Rice Yield Response Research Articles

Alkaline Hydrolyzable‐Nitrogen of Clayey Soils Reduces Supplemental Fertilizer Nitrogen Requirement of Rice in Arkansas

The Illinois Soil Nitrogen Test (ISNT) and the Nitrogen Soil Test for Rice (N‐STaR) are alkaline hydrolyzable‐N (AH‐N) soil test methods that can potentially improve N fertilization of cereal crops by predicting a site‐specific fertilizer‐N rate; however, neither method has been evaluated for rice (Oryza sativa L.) grown on clayey soils. The study objectives were to: (i) evaluate unfertilized (0 kg N ha−1) N uptake and yield response of rice to fertilizer‐N based on ISNT and N‐STaR soil test values of clayey soils sampled in 15‐cm increments to a 60‐cm depth and (ii) calibrate the fertilizer‐N rate required to achieve 95% relative grain yield (FN 95%RGY) with ISNT and N‐STaR. A significant and positive linear relationship (P ≤ 0.001) occurred between AH‐N (ISNT or N‐STaR) and rice‐N response, regardless of sampling depth. Unfertilized N uptake, unfertilized yield (Yield0N), or relative grain yield (%RGY0N) regressed on AH‐N exhibited coefficient of determination (r2) values as great as 0.82, 0.59, and 0.78, respectively. The ability of AH‐N to be calibrated to FN 95%RGY was influenced by sampling depth with the greatest r2 values occurring when clayey soils were sampled from ≤30 cm. The ISNT and N‐STaR explained as much as 90 and 95% of the variability in FN 95%RGY, respectively, at the 0‐ to 30‐cm depth. Alkaline hydrolyzable‐N soil test methods, such as ISNT and N‐STaR, provided an accurate indication of rice response to fertilizer‐N and have the potential to improve fertilizer‐N rate recommendations for rice grown on clayey soils.Core Ideas Inability to predict rice supplemental fertilizer‐N requirement limits usefulness of N recommendations. Sampling depth influenced correlation between alkaline hydrolyzable‐N and rice fertilizer‐N responsiveness. Alkaline hydrolyzable‐N accurately predicted supplemental N requirement across variously N‐fertile clayey soils.

Using boosted tree regression and artificial neural networks to forecast upland rice yield under climate change in Sahel

Climate drivers are key stress factors affecting upland rice yields in Sahel because the region is vulnerable to unfavorable weather and has a very low adaptive capacity. This study modeled upland rice yield responses to climate factors using multiple linear regression, boosted tree regression, and artificial neural networks (ANNs). Four ANNs were explored: ANNMLP (multilayer perceptron), ANNPNN (probabilistic neural network), ANNGFF (generalized feedforward), and ANNLR (linear regression). Then the modeled rice yield function was calibrated and tested against the observed yield data and climate variables of three provinces of Burkina Faso, West Africa. The global climate model (GCM) outputs under the AR4-SR-A1B, A2, and B1 mean ensemble CO2 emissions scenarios were then downscaled and used as input of the calibrated yield response model, in order to forecast yield trends over 2052. The results are three-fold: first, rain (R = 0.402) is the most dominant climate driver in Sahel, followed by the maximum and minimum temperatures (R = -0.313 and R = -0.237, respectively), which clearly reduce yield. Second, the ANNPNN (R = 0.952, MSE = 0.033 ton/ha, NMSE = 0.109 ton/ha, MAE = 0.115 ton/ha) has a great capability in rice yield responses function modeling outperforming boosted tree (R = 0.920, MSE = 0.077 ton/ha, NMSE = 0.208 ton/ha, MAE = 0.223 ton/ha) and the multiple linear regression (R = 0.385, MSE = 0.259 ton/ha, NMSE = 0.852 ton/ha, MAE = 0.340 ton/ha). All linear models performed unsatisfactorily. Third, the projected yields showed a gap of 57.29% with the site-recorded maximum average yields over 2052. From application of ANNPNN, we anticipate that site-specific rice yield may substantially decline with climate change, as rainfall is projected to decrease while temperatures increase. These results should assist in identifying priority adaptation measures for Sahel, such as village rainwater catchment basins supplemented with adapted irrigation technologies, to enhance the resilience of crops.

