Radiation Use Efficiency Research Articles

Decoupling between leaf nitrogen and radiation use efficiency in vegetative and early reproductive stages in high-yielding soybean.

Ontogenic changes in soybean radiation use efficiency (RUE) have been attributed to variation in specific leaf nitrogen (SLN) based only on data collected during seed filling. We evaluated this hypothesis using data on leaf area, absorbed radiation (ARAD), aboveground dry matter (ADM), and plant nitrogen (N) concentration collected during the entire crop season from seven field experiments conducted in a stress-free environment. Each experiment included a full-N treatment that received ample N fertilizer and a zero-N treatment that relied on N fixation and soil N mineralization. We estimated RUE based on changes in ADM between sampling times and associated ARAD, accounting for changes in biomass composition. The RUE and SLN exhibited different seasonal patterns: a bell-shaped pattern with a peak around the beginning of seed filling, and a convex pattern followed by an abrupt decline during late seed filling, respectively. Changes in SLN explained the decline in RUE during seed filling but failed to predict changes in RUE in earlier stages and underestimated the maximum RUE observed during pod setting. Comparison between observed and simulated RUE using a process-based crop simulation model revealed similar discrepancies. The decoupling between RUE and SLN during early crop stages suggests that leaf N is above that needed to maximize crop growth but may play a role in storing N that can be used in later reproductive stages to meet the large seed N demand associated with high-yielding crops.

Sowing density rather than row spacing influences chia radiation use and yield

AbstractChia (Salvia hispanica L.) production worldwide has been encouraged due to its high essential fatty acid content that is effective for reducing cardiovascular affections. However, few studies have assessed the sowing density and row spacing to maximize chia grain yield (GY) and found controversial results. None of them reported effects on radiation interception and use efficiency that could help to clarify the controversial results. The objective of this study was to determine the effects of sowing density and row spacing on radiation interception and radiation use efficiency (RUE) of chia and their effects on chia growth and yield. Two field trials were conducted in Salta, Argentina, during 2017 and 2018, combining two factors: sowing density (5, 9, 13, 17, and 21 plants m−2) and row spacing (0.26 and 0.52 m). Photosynthetically active radiation (PAR) interception (PARi), RUE, biomass and GY components were measured. There was a clear effect of sowing density on the main growth and yield attributes, whereas there were no effects of row spacing. Sowing density had a greater impact on PARi than row spacing. Increasing sowing density increased PARi and RUE through earlier time of maximum PARi, accumulating more PAR producing more biomass and GY. Grain yield, which increased by 73 kg ha−1 per unit increase in plant density, was closely associated with biomass, grain number, and verticillaster number (VN), and negatively associated with 1,000‐grain weight (TGW). Summarizing sowing density rather than row spacing had a greater impact on growth and yield attributes of chia.

Response of Grain Yield and Water Use Efficiency to Irrigation Regimes during Mid-Season indica Rice Genotype Improvement

Understanding the performance of rice (Oryza sativa L.) agronomic traits and efficiency in water usage as well as grain yield under various irrigation regimes is crucial to achieving high resource use efficiency and high yield. In this study, 12 mid-season indica rice genotypes that have been grown in the lower reaches of the Yangtze River for the past 80 years were studied in a field experiment for two years under two irrigation regimes, i.e., conventional irrigation (CI) and alternate wetting and drying irrigation (AWD). The results showed that with genotype improvement in irrigation regimes, the total number of spikelets, shoot and root dry weight, root oxidation activity, total leaf area index (LAI), effective LAI, leaf photosynthetic rate, and abscisic acid contents and zeatin + zeatin riboside contents in root bleeding sap were significantly increased at main growth stages. AWD irrigation synchronously increased rice resource use efficiency (water use efficiency (WUE), radiation use efficiency (RUE), and temperature use efficiency (TUE)) and grain yield. Compared to CI, AWD more significantly enhanced the performances of rice genotypes in all studied traits. Based on our findings, a semi-dwarf hybrid rice genotype has great potential for high resource use efficiency and high yield under alternate wetting and drying irrigation, which was attributed to the improved agronomic characteristics and superior root traits.

