Long-Term Yield and Quality Performance of Perennial Energy Grasses (Agropyron spp.) on Marginal Land

The cultivation of perennial grasses is one of the most desirable alternatives as energy feedstock, but it is difficult to achieve competitive yields under Mediterranean marginal conditions. The aim of this study was to assess the performance of three cool-season grasses (Agropyron spp.) from an agronomic and energetic point of view by comparing the dry matter (DM) yields, rain use efficiency, chemical composition, and biomass quality over an eight-year period in Spain under marginal rainfed conditions. The tall wheatgrass (Agropyron elongatum (Host) Beauv.) cultivars, Alkar (4.8 Mg DM·ha−1) and Jose (4.7 Mg DM·ha−1), achieved the highest yields. Productions below 0.5 Mg DM·ha−1 were obtained when rainfall was lower than 150 mm between March and June. The biomass obtained from the tested grasses showed relatively high contents of ash, silicon, and alkali elements. Net calorific values ranged between 16.7 and 18.5 MJ·kg−1 db. Differences in the composition among species and cultivars are not likely to affect their combustion behavior from a practical point of view. The ash content, as well as the concentrations of K, S, Na, and Cl, tended to decrease over the years. The results offered would be very useful for the implementation of this type of crop in marginal land.

Agronomic characteristics and rain use efficiency of sorghum in a semiarid region

Sorghum culture highlighted in animal nutrition because it allows its cultivation of green conservation as silage. This study aimed to evaluate the divergence of agronomic and productive characteristics of 32 sorghum cultivars in the semiarid region. The randomized block design with three replications was used. It was evaluated the dry matter percentage (DM), fresh matter production (FMP) and dry matter production (DMP); stem proportion, panicle, and leaf blade in the plant DM; plant height, nº plants ha-1, stem diameter, leaf number, leaves and panicles length; rain use efficiency (RUE) in kg MS ha-1 mm-1, and water accumulation (WA) in kg ha-1 and kg ha-1 mm-1. The data were analyzed using the Scott-Knott procedure at a 5% significance level. The FMP and DMP showed the formation of two distinct groups, which may be crucial in choosing a more productive cultivar. Moreover, cultivar 17 stood out for presenting high leaf blade participation while cultivars 9, 19, 23, 24, and 32 in panicle participation in DM, which is considered nutritionally better due to higher digestibility than the stem. Besides, for the RUE and WA, two distinct groups were also formed, which can be great to determine cultivars that have higher xerophilic potential, and thus use them for the production of silage in semi-arid conditions. Experimental cultivars showed greater results than those commercials. Studies that evaluate the animal performance of cultivars (3, 6, 9, 17, 19, and 31), could be conducted to prove their nutritional values since these cultivars stood out for presenting interesting productive characteristics.

Trends in Woody and Herbaceous Vegetation in the Savannas of West Africa

We assess 32 years of vegetation change in the West African Sudano-Sahelian region following the drought events of the 1970s and 1980s. Change in decadal mean rain use efficiency is used to diagnose trends in woody vegetation that is expected to respond more slowly to post-drought rainfall gains, while change in the slope of the productivity–rainfall relationship is used to infer changing herbaceous conditions between early and late periods of the time series. The linearity/non-linearity of the productivity–rainfall relationship and its impact on the interpretation of overall greening trends, and specific woody and herbaceous vegetation trends, is also examined. Our results show a mostly positive association between productivity and rainfall (69% of pixels), which can be best described as linear (32%) or saturating (37%). Choosing the ‘best’ model at a specific location using Akaike Information Criterion has no discernible effect on the interpretation of overall greening or herbaceous trends, but does influence the detection of trends in woody vegetation. We conclude that widespread recovery in woody vegetation is responsible for the post-drought greening phenomenon reported elsewhere for the Sahel and Sudanian sub-regions. Meanwhile, trends in herbaceous vegetation are less pronounced, with no consistent indication towards either herbaceous degradation or recovery.

