Yields and Land-Use Efficiency of Maize-Cowpea Crop Rotation in Comparison to Mixed and Monocropping on an Alfisol in Northern Ghana

Results reported in the literature with regard to productivity of intercropping systems in comparison to sole cropping are very inconsistent. A field experiment was therefore conducted in the northern part of the Guinea Savanna in Ghana to compare the productivity of maize/cowpea mixed cropping, maize/cowpea relay intercropping with maize/cowpea rotation and maize monocropping over a 4-year period. The treatments included two levels of nitrogen (0 and 80 kg of N ha⁻¹ y ⁻¹ as urea) and two levels of phosphorus application (0 and 60 kg of P ha⁻¹ y⁻¹ as Volta phosphate rock). At all levels of N and P application, maize yields of the intercropping systems, especially of maize/cowpea mixed cropping, were significantly lower than in sole cropping. Highest maize yields were obtained in maize/cowpea rotation, which in contrast to the other cropping systems did not show any reductions in yields over years. Cowpea yields were generally less affected by the cropping system, but were notably depressed when cowpea was relay-intercropped with maize. In treatments without fertilizer application (N and P) Land Equivalent Ratios (LER) and Area x Time Equivalency Ratios (ATER) generally indicated lower productivity of the intercropping systems as compared to sole cropping, with the maize/cowpea rotation showing the highest productivity. Conversely, fertilizer application resulted in higher productivity of the intercropping systems over the 4-year period. Productivity on the basis of ATER was generally lowest in maize/cowpea relay-intercropping as a consequence of the long time of land occupation. All of the parameters indicate low productivity of maize monocropping, clearly demonstrating that crop sequence as well as fertilizer application must be considered as important for maintaining high production levels at this site.     

作物超高产栽培与株型育种的光合作用基础——-以水稻为例

粮食安全问题是中国乃至世界未来面临的重要问题。提高作物的光合作用对解决粮食安全保障具有重要意义。作物叶片利用光能的能力受外界环境的影响,同时群体对小环境的影响反过来又影响叶片的光合作用。本文以水稻为例从栽培和株型育种两个方面讨论了优化群体结构、实现作物超高产的途径。     

Explaining rice yields and yield gaps in Central Luzon,Philippines: An application of stochastic frontier analysis and crop modelling

Explaining yield gaps is crucial to understand the main technical constraints faced by farmers to increase land productivity. The objective of this study is to decompose the yield gap into efficiency, resource and technology yield gaps for irrigated lowland rice-based farming systems in Central Luzon, Philippines, and to explain those yield gaps using data related to crop management, biophysical constraints and available technologies.Stochastic frontier analysis was used to quantify and explain the efficiency and resource yield gaps and a crop growth model (ORYZA v3) was used to compute the technology yield gap. We combined these two methodologies into a theoretical framework to explain rice yield gaps in farmers’ fields included in the Central Luzon Loop Survey, an unbalanced panel dataset of about 100 households, collected every four to five years during the period 1966–2012.The mean yield gap estimated for the period 1979–2012 was 3.2 ton ha⁻¹ in the wet season (WS) and 4.8 ton ha⁻¹ in the dry season (DS). An average efficiency yield gap of 1.3 ton ha⁻¹ was estimated and partly explained by untimely application of mineral fertilizers and biotic control factors. The mean resource yield gap was small in both seasons but somewhat larger in the DS (1.3 ton ha⁻¹) than in the WS (1.0 ton ha⁻¹). This can be partly explained by the greater N, P and K use in the highest yielding fields than in lowest yielding fields which was observed in the DS but not in the WS. The technology yield gap was on average less than 1.0 ton ha⁻¹ during the WS prior to 2003 and ca. 1.6 ton ha⁻¹ from 2003 to 2012 while in the DS it has been consistently large with a mean of 2.2 ton ha⁻¹. Varietal shift and sub-optimal application of inputs (e.g. quantity of irrigation water and N) are the most plausible explanations for this yield gap during the WS and DS, respectively.We conclude that the technology yield gap explains nearly half of the difference between potential and actual yields while the efficiency and resource yield gaps explain each a quarter of that difference in the DS. As for the WS, particular attention should be given to the efficiency yield gap which, although decreasing with time, still accounted for nearly 40% of the overall yield gap.     