Response of rice yield and yield components to elevated [CO2]: A synthesis of updated data from FACE experiments

Abstract Rice is the most widely consumed staple food for more than half of the world’s population. Rising atmospheric carbon dioxide concentration [CO2] is expected to improve crop yields in the future. Rice responds to elevated [CO2] through photosynthesis improving yield components. This response depends on rice types, climate and fertilizers. However, the determinants of rice yield and the contribution of yield components at elevated [CO2] are far from certain. We extracted data from articles published before the end of 2018. These articles reported the responses of rice yield and yield components to elevated [CO2] at FACE conditions across four locations in China and Japan. Using CART (Classification and regression tree, a nonparametric modeling approach to recursively partition predictor variables) and regression models, we identified the principal determinants and the contribution of yield components to yield at elevated [CO2]. Elevated [CO2] (∼200 μmol mol−1 above ambient) increased rice yields by 13.5% (n = 93), 22.6% (n = 10) and 32.8% (n = 17) for japonica, indica and hybrid cultivars. The type of rice cultivars dominantly determined the response of spikelets per panicle, while temperature is of greatest importance in determining the response of filled spikelets percentage to elevated [CO2]. Optimal nitrogen rates at elevated [CO2] are site-specific, depending on local soil fertility and temperature. The contribution of post-heading elevated [CO2] to yield is higher for indica and hybrid (24%) than for japonica cultivars (13%). Lower benefit of japonica cultivars from post-heading elevated [CO2] is likely attributed to an intensive photosynthetic acclimation. Our findings highlight the importance of pre- and post-heading CO2 fertilization effect and nitrogen management in yield benefits from elevated [CO2], and the necessity for crop modelers to incorporate the knowledge from FACE studies into models so that models become more accurate, rigorous and robust.

Validation of Soil‐Test‐Based Phosphorus and Potassium Fertilizer Recommendations for Flood‐Irrigated Rice

Soil testing is a widely accepted practice for evaluating soil‐P and soil‐K availability but can be inconsistent for making accurate fertilizer‐P and fertilizer‐K recommendations. Our research objectives were to assess the accuracy of established soil‐ and tissue‐P and ‐K concentration interpretations for predicting flood‐irrigated rice (Oryza sativa L.) yield response to fertilization at three levels of significance (p ≤ 0.05, 0.10, and 0.25). Six treatments combining two fertilizer‐P rates (0 or 32 kg P ha−1) and four fertilizer‐K rates (0, 56, 84, 112 kg K ha−1) were applied at 24 sites. Soil‐test P (STP) interpretations were 40% accurate, regardless of the significance level, and whole‐plant‐P concentrations at the V6‐V7 stage were 50% accurate. Soil‐test K (STK) interpretations were 40 (p ≤ 0.05 and 0.10) and 36% (p ≤ 0.25) accurate, and whole‐plant‐K concentrations at the R2‐R3 stage were 61% (p ≤ 0.25) or 62% (p ≤ 0.05 and 0.10) accurate in predicting the yield response to K fertilization. Nearly all of the error in both soil‐test‐ and whole‐plant‐P and ‐K concentration interpretations occurred in the suboptimal categories. The accuracy (p ≤ 0.05) of yield response predictions for levels where no fertilizer was recommended was 100% for STP and 86% for STK and 82 to 100% for whole‐plant‐P and ‐K concentrations. The false‐positive error was the most common soil‐test recommendation inaccuracy and suggests that fertilizer recommendations are skewed to reduce the risk of yield loss from insufficient fertilization.Core Ideas Tissue analysis is more accurate at predicting flood‐irrigated rice response to P and K fertilization than Mehlich‐3 extractable P and K. False positive errors are the most common soil‐test‐based interpretation errors for flood‐irrigated rice. Mehlich‐3 extractable P is not a good predictor of rice yield response to P fertilization. The most accurate fertilizer P and K recommendations were interpreted at the 0.05 and 0.10 significance levels.

