Response Of Grain Yield Research Articles

Yield Response of Rice to Added Phosphorous and Potassium Fertilizer in the Dry Zone of Sri Lanka

Purpose: Continuous application of Phosphorous (P) and Potassium (K) fertilizer over a long period in rice (Oryza sativa L) cultivation may lead to their accumulation in the soils. So, further addition of such fertilizers may be a waste in rice cultivation and also lead to environmental pollution. Thus, field experiments were carried out to study the yield response of rice to added P and K fertilizer under irrigated conditions in Low Humic Gley soils in the Dry Zone of Sri Lanka. Research Method: For the P response study, an experiment was conducted over three consecutive seasons in a rice field where P fertilizer had not been applied for 10 years before the initiation of the experiment, and for the K response study, an experiment was conducted over two consecutive seasons in a rice field where recommended K fertilizer had been continuously applied before the initiation of the experiment. Data on grain yield and yield components, milling quality, important soil properties, and soil and plant P and K contents were recorded and analyzed statistically. Findings: Grain yield, yield components and milling quality of rice did not respond to added P fertilizer over three consecutive seasons in a rice field where P fertilizer had not been applied 10 years before the initiation of the experiment. Soil P analysis indicated that enough soil P was available to maintain an adequate plant P level so that application of P fertilizer in rice cultivation can be avoided at least for about 11½ years (10 years + three seasons) without affecting grain yield and milling quality in Low Humic Gley soils in the Dry Zone of Sri Lanka while saving the cost for P fertilizer. The short-term response of grain yield in rice to added K fertilizer appeared dependent on the grain yield level obtained. No yield response of rice to added K was observed up to the yield level of about 4 t/ha. Thus, the application of K fertilizer can be avoided over two consecutive seasons without affecting grain yield in rice in Low Humic Gley soils in the Dry Zone of Sri Lanka if the yield level is 4t/ha or lower. Research Limitation: Further studies at different locations in farmers’ fields are needed to confirm the applicability of the findings of the present study in farmers’ fields in the Dry Zone of Sri Lanka. Originality/ Value: Long term (over 11½ years) P response study in rice. Such a long-term P response study in rice has not been reported to date. The short-term K response in rice is dependent on the grain yield level achieved.

Effects of free-air temperature increase on grain yield and greenhouse gas emissions in a double rice cropping system

The responses of grain yield and greenhouse gas (GHG) emissions to climate warming in rice paddies are serious concerns for both global food security and climate change mitigation. However, the impact of free-air temperature increase (FATI) on grain yield and methane (CH 4 ) and nitrous oxide (N 2 O) emissions remains unclear for one of the most globally significant rice production practices: the double rice cropping system. Here, we conducted a two-year field experiment to examine the effect of FATI by infrared heaters on grain yield and CH 4 and N 2 O emissions in a double rice field in subtropical China. FATI increased rice canopy temperature by 2.0 °C and soil temperature by 1.2 °C on average but had no effect on either early or late rice yield production. FATI did not affect CH 4 emissions, but significantly increased N 2 O emissions in both the early and late rice seasons. Averaged across two years, N 2 O emissions increased by 0.3 kg ha −1 and 0.7 kg ha −1 in the warmed plots for the early and late rice seasons, respectively. Consequently, FATI enhanced the global warming potential (GWP) and GHG intensity (i.e., yield scaled GWP) in the double rice cropping system. In addition, warming increased the abundance of ammonia-oxidising bacteria, ammonia-oxidising archaea, and a nitrite reductase gene ( nirS ), but decreased that of a nitrous oxide reductase gene ( nosZ ). Our results indicate that warming by FATI does not affect grain yield and CH 4 emissions but stimulates N 2 O emissions in the double rice cropping system and therefore promotes a potential positive feedback with future climate warming. • Free-air temperature increase (FATI) with infrared heater was performed in a double rice field. • Moderate warming by FATI had no significant effect on rice yield. • Moderate warming by FATI did not significantly affect CH 4 emissions. • Moderate warming by FATI stimulated N 2 O emissions.