Minimizing trade-offs between wheat yield and resource-use efficiency in the Nile Delta – A multi-model analysis

Current wheat crop management practices in the Nile Delta of Egypt are unsustainable due to the overuse of limited water resources. Therefore, the aim of this study was to investigate opportunities to maximize wheat yield and resource efficiency including irrigation water use efficiency (WUE), nitrogen use efficiency (NUE), and solar radiation use efficiency (RUE). Three wheat simulation models (CERES, CROPSIM and NWheat) of the Decision Support System for Agrotechnology Transfer (DSSAT) were calibrated and evaluated for the modern spring wheat cultivar Sakha95 across field experiments with sowing date and irrigation treatments over three successive growing seasons. All three crop models showed a satisfactory agreement between simulated and measured grain yield and water use under both limited and unlimited conditions. The three crop models were then used to simulate yield, WUE, NUE and RUE under various N and irrigation treatments for 10 sites representing the wheat growing area of the Nile Delta using historical weather data from 1981 to 2010. Increasing nitrogen fertilizer to 300 kg N ha -1 improved grain yield across the Nile Delta (to 9800 kg ha -1 ), WUE (to 30.6 kg ha -1 mm -1 ), and RUE (to 0.89 g MJ -1 ), but with diminishing returns for each kilogram of fertilizer applied and, hence, a decreasing NUE (to 28.9 kg grain yield kg N -1 ). Irrigation at 80% plant available water depletion was the optimal treatment, which minimized water use with a slight decline in grain yield (7992 kg ha -1 ), WUE (28.0 kg ha -1 ), and RUE (0.67 g MJ -1 ). For food security and optimal utilization of available solar radiation, the highest yield seems most desirable. However, with limited water and N fertilizer resources, a high WUE and NUE could be more critical for a sustainable wheat production in the Nile Delta and other irrigated arid wheat growing regions. • Sustainable wheat yield is uncertain in Nile Delta due to overuse of limited water. • Increased N to 300 kg N ha -1 improved GY, WUE, and RUE while decreasing NUE. • Deficit irrigation of 80% PAW reduced trade-offs between GY, and efficiencies. • Higher N (250 kg ha -1 ) reduced trade-offs between GY, and resources efficiencies. • In low water and N, a high WUE and NUE is critical for sustainable wheat production.

Eco-physiological yield determinants in four potato genotypes grown in a temperate environment

The eco-physiological yield determinants of four potato genotypes suitable for processing into French fries were studied. Field trials were carried out during the growing seasons 2016/17 and 2017/18 at Balcarce, Argentina (−37.85 S, −58.19 W). Genotypes, identified as Bal1, Bal2, Bal3 and Bal4, have growing cycles of 95–105, 100–110, 110–120, and 120–130 days after emergence, respectively. Intercepted photosynthetic active radiation (PARint), radiation use efficiency (RUE), harvest index (HI) and tuber yield were evaluated during both growing seasons. Bal4 achieved the highest dry matter tuber yield in both growing seasons, with 1412 and 1879 g mˉ² for 2016/17 and 2017/18, respectively. Due to a combination of a high PARint and RUE values, tuber dry matter in Bal4 was 20–30 % higher than that achieved by other genotypes. PARint throughout the growing cycle was 1025 and 1121 MJ mˉ² for Bal4, for 2016/17 and 2017/18 seasons, respectively; these values were 10–22 % higher than those observed for the other genotypes. RUE was 1.66 and 2.02 g MJˉ 1 for Bal4 in 2016/17 and 2017/18 growing seasons, respectively, these values are 14–18 % higher than those observed for the other genotypes. HI varied between 0.81 and 0.87 for all genotypes, in both seasons. PARint, and RUE were the two most critical yield determining factors that explained the differences in tuber dry matter yield between the potato genotypes. Bal4 showed highest yields due to a particular combination of high PARint and high RUE, not reported in the literature, so far. These results could contribute to improve early selection in future breeding programs, to better adjust growth models and to establish specific management strategies for a particular genotype. • The eco-physiological yield determinants of four potato genotypes were studied. • Genotypes differed in cycle length and in intercepted radiation. • Genotypes also differed in radiation use efficiency and in harvest index. • One genotype combined high radiation interception and high radiation use efficiency.

