ZmmiR1432-ZmCML21-ZmPMA2 Module Affects Maize Low Phosphate Tolerance via Regulating Organic Acid Secretion.

The winter wheat and summer maize double cropping system is the primary cropping pattern for wheat and maize in dryland areas of China. The management of tillage in this system is typically conducted before wheat sowing. However, few studies have validated and quantified the impact of tillage methods before wheat sowing and irrigation practices during the wheat season on the yield formation and water use efficiency of summer maize. Therefore, this study hypothesized that subsoiling before wheat sowing improves maize yield and WUE by enhancing soil moisture retention and plant development. A three-year field experiment with a two-factor split-plot design was conducted at the junction of the Loess Plateau and the Huang-Huai-Hai Plain in China for validation, from 2019 to 2022. Three tillage methods before wheat sowing (RT: rotary tillage; PT: plowing, SS: subsoiling) were assigned to the main plots, and two irrigation practices during wheat growing season (W0: zero-irrigation; W1: one-off irrigation) were assigned to subplots. We measured the soil moisture, grain yield, dry matter accumulation, nitrogen (N), phosphorus (P), and potassium (K) accumulation, and water use efficiency of summer maize. The results indicated that subsoiling before wheat sowing increased soil water storage at the sowing of summer maize, thereby promoting dry matter and nutrient accumulation. Compared to rotary tillage and plowing, subsoiling before wheat sowing increased grain yield and water use efficiency of maize by an average of 19.5% and 21.8%, respectively. One-off irrigation during the wheat season had negative effects on pre-sowing soil water storage and maize productivity in terms of yield and dry matter accumulation. However, subsoiling before wheat sowing can mitigate these negative effects of one-off irrigation. Correlation analysis and path model results indicated that tillage methods before wheat sowing had a greater impact on soil water storage and maize productivity than irrigation practices during wheat growing season. The most direct factor affecting maize yield was dry matter accumulation, whereas the most direct factor affecting water use efficiency was nutrient accumulation. The technique for order preference by similarity to an ideal solution (TOPSIS) comprehensive evaluation indicated that subsoiling before wheat sowing was superior for achieving high maize yield and water use efficiency under the practice of one-off irrigation during the wheat season. These findings offer practical guidance for optimizing soil water use and maize productivity in drylands.

Intercropping is the cultivation of two or more crop species simultaneously in the same field, while relay intercropping means that the growing periods of the crop species are only partially overlapping. Intercropping has advantages with respect to productivity, resource capture, build-up of soil organic matter, and pest and disease suppression. This thesis aims to quantify and explain the yield advantages in wheat-maize relay intercropping and to assess the importance of intercropping for food production and land use efficiency. Wheat-maize intercropping had land equivalent ratios around or above one in two experiments in the Netherlands. Wheat in border rows showed major yield increases, and this yield increase was due to increases in the number of tillers per plant and the number of kernels per ear. The yield advantage of intercropped wheat was associated with a high radiation interception and radiation use efficiency (RUE). Under Dutch growing conditions, maize performance in the intercrop was constrained. Intercropping had a negative effect on the yield per plant and radiation use efficiency of maize. A strip intercrop model was developed, parameterized and tested with data on wheat-maize intercropping in the Netherlands. The model simulates radiation interception and growth in relay-strip intercrops with two species in different planting configurations. The model also allows simulating the consequences of border row effects for total system productivity. Bayesian analysis was applied to calibrate radiation use efficiency of wheat and maize in sole crops and intercrop. Intercropped wheat had higher a RUE than sole wheat, while intercropped maize had a lower RUE than sole maize. Intercropped maize had less favourable leaf traits (e.g. nitrogen content) during the flowering stage than sole maize in 2014, but the leaves in the intercrop had a higher photosynthetic rate than those in the sole crop. Possible explanations for this finding include differences between sole and mixed crops in water acquisition from soil, light distribution in the canopy, nitrogen distribution within the leaf and the contribution of the ear leaf to the growth of the cob. The low radiation use efficiency in intercropped maize may relate to nitrogen deficiency during grain filling. New concepts for potential yield, yield gain and yield gap in intercropping were developed in this thesis. Using crop model simulations and farm survey data, those concepts were operationalized in the context of wheat and maize production in an oasis area (Zhangye city) in northwest China. Wheat-maize intercropping resulted in substantial yield gains under potential and actual growing conditions. A comparison of potential and actual yields indicated a yield gap of 33% for sole wheat, 49% for sole maize, 15% for intercropped wheat, and 51% for intercropped maize. The land use analysis showed that discontinuing the use of intercropping in this region will decrease grain production substantially. Overall, this thesis studied the growth and productivity of wheat-maize intercropping at organ, plant and cropping system level, and also assessed its contribution to grain production at a regional level. The findings suggest that intercropping of food crops provides opportunities to meet increasing food demands. New technologies are needed to make strip intercropping efficient in terms of labour use and breeding should pay attention to cultivars that are suitable for intercropping.