Effect of mineral N fertilizer and organic input on maize yield and soil water content for assessing optimal N and irrigation rates in Central Kenya

Maize ( Zea mays L.) is an important food crop in Kenya, while low and erratic rainfall, and low nutrient input mainly result in low maize yield. This study were to assess optimal nutrient and irrigation management practice for maize in central Kenya based on field experiment combined with modeling simulation. On-farm experiment with four treatments including no fertilizer (N0), N applied at dose of 100 kg ha –1 only in the form of a chemical fertilizer (N100) or combined with animal manure (N100M) or straw (N100S) has been conducting since 2013 in central Kenya. The Decision Support System for Agro-technology Transfer–Cropping System Model (DSSAT–CSM) was firstly calibrated under the relative optimal treatment N100M, and it was then evaluated for the rest three treatments for 6 maize growing seasons from 2014 to 2018. The responses of grain yield to different irrigation and fertilizer regimes were simulated using the calibrated DSSAT–CSM. The combination of fertilizer and manure (N100M) resulted in the highest yield and that of fertilizer and straw (N100S), in the highest level of soil water content in each soil layer. The model (DSSAT-CSM) successfully predicted both grain yield (normalized root mean square error, or nRMSE , of 21–37% and the index of agreement, or d , of 0.89–0.93) and changes in water content of each soil layer ( nRMSE < 20% and d > 0.70) in all treatments except N100S. The yield was most sensitive to any deficit in soil water content (dry spells) at the beginning of grain-filling stage, and the best regime for high yield, high water-use efficiency, and high agronomic efficiency comprised irrigation at 50–70 mm during that stage combined with fertilizer N at 100–120 kg ha –1 . The estimated magnitude yield gain with respect to optimal nutrition and irrigation ranged from 2 to 4 t ha –1 in different crop seasons. Optimal application of irrigation at the sensitive stage, fertilizer N, animal manure, and straw mulching holds great potential as an integrated farming practice for high grain yield and for efficient use of resources in maize cultivation in semi-arid parts of Kenya. • Optimal fertilizer practice and irrigation strategy was assessed for maize in Kenya. • The combination of mineral fertilizer, manure, and straw mulching is recommended. • DSSAT can be used to predict maize yield and soil water content in central Kenya. • Irrigation at 50 mm in early grain filling together with N at 100 kg ha –1 is optimal.

Effect of nitrogen topdressing on planting density response of grain yield in maize with different planting pattern cultivation

AbstractWe investigated the maize grain yield in response to nitrogen topdressing at different planting densities and planting patterns (twin row, TR; narrow row, NR; and conventional row, CR) over 3 years using early‐maturing cultivars. The P8025 grain yield was higher with a nitrogen topdressing of 6 g/m2 (N6) than without a nitrogen topdressing (N0) at all planting densities in 2017, 2018, and 2019. The difference between the nitrogen topdressing treatments was largest at a planting density close to 10 plants per square meter, which resulted in the highest grain yield in the N0 plot. The rank order for the grain yields among planting patterns was TR ≥ NR &gt; CR in the three analyzed years. Changes in grain yield associated with planting densities followed significant negative quadratic regression curves for all planting patterns. In both the N0 and N6 plots, the grain yield response to planting density was more stable for TR cultivation than for CR and NR cultivation. The rank order for the nitrogen use efficiency (NUE) among planting patterns was TR ≥ NR ≥ CR. The differences in the NUE among planting patterns were higher at higher planting densities. The high NUE observed for TR and NR cultivation was due to the high topdressed nitrogen absorption rate (Nab) at a planting density less than 8.9 plants per square meter as well as the efficiency of the grain yield increase resulting from absorbed nitrogen (Ngy) at a planting density greater than 10.3 plants per square meter. The higher NUE for TR cultivation than for NR cultivation at 12.1 plants per square meter was because of a difference in Ngy and was unrelated to Nab. These results suggest that the improvement of planting pattern (TR, NR) can enhance the effect of topdressed nitrogen on grain yield in maize due to the increase of Nab or Ngy according to the planting density.

