Effect of deficit irrigation on physiological, biochemical, and yield characteristics in three baby corn cultivars (Zea mays L.)

The main problem in the production of crops in arid and semi-arid regions of the world is the lack of water and its effect on the plant in the form of drought stress. Cultivation of key crops such as corn, which also requires a lot of water, is not possible in these areas except by applying water consumption management methods. Among the most important of these methods is deficit irrigation. The effect of deficit irrigation on relative water content (RWC), malondialdehyde (MDA), compatible osmolytes (proline and soluble sugars), antioxidant enzymes, and yield was studied in three baby corn cultivars in a field experiment using a randomized complete block design (RCBD) with split-plots and three replications. Three levels of deficit irrigation (0, 20, and 40% deficit) constituted the main plots and three cultivars of baby corn (Challenger, Basin, and Passion) constituted the sub plots. Analysis of variance showed that deficit irrigation had a significant effect on all variables. Cultivar (Challenger, Basin and Passion) had a significant effect on proline (0%, 41.5% and 73.2%), carbohydrates (23.9%, 15.4% and 0%), and MDA content (0%, 26.1% and 41.2%), as well as peroxidase (POD) (0%, 136.1% and 227.9%) levels respectively. The interaction between deficit irrigation and cultivar had a significant effect on proline, carbohydrates, and POD. RWC decreased (26.9, 6.5 and 0%) with increasing irrigation deficit (0, 20 and 40%) respectively while proline (0, 23.7 and 64.8%), carbohydrates (0, 29.7 and 34.09%), catalase (CAT) (0, 20.8 and 70.1%), and POD (0, 55.05 and 113.2%) increased under the same conditions. Carbohydrate content was higher in the Basin and Challenger cultivars (21.71 and 19.07) and proline (145.9), POD (193.9), and MDA content (8.53) were higher in the Passion cultivar. Among the studied cultivars, the highest yield was achieved by the Passion cultivar (37.02 and 62.9% more than Challenger and Basin cultivars respectively). In general, the results showed that drought stress caused an increase in compatible osmolyte content and the activity of antioxidant enzymes. However, this increase could not offset the effects of drought stress on yield in the 40% deficit treatment.

Planting models and deficit irrigation strategies to improve radiation use efficiency, dry matter translocation and winter wheat productivity under semi-arid regions

The dry-land farming system of China relies on plastic film mulching and natural rainfall to mitigate damage caused by drought. However, the applications of deficit irrigation modes combined with the planting models can significantly increase production of wheat, dry matter translocation and radiation use efficiency (RUE) remains unidentified. Thus, in 2016-2018, we conducted field trials that implemented four deficit irrigation modes (IJF: irrigation at jointing and flowering stages; IF: irrigation at flowering stage; IJ: irrigation at jointing stage; NI: no irrigation) under two cultivation patterns (ridge furrow rainfall harvesting system (RF); traditional flat cultivation (TF)). The results indicated that the effects of RF system with deficit irrigation (IJF: 250 mm) could significantly increase the soil moisture, and thus enhanced LAI, I_n value, IPAR, RUE, and PAR capture ratio than that of TF-NI planting. This is due to decreased canopy light transmittance (LT), reflection and penetration ratio of PAR, as a result considerable improve the biomass translocation and grain yield. Owing to the very low soil water content after the seed-filling, the LAI, IPAR, and I_n value decreased during the seed-filling under water stress, ultimately affecting the dry matter translocation efficiency. While the IJF and IF treatments provided water for reproductive growth stage, therefore, the production of wheat and RUE were significantly maximum compared with IJ and NI irrigation mode. Under the RF system with IJF, IF, and IJ treatments the grain yield increased by 81.2%, 56.8%, 45.6% and 17.2%, then that of TF-NI treatment, respectively. The highest RUE (1.93 g MJ^-1), dry-matter translocation (154.2%) and seed yield (81.2%) were obtained in the RF-IJF treatment compared with TF-NI. Therefore, the RF-IJF treatment significantly improved the earlier development and rapid plant growth, which is a suitable planting model for increasing soil moisture, LAI, RUE, DMT, and winter wheat production.