Identifying the changes of grain yield and nitrogen use traits will facilitate the development of new maize hybrids with high yield and nitrogen use efficiency. In this study, 12 typical maize hybrids released from 1981 to 2010 in Shaanxi Province were grown in the field under three N rates(0, 120, and 240 kg ha–1) from 2011 to 2012 in Shaanxi, Northwest China. Nitrogen use efficiency and agronomic traits of maize were investigated. The result indicates that grain yield of maize hybrids increased with the increase of nitrogen rates, and the modern maize hybrids(2000s) showed better grain yield than the old ones(1980s) at three nitrogen levels. The yield genetic gains were 46, 65, and 83 kg ha–1 per year at N0, N120, and N240 levels repeat. The modern hybrids showed better biomass and grain yield than the old ones, but there was no clear changing trend in stover yield between hybrids of different ears. Increments of grain yield were achieved mainly through increasing the kernel number per ear, 1000-kernel weight and biomass, and the coefficient of light extinction decreased with the time process of cultivar development from 1981 to 2010. Changes of plant structure would allow the modern maize hybrids to improve light capture resulting in better grain yield than those of the old ones. For nitrogen use point of view, irrespective of nitrogen treatments, nitrogen use efficiency(NUE) of hybrids released increased in responses of time. But nitrogen use efficiency decreased with increasing nitrogen application rates, and nitrogen use efficiency(NUE) was highly correlated with N uptake efficiency(NUpE, r = 0.75), and not with N physiological efficiency(NUtE, r = 0.42). Increased NUE positively correlated with improved N uptake efficiency(NUpE), due to the greater post-anthesis N accumulation. The results indicated that improvements of 1000-kernel weight, kernel number per ear and nitrogen uptake efficiency(NUpE) should be considered during breeding for high yield and high nitrogen use efficiency of maize under low nitrogen and water limited conditions.

Crop rotation is known to enhance crop yields. It is therefore recommended, regardless of rainfall and soil type, as a counter measure for the risks associated with monoculture maize (Zea mays). Experience in the western Highveld where rainfall is low and erratic, has shown that the yield of maize does not necessarily improve as expected when preceded by alternative crops, but in fact, is often reduced. The present study was initiated to determine the effect of crop rotation with cowpea, groundnut, soyabean, sunflower or fallow on the yield and rainfall use efficiency of maize under marginal conditions on the western Highveld. Dryland maize was grown in five crop rotation systems on Hutton type soils at the farms Holfontein (four years) and Noodshulp (five years), both situated close to Ottosdal (26° 49’ S; 26° 00’ E). The soil profiles had an effective depth of <1.5 m at Hol-fontein and 1.25 m at Noodshulp. Crop rotation systems consisted of two-year rotations of cowpea-, groundnut, soybean-, sunflower-, and fallow-maize; as well as groundnut-, soybean-, and sunflower-fallow. A continuous monoculture maize treatment was included to serve as control. At Noodshulp where the rainfall was more variable, crop rotation induced maize yield deviations from the monoculture control occurred more often than at Holfontein. Apart from yield neutral and positive effects, instances of a decline in maize yield in some years due to crop rotation with cowpea, groundnut and sunflower also occurred. Taking the long-term rotational effect and the possibility of a yield decline into account, fallowing and the rotational crops ranked from best to worse were groundnut, soyabean, fallowing, cowpea and sunflower. The long-term effect of cowpea on the yield of maize was neutral and that of sunflower negative. The mean rainfall use efficiency of monoculture maize was, with the exception of maize preceded by groundnut, similar to that of maize grown in rotation.