CLIMATE CHANGE IMPACT AND RESPONSE OF RICE YIELD

Abstract. Rice is an important cereal crop and part of daily diet not only in India but also throughout Asia. Agriculture is highly dependent on the variations in temperature, precipitation and solar radiation and long-term climate patterns. The pattern of changing climate in last 30 years indicate that predictable and possible changes in rainfall and temperature can reduce agriculture outputs and yields particularly for rice and wheat significantly. The main aim of this research paper is to study the Kharif Rice Productivity in Hisar, Haryana under changing climate. The study focuses on the impacts of climate change namely intensity, timings and spatial distribution of rainfall. Kharif rice is more vulnerable to meteorological drought due to growing uncertainties in monsoon rains under the changing climate patterns. The study of seasonal changes in precipitation at decadal scale for observed and CORDEX projected precipitation for the selected region was done to understand the impacts of climate change. Along with this, DSSAT Crop Simulation Model was run to quantify the water stress in the years with more negative rainfall departure and to identify the reasons for variability in yield. DSSAT model was able to simulate phenological events and final grain yield at maturity stage with reasonable accuracy under varied weather conditions. The analysis of the simulated results indicates the association between yield and rainfall amount and its distribution during the season and different phenological growth stages of rice. The results further indicate that water stress at important stages such as Booting, Heading and Flowering majorly impact the final yield.

The potential role of sucrose transport gene expression in the photosynthetic and yield response of rice cultivars to future CO2 concentration.

The metabolic basis for observed differences in the yield response of rice to projected carbon dioxide concentrations (CO2) is unclear. In this study, three rice cultivars, differing in their yield response to elevated CO2, were grown under ambient and elevated CO2 conditions, using the free‐air CO2 enrichment technology. Flag leaves of rice were used to determine (1) if manipulative increases in sink strength decreased the soluble sucrose concentration for the ‘weak’ responders and (2), whether the genetic expression of sucrose transporters OsSUT1 and OsSUT2 was associated with an accumulation of soluble sugars and the maintenance of photosynthetic capacity. For the cultivars that showed a weak response to additional CO2, photosynthetic capacity declined under elevated CO2 and was associated with an accumulation of soluble sugars. For these cultivars, increasing sink relative to source strength did not increase photosynthesis and no change in OsSUT1 or OsSUT2 expression was observed. In contrast, the ‘strong’ response cultivar did not show an increase in soluble sugars or a decline in photosynthesis but demonstrated significant increases in OsSUT1 and OsSUT2 expression at elevated CO2. Overall, these data suggest that the expression of the sucrose transport genes OsSUT1 and OsSUT2 may be associated with the maintenance of photosynthetic capacity of the flag leaf during grain fill; and, potentially, greater yield response of rice as atmospheric CO2 increases.

Responses of indica rice yield and quality to extreme high and low temperatures during the reproductive period

Extreme temperatures will likely occur with greater frequency and intensity under the conditions of climatic warming, presenting a serious challenge for future crop development. The responses of rice yield and quality to extreme high (HT) and low temperature (LT) during precise reproductive periods are still unclear. Therefore, we conducted a walk-in climate chamber experiment with two indica cultivars and three temperature treatments –CK: 20–28 °C, LT: 12–20 °C and HT: 28–36 °C as the mean values of night-day temperatures– for seven days in four key periods –the last week of pre-heading, and the first, second and third week of post-heading–, respectively. Extreme temperatures reduced rice leaf chlorophyll fluorescence, photosynthetic rate and dry matter translocation, consequently decreasing the grain yield by 5–13 percent under LT and 12–15 percent under HT. The most sensitive periods of rice yield to extreme temperatures were found during the last week of pre-heading and the first week of post-heading. Extreme temperatures significantly declined the grain appearance, milling and cooking quality traits with inversely enhanced chalkiness, broken rice and gelatinization temperature. The most responsive period of rice quality to extreme temperatures occurred during the second week of post-heading. HT exhibited a more severe impact on rice quality than by LT. Our results indicate that the responses of rice yield and quality to extreme temperatures are different among reproductive periods.