Biochar Implications Under Limited Irrigation for Sweet Corn Production in a Semi-Arid Environment

The integration of biochar and deficit irrigation is increasingly being evaluated as a water-saving strategy to minimize crop yield losses under reduced irrigation in arid and semi-arid regions such as West Texas. A 2-year (2019 and 2020) open-field study evaluated the effect of two types of biochar amendments (hardwood and softwood) and three irrigation rates [100, 70, and 40% crop evapotranspiration (ET _c ) replacement] on the physiology, plant growth, and yield of sweet corn in semi-arid West Texas. All experimental units were replicated four times in a split-plot design. The chlorophyll content (Chl _SPAD ) in 40% ET _c dropped significantly compared to 100% ET _c and 70% ET _c during the reproductive phase. Although water stress under 40% ET _c decreased photosynthesis (P _n ) to limit transpiration (E) by stomatal closure, it improved intrinsic water use efficiency (iWUE). The above-mentioned gas exchange parameters were comparable between 100% ET _c and 70% ET _c . Both biochar treatments increased Chl _SPAD content over non-amended plots, however, their effect on gas exchange parameters was non-significant. All growth and yield-related parameters were comparable between 100% ET _c and 70% ET _c , but significantly greater than 40% ET _c , except water productivity (WP). Both deficit irrigation treatments improved WP over full irrigation in 2019, but in 2020, the WP gains were observed only under 70% ET _c . Hardwood biochar decreased soil bulk density and increased soil porosity, but it had a marginal effect on the water retention characteristics. These results suggest that 70% ET _c can be used as an alternative to full irrigation to save water with a minimal yield penalty for sweet corn production in the West Texas region. The hardwood biochar application improved the vegetative biomass significantly but yield marginally during the first 2 years of application. A long-term study is required to test the effect of biochar under deficit irrigation beyond 2 years.

Sorghum mitigates climate variability and change on crop yield and quality

Global food insecurity concerns due to climate change, emphasizes the need to focus on the sensitivity of sorghum to climate change and potential crop improvement strategies available, which is discussed in the current review to promote climate-smart agriculture. Climate change effects immensely disturb the global agricultural systems by reducing crop production. Changes in extreme weather and climate events such as high-temperature episodes and extreme rainfalls events, droughts, flooding adversely affect the production of staple food crops, posing threat to ecosystem resilience. The resulting crop losses lead to food insecurity and poverty and question the sustainable livelihoods of small farmer communities, particularly in developing countries. In view of this, it is essential to focus and adapt climate-resilient food crops which need lower inputs and produce sustainable yields through various biotic and abiotic stress-tolerant traits. Sorghum, "the camel of cereals", is one such climate-resilient food crop that is less sensitive to climate change vulnerabilities and also an important staple food in many parts of Asia and Africa. It is a rainfed crop and provides many essential nutrients. Understanding sorghum's sensitivity to climate change provides scope for improvement of the crop both in terms of quantity and quality and alleviates food and feed security in future climate change scenarios. Thus, the current review focused on understanding the sensitivity of sorghum crop to various stress events due to climate change and throws light on different crop improvement strategies available to pave the way for climate-smart agriculture.

Soil water deficit promotes the effect of atmospheric water deficit on solar-induced chlorophyll fluorescence

Solar-induced chlorophyll fluorescence (SIF) is a novel optical signal that has been successfully used to track plant dynamics with the influence of soil water deficit. However, the effect of atmospheric water deficit on SIF under the impact of soil water deficit still remains unclear. Here, continuous measurements of SIF (at 760 nm, F760) of winter wheat under different soil water deficit were collected with a self-developed system. Additionally, soil moisture and atmosphere parameters [including air temperature (Ta), relative air humidity (Rh), and photosynthetically active radiation at 400-700 nm (PAR)] were also synchronously collected by common commercial devices. Vapor pressure deficit (VPD) was calculated based on the measurements of Ta and Rh. The results showed that the driving effect of PAR on F760 was obvious as we expected. Additionally, such effects of PAR on AF760 (F760/PAR) and Fy760 (F760/L685, L685 was canopy radiance at 685 nm) still existed when the PAR influences were partially removed by the calculation of F760/PAR and F760/L685. Furthermore, the relationship of PAR with AF760 or Fy760 was observed to be strengthened under the situation of water deficit through the analysis of Pearson correlations. With the influence of PAR, the accelerative effect of VPD on SIF under soil water deficit was not always observed in our study. Nevertheless, when the effect of PAR was removed by using partial correlation, VPD showed much stronger correlation with SIF in soil water stressed plot than that in unstressed one both at diurnal and seasonal scales. These results revealed that soil water deficit might promote the effect of atmospheric water deficit on SIF. This study has great significance for the application of SIF in drought monitoring and health assessments in terrestrial ecosystem.

