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Adaptive management on rainfed agricultural ecosystem is crucial to improve field productivity and soil carbon sequestration under climate change, particularly in semiarid east African Plateau (EAP). We first introduced ridge-furrow (RF) farming system with plastic mulching and balanced fertilization into EAP to explore its effects on maize growth, yield formation, water use and soil carbon sequestration in a typical semiarid site of EAP in long but cool (2012) and short but warm (2013) rainy seasons. Local maize ( Zea mays L.) hybrid, KCB was used in field experiments including three farming patterns: 1) conventional flat planting (FP); 2) RF with transparent polyethylene film (RFT) and 3) RF with black polyethylene film (RFB), in which each pattern was exposed to high fertilization (compound fertilizer) (375 kg ha −1 ), conventional fertilization (225 kg ha −1 ) and zero fertilization respectively. The results indicated that RFT and RFB treatments significantly increased soil water storage in the depth of 0–120 cm, aboveground biomass, grain yield and water use efficiency over two growing seasons. On average, fertilization treatments further increased biomass accumulation, grain yield, leaf area index and WUE by 24.3%, 13.1%, 18.7% and 9.6%, respectively on the basis of sole RFM treatment. Across two seasons, RF mulching with fertilization averagely increased soil organic carbon and C/N ratio (soil organic carbon/soil total nitrogen) by 5.1% and 10.7% respectively. Critically, increased root biomass resulted in more root residue import into soil system due to improved hydro-thermal balance, which may account for biological carbon sequestration effects in this system. In addition, our field demonstration suggested that local farmers benefited from higher economic return from this integrated farming system, showing a high acceptance extent. Taken together, this system could serve as a promising adaptive management on increasing agricultural carbon fixation and maize productivity to cope with food security and climate change in semiarid EAP and other similar areas of Africa. [ABSTRACT FROM AUTHOR]

The observed historical changes in crop phenological events are not only as a sensitive indicator to temperature variations but also the consequence of agronomic management such as adjustment of sowing date, cultivar selection and innovative farming practices. Clarifying how these factors influence crop phenology is of paramount importance in understanding/implementing adaptation strategies to future climate change. Changes in phenophases of dryland spring-sown wheat and maize were investigated using the observed phenological data from 1992 to 2013 across the Loess Plateau. Using a series of phenological growth models, we illustrated that once the varietal effect was fixed, rising temperature alone produced a general advancement on dates of heading and maturity, leading to a significant shortening of the vegetative phase (5.2 days decade −1 in wheat and 1.1 days decade −1 in maize), a shortened duration of reproductive phase (0.9 and 2.0 days decade −1 respectively) and the length of whole growing season (6.1 days decade −1 in wheat and 3.0 days decade −1 in maize). In contrast, cultivar shifts prolonged the reproductive duration and the growing season length by 2.2 and 4.7 days decade −1 for spring wheat, and 3.3 and 1.5 days decade −1 for maize, respectively. The continuous update of cultivars during the past two decades has offset 63.5% of the shortening effect of growing season length caused by rising temperature for both crops. Our data indicate that adjusting sowing date and shifts to longer season cultivars are the critical adaptive strategies to cope with temperature increases in dryland spring-sown wheat and maize in the Loess Plateau or regions with similar environments. [ABSTRACT FROM AUTHOR]