Yield and N Utilization of Transplanted and Direct‐Seeded Rice with Controlled or Slow‐Release Fertilizer

Core Ideas CSRF application (RBBbasal, RBBBP, SCUBP) increased the NUE in both seedling‐transplanted and direct‐seeded fields. Yield increase of resin‐blending controlled‐release fertilizer was better than that of sulfur‐coated fertilizer under the two planting modes. “Base‐panicle” fertilization with RBB and urea was suitable for the seedling‐transplanted mode. A single basal application of RBB was suitable for direct‐seeded mode for achieving the high yield. ABSTRACTTo understand the response of rice yield and N utilization to controlled or slow‐release fertilizers (CSRFs) under direct‐seeded or seedling‐transplanted modes of rice production, a field experiment with rice variety Wuyunjing 23 was performed in 2013 and 2014. Five treatments, including two CSRFs: sulfur‐coated urea (SCU) and resin‐blending controlled‐release fertilizer (RBB), two fertilization modes: single basal application and a split “base‐panicle” (BP) application, and conventional split fertilization (CONV) as a control, were conducted. The results showed that there was no improvement of yield for SCU application compared with CONV in the seedling‐transplanted and direct‐seeded modes in both years. The yield increasing effect of RBB was better than that of SCU under the two planting modes. The interaction effect between the planting mode and fertilizer treatment on the yield was significant. The yield of RBBBP treatment was the highest in seedling‐transplanted fields, reaching 12.04 t ha−1 in 2013 and 13.44 t ha−1 in 2014. By contrast, the yield of RBBbasal treatment was the highest in direct‐seeded rice, although the difference among the treatments was not significant. The CSRF application (RBBbasal, RBBBP, SCUBP) increased the NUE in both the seedling‐transplanted and direct‐seeded fields. Except for the NUE of RBBbasal, which was the highest for direct‐seeded rice in 2013, the RBBBP treatment showed the highest NUE in seedling‐transplanted and direct‐seeded rice in both years. The results indicated that RBB increased the yield and NUE in both seedling‐transplanted and direct‐seeded modes, and the combined panicle urea and RBB was better in seedling‐transplanted fields, while a single basal application with RBB was better in direct‐seeded rice.

Yield response of upland Rice + Peanut intercropping schemes to Rhizobial (Bio-N) inoculation

Yield response of upland Rice + Peanut intercropping schemes to Rhizobial (Bio-N) inoculation

Differential growth and yield response of hybrid rice (Oryza sativa L.) to seasonal variability

The response of hybrid rice to seasonal changes is largely unknown. This study presents the effort to assess the response of tropical hybrid rice to rainy and winter seasons in alluvial soils at Regional Research Sub-Station under Bidhan Chandra Krishi Viswavidyalaya, Chakdah, West Bengal. Five commercial tropical hybrid rice cultivars together with a local HYV were evaluated in randomized complete block design with three replications. The variety NPH-207 (Champion) produced taller plants and recorded significantly higher number of effective tillers than the local HVY (Satabdi) did during both the seasons. The cultivar NPH-8889 (Karishma) recorded the maximum chlorophyll content at all dates of observations and it was statistically at par with NPH-207 (Champion). The values of all measured yield components were higher in the hybrid cultivar NPH-207 (Champion) in comparison with any other tested cultivars. Consequently, NPH-207 (Champion) produced significantly higher grain and straw yield, accounting 67.9 and 50.1% more than those obtained from HYV in rainy season, while 98.2 and 103% more than those obtained from HYV in winter season, respectively. The significant and positive correlations with grain yield were observed between plant height, 1000 grain weight and chlorophyll content at 30 DAT both in rainy and winter season.

Response of Rice Yield and Yield Components as well as Grain Quality to Number and Levels of Zinc Foliar Spraying Application

TWO field experiments were conducted during the summer season of 2014 and 2015 growing successive seasons at the Experimental Station of Faculty of Agriculture, Ain Shams University, Shalakan, Kalubia Governorate, Egypt, to investigate the response of rice crop yield and yield components as well as grain quality to the number (once, 45 DAS; twice, 60 DAS and thrice, 75 DAS) and levels (0, 200, 400, 600 and 800ppm Zn) of zinc foliar spraying application. Experimental design was split plot design with three replications, where, number of zinc foliar application occupied the main plots and zinc levels distributed in the sub plots. Application of 600ppm Zn gave the highest values of panicle number/m2, panicle length, spikelets numbers/panicle, panicle weight, filled grains percent, filled grains numbers/panicle and 1000 grain weight. Foliar application of 600ppm Zn showed the highest values of grain crude protein content, soluble carbohydrate, GNY, SNY, TNY, NRE and NUE. Thrice zinc foliar application gave the maximum values of panicle length, spikelets numbers/panicle, panicle weight, filled grains percent and filled grains numbers/panicle. While, panicle number/m2 and 1000 grain weight were slightly affected by number of zinc foliar application. Application of thrice zinc foliar application at the level of 600ppm exhibited the highest values of grain, straw, biological and GCP yields as well as most of yield attributes and nitrogen physiological parameters.