Feasibility of yield estimation based on leaf area dynamics measurements in rice paddy fields of farmers

Rice yield is an important factor for farmers when reviewing crop management planning and cultivation operations. In previous studies, a non-destructive, labor-saving method has been proposed to determine yield using spectral information from remote sensing. This method assumes that molecule number (e.g., chlorophyll content in leaves) and biophysical information (e.g., leaf area) cause spectral variations. However, spectral information cannot reflect the influence of physiological factors because of the limitations of this method. In this study, we investigated solar radiation use efficiency (RUE), which reportedly reflects physiological changes in crops. Time-series data of leaf area index were collected over five years in rice paddy fields of farmers to calculate and investigate the variation in RUE. The results showed that RUE varied among the survey points but did not differ significantly by year. The mean absolute error of yield estimation ranged from 68.2 g m −2 to 102.2 g m −2 depending on the yield estimation method and from 36.8 g m −2 to 454.1 g m −2 depending on the RUE. Among the estimation methods, the highest accuracy was achieved using leaf area dynamics. These results provide insights into both the effectiveness of leaf area dynamics in yield estimation and the potential errors when using remote sensing. • Solar radiation use efficiency differs by location, planting method, and year. • Error in yield estimation using leaf area differs by solar radiation use efficiency. • Leaf area dynamics is effective in improving the accuracy of rice yield estimation.

Quantifying physiological determinants of potential yield in mungbean (Vigna radiata (L.) Wilczek)

A comprehensive understanding of key drivers of grain yield is essential to identify opportunities to improve productivity in mungbean ( Vigna radiata (L.) Wilczek). The objective of this study was to assess and quantify physiological factors underpinning yield of mungbean grown in non-water-limiting conditions. Two field experiments, employing three genotypes (Jade-AU, Opal-AU and Satin II) and four canopy density treatments were conducted in the summer growing season (Jan-Mar) of 2019 and 2020 at Gatton campus, The University of Queensland, Australia. Crop leaf area dynamics, radiation interception, extinction coefficient ( k ), radiation use efficiency (RUE), total dry matter (TDM) (above ground dry matter) and grain yield (GY) were measured. Leaf area index (LAI), influenced by the canopy density treatments, was the key driver of differences in radiation interception. The variation in intercepted radiation resulted in differences in TDM and GY across canopy density treatments. Genotypes did not differ significantly and partitioned more than 90% of TDM to pod development. The radiation extinction coefficient, k , was stable and estimated to be 0.68, while average RUE was calculated as 1.3 g MJ -1 . Variations in GY were strongly associated with grain number, which was related to intercepted radiation per unit of accumulated temperature around flowering. Using this quantification of the physiology of crop growth and yield in mungbean to form a simple crop model, simulations suggested that median potential yields of 1.88–2.48 tonnes ha −1 were possible in NE Australian production environments, with greater yield associated with spring sowing. Understanding the physiological basis of the very low RUE in mungbean was considered a key avenue to improve potential yield. This study has provided a quantitative framework for potential yield that will enable more comprehensive modelling of crop adaptation in mungbean. • This study highlights the importance of identifying key physiological determinants of yield for increasing productivity in mungbean. • Leaf area index differences in response to varying canopy density treatments was the key driver of differences in radiation interception and biomass. • Radiation use efficiency for current commercial mungbean was found to be 1.3 g MJ −1 . • Intercepted radiation per unit of accumulated temperature between flowering and maturity was significantly associated with grain number. • Simulations of potential yield indicated 2.5 tonnes ha −1 was attainable in NE Australia and higher yield occurred in spring planting.

