Above and Belowground Relative Yield Total of Clover–Ryegrass Mixtures Exceed One in Wet and Dry Years

Grassland mixtures hold the potential for increasing biomass and productivity. In a field experiment, monocultures and mixtures of eight white clover (Trifolium repens L.) genotypes and perennial ryegrass (Lolium perenne L.) were analyzed over three years (2015, 2016, and 2018) for their species-specific aboveground and belowground biomass. Roots were analyzed by Fourier transform infrared (FTIR) spectroscopy to identify species-specific root mass, vertical distribution, and belowground relative yield total (RYT). Aboveground biomass decreased strongly from 2015 to 2018. Aboveground and belowground RYT were always significantly higher than one. Aboveground biomass overyielded in 2016 and 2018 compared to monocultures. Monocultures of perennial ryegrass displayed a significantly higher proportion of roots in shallow soil layers than white clover in two of the three examined years. In mixtures, these differences in vertical root distribution between both species were not present and perennial ryegrass, and white clover occupied similar vertical niches in 2015 and 2016. Interestingly, in the dry year 2018, white clover had a higher proportion of roots in shallow soil layers than perennial ryegrass in mixtures.

The Effect of Intercropping and Nitroxin Biofertilizer on Yield Components and Relative Yield Total of Purslane (Portulaca oleracea L.) and Dragon’s Head (Lallemantia iberica Fisch. & C.A. Mey)

A field study was conducted in order to evaluate the effects of intercropping and biofertilizers on yield and yield components of purslane (Portulaca oleracea L.) and dragon’s head (Lallemantia iberica Fisch. and C.A. Mey). The experiment was factorial on the basis of a randomized complete block design with three replications. The first factor was an additive intercropping system including monocultured purslane, monocultured dragon’s head, intercropping of 100% purslane + 25% dragon’s head, intercropping of 100% purslane + 50% dragon’s head, intercropping of 100% purslane + 75% dragon’s head; the second factor was nutrient treatments including application of 50% inorganic N fertilizer (urea) + nitroxin, inorganic N fertilizer (urea), nitroxin and no fertilizer. Results showed that as the density of dragon’s head increased, the number of branches in purslane decreased. In purslane, the number of capsules was significantly affected by intercropping and application of biofertilizers. In both crops, the effects of treatments on yield were significant. Results clearly showed that Relative Yield Total (RYT) was always higher in intercropping than monocultured systems. The highest RYT was observed in intercropping of 100% purslane + 50% dragon’s head with the application of 50% inorganic N fertilizer (urea) + nitroxin. Therefore, combination usage of biofertilizers and inorganic N fertilizers can improve yields in purslane/dragon’s head intercropping.

Productivity, relative yield and plant growth of forage corn intercroppedwith soybean under different crop combination ratio

An experiment was carried out to evaluate influence of different crop combination ratios of corn and soybean in terms of forage yield in corn-soybean intercropping. The experiment compared both corn and soybean as monocultures and in different intercropping ratios from 25:75, 50:50 and 75:25 of corn to soybean. The crop combination ratio had significant effects on physiological traits and dry matter yield of forage. The ratio of 75:25 and 50:50 recorded DM yields similar to those of monocropped corn (14.77 t/ha). Relative yield total (RYT) values of intercropping were higher than that of monocrop corn and soybean. Mixtures with 50:50 combination ratio had higher mean total relative yield values (1.15) in comparison with the other ratios. Land equivalent ratio (LER) increased with corn-soybean intercropping and the highest total LER value was recorded with 50:50 ratio (1.13). The crop ratio of 50:50 gave the best combination based on DM yield, relative yield, LER of the combined forage.

Yield Evaluation of Three Sesame (Sesamum indicum L.) Varieties Intercropped with Maize (Zea mays L.) in a Southern Guinea Savannah Location, Nigeria

Field experiments were conducted from July to November during the 2012 and 2013 cropping seasons, at the Research Farm, University of Agriculture, Makurdi, Nigeria, to evaluate the yields of two newly introduced sesame varieties (Ex Sudan and SN 603) against the commonly grown variety “E-8” under intercropping with maize variety ‘Oba 98’. The trial area consisted of a total of seven treatments, replicated three times in a randomized complete block design. The results showed that, though maize yield was not significantly (P ≤ 0.05) affected by intercropping with sesame varieties, however, intercropped yield of sesame variety ‘Ex Sudan’ was significantly (P ≤ 0.05) greater by 26.8 % and 25.6 % respectively, in years 2012 and 2013, compared to that obtained from intercropped sesame variety ‘SN 603’, and by 19.5 % and 20.9 % respectively, in years 2012 and 2013, compared to that produced from intercropped popular sesame variety ‘E-8’. Intercropping maize variety ‘Oba 98’ with sesame variety ‘Ex Sudan’ gave the highest total intercrop yield, greatest biological efficiency with a relative yield total values of 0.87 and 0.91 respectively, in 2012 and 2013. The combination also recorded the highest land equivalent ratio (LER), highest land equivalent coefficient, highest area x time equivalent ratio (ATER), highest total monetary returns (N584,200 and N588,600 respectively, in years 2012 and 2013) and highest monetary equivalent ratio (MER). The implication of study showed that sesame variety ‘Ex Sudan’ performed best and could therefore be recommended as a potential replacement for the popular variety ‘E-8’ under intercropping with maize variety ‘Oba 98’ in Makurdi, Nigeria.