Sorghum (Sorghum bicolor L.) yield response to rainwater harvesting practices in the semi-arid farming environments of Zimbabwe: A meta-analysis

Rainwater harvesting practices are increasingly gaining recognition as viable adaptation strategies to overcome rainfall variability caused by climate change in semi-arid regions of Zimbabwe. A meta-analysis was conducted to provide a comprehensive quantitative synthesis of biophysical conditions (rainfall, soil texture, N fertility, mulch) under which basins, rippers, and tied ridges affected sorghum yields in semi-arid areas of Zimbabwe. Rainfall amount (<600 mm, 600–1000 mm), soil texture (20 % clay, 20–35 % clay), mulch (basin + mulch, ripper + mulch, tied ridges + mulch), and fertility (0–30 kg N/ha, 30–100 kg N/ha) were used to evaluate the response of sorghum grain yield to rainwater harvesting practices. Grain yield response was compared to the control (conventional practice) using the weighted mean yield difference approach. The results showed comparable sorghum grain yields in all the rainwater harvesting practices across the biophysical conditions, except under rainfall and soil textural classes. Tied ridges had a significant (p < 0.05) negative sorghum grain yield response (−0.25 t/ha) under <600 mm of rainfall, while ripper planting resulted in a substantial negative grain yield response (−0.32 t/ha) under 600–1000 mm of rainfall. Ripper planting reduced grain yield significantly (p < 0.05) (−1.06 t/ha) in soils with 20–35% clay. The results suggest that basins, rippers, and tied ridges did not improve sorghum grain yield across all agronomic conditions.

Cowpea Genotypic Variations in N2 Fixation, Water Use Efficiency (δ13C), and Grain Yield in Response to Bradyrhizobium Inoculation in the Field, Measured Using Xylem N Solutes, 15N, and 13C Natural Abundance

To evaluate cowpea genotypic differences in response to inoculation with Bradyrhizobium sp. strains BR 3267 and CB756 in the field, 15 genotypes were assessed for N2 fixation using 15N natural abundance and assays of xylem N solutes (ureides, nitrates, and amino-N). Carbon isotope discrimination (δ13C) was used as a surrogate for water use efficiency and grain yield determined at maturity. Within each location, the tested cowpeas elicited contrasting responses to inoculation with either Bradyrhizobium strains. For example, inoculating Apagbaala and IT90K-277-2 with strain BR 3267 doubled N-fixed and grain yield at Nyankpala when compared to inoculation of the same genotypes with strain CB756, whereas the inoculation of Padituya with strain CB756 increased those same parameters relative to non-inoculation. Similar contrasting results were also obtained at Savelugu and Gbalahi, where bacterial inoculation with each strain resulted in up to a five-fold increase in N-fixed and a four-fold increase in grain yield depending on the cowpea/inoculant combinations used and the planting location. The main effect of genotype showed that the percent N derived from N2 fixation (%Ndfa) by the test cowpeas ranged between 74.4 and 89.8%, 11.7 and 50.5%, and 71.9 and 90.3% at Nyankpala, Savelugu, and Gbalahi, respectively. The genotypes grown at Savelugu generally exhibited low %Ndfa which was augmented by greater soil N uptake leading to grain yield increases, a finding supported by significant positive correlations when N-fixed and N content were each plotted against grain yield within locations. The inverse relationship between symbiosis and soil N uptake was also supported by negative correlations between xylem nitrate concentration and relative ureide N abundance (RU-N), and between xylem nitrate concentration and %Ndfa measured from 15N natural abundance. Some high yielding genotypes also elicited greater water use efficiency (δ13C), a trait that could be exploited for increased cowpea production in water limiting environments. This study demonstrates the presence of genotypic differences in cowpea response to inoculation in the field and contributes to the literature regarding the factors influencing legume inoculation response in the tropics.

Controlled‐release nitrogen fertilizer management influences grain yield in winter wheat by regulating flag leaf senescence post‐anthesis and grain filling

