Panicle Yield Research Articles

Effect of planting density and number of seedlings per hill on certain yield and quality traits in rice

The present study was initiated for two consecutive years to find out the effect of planting density and number of seedlings per hill on certain yield and quality traits in rice. The experiment was laid out in split-split plot design with three replications as number of seedlings per hill as main plot, planting density as sub-plot and variety as sub-sub plot. It was concluded that the increase in planting density from 33 plants/m2 to 67 plants/m2 increased the milling recovery and head rice recovery in all cases. Further, milling recovery and head rice recovery significantly increased with increase in number of seedlings planted per hill from 1 to 3, suggesting that with higher number of main tillers contribute to higher milling and head rice recovery.The economic benefit for all the varieties was highest at S2D1 (2 seedlings / hill and 33 hill / m2) in all the cases, which was mainly due to optimum head rice yield and lower seed cost at this treatment. Further, maximum ear bearing tillers (EBT), fertile spikelets per panicle and grain yield was observed with one seedling / hill.

Biomass accumulation and partitioning of newly developed Green Super Rice (GSR) cultivars under drought stress during the reproductive stage

Drought is a major abiotic threat in rice production; thus, there is a need to develop adaptable rice varieties that can withstand drought stress and still produce high yield in non-stressed environments. Green Super Rice (GSR) cultivars address this issue. These cultivars are bred through an innovative introgression breeding strategy that requires less irrigation water and chemical inputs without compromising grain quality and yield. This study verified the physiological efficiency and performance of newly developed GSR cultivars that previously showed favorable response to drought during advanced yield trials. Five drought-tolerant GSR cultivars and two checks were subjected to continuously flooded (CF) and drought-stressed environments during the dry seasons of 2011 and 2012 at the International Rice Research Institute (IRRI) experimental farms in Los Baños, Philippines. The cultivars’ ability to allocate assimilates and accumulate biomass under drought stress during the reproductive stage was verified. Leaf area index (LAI), biomass dry weight, and panicle yield were measured at the panicle initiation (PI), flowering (FL), and physiological maturity (PM) of the sample cultivars. All the cultivars performed satisfactorily in the CF environment with grain yield ranging from 5 to 11.5tonsha−1. Water stress during the reproductive stage significantly reduced grain yield by 75–88% in the moderate drought (soil water tension between 100 and 300kPa in upper 15cm soil layer) and 77–96% in the severe drought (soil water tension >300kPa in upper 15cm soil layer) experiments. The shortened reproductive duration mainly contributed to the significant reduction in yield under drought stress. Two GSR cultivars, GSR IR1-5-S10-D1-D1 and IR83142-B-19-B, responded well in severe drought environments, with grain yield almost similar to the drought check (1.79tonsha−1). Under moderate drought stress, there was a relative yield advantage of 25% and 40% for the two GSR cultivars over the drought check, respectively. Yield advantage across environments, varying from fully irrigated to drought-stressed, was 31–36%. These two GSR cultivars were effective in mobilizing stored carbohydrates from the vegetative organs to the panicles and not shortening the duration from flowering to maturity, to allow all reserved carbohydrates be allocated to storage organs as a mechanism to cope with drought stress. Lower leaf area index (LAI), which allowed balanced biomass accumulation and lower transpiration, without a significant decrease in grain filling duration, was another drought-coping strategy. These physiological responses and characteristics apparently enabled the GSR cultivars to withstand drought stress; these are key indicators for varietal selection in drought-prone environments, particularly in severe drought stress in the reproductive stage. Despite the poor ability of some cultivars to cope with severe drought, three out of five selected GSR cultivars produced grain yield (2.0–2.9tonsha−1) that was the same or higher than the drought check in moderate drought stress. The introgression breeding technique applied in the newly developed drought-tolerant cultivars through the GSR breeding strategy was found to be effective. It could produce high yields in both CF and water-limited environments, and thus, it could serve as a model for other breeding programs to adopt.