The Effect of Planting Time and Plant Density on Radiation Use Efficiency (RUE) on Lowland Rice (Oryza sativa L.) Cv. Inpari 30

The right planting time and plant density in rice cultivation in the rainy season affect the generative phase, where absorption of solar radiation intensity more efficiently increases productivity. This study aims to improve the absorption of energy efficiency of solar conversion with differences in planting time and planting density. The experiment was carried out from January to June 2019 in the experimental garden of Brawijaya University, Malang City, East Java. The research design used is a nested design with three replication. The main factor is planting time which consists of 3 levels, namely: January (B1); February (B2); March (B3). The nested factor is plant density which consists of 3 levels, namely: 111.111 plant ha-1 (T1); 166.667 plant ha-1 (T2); 226,667 plant ha-1 (T3). Data analysis used variance (ANOVA). If the results are significantly different, then the honest significant difference test (HSD) is continued at the 5% level. The results showed the differences in total leaf area index, plant dry weight, panicle weight every clump, grain weight every clump, grain weight every harvest plot, yield per hectare, and radiation use efficiency (RUE). The planting time in March has a higher RUE value than the planting time in January or February. The yield per hectare shows the planting time in March is higher than the planting time in January or February planting time. Plant density of 30x30 cm shows yields per hectare higher than planting density of 30x20 cm and planting density of 40x20x12.5 cm.Â

Double zero-tillage and foliar-P nutrition coupled with bio-inoculants enhance physiological photosynthetic characteristics and resilience to nutritional and environmental stresses in maize-wheat rotation.

Conventionally tilled maize–wheat cropping system (MWCS) is an emerging cereal production system in semi-arid region of south-Asia. This system involves excessive tillage operations that result in numerous resource- and production-vulnerabilities besides impeding environmental-stresses. Likewise, phosphorus is a vital nutrient that limits crop growth and development. It’s a matter of great concern when ∼80% of Indian soils are low to medium in available-P due to its sparing solubility, resulting in crop stress and low yields. Hence, crop productivity, photosynthetic parameters and resilience to nutritional and environmental stresses were assessed in a MWCS using four crop-establishment and tillage management (CETM) practices [FBCT-FBCT (Flat bed-conventional tillage both in maize and wheat); RBCT-RBZT (Raised bed-CT in maize and raised bed-zero tillage in wheat); FBZT-FBZT (FBZT both in maize and wheat); PRBZT-PRBZT (Permanent raised bed-ZT both in maize and wheat)], and five P-fertilization practices [P100 (100% soil applied-P); P50+2FSP (50% soil applied-P + 2 foliar-sprays of P through 2% DAP both in maize and wheat); P50+PSB+AM-fungi; P50+PSB+AMF+2FSP; and P0 (100% NK with no-P)] in split-plot design replicated-thrice. The results indicated that double zero-tilled PRBZT–PRBZT system significantly enhanced the grain yield (6.1; 5.4 t ha–1), net photosynthetic rate (Pn) (41.68; 23.33 μ mol CO2 m–2 s–1), stomatal conductance (SC) (0.44; 0.26 mol H2O m–2 s–1), relative water content (RWC) (83.3; 77.8%), and radiation-use efficiency (RUE) (2.9; 2.36 g MJ–1) by 12.8–15.8 and 8.5–44.4% in maize and wheat crops, respectively over conventional tilled FBCT–FBCT. P50+PSB+AMF+2FSP conjugating soil applied-P, microbial-inoculants and foliar-P, had significantly higher Pn, SC, RUE and RWC over P100 besides saving ∼34.7% fertilizer-P under MWCS. P50+PSB+AMF+2FSP practice also had higher NDVI, PAR, transpiration efficiency and PHI over P100. Whereas lower stomatal limitation index (Ls) was observed under PRBZT–PRBZT system as compared to the conventional FBCT–FBCT system indicating that P is the limiting factor but not stomata. Hence, optimum P supply through foliar P-fertilization along with other sources resulted in higher grain yield by 21.4% over control. Overall, double zero-tilled PRBZT–PRBZT with crop residue retention at 6 t/ha per year, as well as P50+PSB+AMF+2FSP in MWCS, may prove beneficial in enhancing the crop productivity and, thereby, bolstering food security in semi-arid south-Asia region.