Root growth dynamics and yield responses of rice (Oryza sativa L.) under drought—Flood abrupt alternating conditions

Drought and flash flooding are two common water stresses that negatively affect the rice growth and development in South China. Unfortunately, in some cases, rice plants have to experience these two stresses within a short time. A study on root plasticity responses and their relationships with grain yield (GY) in rice under drought–flood abrupt alternating (DFAA) water stresses at jointing–booting stage was conducted in a specially designed experimental pool. The two-year outdoor pot experiment was composed of six DFAA treatments with combinations of different droughts and floods. Three additional treatments, namely, the drought-followed-by-no-flood (DNF), no-drought-followed-by-flood (NDF), and control treatment, were prepared for each of the DFAA treatment. Results showed that responses of root and yield related traits in rice to DFAA were not the additive effect of drought alone and flooding alone and there existed interaction (positive/negative compensation) between them. DFAA increased bleeding intensity (BI) significantly at the end of flooding, but the increases were less than those of DNF. Compared to DNF and NDF, DFAA showed the highest reduction in total root length, root and shoot dry weight, root mean diameter, root surface area (RSA), and root volume at the end of flooding. However, specific root length and RSA/root volume ratio increased. Root/shoot ratio in DFAA and DNF varied from 2016 to 2017, while it was enhanced in NDF in both years. During recovery period, differences in root traits among treatments still existed. The preceding drought weakened the effects of subsequent flooding on GY in rice. The yield losses in DNF, DFAA, and NDF (reduced by 13.0%, 24.9%, and 33.5% on average, respectively) were mainly attributed to a smaller total number of spikelets and thinner filled spikelets. The percentage of filled grains (FG) depended on the degrees of drought and flooding. Rewatering after drought tended to increase FG, while flooding after drought tended to decrease it. Yield-related traits in DFAA were significantly associated with most of root traits at the end of flooding, while these correlations were not significant in DNF and NDF.

Response of rice (Oryza sativa L.) on seedling age and number of seedlings per planting hole

The objectives of this research were to investigate the growth and yield response of paddy rice on transplanting seedling ages and number of seedlings per planting hole. This research was conducted in October 2016 until January 2017 in Petuaran Hulu Village, Pegajahan Subdistrict, Serdang Bedagai Regency, North Sumatera Province. The experimental design used was a Randomized Block Design with two factors and three replications. The first factor was the age of transplanting seedlings with four levels (12, 16, 20, and 24 days). The second factor was the number of seedlings per planting hole with four levels (1, 2, 3, and 4 seedlings per planting hole). Analysis of Variance was conducted in order to see the effect of the treatments. The treatments that showed significant effect was tested with Duncan to compare among treatments effect. The results showed that transplanting seedling age and number of seedlings per planting hole had significant effect on plant height, number of tillers, but no significant effect on stem diameter, number of productive tillers, panicle length, and productivity. The effect of interaction of the two treatments had no significant effect on all observed parameters. Transplanting seedling age of 12 days and one seedling per planting hole was suggested to be applied for rice cultivation.