Effects of Severe Water Stress on Maize Growth Processes in the Field

In this study, we investigated the effects of water stress on the growth and yield of summer maize (Zea mays L.) over four phenological stages: Seedling, jointing, heading, and grain-filling. Water stress treatments were applied during each of these four stages in a water-controlled field in the Guanzhong Plain, China between 2013 and 2016. We found that severe water stress during the seedling stage had a greater effect on the growth and development of maize than stress applied during the other three stages. Water stress led to lower leaf area index (LAI) and biomass owing to reduced intercepted photosynthetically active radiation (IPAR) and radiation-use efficiency (RUE). These effects extended to the reproductive stage and eventually reduced the unit kernel weight and yield. In addition, the chlorophyll content in the leaf remained lower, even though irrigation was applied partially or fully after the seedling stage. Severe and prolonged water stress in maize plants during the seedling stage may damage the structure of the photosynthetic membrane, resulting in lower chlorophyll content, and therefore RUE, than those in the plants that did not experience water stress at the seedling stage. Maize plants with such damage did not show a meaningful recovery even when irrigation levels during the rest of the growth period were the same as those applied to the plants not subjected to water stress. The results of our field experiments suggest that an unrecoverable yield loss could occur if summer maize were exposed to severe and extended water stress events during the seedling stage.

Influence of composted poultry manure and irrigation regimes on some morpho-physiology parameters of maize under semiarid environments

Poultry manure (PM), a rich source for crop nutrients, is produced in ample quantities worldwide. It provides necessary nutrient to soil and has a potential to improve plant water holding availability under semiarid environment. The effect of composted poultry manure (CPM) and irrigation regimes on morpho-physiology of selective maize (Zea mays L.) hybrids (H₁ = drought tolerant, H₂ = drought sensitive) was investigated in this study. Two field experiments were conducted during 2010 and 2011 under randomized complete block design with split split-plot arrangements and three replications of each treatment. Irrigation regimes (I₁ = 300, I₂ = 450, I₃ = 600 mm) were kept in main plots; the two maize hybrids (H₁ and H₂) in sub-plots and nutrient levels (L₁ = recommended rate of NPK (control), L₂ = 8 t ha^-1 CPM, L₃ = 10 t ha^-1 CPM, and L₄ = 12 t ha^-1 CPM) were arranged in sub sub-plots. The drought tolerant hybrid showed best growth under all treatments. Results revealed that maximum leaf area index (LAI) was recorded with the application of the recommended dose of NPK. Low irrigation regimes (I₁ and I₂) highly significantly (P < 0.01) reduced the photosynthesis and transpiration rate in both hybrids while application of 12 t ha^-1 CPM was able to partially alleviate the effect of water stress on these parameters. Resultantly, the application of 12 t ha^-1 CPM enhanced the plant growth and increased grain yield (21%; 4.17 vs 5.27) under limited water availability (I₂L₄) as compared to the recommended dose of NPK (I₂L₁). However, the nutrient application under control treatment had maximum grain yield. Therefore, shortage of water for maize production might be partially alleviated by the application of 12 t ha^-1 CPM.