Spatial–Temporal Variation of ANPP and Rain-Use Efficiency Along a Precipitation Gradient on Changtang Plateau, Tibet

Aboveground net primary productivity (ANPP) and rain-use efficiency (RUE) are important indicators in assessing the response of ecosystems to climate change. In this paper, the Changtang Plateau in the Tibetan Autonomous Region was selected as the study area to analyze the spatial and temporal changes of ANPP and RUE in grassland communities and their response to climate change. The results showed the following:(1) The spatial pattern of ANPP was closely related to rainfall on the Changtang Plateau. The average ANPP over the past 15 years increased gradually from the arid west to the humid east. A consistent pattern was exhibited in different grassland types and climate zones. (2) The RUE was higher at the east and west edges of the Changtang Plateau, especially in the arid west, but was lower in the center. From the perspective of different climatic zones, the average RUE in the southern Tibetan semiarid climate zone and the Ngari arid climate zone was significantly higher than that in other climate zones. However, the average RUE in different grassland types only varied from 0.07 to 0.09 g·m−2·mm−1. The spatial variation in RUE was more distinct in different climatic zones than in different grassland types. (3) Climate change influenced the interannual variation of ANPP and RUE, but the response of ANPP to rainfall showed a significant lag. The interannual change in RUE was negatively correlated with changes in precipitation. (4) In general, a greater area showed a significant increase rather than a decrease in ANPP on the Changtang Plateau, which meant that the grassland condition is improving. The temporal variation patterns of ANPP and RUE in different climate zones were consistent with the overall patterns on the Changtang Plateau, while the variation was not significant in different grassland types.

Rain Use Efficiency in Southern Romania after Using the Device for Soil Modelling in Interrupted Furrows for Weeding Crops -DMBC-5

The global impact of climate change, with the potential to affect agriculture through changes in temperature, rainwater distribution and amount, leads to the need to develop integrated technologies that increase rain use efficiency and support soil and environmental quality, ensuring higher agricultural outputs with lower costs. Soil modeling in interrupted furrows is a very efficient rainwater harvesting system, but has not yet been scientifically assessed for the conditions in Southern Romania as the other soil working systems have been. For this purpose, a soil modeling device consisting of a frame with triangle for coupling to the tractor, wheels for adjusting and limiting the working depth, soil loosening knives, ridge ploughs and furrow compartmenting equipment was compared with the conventional technology for sunflower culture in two localities in Southern Romania: Crânguri in Giurgiu County and Mărculeşti in Calarasi County. The device for soil modeling in interrupted furrows for weeding crops provides a viable option that has positive effects on soil properties and ensures increased crop yields compared to conventional works as well as the opportunity to increase the efficiency of water recovery in agriculture by harvesting rainwater.

Changes of Grassland Rain Use Efficiency and NDVI in Northwestern China from 1982 to 2013 and Its Response to Climate Change

The grasslands in arid and semi-arid regions rely heavily on the use of rain, thus, improving rain use efficiency (RUE) is essential for securing sustainable development of grassland ecosystems in these areas with limited rainfall. In this study, the spatial and temporal variabilities of RUE for grassland ecosystems over Northwestern China during 1982–2013 were analyzed using the normalized difference vegetation index (NDVI) and precipitation data. Results showed that: (1) Although grassland area has decreased gradually over the past 30 years, the NDVI in most areas showed that the vegetation was gradually restored; (2) The trends of RUE increased in the east of Northwestern China and decreased in the west of Northwestern China. However, the trends of RUE for the high-coverage grasslands (vs. low-coverage grassland) increased (decreased) significantly over the past 30 years. (3) The RUE for the grasslands was positively correlated with air temperature, while it was negatively correlated with the change of annual mean precipitation in northwestern China. Moreover, the obvious RUE increasing trends were found in the vegetation restoration areas, while the RUE decreasing trends appeared in the vegetation degradation areas. This study will be helpful for understanding the impacts of climate change on securing the sustainable development of grassland ecosystems in arid and semi-arid regions.