No-tillage permanent bed planting and controlled traffic in a maize-cotton irrigated system under Mediterranean conditions: Effects on soil compaction,crop performance and carbon sequestration

Under irrigated Mediterranean conditions, no-tillage permanent bed planting (PB) is a promising agriculture system for improving soil protection and for soil carbon sequestration. However, soil compaction may increase with time up to levels that reduce crop yield. The aim of this study was to evaluate the mid-term effects of PB on soil compaction, root growth, crop yield and carbon sequestration compared with conventionally tilled bed planting (CB) and with a variant of PB that had partial subsoiling (DPB) in a Typic Xerofluvents soil (Soil Survey Staff, 2010) in southern Spain. Traffic was controlled during the whole study and beds, and furrows with (F + T) and without traffic (F − T), were spatially distinguished during measurements. Comparisons were made during a crop sequence of maize (Zea mays L.)—cotton (Gossypium hirsutum L.)—maize, corresponding to years 4–6 since trial establishment. After six years, soil compaction was higher in PB than in CB, particularly under the bed (44 and 27% higher in top 0.3- and 0.6-m soil layers, respectively). Around this time, maize root density at early grain filling was 17% lower in PB than in CB in the top 0.6-m layer. In DPB, the subsoiling operation was not effective in increasing root density. Nevertheless, root density appeared to maintain above-ground growth and yield in both PB and DPB compared to CB. Furthermore, at the end of the study, more soil organic carbon was stocked in PB than in CB and the difference increased significantly with a depth down to 0.5 m (5.7 Mg ha⁻¹ increment for the top 0.5-m soil layer). Residues tended to accumulate on furrows, and this resulted in spatial and temporal differences in superficial soil organic carbon concentration (SOC) in the permanent planting systems. In PB, SOC in the top 0.05-m layer increased with time faster in furrows than on beds, and reached higher stable values (1.67 vs. 1.09% values, respectively). In CB, tillage homogenized the soil and reduced SOC in the top 0.05-m layer (average stable value of 0.96% on average for beds and furrows).     

Accounting for both parameter and model structure uncertainty in crop model predictions of phenology: A case study on rice

We consider predictions of the impact of climate warming on rice development times in Sri Lanka. The major emphasis is on the uncertainty of the predictions, and in particular on the estimation of mean squared error of prediction. Three contributions to mean squared error are considered. The first is parameter uncertainty that results from model calibration. To take proper account of the complex data structure, generalized least squares is used to estimate the parameters and the variance-covariance matrix of the parameter estimators. The second contribution is model structure uncertainty, which we estimate using two different models. An ANOVA analysis is used to separate the contributions of parameter and model uncertainty to mean squared error. The third contribution is model error, which is estimated using hindcasts. Mean squared error of prediction of time from emergence to maturity, for baseline +2 °C, is estimated as 108 days², with model error contributing 86 days², followed by model structure uncertainty which contributes 15 days² and parameter uncertainty which contributes 7 days². We also show how prediction uncertainty is reduced if prediction concerns development time averaged over years, or the difference in development time between baseline and warmer temperatures.     

江淮下游不同播期对稻–麦周年作物产量、品质及温光资源利用的影响

对江淮下游稻麦两熟高产优质种植模式周年气候资源分配和利用特征的探究,可以为当地机插水稻–小麦周年产量和气候资源利用效率的提高提供一定的理论依据。在泰州兴化市,水稻季以迟熟中粳南粳9108和中熟中粳连粳11为材料,设置5月22日(R-Ⅰ)、5月29日(R-Ⅱ)和6月5日(R-Ⅲ) 3个播期,小麦季以冬小麦宁麦13为材料,设置11月5日(W-Ⅰ)、11月15日(W-Ⅱ)和11月25日(W-Ⅲ) 3个播期,分析了不同播期下机插水稻–小麦周年高产优质形成与稻季、麦季资源分配特征。结果表明,水稻季,随着播期推迟,迟熟中粳南粳9108产量、温光资源量及其生产效率均显著下降,中熟中粳连粳11温光资源量呈下降趋势,但产量及温光利用率呈先升后降趋势,各播期迟熟中粳产量均高于中熟中粳。小麦季,产量、温光资源量及其生产效率均随播期推迟有不同程度降低。从周年生产看,周年稻麦产量随两季作物播期的推迟显著降低,其中迟熟中粳南粳9108播期R-Ⅰ与小麦播期W-Ⅰ组合在所有处理中产量最高。水稻产量占周年产量比例最高为62.99%,最低为55.86%。两季间积温分配率水稻季最高为68.38%,小麦季最高为34.14%。...     

Construction and characterization of 3-S Lines, an alternative population for mapping studies in rice (Oryza sativa L.)