AbstractControlled‐release nitrogen fertilizer (CRNF) is expected to meet the nutrient demands for crop growth with single fertilizer application, so as to achieve high‐yield, high‐efficiency, and labor‐saving cultivation. However, under current CRNF practices, a single application of CRNF in winter wheat (Triticum aestivum L.) usually fails to achieve satisfactory effects due to insufficient nitrogen (N) supply in the later growth stage, contributing to premature leaf senescence and poor grain filling. To determine a reasonable CRNF application strategy for improving the grain weight and yield of winter wheat, the responses of leaf senescence, photosynthetic capacity, grain‐filling characteristics, and grain yield to different CRNF types [polymer‐coated urea (PCU), sulfur‐coated urea (SCU), and urea‐formaldehyde (UF)] and fertilization practices [single fertilization (P1) and twice‐split fertilization (P2)] were investigated. The results showed that, compared with P1, P2 increased the activities of catalase, peroxidase, and superoxide dismutase, alleviated the accumulation of malondialdehyde, delayed flag leaf senescence, and enhanced the net photosynthetic rate (Pn) of the flag leaves, which promoted assimilate accumulation and transport to the grains. These advantages in P2 improved the grain‐filling process of wheat, with the active filling duration (T), average filling rate (G), and maximum filling rate (Gmax) in P2 all being higher than those in P1, which significantly increased the 1000‐grain weight (TGW) and grain yield of wheat. Among the three CRNFs, PCU showed advantages in Pn at the milk‐ripe stage (Zadoks growth stage, GS75), dry matter accumulation post‐anthesis, T, Gmax, and G, which contributed to TGW and grain yield. Overall, our study suggested that the twice‐split application of CRNF could substantially delay leaf senescence post‐anthesis and increase photosynthetic capacity, thus improving grain filling and productivity in winter wheat.

Responses of Canopy Functionality, Crop Growth and Grain Yield Of Summer Maize to Shading, Waterlogging, and Their Combination Stress at Different Crop Stages

Responses of Canopy Functionality, Crop Growth and Grain Yield Of Summer Maize to Shading, Waterlogging, and Their Combination Stress at Different Crop Stages

Response of physiological characteristics and grain yield of winter wheat varieties to long-term heat stress at anthesis

Heat stress has become more common in recent years, limiting wheat production in Huang-Huai-Hai plain in China. To identify the effect of long-term heat stress on wheat production, two heat-resistant (JM44, JM23) and two heat-sensitive (XM26, GC8901) wheat varieties were sown in heat tents and normal conditions, and heat stress (9 to 12&#x2103; higher than control) was imposed for seven days at post-anthesis. All varieties under heat stress exhibited early senescence and reduced grain-filling rate, while the grain-filling period of heat-tolerant varieties was longer than that of the heat-sensitive. Furthermore, long-term heat stress significantly reduced kernel mass, grain number, harvest index, chlorophyll content, maximum quantum yield of PS&#x2161; photochemistry, effective quantum yield of PS&#x2161; photochemistry, photosynthetic rate, and transpiration efficiency. In addition, the distribution of dry matter to vegetative organs, catalase activity, and malondialdehyde content increased. These results indicated that the lesser yield reduction of heat-resistant varieties (11-26%) than that of heat-sensitive (16-37%) is due to relatively higher antioxidative and photosynthetic performance and higher assimilation in the grain from vegetative organs.

Implications of Experimental Design on Predicting Economic Optimum Nitrogen Rates in Rice

Nitrogen (N) response studies in rice (Oryza sativa L.) are conducted to provide grower recommendations with economically optimum N rates (EONRs). This study was conducted to determine if experimental design alters the predicted EONR for rice. The effects of experimental design and soil texture on predicted EONR were investigated near Arcola, Greenville, Minter City, and Shaw, MS on soil textures ranging from sandy loam to clay. The response of rice grain yield to seven N fertilizer rates was fitted with a quadratic equation, and the quadratic trend was compared between the randomized complete block (RCB) and split-plot (SP) designs. No differences were detected between RCB and SP designs for rice grain yield response to N rate; therefore, either design, RCB or SP, would be appropriate for use in N response studies for rice.

Evaluation of exotic oat (Avena sativa L.) varieties for forage and grain yield in response to different levels of nitrogen and phosphorous.

A field experiment was conducted during the Rabi season 2017–2018 (October–March) at the University of Agriculture, Peshawar research farm to examine the influence of different nitrogen (N) and phosphorus (P) levels on two different oat varieties: Australian and Ukrainian. The treatments included control and three levels of nitrogen and phosphorus at 30, 60, and 90 kg ha−1. The treatments were arranged in randomized complete block design (RCBD) and replicated three times. The findings showed that the oat varieties were significantly different from one another in yield and yield parameters. The Australian variety recorded higher emergence (49 plants m−2), days to emergence (15 days), days to flowering (122 days), days to maturity (145 days), plant height (142.7 cm), number of leaves (6.03 leaves plant−1), number of tillers (92.2 tillers m−1), biological yield (8,179.2 kg ha−1), and grain yield (3,725.6 kg ha−1) than the Ukrainian variety. Similarly, different N and P levels, the maximum days to emergence, days to flowering, and days to maturity were recorded in a control plot. The application of 105 kg N + 90 kg P ha−1 was statistically similar to the application of 105 kg N + 60 kg P ha−1. Maximum emergence (60 plants m−2), number of leaves (7.0 leaves plant−1), plant height (118.6 cm), number of tillers m−1 (102.6), biological yield (9,687.5 kg ha−1), and grain yield (4,416.7 kg ha−1) were determined in Australian variety. Based on the findings of this study, the Australian variety performed better in terms of yield and yield components and the application of N and P fertilizers at the rate of 105 kg N + 60 kg P ha−1 produced the best results in both oat varieties.