Interrelationship and cause effect analysis among panicle yield attributing traits in lowland Traditional Rice

Yield component analysis provides a framework for identifying potentially useful traits for yield improvement. A field experiment was conducted for two consecutive years to evaluate the forty four low land traditional rice cultivars for twenty three panicle yield and its attributing traits during kharif season at the Zonal Adaptive Research Station, Krishnagar, Nadia, West Bengal, India. Significant varietal differences were observed for all the characters. Among the panicle yield attributing traits, number of primary branches per panicle, number of grains on primary branches panicle-1, number of spikelets on primary branches panicle-1, grain length, grain breadth, grain thickness, kernel breadth, kernel thickness, 100 grain weight, 100 kernel weight correlated significantly and positively with panicle yield both at the genotypic and phenotypic levels. Results of path analysis showed that the direct positive effect on panicle yield was greatest for number of spikelets on secondary branches panicle-1 (0.998) which is followed by number of grains on secondary branches panicle-1 (0.948), grain length (0.755), and number of spikelets on primary branches panicle-1 (0.625), grain thickness (0.392) and fertility % of spikelets on primary branches panicle-1 (0.378). Few characters like number of primary branches panicle-1, number of spikelets panicle-1, by number of grains on primary branches panicle-1 and grain breadth showed negative direct effect on panicle yield even though the genotypic correlation coefficients on panicle yield were positive. The study revealed that the direct selection of the above said traits might be rewarding for panicle yield improvement since they revealed a true relationship with the panicle yield.

태풍 “볼라벤”에 의한 벼 생육시기별 변색립 발생정도와 수량 변이

태풍 “볼라벤”에 의한 벼 생육시기별 변색립 발생정도와 수량 변이

Response of new rice for Africa (NERICA) varieties to different levels of nitrogen fertilization in Zimbabwe

The new rice for Africa (NERICA) varieties were bred and released in West Africa. This rice has high yield, good quality and other agronomic traits that include adaptability to harsh environments found in Africa. Zimbabwe, recently introduced NERICA varieties, however, the best performing NERICA varieties under local conditions were not known and the optimum level of nitrogen fertilization for those varieties was unknown. A study was carried out to evaluate the response of introduced NERICA varieties to different levels of nitrogen fertilization in Zimbabwe during the 2011/2012 summer season. A four by four factorial experiment in a randomized complete block design was used. One factor consisted of four levels of nitrogen (0, 39.5, 64.5, and 89.5 kg / ha) and the other had four varieties (NERICA 1, NERICA 3, NERICA 7 and Mhara 1). Analysis of variance showed that there was no significant interaction between nitrogen fertilization rates and varieties. However, significant nitrogen effects (P < 0.05) were found on plant height, panicle length, filled grains per panicle, unfilled grains per panicle, grains per panicle and grain yield. Grain yield for level 1 (0 kg N / ha) was significantly reduced compared to nitrogen addition, but level 2 (39.5 kg N / ha), level 3 (64.5 kg N / ha) and level 4 (89.5 kg N / ha) were not significantly different. This showed that the optimum level of nitrogen fertilization is 39.5 kg N / ha. Varieties showed significant differences (P < 0.05) for days to 50% heading, plant height, filled grains per panicle, filled grain ratio, grains per panicle, 1000 grain weight and grain yield. All NERICA varieties performed better than the local check variety, Mhara 1 and NERICA 3 had the best yield followed by NERICA 7. Growing of these NERICA varieties using the nitrogen rate of 39.5 kg / ha can boost rice yield in Zimbabwe. Key words: Upland rice, new rice for Africa, nitrogen fertilization, grain yield.

Development of a pearl millet Striga-resistant genepool: Response to five cycles of recurrent selection under Striga-infested field conditions in West Africa

Striga hermonthica (Del.) Benth. is a persistent threat to pearl millet [Cenchrus americanus (L.) Morrone, comb. nov.] production, especially in West Africa. This study aimed at evaluating the response of a diversified pearl millet genepool to five cycles of recurrent selection targeting Striga resistance and panicle yield, and to a lesser extent downy mildew [Sclerospora graminicola (Sacc.) J. Schroet.] resistance. Two-hundred full-sib families (FS) representing the C5 selection cycle were evaluated together with the genepool parental landraces, experimental varieties derived from previous cycles and local checks in Striga-infested fields at Sadoré (Niger) and Cinzana (Mali). Substantial and mostly significant selection progress could be documented. The accumulated percentage gain from selection amounted to 51%/1% lower Striga infestation (measured by area under Striga number progress curve, ASNPC), 46%/62% lower downy mildew incidence, and 49%/31% higher panicle yield of the C5-FS compared to the mean of the genepool parents at Sadoré/Cinzana, respectively. Experimental varieties selected from previous cycles also revealed lower ASNPC and mostly higher yield compared to genepool parents at their selection sites. Significant genetic variation among the C5-FS and operative heritabilities of 76% (Cinzana), 84% (Sadoré) and 34% (combined across locations) for ASNPC will enable continued selection gain for Striga resistance. High genotype×environment interaction variances for all target traits suggest that different experimental varieties need to be extracted from the genepool for different sites. The genepool-derived varieties will be further validated on-farm and are expected to contribute to integrated Striga control in pearl millet in West Africa.