Most traits of agronomic importance in rice are quantitative in nature and are controlled by polygenes, called quantitative trait loci (QTL). Understanding the nature and effect of QTLs are important for rice breeding to achieve higher yield and stability. Single segment substitution lines (SSSLs or 3-S Lines) were developed through simple sequence repeats (SSR) marker-facilitated backcrossing methods for Hua-Jing-Xian 74 (HJX74) with the donor segment from six elite germplasm and was characterized. Complete genome survey was carried out with 258 polymorphic SSR markers. Polymorphism of the donors with the recurrent parent varied between 32.98 and 60.73% with an average of 47.81%. Japonica donors were more polymorphic than indica donors. Number of substitution segments per plant decreased with the advancement of backcross generations. In BC₂F_1, BC₃F₁, BC₃F₂ and BC₃F₃ the average number of substitution segment per plant were 12.5, 5.98, 1.69 and 1.46, respectively. Average size of substitution segments also decreased with the number of times plants were backcrossed and selfed. In BC₂F₁, BC₃F₁, BC₃F₂ and BC₃F_3, average size of the segments was 25.43, 22.38, 20.78 and 18.15 cM, respectively. The rate of reduction of segment size was more in backcross (11.99%) than selfing (7.15%) generations. Percent recovery of recurrent parent genome in BC₂F₁, BC₃F₁, BC₃F₂ and BC₃F₃ was 82.24, 92.55, 98.04 and 98.52%, respectively. A total of 111 SSSLs comprising of 43 unique types were developed in BC₃F₂ and BC₃F₃. The estimated length of the segments in SSSLs ranged from 2.00 to 64.80 cM with an average of 21.75 cM, and 6.05 to 48.90 cM with an average of 20.95 cM in BC₃F₂ and BC₃F₃, respectively. Total length of all substitution segments was 2367.5 cM that covered 704.50 cM (39.25%) of the entire rice genome. Effective development and successful utilization of 3-S Lines for analysis of QTLs and mapping of genes established the suitability of the SSR marker facilitated backcross breeding approach for 3-S Lines development and its utilization.     

Epistasis among the three major flowering time genes in rice: coordinate changes of photoperiod sensitivity,basic vegetative growth and optimum photoperiod

Flowering time is affected not only by photoperiod sensitivity (PS) but also by basic vegetative growth (BVG) and optimum photoperiod (OP), although their developmental and genetic relationships are not well understood. The present study was carried out in rice to examine to what extent these three developmental components are modified by the three flowering time genes, Se1 (= Hd1), Ef1 and e1 (= m-Ef1), which are known to contribute to flowering time in temperate and tropical regions of rice cultivation. Photoperiodic response curves were estimated under controlled conditions of different growth regimes, using eight near-isogenic lines possessing different combinations of the alleles at the three loci. The results showed that each of the components is greatly affected by the main effect of the genes, temperature and their epistasis, indicating that none of the three genes controls flowering time by altering any single component in PS, BVG or OP. Epistasis was detected more frequently among the three genes than reported before, suggesting that epistasis contributes to flowering time by changing PS, BVG and OP differently. The comparison of the nucleotide sequences suggested that Ef1 is the same as Early heading date 1 (Ehd1). Since the two genes Se1 (= Hd1) and Ef1 (= Ehd1) are known to up-regulate the rice homolog of Arabidopsis FT, it is suggested that the detected epistasis may respond to diverse environments by modulating the CO/FT system conserved in flowering plants.     

Identification of near-isogenic lines: an innovative approach,validated for root and shoot morphological characters in a mapping population of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Near-isogenic lines (NILs) constitute valuable tools in genetic investigations and plant breeding programs. Conventional methods for developing these are time consuming and tedious. An innovative method for identifying NILs is proposed and validated. The method involves computation of simple correlation coefficients of all possible pairs of genotypes within a mapping population using molecular marker data, and phenotypic characterization of those pairs with very high positive correlation. The pairs having both genomic and phenotypic similarity except for a single trait are considered as NILs. This strategy was tested with a doubled haploid mapping population involving CT9993 and IR62266. This population was saturated with 315 markers and comprised 154 lines. The pairs showing very high correlation coefficients (0.70–0.97) and differing for less than 10% of the markers were considered as Genotypically Closely Related Pairs (GCRPs). Graphical genotyping was employed to visualize the genome of the closely related lines. A total of 39 such pairs were subjected to rigorous evaluation for root and shoot morphological traits in two contrasting moisture regimes. Four GCRPs under well-watered condition and ten GCRPs under low moisture stress condition are statistically significant for a single phenotypic trait and are considered as NILs for their respective traits and would be the valuable materials for genetic studies. Mapped QTLs and candidate genes were employed to explain the probable cause of phenotypic difference in NILs.