The Response of Grain Yield and Root Morphological and Physiological Traits to Nitrogen Levels in Paddy Rice.

Rice (Oryza sativa L.) is an important crop in China. Although it is known that its yield is restricted by nitrogen (N) supply, the response of the root system to N supply specifically has not been systematically explored. This study aimed to investigate the effect of N uptake on grain yield to clarify the relationships between root morphophysiological traits and N uptake, and to understand relation between phytohormones and root morphophysiological traits. Two N-efficient absorption cultivars (NEAs) and two N-inefficient absorption cultivars (NIAs) were grown in the field, and three N conditions, deficient N (60 kg ha–1), intermediate N (180 kg ha–1), and sufficient N (240 kg ha–1), were applied during the growing season. The results showed higher dry matter and grain yield in NEAs than in NIAs, which was mainly attributed to increased N uptake in the mid- and late growth stages under all N conditions. And NEAs have different root regulation methods to obtain higher N accumulation and yield under different N supply conditions. Under lower N conditions, compared with NIAs, NEAs shown greater total root length, root oxidation activity, and root active absorbing surface area and smaller root diameter owing to higher indole-3-acetic acid and cytokinin content and lower 1-aminocyclopropane-1-carboxylic acid content in the early growth stages to respond to low N stress faster, laying a morphophysiological basis for its high N-uptake capacity in the mid- and late growth stages. Under higher N conditions, NEAs had higher root oxidation activity and root active absorbing surface area for N uptake and yield formation owing to higher abscisic acid and cytokinin content in the mid- and late growth stages, which improved the seed setting rate, thereby increasing the rice grain yield. These results suggest that NEAs can optimize the morphophysiological characteristics of roots through phytohormone regulation to adapt to different nutrient conditions, thereby promoting N accumulation and yield formation in rice.

Phenotypic Traits, Grain Yield and Yield Components of Maize Cultivars Under Combinations of Management Practices in Semi-arid Conditions of Iran

In semi-arid regions, selecting cultivars and planning management practices are critical issues for improving yields and reducing risks of maize cultivation in the short summer cropping season. This study aimed to assess the responses of grain yield (GY) and important phenotypic characteristics of maize cultivars from different maturity groups under various irrigation regimes, planting dates, and nitrogen rates, in a 2-year experiment. According to the clusters identified in the loading plot, stover yield, radiation use efficiency (RUE), height, leaf greenness index, stem weight, and ear size during flowering (VT/R1) were strongly correlated with GY, yield components and harvest index. Based on analysis of variance, more irrigation or N, or their interaction often increased GY, rows ear−1, grains row−1 and hundred-grain weight. Late planting decreased GY of KSC704 (late maturity cultivar). KSC260 (early maturity cultivar) had greater flexibility in planting time, required less days for maturity, and had less water consumption. The findings highlight the physiological basis of the relationship between the different phenotypic characteristics and how they affect GY and its components. They were in line with the established theories that higher RUE, biomass and sink activity (e.g. grain weight and numbers, and larger ear size) are associated with better genetic gains to produce high GY. Although the results were not consistent between years, findings suggested the good performance of recently released early maturity cultivars for use during the summer growing season.

Responses of Grain Yield and Yield Related Parameters to Post-Heading Low-Temperature Stress in Japonica Rice.