• Maize yield responses to increasing planting densities were studied in RFM system. • Individual yield declined while population one increased first and then decreased. • This difference resulted from improved soil water availability as affected by RFM. • Optimal density had better trade-off between reproductive and vegetative growth. • Allometric R–V relationship explained density-dependent yield formation under RFM. The law of constant final yield and allometric theory have been seldom used to explore density-dependent yield formation and water use in rainfed farming systems, particularly in ridge-furrow mulching (RFM) system of maize. A two-year RFM field experiment was conducted using maize variety Yuyuan7879 in semiarid Kenya from 2015 to 2016, with four planting densities: 5.2 × 104 (D52, conventional density), 6.0 × 104 (D60), 6.9 × 104 (D69) and 8.5 × 104 (D85) plants per hectare. The grain yield and aboveground biomass per plant were significantly decreased with increasing density across two growing seasons. However, the population grain yield significantly was increased from D52 to D60 (from 3395.1–4471.7 kg ha−1) but declined significantly from D60 to D69 and D85 (p < 0.05) in 2015 and 2016, respectively. Meanwhile, the population aboveground biomass was significantly promoted from D52 to D60 (p < 0.05) and then remained relatively stable in D69 and D85, achieving a state of constant final yield. Under the improved soil storage, the RFM system raised the rational planting density from conventional D52 to D60 with regard to population yield. Water use efficiency for population yield (WUE G) was the highest at D52 and D60, followed by D69, and the lowest at D85. However, the WUE for the aboveground biomass (WUE A) was significantly lower in D52 than D60 and D85. Principal component analysis suggested that the population grain yield and WUE G were significantly positively associated with the reproductive allocation and leaf growth. This result was further affirmed by the allometric relationship between leaf biomass and body size, since the allometric exponent (<1) was raised with density. Allometric relationship between reproductive and vegetative mass demonstrated that the D60 treatment achieved a relatively balanced allocation of photosynthetic products into reproductive organs in comparison with other treatments. The RFM application significantly improved the availability of soil water, and the rational planting density of maize for better yield and WUE G. Thus, this phenomenon mechanically resulted from relatively better trade-offs between reproductive and vegetative growth, together with moderately increased leaf growth. [ABSTRACT FROM AUTHOR]

Extensive studies have been conducted on the impacts of plastic film residue on crop productivity in dryland agriculture. However, the relevant results were inconsistent or even opposite, which was most probably affected by both the size and concentration of residual films. To clarify this issue, a three-year (2019–2021) field experiment was conducted to examine plastic residue landfill effects on maize productivity using three sizes (0.4 × 0.4 cm2 (small), 4 × 4 cm2 (medium), and 10 × 10 cm2 (large)) under the low and high addition concentrations in an irrigated maize field. The data indicated that medium-sized residues significantly reduced maize yield by 7.3% and 13.8% in low and high addition levels respectively, relative to non-landfill group (CK) (p < 0.05). Large and small-sized residues under low level had no significant impact on yield (p > 0.05), while high amounts of small residues turned to positively influence yield. This trend was closely correlated with soil temperature, soil moisture, key enzyme activities, macroaggregate proportion, soil organic carbon and total nitrogen contents. Structural equation modelling and relative importance analyses demonstrated soil hydrothermal (27.4%), soil nitrogen (22.0%), and physical properties (21.1%) as primary drivers. A general trend was that the sizes of residues showed evidently greater impacts than their addition levels. Moreover, medium residues showed negative effects, while large and small ones had neutral or positive effects. For the first time, our findings confirmed the size- and concentration-dependent effects of plastic residues on crop productivity and provided a novel insight into plastic film pollution assessment & management in agricultural ecosystems. • Medium plastic residues evidently reduced maize yield across the concentrations. • Large and small plastic ones turned to neutrally and positively affect maize yield. • Soil hydrothermal and nutrient status were affected by residue size & concentration. • Residue size showed greater impacts on maize productivity than its concentration. • This study filled knowledge gap in understanding plastic residue production effect. [ABSTRACT FROM AUTHOR]

It is unclear how interspecific resource competition affects crop leaf senescence in association with nitrogen (N) remobilization and overyielding in semiarid intercropping systems. To address this issue, maize intercropped with soybean (weakly competitive species) and wheat (strongly competitive species) was examined across three consecutive years to explore the effects of resource competition on maize relative and absolute yield gain, leaf senescence traits, N remobilization and physiological activities in a typical semiarid site. High yield (171.8 g plant−1), relative yield (0.63) and net effect (0.99 t ha−1) of maize were observed in the maize soybean intercropping system, while the opposite trend was found in the maize wheat intercropping systems. Overall, maize benefited from intercropping with soybean but was negatively affected by intercropping with wheat. Interestingly, both intercropping systems significantly delayed the onset time of maize leaf senescence by approximately 5–20 days and prolonged the senescence duration by approximately 8–18 days. Intercropping with soybean increased maize leaf dry matter remobilization from 7.3 to 12.5 g per plant−1 and reduced N remobilization from 0.81 to 0.45 g plant−1, respectively. However, when intercropped with wheat, dry matter and N remobilization of maize leaves were decreased, at 4.8 and 0.13 g plant−1, respectively. Therefore, excessive delay and prolonged leaf senescence reduced leaf dry matter translocation and N to the grain which impaired yield formation. Our findings provided novel insights into the physiological mechanism of overyielding from the perspective of leaf senescence traits and remobilization function in the semiarid intercropping systems. [Display omitted] • Interspecific competition affects leaf senescence traits and N remobilization in maize. • Interspecific competition delayed the onset time and the duration of leaf senescence. • High competitiveness promoted physiological vigor in leaves, which promotes C&N remobilization. • Leaf senescence as affected by resource competition provides new insights into overyielding. [ABSTRACT FROM AUTHOR]