A comparative screening of hybrid, modern varieties and local rice cultivar for brown leaf spot disease susceptibility and yield performance

Five rice cultivars, one hybrid (WR96), three modern (BR16, BR26, and BRRI Dhan27) and one local (Pari) were screened for reaction to brown leaf spot disease caused by Cochliobolus miyabeanus and performance of yield-related characters. The severity of brown leaf spot varied with growth stages of rice plant as well as different cultivars tested under field condition. Low disease severity was observed at maximum tillering stage compared to moderate to high at dough stage, with hybrid cultivar WR96 showing highest disease, while local cultivar Pari had the lowest. Brown spot disease severity in different cultivars under induced epiphytic condition also followed the similar trend. The results also revealed that most of the yield-contributing characters examined showed wide variations among the cultivars. Modern cultivar BR16 produced the highest panicle length, number of grain per panicle and grain yield per hectare. At the same time as local cultivar Pari generated the lowest number of tiller per plant, panicle length, grain number per panicle and grain yield per hectare. Moreover, hybrid cultivar WR96 produced the highest percentage of spotted grain per panicle and seed yielding C. miyabeanus, and also the lower percentage of seed germination, while the reverse was observed in local cultivar Pari. These findings may allow producers and breeders to select rice cultivar, resistant or tolerant to brown leaf spot disease and to avoid significant reductions in grain yields.

Agronomic and physiological responses of pearl millet ecotype (Pennisetum&lt;br&gt;glaucum (L.) R. Br.) to saline irrigation

The objective of this study was to identify morphological and physiological traits for salinity tolerance in Tunisian autochthonous ZZ pearl millet ecotype (Pennisetum glaucum (L.) R. Br) under local conditions. ZZ ecotype was cultivated under different levels of salinity and growth parameters, water relations and mineral content were measured. Results showed that ZZ pearl millet ecotype was unable to store the large amounts of salt in the leaves, while maintaining high leaf water content and without a grave consequent on panicle yield. This ecotype is fitted for a selective sodium sequestration in the vacuole.

Multivariate analysis for yield and its component traits in rice (Oryza sativaL.) under alkaline soil condition

A study was undertaken to assess the response of rice genotypes grown under alkaline soil condition using various multivariate analytical tools. ANOVA and MANOVA revealed significant differences among 33 genotypes for different traits. Principal component analysis (PCA) grouped the traits into three components, which jointly explained 67% of the total variation. Largest variation was explained by total biomass, spikelet per panicle and grain yield per panicle. When different alkalinity groups were compared in pairwise fashion using SIMPER analysis, it was found that there is no common trait to differentiate between the groups. Considering all traits together, Vikas and KMR 3 were identified as the most suitable genotypes which can be utilized as donors for tolerance to alkalinity.

Performance of Wheat and Paddy Intercropped under Casuarina Equisetifolia based Agri-Silvicultural System on Sodic Wasteland

A field experiment was conducted during rabi and kharif season, 2009-10 at main Experiment Station (Forestry), Kumarganj, Faizabad, U.P. to evaluate the performance of Wheat and Paddy intercropped under Casuarina equisetifolia based Agri-silvicultural System. The system comprises three varieties of wheat (NW-1067, NW-1014, and HD-2643) and three varieties of Paddy (Sarjoo-52, Narendra Usar-2 and Narendra Usar-3). The experiment was laid in a factorial randomized block design with three replications. . Under this study plant height and straw yield were found better for Wheat variety HD-2643 (plant height 96.00 cm and straw yield 2.47 t ha-1) and Paddy variety Narendra Usar -2 (plant height 94.33 cm and straw yield 2.41 t ha-1), when the crop was grown 1 m away from tree base. However, maximum number of per ear/ panicle, test weight (1000-grain weight) and grain yield were recorded in case of Wheat variety NW-1067 (1.26 t ha-1) and Paddy variety Narendra Usar-2 (1.65 t ha-1), when the crop was grown in open area. Amongst different varieties, Wheat variety NW-1067 and Paddy variety Narendra Usar-2 were found better for cultivation under this study.