Effects of row spacing on soil nitrogen availability, wheat morpho-physiological traits and radiation use efficiency

Optimizing row spacing is an important measure to exploit the full yield potential, achieve a continuous increase in wheat yield and green development without increasing input. The objective of this study was to compare the effects of wide–narrow row spacing pattern (12 cm-12 cm-12 cm-24 cm, R1) and conventional uniform row spacing mode (20 cm, CK; 12 cm. R2) on nitrogen (N) availability in soil, canopy structure, photosynthetic characteristics, radiation use efficiency (RUE) and yield. The results showed that R1 increased the relative abundance of ammonia-oxidizing bacteria and ammonia-oxidizing archaea in the rhizosphere compared to CK. Nitrate in soils treated R1 at post-anthesis and nitrogen use efficiency of the plant were 59.92% and 27.01% higher than those treated with CK, respectively. Above-ground growth of wheat showed that R1 increased leaf area index by 27.42%, specific leaf weight by 22.67% and leaf photosynthetic rate by 8.86%, respectively compared to CK. R2 had similar availability of N and plant growth as CK. Moreover, the ability of the plant to allocate more nitrogen to grains was enhanced at post-anthesis with R1 than it with CK and R2, which greatly improved the RUE by 10.13% and 2.27%. As the result, the yield for R1 increased by 27.54% and 21.46%, respectively, compared to CK and R2. Therefore, using wide–narrow row spacing pattern (R1) is a practically and environmentally feasible approach for wheat production without extra input in the straw-returning wheat-corn rotation system.

Wheat traits and the associated loci conferring radiation use efficiency.

Wheat (Triticum aestivum L.) radiation use efficiency (RUE) must be raised through crop breeding to further increase the yield potential, as the harvest index is now close to its theoretical limit. Field experiments including 209 wheat cultivars which have been widely cultivated in China since the 1940s were conducted in two growing seasons (2018-2019 and 2019-2020) to evaluate the variations of phenological, physiological, plant architectural, and yield-related traits and their contributions to RUE and to identify limiting factors for wheat yield potential. The average annual genetic gain in grain yield was 0.60% (or 45.32 kg ha-1 year-1 ; R2 = 0.44, P < 0.01), mainly attributed to the gain in RUE (r = 0.85, P < 0.01). The net photosynthetic rates were positively and closely correlated with grain RUE and grain yield, suggesting source as a limiting factor to future yield gains. Thirty-four cultivars were identified, exhibiting not only high RUE, but also traits contributing to high RUE and 11 other critical traits - of known genetic basis - as potential parents for breeding to improve yield and RUE. Our findings reveal wheat traits and the associated loci conferring RUE, which are valuable for facilitating marker-assisted breeding to improve wheat RUE and yield potential.

Global Sensitivity Analysis of Key Parameters in the APSIMX-Sugarcane Model to Evaluate Nitrate Balance via Treed Gaussian Process

Difficulties in direct monitoring of nitrate balance in agricultural fields reveal the importance of modeling and quantifying the affecting parameters on nitrate balance. We constructed meta-models for APSIMX-Sugarcane using the treed gaussian process and conducted a global sensitivity analysis for nitrate uptake and leaching under three conditions: (1) bare land (BL) to examine the influence of soil hydraulic characteristics, (2) N-free treatment under radiation use efficiency (RUE) ranges (i) 1.2–1.8 [N-free(a)] and (ii) 1.8–2.5 [N-free(b)], and (3) urea conditions to examine the influence of plant growth. Generated meta-models showed good accuracy (for all conditions: R2 &gt; 0.70; NRMSE &lt; 16%; AI &gt; 0.90). The most influential parameters (sensitivity indices ≥ 0.02) were as follows: for leached NO3−N in BL: the parameter rerated to saturated flow-proportion of water between saturation and field capacity (SWCON) of all soil layers; for NO3− uptake and leached NO3−N in N-free(a) and urea: RUE of the phenological stage (PS) 3 (RUE3) and 4, tt_emerg_to_begcane, green_leaf_no, and y_n_conc_crit_leaf of PS 4 (NCL4); in N-free(b): RUE3, NCL4, and SWCON of soil layers 0–15 cm; 15–30 cm, which confirmed that influential parameters were depended on N-stress. The outcomes of this study are useful for enhancing the accuracy and efficiency of crop modeling.