Plastic film residuals are increasingly remaining in cultivated lands. However, it is a critical issue how residual plastic type and thickness affect soil properties and crop yield. To address this issue, in situ landfill was conducted using thick polyethylene (PEt1), thin polyethylene (PEt2), thick biodegradable (BIOt1), thin biodegradable (BIOt2) residues, and CK (control) with no residues landfill in a semiarid maize field. The findings demonstrated that the impact of various treatments on soil characteristics and maize yield varied considerably. Soil water content decreased by 24.82% in PEt1 and 25.43% in PEt2, compared to BIOt1 and BIOt2, respectively. BIOt2 treatment increased soil bulk density by 1.31 g cm−3 and lowered soil porosity by 51.11%, respectively; it also elevated the silt/clay proportion by 49.42% relative to CK. In contrast, microaggregate composition in PEt2 was higher (43.02%). Moreover, BIOt2 lowered soil nitrate (NO 3 −) and ammonium (NH 4 +) content. Compared with other treatments, BIOt2 resulted in significantly higher soil total nitrogen (STN) and lower SOC/STN. Finally, BIOt2 exhibited the lowest water use efficiency (WUE) (20.57 kg ha−1 mm−1) and yield (6896 kg ha−1) among all the treatments. Therefore, BIO film residues exhibited detrimental impacts on soil quality and maize productivity compared to PE film ones. Considering film thickness, thin residual films more evidently influenced soil quality and maize productivity than thick film ones. [Display omitted] • BIO enhanced soil bulk density and lowered porosity, while thick PE residues didn't. • BIO significantly reduced SOC/STN, but thick PE residues exhibited a minor effect. • Relative to thick PE and CK, BIO residue lowered soil inorganic nitrogen. • WUE and yield decreased under BIO residues, while thick PE ones had a slight effect. • Thick PE and thin BIO residues had the least and most harmful impact, respectively. [ABSTRACT FROM AUTHOR]

• CPT and ZT improved farmland soil properties in China's Loess Plateau. • CPT and ZT changed the diversity and composition of rhizobacterial communities. • CPT had the potential to increase the total biomasses and N accumulations of crop. • Crop species had weaker effects on rhizobacteria than those of tillage practices. • Rhizosphere bacterial communities were weakly correlated with crop development. Conservation tillage, that is, reduced or zero tillage, can change the soil ecological environment and rhizosphere bacterial communities. Here, we investigated temporal variations in rhizosphere bacterial communities during crop development and their relationships with crop growth characteristics under three tillage practices (Plow tillage (PT), chisel plough tillage (CPT), and zero tillage (ZT)) in maize and soybean fields on the Loess Plateau of China. Conservation tillage (CPT and ZT) practices significantly increased the contents of soil moisture (3.62–13.13%), soil organic carbon (29.19–39.67%), and nitrogen (38.69–60.23%) and decreased soil pH (1.15–3.76%). The overall responses of rhizosphere bacterial community composition to tillage practice and phenological period were taxonomically consistent across maize and soybean fields, and changes were predominantly observed in the relative abundances of dominant bacterial phyla. Co-occurrence network analysis indicated that the average connectivity degree among 16S operational taxonomic units was higher under PT (38.92% and 73.60%) practice than under CPT and ZT practices. CPT practice tended to increase the total biomass and nitrogen accumulation of maize and soybean compared with PT practice, whereas ZT practice significantly (P < 0.05) decreased them. Partial least squares path modeling analysis showed that temporal variations in the rhizosphere bacterial communities (explained variations in maize and soybean fields were 94.7% and 92.7%, respectively) were regulated by tillage practices and phenological periods, and partly explained the changes in growth dynamics of maize and soybean (0.161 and 0.031, respectively). Overall, CPT practice could improve the soil ecological environment and promote crop growth in the China's Loess Plateau. Therefore, we recommend that CPT practice should be adopted in semi-arid agricultural areas to improve the potential relationships between the underground and aboveground in agroecosystems. [ABSTRACT FROM AUTHOR]