Discovery of QTLs increasing yield related traits in common wild rice

Common wild rice (Oryza rufipogon) is an important genetic resource. Discovery of desirable alleles in wild rice will make important contributions to rice genetic improvement. In this study, Zhenshan 97 as the recurrent parent and wild rice as the donor parent were used to develop a BC2F1 population. One plant BC2F1-15 in the population showed distinct phenotype from Zhenshan 97 was selected to produce a population of BC2F5 by continuous self-crossing. The genotype assay of the plant BC2F1-15 with 126 polymorphic SSR markers evenly distributed on 12 chromosomes showed that it was heterozygous at 30% of the control marker loci. Four, 3, 4, 2, and 1 QTLs were detected for heading date, plant height, spikelets per panicle, grain weight, and single plant yield in the BC2F5 population, respectively. One QTL region flanked by the marker interval of RM481-RM2 on chromosome 7 had pleiotropic effects on heading date, spikelets per panicle, and grain yield per plant, and the alleles of wild rice increased phenotypic values. At the other 3 QTLs for spikelets per panicle, common wild rice had positive effects. These results clearly showed that common wild rice carried desirable alleles for yield related traits. The favorable alleles from common wild rice are new valuable genes for rice breeding.

Studies on Variability and Interrelationship of Panicle Components and Their Association with Grain Yield in Traditional Rice

Forty four lowland traditional rice genotypes were evaluated during kharif season of 2009-10 at Zonal Adaptive Research Station, Krishnagar, Nadia, West Bengal for 23 panicle yield and its attributing traits. Significant varietal differences were observed for all the characters. The GCV was less than PCV for all the characters indicating considerable influence of the environment on their expression. High GCV and PCV were observed for number of grains on secondary branches panicle, number of spikelets on secondary branches panicle, 100 grain weight, 100 kernel weight, panicle yield, number of secondary branches panicle and number of spikelets panicle whereas, the remaining characters expressed low to medium GCV. High heritability along with high genetic advance as percentage of mean were exhibited by number of spikelets on secondary branches panicle, number of grains on secondary branches panicle, 100 grain weight, 100 kernel weight and panicle yield indicating their control by additive gene action and chances of further improvement by selection. Among the panicle yield attributing traits, number of primary branches per panicle, number of grains on primary branches panicle, number of spikelets on primary branches panicle, grain length, grain breadth, grain thickness, kernel breadth, kernel thickness, 100 grain weight, 100 kernel weight correlated significantly and positively with panicle yield both at the genotypic and phenotypic levels whereas, high significant and positive genotypic and phenotypic association revealed between number of secondary branches panicle and number of spikelet panicle, number of spikelets on secondary branches panicle and number of grains on secondary branches panicle.

Combining Ability for Yield and its Components in Ethiopian Sorghum (&lt;i&gt;Sorghum bicolor&lt;/i&gt; (L.) Moench) Landraces

Crossing sorghum [Sorghum bicolor (L.) Moench] obtained from different areas of Ethiopia were done in 2004/05 cropping season. In 2005/06 evaluation of 15 F1s with their parents were done in a randomized complete block design with three replications at Bako. The study was conducted to estimate combining ability and determine type of gene actions involved in the inheritance of yield and yield components traits. Analysis of variance revealed that mean squares due to genotypes, parents and crosses were highly significant (P<0.01) for all the traits except for 100 kernel weight that were significant for crosses. Mean squares due to general combining ability (GCA) and specific combining ability (SCA) were highly significant for all characters studied, except non significant SCA for 100 kernel weight. For yield, three of the parents, 212646, 69543 and 69193 had the best general combiner and incorporating these parents for grain yield per panicle in sorghum breeding may be importatnt. Based on specific combining ability analysis for grain yield per panicle five hybrids 69543 x 223506, 212646 x 223506, 97MW5122 x 212646, 97MW5122 x 69543 and 212646 x 69193 were the best in the experiment. The estimate of variance components showed that the variance due to SCA was higher in magnitude than GCA in the case of days to maturity, panicle width, panicle weight, kernel number per panicle and grain yield. Therefore, these traits were predominantly under the control of non-additive type of gene actions. Whereas variance of GCA was higher than SCA in the case of days to flowering, plant height, leaf number per plant, leaf length, leaf width, leaf area, panicle length and 100 kernel weight indicating that additive type of gene action was playing a greater role in the inheritance of these traits. Keywords: Combining Ability; Diallel; Gene Action; Sorghum bicolor

Fine Mapping of qPAA8, a Gene Controlling Panicle Apical Development in Rice

In rice, one detrimental factor influencing single panicle yield is the frequent occurrence of panicle apical abortion (PAA) under unfavorable climatic conditions. Until now, no detailed genetic information has been available to avoid PAA in rice breeding. Here, we show that the occurrence of PAA is associated with the accumulation of excess hydrogen peroxide. Quantitative trait loci (QTLs) mapping for PAA in an F(2) population derived from the cross of L-05261 (PAA line) × IRAT129 (non-PAA variety) identified seven QTLs over a logarithm of the odd (LOD) threshold of 2.5, explaining approximately 50.1% of phenotypic variance for PAA in total. Five of the QTLs with an increased effect from L-05261, were designated as qPAA3-1, qPAA3-2, qPAA4, qPAA5 and qPAA8, and accounted for 6.8%, 5.9%, 4.2%, 13.0% and 12.2% of phenotypic variance, respectively. We found that the PAA in the early heading plants was mainly controlled by qPAA8. Subsequently, using the sub-populations specific for qPAA8 based on marker-assisted selection, we further narrowed qPAA8 to a 37.6-kb interval delimited by markers RM22475 and 8-In112. These results are beneficial for PAA gene clone.