Radiation use efficiency and biomass production of maize under optimal growth conditions in Northeast China.

Accurate crop growth and radiation use efficiency (RUE) measurements under optimal growth conditions are required to predict grain yield near the genetic growth potential and estimate climate change effects on crop production. Research was conducted to quantify RUE of maize during the whole growth period, vegetative period (VP, phenological development stage DVS < 1.0), and reproductive period (RP, DVS ≥ 1.0) under the optimal growth condition in Northeast China. Maize was grown in three population density treatments (9.0, 7.5, and 6.0 plants m-2, referred to HD, MD, and LD respectively) over three growing seasons (2017-2019). The maximum Leaf Area Index (LAI) was observed after the anthesis period (DVS = 1.2), ranged from to 4.9 to 6.9, and then gradually decreases. Photosynthetically active radiation (PAR) intercepted by the canopy of maize was approximate 10% during the early stage of the vegetative period (DVS < 0.3). Then greatest differences occurred during the late vegetative period (DVS = 0.3 to 0.8). When DVS > 1.0, there is no significant difference between the three population density conditions. Estimates of RUE were obtained based on the intercepted PAR (IPAR) and absorbed PAR (APAR). RUE value was 3.97 g MJ-1 APAR or 3.73 g MJ-1 IPAR in the whole growth period, and did not vary among density treatments. Moreover, maximum RUE occurred during VP (4.11 g MJ-1 APAR) and declined during RP (3.95 g MJ-1 APAR). Therefore, we recommend that maize models that rely on RUE for aboveground biomass accumulation should be using a value of 3.97 g MJ-1 APAR for predicting optimum maize grain yield in Northeast China, especially for the potential yield.

Evaluating the effect of sugarcane planting methods on growth and radiation use efficiency of its different varieties

To examine the growth and radiation use efficiency (RUE) of different sugarcane cultivars (HSF 240, CP 77-400 &amp; CPF 249) under two planting methods (2.5 feet apart single row, a farmers’ practice, and 4 feet apart dual rows deep trench plantings, a recommended practice) at Research Farm of Sugarcane Research Institute (SRI), Ayub Agricultural Research Institute (AARI), Faisalabad during 2019-20. The experiment was carried out in randomized complete block design with split-plot arrangement in three repeats. The results showed maximum dry matter (3348.24 g m-2), CGR (21.49 g m-2 day-1), mean CGR (12.78 g m-2 day-1), LAI (7.81), leaf area duration (1290.32 days), along with radiation use efficiency for total dry matter (2.16 g MJ-1) and cane yield (6.32 g MJ-1) in 4 feet apart dual rows trench planting in comparison to 2.5 feet apart single row trench planting, 2.08 g MJ-1 and 5.70 g MJ-1, respectively. On the other hand, higher dry matter (3451.42 g m-2), CGR (21.54 g m-2 day-1), mean CGR (13.16 g m-2 day-1), LAI (8.01), LAD (1324.58 days), RUE for dry matter production (2.20 g MJ-1) and cane yield (6.53 g MJ-1) was recorded in variety CP 77-400, a direct introduction to SRI, as compared with local material, HSF 240 and CPF 249 and occupying large area in whole Punjab-Pakistan.

Yield and Resource Utilization Efficiency Gap in Early Maturing Japonica Rice Cultivars under Different Management Strategies—A Different Location Investigation