Fertilizer Use Efficiency and Profitability of Irrigated Rice in Mali and Niger

Nutrient response functions for irrigated rice in the Sahel were determined. Yield response of irrigated rice to applied N and P has good profit potential. Response to micronutrients occurred in Mali but not in Niger. The response functions can be used in fertilizer use optimization decision tools. Rice (Oryza sativa L. and O. glaerrima Steud.) is an important food crop in Africa. Maximizing profitability of fertilizer use requires determination of nutrient response functions. Five trials were conducted in the Niger River valley of Mali and Niger. The objectives included determination of nutrient response functions for irrigated rice, other nutrient deficiencies, and profitability of fertilizer use. Average trial grain yields were 3.07, 4.09 and 5.49 Mg ha−1 in Niger and on Danga and Moursi soil types in Mali, respectively. Nitrogen response was curvilinear to plateau in all cases except for a linear response for Danga soil in Mali. Yield increases with 150 kg ha−1 N ranged from 0.7 to 1.7 Mg ha−1. Responses to P were curvilinear with grain yield increases of approximately 0.3 and 1.7 Mg ha−1 in Niger and Mali, respectively, with 30 kg ha−1 P. The economically optimal rate (EOR) for N when fertilizer use cost was 4.5 times the value of rice grain (kg kg−1) ranged from 62 to >150 kg ha−1. The EOR of P ranged from 27 to 33 kg ha−1 in Mali and from 12 to 16 kg ha−1 in Niger, depending on the relative cost of fertilizer P. Agronomic efficiency of N varied from <10 to 20 kg kg−1, and of P with 10 kg ha−1 P from 49 to 95 kg kg−1, depending on location. Net returns to N and P use exceeded 100%. This information is applicable in nutrient management decision tools oriented to farmer profitability in Mali and Niger.

Influence of Soil Amendments on the Growth and Yield of Rice in Acidic Soil

In Malaysia, about 0.5 million ha of acid sulfate soils are found scattered over the east, west, and Sabah and Sarawak regions that can potentially be cultivated with paddy. This type of soil is acidic and not immediately suitable for crop production unless improved by applying some amendments. Thus, the current study was carried out to investigate the effects of various types of soil amendments on the growth, yield, and physiological responses of rice grown in extremely acidic conditions using ground magnesium limestone (GML), basalt, biochar, and compost as soil amendments. The acid sulfate soil with a pH of 3.76 was obtained from a paddy field in Merbok, Kedah. The plant responses were evaluated based on agronomic, physiological, and yield performance. The compost-treated rice showed the best performance in all three criteria. Compost treatment increased the soil pH up to 6.25. Physiological performances such as chlorophyll, photosynthetic rate, and water use efficiency were higher after compost treatment, while transpiration and stomatal conductance showed the highest after GML treatment. It can be concluded that the addition of compost as a soil amendment can increase soil pH and create favorable soil conditions for rice cultivation in acid sulfate soil, leading to improved rice growth performance.

Improving yield and nitrogen use efficiency through alternative fertilization options for rice in China: A meta-analysis

Applying alternative fertilization practices instead of conventional fertilizers might improve rice yield and nutrient use efficiency in rice cropping systems. However, the results range widely among individual studies, making generalizations difficult. Here, we investigated five alternative fertilization options (slow-release nitrogen fertilizer, SRF; organic fertilizer, OF; straw return, SR; green manure, GM; secondary/micronutrient fertilizer, SMF) and performed a meta-analysis to quantify their effects on rice yield and nitrogen (N) use efficiency across different rice types in China. Yield responses were significantly positive under all alternative fertilization options relative to those obtained with conventional fertilization, and the magnitude of yield increase exhibited the following the order: OF (7.8%) > SRF (7.4%) > GM (6.7%) > SR (5.4%) > SMF (4.6%). Furthermore, the recovery efficiency (REN), agronomic efficiency (AEN), and the partial factor productivity of nitrogen (PFPN) were increased by 6.0–34.8%, 10.2–29.5%, and 4.7–6.9%, respectively under the alternative fertilization options relative to conventional fertilization. The application of SRF and SMF generated higher yield responses in single rice than in other rice types, whereas OF and SR application resulted in better performance in early and middle rice. The rice yield response was maximized when approximately 70% slow-release N was combined with approximately 30% conventional N according to the quadratic relationship between the percentage of slow-release N substituting conventional N and the yield response. It was estimated that the total N rate could be reduced by up to 32% without yield loss with the application of slow-release N fertilizer instead of conventional N fertilizer. When organic N fully or partially substituted inorganic N, yield response declined with increasing substitution level, and the substitution proportion needed to be controlled below 20% to maintain rice yield. The meta-analysis results clearly demonstrate that appropriate alternative fertilization options can increase both rice yield and nitrogen use efficiency, and that conventional chemical fertilizers can be partially replaced with alternative ones without negatively affecting rice productivity.