There is unprecedented increase in low-temperature stress (LTS) during post-heading stages in rice as a consequence of the recent climate changes. Quantifying the effect of LTS on yields is key to unraveling the impact of climatic changes on crop production, and therefore developing corresponding mitigation strategies. The present research was conducted to analyze and quantify the effect of post-heading LTS on rice yields as well as yield and grain filling related parameters. A two-year experiment was conducted during rice growing season of 2018 and 2019 using two Japonica cultivars (Huaidao 5 and Nanjing 46) with different low-temperature sensitivities, at four daily minimum/maximum temperature regimes of 21/27 °C (T1), 17/23 °C (T2), 13/19 °C (T3) and 9/15 °C (T4). These temperature treatments were performed for 3 (D1), 6 (D2) or 9 days (D3), at both flowering and grain filling stages. We found LTS for 3 days had no significant effect on grain yield, even when the daily mean temperature was as low as 12 °C. However, LTS of between 6 and 9 days at flowering but not at filling stage significantly reduced grain yield of both cultivars. Comparatively, Huaidao 5 was more cold tolerant than Nanjing 46. LTS at flowering and grain filling stages significantly reduced both maximum and mean grain filling rates. Moreover, LTS prolonged the grain filling duration of both cultivars. Additionally, there was a strong correlation between yield loss and spikelet fertility, spikelet weight at maturity, grain filling duration as well as mean and maximum grain filling rates under post-heading LTS (p < 0.001). Moreover, the effect of post-heading LTS on rice yield can be well quantified by integrating the canopy temperature (CT) based accumulated cold degree days (ACDDCT) with the response surface model. The findings of this research are useful in modeling rice productivity under LTS and for predicting rice productivity under future climates.

Long-term conservation agriculture improves water properties and crop productivity in a Lixisol

Climate variability increasingly affects smallholder farmers in southern Africa. Conservation Agriculture (CA) practices have been proposed to improve the resilience of farming systems against the adversities of climate, specifically moisture stress. However, lack of detailed field data on soil water and chemical dynamics leads to over-reliance on simulation models without concrete evidence and ground-truthing of results. Here, we test the effects of different CA and conventional tillage (CP) practices on soil moisture content and water infiltration rate over a 14-year trial period. We also report soil chemical properties measured over 10 years from 0 to 30 cm soil depth. As study object, we used a CA long-term trial at the Monze Farmer Training Centre in Southern Zambia as it included different cropping systems and had parallel infiltration, soil moisture, soil chemical and crop yield measurements. Our results showed significant differences in average soil moisture in the first 60 cm among the cropping systems in different years with the basins plus mulching system having highest moisture content in most of the years. The interaction of cropping systems and years significantly affected water infiltration rate with highest final infiltration rates averaging 48.5 mm h−1 in the CA-based systems and the lowest in CP which averaged 12.6 mm h−1. Soil chemical properties did not significantly differ across the systems but across seasons and depths or their interaction. For crop yield, a direct seeded maize-cotton rotation (DS-MC) consistently had the highest grain yields across most of the years as compared to the CP practice. Maize grain yield significantly differed among the years with a strong influence from the rainfall. Regression analysis revealed significant effect of seasonal rainfall on both soil moisture content and crop yield. The DS-MC system showed high responses of grain yield to rainfall and moisture. This was caused by increased available water and a greater buffering capacity against water stress in the cotton rotation. Systems that conserve moisture, increase infiltration and yield are of paramount importance in environments of variable rainfall. CA-based systems may therefore have the potential to buffer the effects of climate variability and may provide greater resilience.

Improving Grain Zinc Concentration in Wetland and Upland Rice Varieties Grown under Waterlogged and Well-Drained Soils by Applying Zinc Fertilizer

The objective of this study was to evaluate the responses in grain yield and zinc concentration of wetland and upland rice varieties to Zn fertilizer application and different growing conditions. The wetland (Chainat 1; CNT1) and upland (Kum Hom CMU; KH CMU) rice varieties were grown under waterlogged and well-drained soil conditions with or without Zn fertilizer application. Zinc fertilizer (ZnSO4) was applied at 0 and 60 kg ha−1 in three stages at tillering, booting, and flowering. In the wetland variety, CNT1, grain yield decreased by 18.0% in the well-drained soil compared to the waterlogged conditions, but there was an 8.9% decrease in grain yield in the waterlogged soil compared to the well-drained soil in the upland variety, KH CMU. Applying Zn fertilizer affected yields differently between the varieties, decreasing grain yield by 11.9% in CNT1 while having no effect in KH CMU. For grain Zn concentrations in brown rice, applying Zn fertilizer increased Zn concentration by 16.5–23.1% in CNT1 and KH CMU under both growing conditions. In the well-drained soil, applying Zn fertilizer increased straw Zn concentration by 51.6% in CNT1 and by 43.4% in KH CMU compared with the waterlogged conditions. These results indicated that the wetland and upland rice varieties responded differently to Zn fertilizer application when grown in different conditions. Applying Zn fertilizer in the appropriate rice variety and growing conditions would help farmers to improve both the desirable grain yield and Zn concentration in rice.