Yields of perennial grasses in the summer and at the end of the growing season

The paper deals with the yields of Festulolium, Dactylis glomerata, Arrhenatherum elatius and Festulolium-Dactylis glomerata mixture during the growing season and at the end of the growing season. The yields were assessed in the Bohemian-Moravian upland at 560 m a.s.l. A small-plot experiment was established in three repetitions. The assessment was made in three subsequent years. The experiment was annually fertilized with 50 kg . ha−1 N, 30 kg . ha−1 P and 60 kg . ha−1 K. Evaluated were dry matter yields and RYT values (Relative Yield Total) in the mixture of Festulolium and Dactylis glomerata. In summer, the sward was used either for one cut (harvest in early June) or two cuts (harvests in early June and late July). At the end of the growing season, the stand was harvested in October or in November or in December. Yields of the first cut in early June ranged from 5.90 to 9.12 t . ha−1. Yields of the second cut in late July ranged from 1.05 to 4.60 t . ha−1. Statistic difference between the species was significant (P < 0.05) in the respective cuts. Total yields of dry matter in the growing season ranged from 7.51 to 10.05 t . ha−1. Number of cuts and year showed a statistically highly significant influence (P < 0.01) on DM yields. The mixture of Festulolium and Dactylis glomerata exhibited an additive relation (RYT = 1) in the first cut and an antagonistic relation (RYT < 1) in the second cut. At the end of the growing season, the yields ranged from 0.71 to 2.27 t . ha−1. Average yields of one-cut swards (harvested in summer in early June) were at the end of the growing season 2.27 t . ha−1 and average yields of two-cut swards (harvested in summer in early June and late July) were 0.79 t . ha−1. From October to December, the yields were decreasing from 1.78 to 1.32 t . ha−1. Species, number of cuts in summer, harvest date at the end of the growing season and year showed a statistically highly significant influence (P < 0.01) on dry matter yields. In the first two production years, the mixture of Festulolium and Dactylis glomerata exhi­bi­ted an antagonistic relation (RYT < 1) at the end of the growing season. In the third production year, the relation between Festulolium and Dactylis glomerata as expressed by the RYT value could be identified as synergic (RYT > 1).

Aggressivity: Cucumber vs. Amaranth

A replacement series study was conducted to describe the aggressivity between cucumber, smooth pigweed, and livid amaranth. Cucumber was three times more competitive than smooth pigweed or livid amaranth, under the conditions of this study. However, there was equal competition and no antagonism between smooth pigweed and livid amaranth. Where cucumbers were planted in mixture with either of the two weeds, the relative yield total values were approximately 10 to 20% higher than the monocultures. Cucumber was a superior competitor when grown in mixture with smooth pigweed or livid amaranth, and the following aggressivity hierarchy exists: cucumber > livid amaranth = smooth pigweed. Results from the additive field study indicated that amaranth dry weights were significantly affected by smooth pigweed and livid amaranth density. Dry weight of amaranth was decreased by 48% at Gainesville and 25% at Live Oak, at 18 plants/m2. Despite differences between the Gainesville and Live Oak results, the dry weight data were similar for both smooth pigweed and livid amaranth at each location.

Competition and productivity in crop mixtures: some properties of productive intercrops

Inverse yield–density relationships were used to evaluate how competitive balances in mixed plant species associations may influence productivity, as measured by three indices : Relative Yield Total (RYT), Relative Land Output (RLO), and Total Land Output (TLO). Parameters of the inverse relationships, which express competitive influences and plant growth potential in the absence of competition, were incorporated into expressions used to predict RYT, RLO and TLO. Initial parameter values were derived from 25 experiments on binary species mixtures, and parameter values were systematically varied over a 100-fold range. Response to parameter manipulation was also investigated in five specific binary associations representing a broad range of relative mixture productivity. As indicated by RLO or RYT, and in accord with ecological concepts of niche differentiation, high productivity of mixtures relative to monocultures occurred if between-species competition was low. As indicated by TLO, the total combined productivity of the mixed species was enhanced by higher potential growth per plant in the absence of competition. Lower within- and between-species competition also increased TLO. There was a significant positive correlation between RYT and RLO. Relative and total measures of mixture productivity, however, showed different responses to parameter manipulation, and were not correlated.

Inter-Specific Competition Between Seedlings of Pinus radiata, Eucalyptus regnans and Acacia melanoxylon

A replacement series experiment was carried out to determine the competitive aggressiveness of three species, P. radiata, E. regnans and A. melanonylon towards each other at seedling stage. Seedlings of the three species were grown at an overall density of six plants per pot for each species combination, providing all combinations of two species from 0:6 to 6:O. In addition, seedlings were grown in pure stands from one plant to six plants per pot for the three species. The relative crowding coefficient, the relative yield total, the relative effects of intra- and inter-specific competition on the yield of each species were the four indices calculated. Acacia melanoxylon was the most aggressive species, followed by P. radiata then E. regnans. In comparison with their corresponding monoculture, A. melanonylon in mixtures showed the smallest decrease in shoot/root ratio, whilst P. radiata had a greater decrease and E. regnans showed the greatest reduction. The average relative yield total of E. regnans and A. melanoxylon was close to 1 for both shoots and roots, indicating an almost complete overlap in resource use between the two native species. The relative yield total of P. radiata and E. regnans was 1.27 for shoots and 1.48 for roots, suggesting a possible difference in resource use between them. The results of this experiment provide a valuable qualitative insight into the relative magnitudes of the effects of inter- and intra-specific competition between the seedlings of the three species.