Determination of uptake, accumulation, and stress effects in corn (Zea mays L.) grown in single-wall carbon nanotube contaminated soil

Single-wall carbon nanotubes (SWNTs) are projected to increase in usage across many industries. Two studies were conducted using Zea L. (corn) seeds exposed to SWNT spiked soil for 40 d. In Study 1, corn was exposed to various SWNT concentrations (0, 10, and 100 mg/kg) with different functionalities (non-functionalized, OH-functionalized, or surfactant stabilized). A microwave induced heating method was used to determine SWNTs accumulated mostly in roots (0-24 μg/g), with minimal accumulation in stems and leaves (2-10 μg/g) with a limit of detection at 0.1 μg/g. Uptake was not functional group dependent. In Study 2, corn was exposed to 10 mg/kg SWNTs (non-functionalized or COOH-functionalized) under optimally grown or water deficit conditions. Plant physiological stress was determined by the measurement of photosynthetic rate throughout Study 2. No significant differences were seen between control and SWNT treatments. Considering the amount of SWNTs accumulated in corn roots, further studies are needed to address the potential for SWNTs to enter root crop species (i.e., carrots), which could present a significant pathway for human dietary exposure.

Effect of water-saving irrigation regime on whole-plant yield and nutritive value of maize hybrids

BACKGROUND

The effect of a water-saving irrigation regime on yield, chemical composition, rumen in situ dry matter disappearance (DMD) and neutral detergent fiber disappearance (NDFD), along with 7 h in vitro starch degradability (7 h IVSD), in maize hybrids selected for whole-plant silage making was investigated. A plot experiment was conducted in a continental climate location and four commercial maize hybrids (FAO class 700) were used in a completely randomized design with a factorial arrangement of irrigation treatments (fully irrigated (FI) and water-saving regime (WS)) and four replicates/treatment. The total amount of irrigation water was 494 mm in FI plots and 367 mm in WS plots, the latter achieved by skipping irrigations at vegetative growth stage, silking and blistering.

RESULTS

Whole-plant yield, chemical composition, DMD, NDFD and 7 h IVSD slightly differed among hybrids and were not influenced by irrigation treatments. Plant dry matter content was lower in FI than WS plots (320 vs. 341 g kg⁻¹) , respectively; P < 0.05). Differences among hybrids were recorded for starch and acid detergent fiber contents (P < 0.05).

CONCLUSIONS

The lack of differences on yield and nutritive value in tested maize hybrids grown under different water supply suggests the water-saving regime could be suitable for an optimal use of available water in maize management.

The effect of fertiliser P on crop biomass production, partitioning, and quality in 'Challenger' sweet corn

Sweet corn kernel yield responds to phosphorous (P) supply, but whether the response is mediated through a general increase in crop biomass or increased partitioning to kernels is unclear. Furthermore, changes in ear quality (ear length, diameter, and unfilled tip length) may also result from changes in crop biomass or partitioning. This research quantifies the partitioning between vegetative and reproductive (including ear quality) components for field-grown sweet corn crops, with a range of total biomass yield resulting from different rates of P fertiliser. To do this, ‘Challenger’ sweet corn was sown in 2 consecutive seasons (2001–02 and 2002–03) on a low-P site (Olsen P = 6.5 μg/g) at Lincoln, Canterbury, New Zealand. Five rates of P fertiliser were applied in each season. In 2001–02, 0, 50, 100, 150, or 200 kg P/ha was applied. These were followed by an additional 0, 0, 10, 20, and 40 kg P/ha in 2002–03. This gave a fertiliser range of 0–240 kg P/ha over 2 years. The resulting range in crop biomass (9.7–16.7 t DM/ha) was conservatively partitioned to vegetative (45%), rachis and husk leaf (32%), and kernel (23%) fractions, indicating that kernel yield responses were solely related to changes in crop biomass. The number of harvestable ears increased by 0.39 ears/m2 for every 1 t DM/ha increase in crop biomass. Similarly, ear quality was related to the kernel yield per primary ear. Specifically, the unfilled tip length decreased by 3.1 mm and individual kernel dry mass increased by 16 mg for every 10 g increase in kernel DM per ear. These results show that P fertiliser should be applied at optimum rates (in these experiments ≥100 kg P/ha) to maximise sweet corn crop biomass, which in turn will lead to maximum kernel yield and ear quality. The conservative partitioning of crop biomass suggests that other agronomic factors that increase total biomass production are likely to have a similar effect on crop yields.