The Contribution of Soil Tillage and Nitrogen Rate to the Quality of Maize Grain

Genome-wide association studies of grain yield and quality traits under optimum and low-nitrogen stress in tropical maize (Zea mays L.)

Genome-wide association study (GWAS) demonstrated that multiple genomic regions influence grain quality traits under nitrogen-starved soils. Using genomic prediction, genetic gains can be improved through selection for grain quality traits. Soils in sub-Saharan Africa are nitrogen deficient due to low fertilizer use and inadequate soil fertility management practices. This has resulted in a significant yield gap for the major staple crop maize, which is undermining nutritional security and livelihood sustainability across the region. Dissecting the genetic basis of grain protein, starch and oil content under nitrogen-starved soils can increase our understanding of the governing genetic systems and improve the efficacy of future breeding schemes. An association mapping panel of 410 inbred lines and four bi-parental populations were evaluated in field trials in Kenya and South Africa under optimum and low nitrogen conditions and genotyped with 259,798 SNP markers. Genetic correlations demonstrated that these populations may be utilized to select higher performing lines under low nitrogen stress. Furthermore, genotypic, environmental and GxE variations in nitrogen-starved soils were found to be significant for oil content. Broad sense heritabilities ranged from moderate (0.18) to high (0.86). Under low nitrogen stress, GWAS identified 42 SNPs linked to grain quality traits. These significant SNPs were associated with 51 putative candidate genes. Linkage mapping identified multiple QTLs for the grain quality traits. Under low nitrogen conditions, average prediction accuracies across the studied genotypes were higher for oil content (0.78) and lower for grain yield (0.08). Our findings indicate that grain quality traits are polygenic and that using genomic selection in maize breeding can improve genetic gain. Furthermore, the identified genomic regions and SNP markers can be utilized for selection to improve maize grain quality traits.

Long-term effect of conservation agriculture on the composition and nutritional value of durum wheat grains grown over 2 years in a Mediterranean environment

BACKGROUND

Given the interest in mitigating the consequences of soil deterioration and climate change impacts on durum wheat grain, the objective of our study was to evaluate the effect of two soil management systems - conservation agriculture (CA) and conventional tillage (CT) - on the grain composition and nutritional value of two durum wheat varieties (Karim and Monastir) grown over two cropping seasons (2018-2019 and 2019-2020).

RESULTS

The soil management system had an impact on all studied parameters, namely 1000-kernel weight (TKW), proximate composition, energy value, total phenol content (TPC), antioxidant capacities (DPPH and ABTS) and mineral elements (K, P and Na), excluding hectoliter weight. CA resulted in high moisture content, crude protein, P, K, Na, TPC, DPPH and ABTS. However, TKW, crude fat, crude ash, energy value, and total carbohydrate were higher when using CT.

CONCLUSION

A 2-year adoption of conservation agriculture after a long-term conversion enhanced some compositional parameters and nutritional value of durum wheat varieties. The interaction with year and/or variety was very influential. © 2022 Society of Chemical Industry.

The Effect of Different Tillage Methods and Nitrogen Chemical Fertilizer on Quantitative and Qualitative Characteristics of Corn

Selection of suitable tillage and application of optimal nitrogen fertilizer are essential to achieve optimal efficiency in crop management. In order to investigate the effect of tillage and nitrogen fertilizer on photosynthetic pigments and quantitative and qualitative traits of corn grain, an experiment was conducted in the research farm of Islamic Azad University, Chalous Branch, Mazandaran Province, Iran, in 2016 and 2017. Experimental factors were tillage at three levels, including no-tillage (NT), conservation tillage (MT), and conventional tillage (CT) in the main plot, and nitrogen fertilizer at four levels (no nitrogen fertilizer application and 33, 66, and 100% of the recommended amount of nitrogen fertilizer) in a subplot. The results showed that, in tillage treatments, increasing nitrogen fertilizer application increased photosynthetic pigments. Carotenoids and chlorophyll b were not significantly different in CT and MT treatments. Nitrogen and grain protein, yield components, and biological yield increased with the increasing use of recommended nitrogen fertilizer. The highest grain and biological yields in MT in the second year were observed at 11633.15 and 16644.16 kg·ha¹, respectively. Grain and biological yield in the second year than the first year were further increased in NT and MT treatments compared to CT. Yield in MT and NT treatments improves over time. Due to the time limit in land preparation in the study area, the use of MT with 100 and 66% of the recommended nitrogen fertilizer can replace CT in the area.