Modelled yield and water use efficiency of maize in response to crop management and Southern Oscillation Index in a soil-climate transect in Argentina

Black soldier fly frass fertilizer (BSFFF) is increasingly gaining momentum worldwide as organic fertilizer. However, research on its performance on crop production remains largely unknown. Here, we evaluate the comparative performance of BSFFF and commercial organic fertilizer (SAFI) on maize (H513) production. Both fertilizers were applied at the rates of 0, 2.5, 5, and 7.5 t ha-1, and 0, 30, 60, and 100 kg nitrogen (N) ha-1. Mineral fertilizer (urea) was also applied at 0, 30, 60 and 100 kg N ha-1 to establish the N fertilizer equivalence (NFE) of the organic fertilizers. Maize grown in plots treated with BSFFF had the tallest plants and highest chlorophyll concentrations. Plots treated with 7.5 t ha-1 of BSFFF had 14% higher grain yields than plots treated with a similar rate of SAFI. There was a 27% and 7% increase in grain yields in plots treated with 100 kg N ha-1 of BSFFF compared to those treated with equivalent rates of SAFI and urea fertilizers, respectively. Application of BSFFF at 7.5 t ha-1 significantly increased N uptake by up to 23% compared to the equivalent rate of SAFI. Likewise, application of BSFFF at 100 kg N ha-1 increased maize N uptake by 76% and 29% compared to SAFI and urea, respectively. Maize treated with BSFFF at 2.5 t ha-1 and 30 kg N ha-1 had higher nitrogen recovery efficiencies compared to equivalent rates of SAFI. The agronomic N use efficiency (AEN) of maize treated with 2.5 t ha-1 of BSFFF was 2.4 times higher than the value achieved using an equivalent rate of SAFI. Also, the AEN of maize grown using 30 kg N ha-1 was 27% and 116% higher than the values obtained using equivalent rates of SAFI and urea fertilizers, respectively. The NFE of BSFFF (108%) was 2.5 times higher than that of SAFI. Application rates of 2.5 t ha-1 and 30 kg N ha-1 of BSFFF were found to be effective in improving maize yield, while double rates of SAFI were required. Our findings demonstrate that BSFFF is a promising and sustainable alternative to commercial fertilizers for increased maize production.

Alternative management practices are needed to minimize the need for chemical fertilizer use in non-leguminous cropping systems. The use of biological agents that can fix atmospheric N has shown potential to improve nutrient availability in grass crops. This research was developed to investigate if inoculation with Azospirillum brasilense in combination with silicon (Si) can enhance N use efficiency (NUE) in maize. The study was set up in a Rhodic Hapludox under a no-till system, in a completely randomized block design with four replicates. Treatments were tested in a full factorial design and included: i) five side dress N rates (0 to 200 kg ha-1); ii) two liming sources (Ca and Mg silicate and dolomitic limestone); and iii) with and without seed inoculation with A. brasilense. Inoculation with A. brasilense was found to increase grain yield by 15% when N was omitted and up to 10% when N was applied. Inoculation also increased N accumulation in plant tissue. Inoculation and limestone application were found to increase leaf chlorophyll index, number of grains per ear, harvest index, and NUE. Inoculation increased harvest index and NUE by 9.5 and 19.3%, respectively, compared with non-inoculated plots. Silicon application increased leaf chlorophyll index and N-leaf concentration. The combination of Si and inoculation provided greater Si-shoot accumulation. This study showed positive improvements in maize growth production parameters as a result of inoculation, but the potential benefits of Si use were less evident. Further research should be conducted under growing conditions that provide some level of biotic or abiotic stress to study the true potential of Si application.