High input costs and poor management options have resulted in a large rice yield gap. Thus, there is a need to reduce production costs and improve resource-use efficiency by using new cultivation techniques at different locations. The objective of this study was to determine yield and utilization efficiency gaps in early maturing japonica rice under four treatments; no nitrogen application (N0), local farmer practice (FP), high-yield, high-efficiency practice (HYP), and super-high-yield practice (SHY). The average yields under N0, FP, HYP, and SHY were 5012, 7356, 8448, and 9629 kg ha−1, respectively. Differences among treatments were as: N0 to FP (gap 1); FP to HYP (gap 2); and HYP to SHY (gap 3). Yield gaps 1, 2, and 3 were 2337, 1092, and 1181 kg ha−1, respectively. Yield gap was positively associated with panicles per square meter. Yield under HYP and SHY was 14.8% and 30.9% higher than that under FP, respectively. This increase in yield was mainly associated with a higher number of panicles. For resources, gaps 1, 2, and 3 were as follows: water-use efficiency, 0.1706, 0.1513, and 0.1089 kg m−3; radiation-use efficiency, 0.3285%, 0.1780%, and 0.0941%; and heat-use efficiency, 1.8685, 1.0339, and 0.8798 kg °C−1 d−1 ha−1, respectively. The yield was positively correlated with water, radiation, and heat-use efficiencies. The differences in yield and resource-use efficiency were significant between sites. A reduction in yield and efficiency gaps can ensure sufficient panicle per square meter, stabilize grain number per panicle, and increase harvest index and biomass. Overall, HYP is a promising option to increase the yield of early maturing japonica rice yield in cold regions.

Performance of Cassava under Lime, Fertilizer, and Legume Intercropping on Exhausted Land in Northern Zambia

Cassava yields of 6 t ha−1 are lower than the potential yield of 20–25 t ha−1 obtained in Northern Zambia. It is grown in legume intercropping with little or no fertilizer, causing nutrient depletion with consequent land abandonment. Therefore, the study objective was to investigate the performance of cassava under lime, fertilizer, and grain legume intercropping on exhausted land in Northern Zambia. A split-split plot design experiment was conducted over two seasons, comprising two lime rates (0 and 300 kg ha−1), two fertilizer rates (0 and 100N : 23P:80 K kg ha−1), and three grain legumes (common beans, cowpea, and soybean) intercropped in cassava and sole cassava arranged in RCBD with three replications. Periodic measurements of leaf area index (LAI), light interception, weather data, and yield components were recorded. A linear mixed model with year as a random factor was performed to assess the treatment effect of lime, fertilizer, and legume species intercropping on cassava growth characteristics, radiation-use efficiency (RUE), and selected yield components. Lime, fertilizer rates, and legume species intercropping were assigned as main, sub-, and sub-sub-treatments, respectively. Fertilization and fertilization + lime treatments in sole cassava and cassava-common bean intercropping significantly increased the RUE and light extinction coefficient (k) compared to nonfertilized and only lime treatments. Lime x fertilizer x cropping system interaction was significant on chlorophyll index and plant height, RUE, tuber yield, HI, and total dry matter (TDM) yield. Cropping system x year interactions were significant on season LAI. On average, every kg of cassava yield loss in intercropping was compensated by 0.46 kg soybean, 0.20 kg common beans, and 0.26 kg of cowpea. NPK fertilizer + lime, NPK fertilizer, and grain legume intercropping may be adopted to increase cassava tuber yields and legume grain yield response on nutrient-depleted soils in high rainfall areas of Zambia.

The Fraction of Intercepted Radiation to Nitrogen Absorption as an Indicator for Assessing Physiological Nitrogen Use Efficiency in Rice

Improving nitrogen (N) use efficiency is important for achieving sustainable rice production in China. Physiological N use efficiency (PNUE) is a measure of a plant’s ability to convert absorbed N into biomass, and can be calculated as the product of the fraction of intercepted radiation to N absorption (FIRNA) and radiation use efficiency (RUE). This study evaluated the relationships between PNUE with FIRNA and RUE in three widely grown, high-yielding rice varieties using data obtained from two N fertilization experiments conducted in 2020 and 2021. The results show that PNUE was significantly positively related to FIRNA, but not significantly related to RUE in all three rice varieties. PNUE increased by 7.4–10.3 g g−1 for each 10 MJ g−1 increase in FIRNA. These results suggest that FIRNA can serve as an indicator for assessing PNUE in rice, which has implications for the phenotypic identification of rice varieties with high PNUE.

Cassava-maize intercropping systems in southern Nigeria: Radiation use efficiency, soil moisture dynamics, and yields of component crops.