Use of Vegetable Residues and Cover Crops in the Cultivation of Maize Grown in Different Tillage Systems

The purpose of research on alternative variants of soil tillage systems related to fertilization, vegetal residues, and cover crops, in the case of the maize crop, is to elaborate and promote certain integrated technologies on conservation agriculture. This paper presents the results of a study conducted in the Transylvanian Plain during 2019–2021, regarding the influence of certain technological and climatic factors on the yield and quality of maize. The objective of the research was to focus on how vegetable residues and cover crops can be integrated into the optimization of the fertilization system of conservation agriculture. A multifactorial experiment was carried out based on the formula A × B × C × D − R: 4 × 2 × 3 × 3 − 2, where A represents the soil tillage system (a1 conventional tillage with moldboard plow; a2 minimum tillage with chisel; a3 minimum tillage with disk; a4 no tillage); B represents the maize hybrid (b1 Turda 332; b2 Turda 344); C represents the vegetable residues and cover crops (c1 vegetable residues 2.5 t ha−1 + 350 kg ha−1 NPK; c2 vegetable residues 2.5 t ha−1 + cover crops mustard; c3 vegetable residues 2.5 t ha−1 + gulle 10 t ha−1); D represents the year (d1 2019; d2 2020; d3 2021); and R represents the replicates. The results emphasized the fact that for the soil conditions from the area taken into account (Chernozem), for maize, a minimum tillage with chisel during autumn + disk harrow in spring + sowing can be considered as an alternative to the conventional tillage system. Yield and quality of maize can be improved and optimized by combined fertilization: vegetable residues and cover crops being supported with different sources of mineral NPK.

Reducing Tillage Affects Long-Term Yields but Not Grain Quality of Maize, Soybeans, Oats, and Wheat Produced in Three Contrasting Farming Systems

Reducing tillage has been widely promoted to reduce soil erosion, maintain soil health, and sustain long-term food production. The effects of reducing tillage on crop nutritional quality in organic and conventional systems, however, has not been widely explored. One possible driver of crop nutritional quality might be the changing soil nitrogen (N) availability associated with reduced tillage in various management systems. To test how reducing tillage affects crop nutritional quality under contrasting conventional and organic farming systems with varied N inputs, we measured nutritional quality (protein, fat, starch, ash, net energy, total digestible nutrients, and concentrations of Ca, K, Mg, P, and S) of maize, wheat, oats, and soybeans harvested from a long-term trial comprised of three farming systems under two tillage regimes: a conventional grain system (CNV); a low-input organic grain system (LEG); and an organic, manure-based grain + forage system (MNR) under conventional full-tillage (FT) and reduced-till (RT) management. Although maize and wheat yields were 10–13% lower under RT management, grain quality metrics including protein, fat, starch, energy, and mineral concentrations were not significantly affected by reducing tillage. Differences in nutrient quality were more marked between farming systems: protein levels in maize were highest in the MNR system (8.1%); protein levels in soybeans were highest in the LEG system (40.4%); levels of protein (12.9%), ash (2.0%), and sulfur (1430 ppm) in wheat were highest in the CNV system, and oat quality was largely consistent between the LEG and MNR systems. As grain quality did not significantly respond to reducing tillage, other management decisions that affect nutrient availability appear to have a greater effect on nutrient quality.

