030012
Chicago/Turabian StyleLauriault, Leonard M., Murali K. Darapuneni, and Gasper K. Martinez. 2024. "Sorghum–Legume Mixtures to Improve Forage Yield and Nutritive Value in Semiarid Regions" Grasses 3, no. 3: 163-173. https://doi.org/10.3390/grasses3030012
APA StyleLauriault, L. M., Darapuneni, M. K., & Martinez, G. K. (2024). Sorghum–Legume Mixtures to Improve Forage Yield and Nutritive Value in Semiarid Regions. Grasses, 3(3), 163-173. https://doi.org/10.3390/grasses3030012