Interactive effects of mulching practice and nitrogen rate on grain yield, water productivity, fertilizer use efficiency and greenhouse gas emissions of rainfed summer maize in northwest China

Soil mulching and nitrogen application have long been applied in rainfed agriculture, but their interactive effects on crop productivity and especially environments remain poorly understood. Field experiments were carried out in 2018 and 2019 to investigate the responses of grain yield, water productivity, nitrogen use efficiency, economic benefit and greenhouse gas (N2O, CO2 and CH4) emissions of rainfed summer maize in northwest China to various mulching practices (NM: no mulching, SM: straw mulching, and RF: ridge-furrow cultivation with film mulching on the ridge), nitrogen rates (N1: 100 kg N ha−1, N2: 200 kg N ha−1 and N3: 300 kg N ha−1) and their interactions. The results showed that there were no significant differences in grain yield, water productivity and NUE between RF and SM irrespective of nitrogen rates, but RF and SM significantly increased grain yield by 12.4% and 7.9%, water productivity by 13.7% and 10.2%, and partial factor productivity by 12.1% and 7.2% compared with NM (7620.8 kg ha−1, 18.86 kg ha−1 mm−1 and 45.3 kg kg−1), respectively. SM obtained comparable net income to RF under N2 (1567.0 and 1632.4 USD ha−1) and N3 (1593.9 and 1709.9 USD ha−1). Grain yield and net income increased by 12.0% and 14.8% from N1 (7408.6 kg ha−1 and 1356.6 USD ha−1) to N2, and by only 5.5% and 3.6% from N2 (8297.3 kg ha−1 and 1558.0 USD ha−1) to N3, respectively. Water productivity was increased by 14.3% from N1 (18.6 kg ha−1 mm−1) to N2, but it decreased by 3.3% in 2018 and increased by 3.0% in 2019 from N2 (23.2 and 19.4 kg ha−1 mm−1) to N3. Both SM and RF increased CO2 emission compared to NM, while N2O emission decreased under SM and increased under RF. RF increased soil CH4 absorption, while CH4 patterns were not consistent under SM. SM significantly decreased global warming potential by 23.1% and greenhouse gas intensity by 29.0% relative to NM (405.4 kg CO2-eq and 52.0 kg CO2-eq t−1 yield), but they were significantly increased by 62.1% and 22.4% compared with NM under RF, respectively. Compared to N1 (74.09 kg kg−1), N2 and N3 decreased partial factor productivity by 44.0% and 60.9%, respectively. N rate had little influence on CO2 and CH4 emissions, but it significantly promoted N2O emission. There were significant interacting effects of mulching practice and nitrogen rate on N2O emission and global warming potential. In conclusion, straw mulching with 200 kg N ha−1 achieved a better balance between agronomic, economic and environmental benefits of rainfed summer maize in northwest China.

Phenotypic Selection and Bulked Sergeant Analysis for 1000-Kernel Weight under Heat Stress in Durum Wheat

Divergent phenotypic selection for 1000-kernel weight (TKW) was performed under heat stress in a population of 120 F7 recombinant inbred lines (RILs) of durum wheat. The direct response to selection for TKW and correlated response in grain yield per plant (GYP) were assessed under favorable and heat stress conditions. Considerable genetic variations were found among the tested RILs for TKW and GYP. Under heat stress, mean TKW of F7 RILs selected in the high and low directions were 62.28 and 34.42g, respectively. Positive and highly significant responses to selection were obtained for TKW in the high (14.92 and 16.29%) and low (20.78 and 26.88%) directions under favorable and heat stress conditions, respectively. Selection for higher TKW produced positive and highly significant correlated response in GYP under heat stress (11.05%), whereas selection for lower TKW produced positive and highly significant correlated responses in GYP under favorable (11.13%) and heat stress (19.33%) conditions. High realized heritability estimates were obtained for TKW (0.74 and 0.75) and GYP (0.65 and 0.71) under favorable and heat stress conditions, respectively. F8 RILs derived from selection for higher TKW showed higher heat tolerance index (averaged 1.20) than RILs selected for lower TKW (0.52), indicating the usefulness of selection for higher TKW in improving heat tolerance. Bulked segregant analysis with 40 simple sequence repeats (SSR) markers identified seven positives alleles located on 2A (1), 3B (2), 4A (1), 5A (1), 6A (1) and 7B (1) chromosomes that were associated with higher TKW as an indicator for heat tolerance.