Maize is a versatile crop in terms of growing season and use, which produces a sizable amount of biomass in a season and removes an ample quantity of nutrients from the soil. Such a nutrient-exhaustive crop needs an exogenous application of nutrients to meet its needs. Hence, precision nutrient management can be a scientific option for maize. Based on the facts, a field experiment was conducted during the Rabi seasons of 2022-23 and 2023-24 at the P.G. Research Farm of the M. S. Swaminathan School of Agriculture, Odisha, India, to evaluate the nutrient removal and nutrient use efficiency of maize. The experiment was carried out in a randomized block design with 13 treatments, replicated thrice. The treatments were: T?: RDF (120-60-60 kg ha?¹ N, P?O? and K?O), T?: 125% RDF (150-75-75 kg ha?¹), T?: 75% RDF (90-45-45 kg ha?¹), T?: 150% RDF (180-90-90 kg ha?¹), T?: RDF + nano urea, T?: 75% RDF + nano urea, T?: LCC 4-based nitrogen management, T?: LCC 5-based nitrogen management, T?: chlorophyll content meter (CCM) sufficiency index 85–90%, T??: CCM sufficiency index 90–95%, T??: nutrient expert (NE) targeted yield 7 t ha?¹, T??: NE targeted yield 9 t ha?¹ and T??: control (0-0-0 kg ha?¹). The recommended dose of 120:60:60 kg ha?¹ N, P?O? and K?O was applied. The highest nitrogen content in grain and stover was recorded with T10 and T4. However, T4 recorded the highest P and K content in grain and stover of maize. The highest agronomic use efficiency (AUE) of maize for the primary nutrients was computed with T2, which was followed by T9 and T12. The highest partial factor productivity (PFP) for N, P and K was T10, closely followed by T9, T12, T4 and T2. The treatment T3 recorded the highest nutrient harvest index (NHI) for primary nutrients, followed by T2 and T1. However, the highest nutrient content in the post-harvest soil denoted values for N with T1, P with T2 and K with T4 and T12. The results concluded that precision nutrient management with split application in maize with optical sensors and decision support systems can be replicated further in various agroclimatic situations and cropping systems.

Water-Yield Relations and Water Use Efficiency of Maize Under Nitrogen Fertigation for Semiarid Environments: Experiment and Synthesis

Scarcity of water is the most severe constraint for development of agriculture in arid and semi-arid areas. Under these conditions, the need to use the available water economically and efficiently is unquestionable. Based on the actual crop need, the irrigation management has to be improved so that the water supply to the crop can be reduced while still achieving high yield. The purpose of this study was to determine the water use efficiency of maize (Katumani cultivar) under deficit irrigation practice and to identify crop growth stages during which the crop can withstand water stress with limited effect on yield. The field experiment was conducted at the experimental farm of Haramaya University located in Dire Dawa, Ethiopia. The treatments consisted of ten different levels/timings of irrigation water application. Treatments T1 and T2 were respectively normal irrigation and 75% deficit irrigation throughout the growing season. T3, T4, T5, and T6 were stressed by 75% at a specific stage: initial stage, development stage, mid season stage, and late season stage respectively. T7, T8, T9, and T10 were stressed by 50% at the respective four growth stages. The result showed that variation in level (amount) of irrigation water application had a significant impact on grain yield. In the case of stress by 75% deficit at a specific stage, the effect of stress was severe during the mid season stage. The mid season stage was the most sensitive to water stress. On the other hand, water deficit during the early and maturity stage had a limited effect on yield. Stressing the crop by 75% deficit throughout the growing season resulted in the highest yield reduction. However, the crop water use efficiency was the lowest (1.72 kg/m3) at optimum irrigation water application and the highest (2.96 kg/m3) at stress of 75% deficit throughout the growth season. Although at individual farmer’s level, maximum yield is obtained when the entire crop water requirement is fulfilled, practicing deficit irrigation could increase the irrigated area as a result of high water use efficiency.

Knowing the inheritance of traits is essential to establish selection strategies in breeding programs. The aim of this study was to determine the genetic control of traits related to the phosphorus use efficiency in maize. A total of 280 progenies were developed according to design III, which were evaluated in the field under high and low phosphorus (P) availability. The genetic variance components were estimated for the agronomic traits and indices that define P use efficiency. The results indicated that the additive and dominance effects were important in explaining the genetic variability for the flowering time, grain yield and P efficiency indices. However, dominance effects prevailed, indicating that breeding efforts should be made to develop hybrids exploiting the heterosis for traits related to P use efficiency.

Effect of acidified biochar on soil phosphorus availability and fertilizer use efficiency of maize (Zea mays L.)