Efficient utilization of incident solar radiation and rainwater conservation in rain-fed smallholder cropping systems require the development and adoption of cropping systems with high resource use efficiency. Due to the popularity of cassava-maize intercropping and the food security and economic importance of both crops in Nigeria, we investigated options to improve interception of photosynthetically active radiation (IPAR), radiation use efficiency (RUE), soil moisture retention, and yields of cassava and maize in cassava-maize intercropping systems in 8 on-farm researcher-managed multi-location trials between 2017 and 2019 in different agro-ecologies of southern Nigeria. Treatments were a combination of (1) maize planting density (low density at 20,000 maize plants ha-1 versus high density at 40,000 maize plants ha-1, intercropped with 12,500 cassava plants ha-1); (2) fertilizer application and management targeting either the maize crop (90 kg N, 20 kg P and 37 kg K ha-1) or the cassava crop (75 kg N, 20 kg P and 90 kg K ha-1), compared with control without fertilizer application. Cassava and maize development parameters were highest in the maize fertilizer regime, resulting in the highest IPAR at high maize density. The combined intercrop biomass yield was highest at high maize density in the maize fertilizer regime. Without fertilizer application, RUE was highest at low maize density. However, the application of the maize fertilizer regime at high maize density resulted in the highest RUE, soil moisture content, and maize grain yield. Cassava storage root yield was higher in the cassava fertilizer regime than in the maize fertilizer regime. We conclude that improved IPAR, RUE, soil moisture retention, and grain yield on nutrient-limited soils of southern Nigeria, or in similar environments, can be achieved by intercropping 40,000 maize plants ha-1 with 12,500 cassava plants ha-1 and managing the system with the maize fertilizer regime. However, for higher cassava storage root yield, the system should be managed with the cassava fertilizer regime.

Radiation use efficiency increased over a century of maize (Zea mays L.) breeding in the US corn belt.

In the absence of stress, crop growth depends on the amount of light intercepted by the canopy and the conversion efficiency [radiation use efficiency (RUE)]. This study tested the hypothesis that long-term genetic gain for grain yield was partly due to improved RUE. The hypothesis was tested using 30 elite maize hybrids commercialized in the US corn belt between 1930 and 2017. Crops grown under irrigation showed that pre-flowering crop growth increased at a rate of 0.11 g m-2 year-1, while light interception remained constant. Therefore, RUE increased at a rate of 0.0049 g MJ-1 year-1, translating into an average of 3 g m-2 year-1 of grain yield over 100 years of maize breeding. Considering that the harvest index has not changed for crops grown at optimal density for the hybrid, the cumulative RUE increase over the history of commercial maize breeding in the USA can account for ~32% of the documented yield trend for maize grown in the central US corn belt. The remaining RUE gap between this study and theoretical maximum values suggests that a yield improvement of a similar magnitude could be achieved by further increasing RUE.

Radiation Use Efficiency and Agronomic Performance of Biomass Sorghum under Different Sowing Dates

Accurate estimation of radiation use efficiency (RUE) at variable timed sowing dates will enhance the prediction of plant dry matter accumulation. The objectives of this study were to (1) determine the impact of three sowing dates on the productivity, performance, and economic feasibility of three biomass sorghum hybrids and (2) evaluate the variability of RUE in the production of biomass sorghum under the effects of variable timed sowing dates. Over a two-year experiment, biomass sorghum hybrids were grown and monitored at different sowing seasons under optimal growth conditions. Average dry biomass (DB) productivity at harvest ranged from 22.71 to 32.77 Mg ha−1. Higher leaf area index (LAI) values (&gt;4.0) represented an intercept of over 95% of incident photosynthetically active radiation (PAR). RUE obtained from the slope of the linear relationship between DB produced and accumulated intercepted photosynthetically active radiation (IPAR) ranged from 2.92 to 4.157 g MJ−1 across growing seasons. Higher RUE values were observed for the energy hybrids in the early and mid-season. They converted IPAR efficiently into DB. Lastly, the economic feasibility of each sorghum hybrid and sowing date was evaluated in terms of their expected net returns. Economic results suggest that the sorghum hybrids considered could be a viable source of biomass season long, with net returns ranging from USD 560.55 ha−1 to USD 1255.06 ha−1.