Effects of Commercial Loan to Agriculture on Rice Yield Response in Nigeria from 1966 to 2015: An Application of Autoregressive Distributed Lag (ARDL) Approach

Effects of Commercial Loan to Agriculture on Rice Yield Response in Nigeria from 1966 to 2015: An Application of Autoregressive Distributed Lag (ARDL) Approach

English

In West Africa, rice (Oryza sativa L. and Oryza glaberrimaI Steud) production is not meeting current demand. Low yields are attributed to diverse biotic and abiotic constraints including nutrient deficiencies, inadequate agronomic practices, and socio-economic constraints. This study quantified yield and profit responses of rainfed rice produced in the Sudan Savanna of Burkina Faso and Mali to fertilizer N, P, K, and Mg-S-Zn-B treatment. The mean yields were 2.2 and 2.4 Mg ha-1 for upland rice in Finkolo and for lowland rice in Longorola in Mali, respectively, and 1.5 and 2.2 Mg ha-1 for upland rice at Boni and Karaba in Burkina Faso. Lowland rice grain yield was not affected by nutrient application at Longorola. The grain yield increases with 30 and 60 kg ha-1 N were, respectively, 0.30 and 0.48 Mg ha-1 at Karaba, 0.21 and 0.34 Mg ha-1 at Boni, and 0.32 and 0.41 Mg ha-1 at Finkolo indicating similarity in response. Grain yield response to P was observed only at Karaba. If fertilizer were applied at 50% rather than 100% of the economically optimum rate, as might be the case for financially constrained farmers, the mean yield increase was 36% less but agronomic efficiency was 23% higher and the profit cost ratio was 66% higher. There was no response to K or to Mg-S-Zn-B. The results, therefore, indicate high potential for profitable response of rainfed upland rice production for Sudan Savanna to fertilizer N but little potential for other fertilizer nutrients. These results should, however, be considered together with other field research results in making fertilizer use decisions. Key words: Agronomic efficiency, economically optimal rate, response function, yield.

Photosynthetic and yield responses of rice (Oryza sativa L.) to different water management strategies in subtropical China

An experiment was performed to study gas exchange and chlorophyll fluorescence responses of rice (Oryza sativa L.) to various regimes, such as flooding-midseason drying-flooding (FDF), flooding-midseason drying-saturation (FDS), and flooding-rain-fed (FR) regimes. Compared to FDF, FR resulted in an obvious decrease in net photosynthetic rate (PN), due to the decrease in stomatal conductance and the increase in stomatal limitation. In contrast, FDS plants did not suffer stomatal limitation and had comparable PN with FDF plants. For diurnal light-saturated electron transport rate and saturation irradiance, FDF performed the best, which was followed by FDS and FR successively. FR and FDS plants tended to suffer from midday depression. FDS reduced irrigated water by 17.2% compared to FDF for comparable yields. The results suggested that FDS can be an effective irrigation regime to save water.

Irrigation methods affect water productivity, grain yield, and growth responses of rice at different levels of nitrogen

Water conservation is an integral part of precision agriculture. In rice (Oryza sativa L.) producing countries, the looming water crisis necessitates the development of water-saving technologies. A field study was conducted to evaluate the advantages of different irrigation methods on water productivity, rice grain yield, and growth responses for the two consecutive years during 2015 and 2016. Two irrigation methods, conventional irrigation (CI) and thin-shallow-moist-dry irrigation (TSMDI), and three nitrogen (N) levels (0, 90, and 180 kg N ha−1) were tested in a split plot design with three replications. The results revealed that TSMDI significantly increased water productivity compared with CI without jeopardizing grain yield, and no significant difference was observed on crop growth parameters between irrigation methods. Two years of study results showed that under both irrigation methods, grain yield ranged from 7.59 to 8.01 t ha−1, 8.61 to 9.26 t ha−1, and 9.30 to 10.01 t ha−1 at 0 kg N ha−1, 90 kg N ha−1, and 180 kg N ha−1, respectively. Thus, TSMDI required the same fertilizer management as CI and saved water up to 16% to 21% when keeping other inputs constant. In the present study, the best combination of water and N application is TSMDI and 180 kg N ha−1, over other treatments9 combinations.