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To change row spacing is a common agricultural practice to adjust plant density to enhance plant growth and development. Here we examined the fine root (≤1.0 mm in diameter) distribution and morpho...

A large portion of the Loess Plateau of China is characterized as “marginal” with serious land degradation and desertification problems. Consequently, two policies, Grain for Green and Western Development Action were established by the Chinese government in response to the demand for ecological protection and economic development in the Loess Plateau. These policies are designed to increase forest cover, expand farmlands, and enhance soil and water conservation, while creating sustainable vegetation restoration. Perennial grasses have gained attention as bioenergy feedstocks due to their high biomass yields, low inputs, and greater ecosystem services compared to annual crops. Moreover, perennial grasses limit nutrient runoff and reduce greenhouse gas emissions and soil losses while sequestering carbon. Additionally, perennial grasses can generate economic returns for local farmers through producing bioenergy feedstock or forage on marginal lands. Here, we suggest a United States model energy crop, switchgrass ( Panicum virgatum L.) as a model crop to minimize land degradation and desertification and to generate biomass for energy on the Loess Plateau.

Understanding the soil respiration characteristics in response to nitrogen and phosphorus addition in farming-withdrawn grasslands within semi-arid loess hilly-gully regions is of great importance for providing a theoretical basis for evaluating the effects of artificial regulation approaches on carbon cycling. We report on a field experiment that was undertaken from May to September 2018 in a farming-withdrawn grassland ecosystem in China, which is dominated by

Application of nitrogen (N) fertilizers without knowing the N-supplying capacity of soils may lead to low N use efficiency, uneconomical crop production, and pollution of the environment. Based on the results from pot experiments treated with soil initial nitrate leaching and native soil, long-term alternate leaching aerobic incubation was conducted to study the disturbed and undisturbed soil N-supplying capacity of surface soil samples in 11 sites with different fertilities on the Loess Plateau. The results indicated that the entire indexes and ryegrass (Lolium perenne) uptake N with soil initial nitrate leaching showed a better correlation than that without soil initial nitrate leaching. Except the correlation coefficients for soil initial nitrate (NO3 −)-N and mineral N extracted by calcium chloride (CaCl2) before aerobic incubation with ryegrass uptake without soil initial nitrate leaching, the correlation coefficients for soil initial NO3 −-N and mineral N extracted by CaCl2 before aerobic incubation...

Aims Decreasing root biomass might be an effective way to increase crop production under drought stress. A winter wheat with root excision was chosen to determine whether 1) root biomass or R/S (root/shoot ratio) is reduced by root excision, 2) competitive ability is reduced by root excision and its link with R/S and 3) competitive ability influences crop production.Methods The effects of root excision on root-to-shoot relations, competition ability and yield characters of winter wheat (Triticum aestivum cv Changwu135) were investigated using a deWit replacement series in a pot study. Root excision was conducted from tillering to jointing. Two culture methods (mono and mixed) were compared. The effect of drought was estimated from two groups of plants, one group maintained at 75% soil FWC and a second at about 50%, after root excision. Soil water was controlled by weight daily. At grain maturity, plants for each pot were harvested, divided into shoot and root, dried and weighed.Important findings The R/S was significantly reduced after root excision in monocultures irrespective of water condition. Furthermore, spike weight and aerial biomass of wheat after root excision were reduced in mixed cultures, indicating that the competitive ability of wheat was reduced after root excision. There was positive correlation between competitive ability and R/S in crop varieties, i.e., the crop with the higher R/S had higher competitive ability. In monocultures, spike weight and yield of wheat after root excision were reduced with a complete water supply. However, the spike weight and yield of wheat were higher after root excision than without excision under drought conditions. This study indicated that the crop with higher competitive ability has a higher production capability with a complete water supply and that the crop could obtain higher yield with the reduction in individual competitive ability under limited water.

Non-hydraulic root-sourced signal (NRS) is so far affirmed to be a unique “early-warning” response to soil drying in plants, but little is known about the quantitative effect of this early-warning mechanism on crop production. To evaluate the link of NRS to a drought tolerance profile, a pot-culture study was carried out in a plant growth chamber with eight spring-wheat (Triticum aestivum L.) cultivars bred in semiarid China. The NRS was judged to begin when there was a significant lowering of stomatal conductance without any change in leaf relative water content (RWC), and the hydraulic root signal (HRS) was judged to begin when leaf RWC changed significantly. Soil water contents (SWC), at which the NRS and HRS were switched on, differed among the eight cultivars. For “Monkhead” and “Jinby,” representing “old” cultivars, the NRS and HRS were initiated successively at about 60% FWC (field water capacity) and 45% FWC, respectively. Conversely, “Longchun8139-2” and “Plateau 602” (recent cultivars) showed the NRS and HRS occurring between 70% FWC and 35% FWC, a much wider range. The events of the other four non-old cultivars were generally intermediate. This threshold range (TR) of soil FWCs between the onset of NRS and HRS also narrowed over the successive developmental stages from seedling to seed filling. Fewer survival days (SD), lower maintenance rate of grain yield (MRGY), and higher lethal leaf water potentials (LLWP) had been found in old cultivars. Widening TR was significantly correlated with increasing SD and MRGY (r = 0.8713** and 0.7318*, respectively), and with decreased LLWP (r = 0.8591**). This survey of different-decade cultivars suggests that advances in grain yield and drought tolerance would be made by targeted selection for a wider TR of root-sourced signals.

Taking two winter wheat (Triticum aestivum L.) cultivars Changwu 135 and Pingliang 40 commonly cultivated in the semi-arid area on Loess Plateau as test materials, and by the method of ecological replacement, a 2-year field experiment was conducted to study the effects of mono- and mixed culture on the grain yield and water use efficiency of the cultivars. The results showed that under mono-culture, Pingliang 40 had a much higher unit area root biomass (367.60 g x m(-2)) than Changwu 135 (297.31 g x m(-2)), and a more uniform root distribution (i.e., a better root type for water absorption), but its grain yield and water use efficiency were lower than Changwu 135. Under mixed culture, the population root biomass of Pingliang 40 and Changwu 135 was 13.36 g * m(-2) and 8.50 g x m(-2) higher than that under mono-culture, respectively, suggesting that mixed population could absorb the water in deeper soil layers, and had higher total unit area biomass, which in turn increased the water use efficiency. Comparing with Pingliang 40, Changwu 135 allocated more dry matter to its productive organ, leading to its higher grain yield, harvest index, and water use efficiency.

The diurnal course of photosynthetic rate, transpiration rate, and leaf water potential (psi L) of five plant species in North Shaanxi loess hilly-gully region were measured in dry seasons. Based on the daily maximum photosynthetic and transpiration rates, daily total assimilation and transpiration, and diurnal change characteristics of psi L, the test plants were classified into different eco-adaptation types. Panicum virgatum L. had high photosynthetic rate, low transpiration rate and high water use efficiency (WUE), and its drought adaptation strategy was to delay dehydration by developing high psi L. Medicago sativa had high photosynthetic and transpiration rates but low WUE, while Lespedeza dahurica had low photosynthetic and transpiration rates and low WUE. Their drought adaptation strategies were the same, namely, by increasing psi L delay dehydration. Bothriochloa ischaemum had high photosynthetic rate, relative high transpiration rate and medium WUE, and its drought-resistant strategy was to decrease psi L to endure dehydration. Astragalus adsurgens had similar characteristics in diurnal courses of photosynthesis with B. ischaemum, and its drought adaption strategy was to delay dehydration by developing low psi psi L.