The expansion of brewery factories with huge production potential of brewery sludge in Ethiopia presents a significant opportunity to enhance sustainable soil and crop productivity. Hence, this field experiment was conducted in North Mecha district, Northwestern Ethiopia, to improve the yield and nnitrogen use efficiency of maize by applying brewery sludge (BS), blended nitrogen, phosphorous and sulfur (NPS) fertilizers alone and in combination. Six treatments (T1: control, T2: 100% recommended dose of blended nitrogen, phosphorous, sulfur (RDNPS (100 kg NPS ha-1)); T3: 75% RDNPS + 25% recommended dose of brewery sludge (RDBS); T4: 50% RDNPS + 50% RDBS; T5: 25% RDNPS + 75% RDBS; T6: 100% RDBS (10 t BS ha-1) were laid out in a Randomized Complete Block Design (RCBD) with three replications. The results revealed that both single and combined fertilizer applications resulted in higher production, nitrogen uptake, and efficiency as compared to no fertilizer application. Notably, the combined application of 75% RDBS with 25% RDNPS produced the highest above-ground biomass yield (23161.9 kg ha-1), grain yield (10620.6 kg ha-1), stover yield (12541.3 kg ha-1), harvest index (45.85%), nitrogen concentration in grain (1.71%) and stover (1.00%), as well as grain (181.72 kg ha-1), stover (124.17 kg ha-1), and total (305.89 kg ha-1) nitrogen uptake. Furthermore, the combined application of 75% RDBS with 25% RDNPS produced the highest grain yield (10620.6 kg ha-1), net benefit (170987.97 Ethiopian Birr (ETB) ha-1), and an acceptable marginal rate of return (MRR) (12613.93%) for maize production in the region. Hence, the study reveals that using BS and blended NPS at precise ratios can improve maize productivity in the North Mecha district. However, as the experiment was carried out only in one location for one cropping season, further studies at different locations for several years or seasons should be conducted to come up with strong and reliable recommendations.

Low soil fertility and high weed infestation are the main culprits for the declining maize production in Western Kenya. Technology packages to address these constraints exist, but their effectiveness is likely to be influenced by variability in soil types and farm management practices in the region. Trials were conducted during the 2008/2009 cropping seasons to investigate the nutrient use efficiency and yield response of maize to some recommended management options for smallholder farmers on three dominant soil types of Western Kenya namely Acrisol, Nitisol and Ferralsol. Irrespective of seasons, average maize yields were highest on Nitisol (3.6 t ha -1 ) and lowest on Ferralsol (2.1 t ha -1 ). Maize yield gaps (difference between potentially achievable and actual yields) differed by season and soils with 4-5 t ha -1 on Nitisol and about 6 t grain ha -1 on Acrisol and Ferralsol. On Nitisol, the largest share of this yield gap (80%) was closed by the addition of mineral fertilizer, while on Ferralsol, reduced tillage could close 25-60% of the yield gap. The highest agronomic (13-39 kg grain kg -1 N) and physiological (50-160%) N use efficiencies were obtained with mineral fertilizers, while the addition of organic amendments resulted in the highest P use efficiency (15-154 kg grain kg -1 P), irrespective of soil type and season. As soil types and management options differentially affect yields and nutrient use efficiency of maize, there is a need for field-specific targeting of technologies to address maize production constraints in Western Kenya.

Elevated atmospheric CO2 concentration (e[CO2]) and varied nitrogen (N) fertilization levels may mediate the different responses of C4 crops to progressive soil drought. In this study, the effects of reduced N (N1, 0.8 g pot−1) and adequate N (N2, 1.6 g pot−1) supply on leaf physiology, plant growth and water use efficiency (WUE) of maize (C4 crop) exposed to progressive soil drought grown at ambient CO2 (a[CO2], 400 ppm) and elevated CO2 (e[CO2], 800 ppm) concentration were investigated. The results indicated that compared with a[CO2], net photosynthetic rate (An) and leaf water potential (Ψl) at e[CO2] were maintained in maize leaves, while stomatal conductance (gs), transpiration rate and leaf hydraulic conductance were decreased, leading to enhanced WUE from stomatal to leaf scale. Despite An and Ψl of e[CO2] plants were more sensitive to progressive soil drought under both N fertilization levels, e[CO2] would increase leaf ABA concentration ([ABA]leaf) but decline the gs response to [ABA]leaf under N1 supply. e[CO2] coupled with N1 fertilization was conducive to enlarging leaf area, promoting specific leaf area, root and total dry mass, whereas reduced stomatal aperture and plant water use under progressive drought stress, contributing to an improvement in plant WUE, implying a better modulation of maize leaf stomata and water status under reduced N supply combined with e[CO2] responding to progressive soil drought. These findings in the current study would provide valuable advice for N management on maize (C4) crop efficient water use in a drier and CO2‐enriched environment.