Regulation of subsoiling tillage on the grain filling characteristics of maize varieties from different eras

Grain filling is the key stage for achieving high grain yield. Subsoiling tillage, as an effective conservation tillage, has been widely used in the maize planting region of China. This study was conducted to explore the effects of subsoiling on the grain filling characteristics of maize varieties of different eras. Five typical maize varieties from different eras (1970s, 1980s, 1990s, 2000s and 2010s) were used as experimental materials with two tillage modalities (rotation tillage and subsoiling tillage). The characteristic parameters (Tmax: the time when the maximum grouting rate was reached, Wmax: the grain weight at the maximum filling rate, Rmax: the maximum grouting rate, P: the active grouting stage, Gmean: the average grouting rate; A: the ultimate growth mass) and rate parameters (T1: the grain filling duration of the gradually increasing stage, V1: the average grain filling rate of the gradually increasing stage, T2: he grain filling duration of the rapidly increasing stage, V2: the average grain filling rate of the rapidly increasing stage, T3: the grain filling duration of the slowly increasing stage, V3: the average grain filling rate of the slowly increasing stage) of grain filling of two tillage modalities were analyzed and compared. The results showed that the filling parameters closely correlated with the 100-kernel weight were significantly different among varieties from different eras, and the grain filling parameters of the 2010s variety were better than those of the other varieties, the P and Tmax prolonged by 4.06–19.25%, 5.88–27.53% respectively, the Rmax and Gmean improved by 5.68–14.81%, 4.76–12.82% and the Wmax increased by 10.14–32.58%. Moreover, the 2010s variety helped the V2 and V3 increase by 6.49–13.89%, 4.55–15.00%. In compared with rotation tillage, the grain yield of maize varieties from different eras increased by 4.28–7.15% under the subsoiling condition, while the 100-kernel weight increased by 3.53–5.06%. Under the same contrast conditions, subsoiling improved the Rmax, Wmax and Gmean by 1.23–4.86%, 4.01–5.96%, 0.25–2.50% respectively, delayed the Tmax by 4.04–5.80% and extended the P by 1.19–4.03%. These differences were major reasons for the significant increases in 100-kernel dry weight under the subsoiling condition. Moreover, subsoiling enhanced the V2 and V3 by 0.70–4.29%, 0.00–2.44%. The duration of each filling stage and filling rate of maize varieties from different eras showed different responses to subsoiling. Under the subsoiling condition, the average filling rate of the 1970–2010s varieties were improved by 1.18%, 0.34%, 0.57%, 1.57% and 2.69%. In the rapidly increasing period, the grain filling rate parameters of the 2010s variety were more sensitive to subsoiling than those of the other varieties. The rapidly increasing and slowly increasing period are the key period of grain filling. Since the 2010s variety and subsoiling all improve the grain filling rate parameters of two periods, we suggest that should select the variety with higher grain filling rate in the rapidly increasing and slowly increasing period, and combine subsoiling measures to improve the grain filling characteristic parameters of maize in production, so as to achieve the purpose of increasing 100 grain weight and yield.

Location and Variety but Not Phosphate Starter Fertilization Influence the Profiles of Fatty Acids, Carotenoids, and Tocochromanols in Kernels of Modern Corn (Zea mays L.) Hybrids Cultivated in Germany

Phosphate is a limiting plant nutrient and essential for corn growth and development. Thus, the impact of phosphate fertilization, location, and the variety of modern corn (Zea mays L.) hybrids on the profiles of fatty acids, carotenoids, and tocochromanols (vitamin E) was assessed in corn grains. Eight different corn hybrids were grown with (52.9 kg of phosphorus per ha) or without starter fertilizer at three experimental sites in Germany. Location (p < 0.05) and genetics (p < 0.001) but not phosphate fertilization significantly altered the concentrations of individual saturated and unsaturated fatty acids, carotenoids, and tocochromanols. Significant (p < 0.05) interaction effects on the concentrations were mainly observed between the variety and the location. In conclusion, the choice of the corn variety had a more significant impact on the biosynthesis of fatty acids, carotenoids, and tocochromanols than the location or phosphate application on phosphate-sufficient soils.