Biomass yield, chemical composition and in vitro digestibility of maize leaves defoliated at different times

This experiment was conducted to determine the effect of defoliation time on the productivity of maize, forage and in vitro digestibility of maize leaves (ML). The response of grain yield, plant height, days to 50% silking, ear height and leaf yield as well as the chemical composition of ML variety "Obasuper" to defoliation time were evaluated in a randomized complete block design with four defoliation treatments 3, 6, 9 weeks after planting (WAP) and undefoliated treatment replicated four times. Results showed that defoliating maize at 9 WAP and beyond did not have any significant (P&gt;0.05) effect on the grain and leaf yield as well as other yield components of maize. Grain and leaf yield at 9 WAP averaged 2778.35 and 975.74 DM kg/ha respectively. The DM, crude protein (CP) and fibre fractions contents of ML varied significantly (P&lt;0.05) among the defoliation treatments with maize defoliated at 9 WAP having a CP content of 12.6%. Ether extract and ash contents were not affected (P&gt;0.05) by defoliation time. The in vitro digestibility of ML decreased significantly (P&lt;0.05) with increase in the time of defoliation ranging from 59.2 and 66.4%. IT was concluded that maize variety "Obasuper" can produce forage of high quality and quantity when defoliated 9 weeks after planting wihout any anyadverse effect on the grain yield of maize.

Peanut response to co‐inoculation of Bradyrhizobium spp. and Azospirillum brasilense and molybdenum application in sandy soil of the Brazilian Cerrado

AbstractThe use of plant growth–promoting rhizobacteria (PGPR) associated with rhizobia may improve biological N fixation, nutrient acquisition, and grain yield of the peanut (Arachis hypogaea L.). However, few studies have reported the effect of inoculation of rhizobia and PGPR in association with Mo in tropical soil conditions. This study examined the effectiveness of (co)inoculation with Bradyrhizobium spp. and/or Azospirillum brasilense and Mo application in improving the yield response of creeping peanut crop (‘RUNNER IAC 886’). The effects of rhizobacteria and Mo on nodulation, crop growth, chlorophyll content, and yield of peanut were investigated in a moderately acidic sandy soil (pH 5.0) from the Brazilian Cerrado during the 2016–2017 and 2017–2018 growing seasons. Four seed inoculation treatments (control [uninoculated seeds], inoculation with Bradyrhizobium spp. strains SEMIA 5079 and SEMIA 5080, inoculation with Azospirillum brasilense strains Ab‐V5 and Ab‐V6, and co‐inoculation of Bradyrhizobium spp. and Azospirillum brasilense) and two Mo levels (0 and 200 mg Mo kg−1 of seed) were studied. Results showed that the effects of the interaction between rhizobacteria and Mo application were not significant (p &gt; .05) for all crop traits. Root nodulation, dry matter accumulation, and chlorophyll content were significantly greater in Mo‐treated peanut plants than control plants in both seasons. However, the response of crop grain yield was significantly greater (17.7%) in Mo‐treated plants only in the 2017–2018 season. Therefore, the improved root nodulation, crop growth, and chlorophyll content resulting from Mo application can lead to increased pod and grain yield in peanut. Inoculation with Bradyrhizobium spp. alone or combined with A. brasilense enhanced root nodulation, chlorophyll content, and peanut grain yield. Over two harvests, average peanut grain yield increased by 25.3 and 24.0% with inoculation of Bradyrhizobium spp. alone and combined with A. brasilense, respectively, compared with noninoculated plants. Due to lower cost and higher profitability, inoculation of Bradyrhizobium spp. alone is the most efficient practice for peanut cropping in sandy soils of the Brazilian Cerrado. Together with Mo application, these agricultural practices can be recommended for Brazilian peanut farmers.