Comportamento de genótipos de arroz de terras altas na Zona da Mata de Pernambuco

Avaliou-se, neste estudo, o comportamento de 12 genótipos de arroz de terras altas na Zona da Mata de Pernambuco quanto a caracteres de importância agronômica. Utilizou-se o delineamento de blocos ao acaso, com 4 repetições, parcelas constituídas de 5 linhas de 4 m e espaçamento de 0,50 m. Os experimentos foram conduzidos no ano agrícola de 2006, entre os meses de abril e agosto, nos municípios de Palmares e Vitória de Santo Antão. Dentre os caracteres avaliados verificaram-se diferenças significativas entre os genótipos para os caracteres: altura de planta, acamamento, ciclo de florescimento e de maturação, perfilhamento médio, comprimento de panículas, peso de mil grãos e rendimento de grãos inteiros. A interação genótipo x ambiente foi significativa para os caracteres altura de planta, ciclo de florescimento e percentual de espiguetas estéreis. Os genótipos Bonança, BRA 1506, CNAs 9045 e BRSMG curinga, apresentaram os melhores comportamentos para os caracteres: altura da planta, acamamento, ciclo de florescimento e de maturação, além de bom perfilhamento e médio rendimento e, portanto, são os mais promissores a serem recomendados para o plantio na referida região, especificamente no período entre os meses de abril a julho.

PHOSPHORUS COATING ON PEARL MILLET SEED IN LOW P ALFISOL IMPROVES PLANT ESTABLISHMENT AND INCREASES STOVER MORE THAN SEED YIELD

SUMMARYPhosphorus (P) is one of the main limiting nutrients in the semi-arid regions where pearl millet is grown; its deficiency leads to poor seedling establishment and eventually poor crop yield. Experiments were carried out in pots and field-like conditions to evaluate the effect of seed priming and seed coating with P on the shoot biomass at two and four weeks after sowing (WAS), and on the panicle and stover yield at maturity of three hybrid varieties of pearl millet in low P Alfisol. Overall, seed priming did not increase shoot biomass at two and four WAS. In pots, seed coating at a rate of approximately 400 g P ha−1 increased vegetative biomass over 400% at early stages, and panicle yield by about 50%, over the non-coated treatment, with genotypic variation in the magnitude of the response. In field-like conditions, seed coating restored stover biomass to 85–100% of that in the non-limiting P treatment, whereas the panicle yield remained 25–35% lower than in the non-limiting P treatment, but still 45–65% higher than the non-coated treatment. P deficiency delayed the time to flowering by 20–24 days compared to the non-limiting P treatment, but plants in the seed coating treatment reduced that gap by 10–14 days. Seed P coating treatment appears a valid option to promote pearl millet seedling establishment and then to boost yield under low soil P conditions. The maintenance of an effect of seed coating on panicle yield in pots suggests a positive early effect on developmental processes before panicle initiation.

Effects of Nitrogen Nutrition on Grain Yield of Upland Rice and Paddy Rice under Different Cultivation Methods

Upland rice and dry-cultivated paddy rice have been attracted more and more attention because of limited water re- sources in China. Researches on interaction between water and nitrogen supplies for crop resistance to drought stress has become the hot topic regarding regulation on nutritional physiology. However, there is little information available on effect of nitrogen (N) nutrition on grain yield and its components of upland rice and paddy rice under different cultivation methods. The objective of this study was to evaluate the difference between upland rice and paddy rice and interaction between cultivation methods and N levels. One upland rice cultivar Zhonghan 3 (japonica) and one paddy rice cultivar Yangjing 9538 (japonica) were grown under moist cultivation (MC, control) or bare dry-cultivation (DC) with three N levels, low amount of N (LN, 100 kg ha-1), normal amount of N (NN, 200 kg ha-1), and high amount of N (HN, 300 kg ha-1). The results showed that, compared with NN, the grain yield under HN was lower for both upland and paddy rice under DC and for paddy rice under MC, whereas higher for upland rice under MC. With the increase in N levels, upland rice and paddy rice showed higher productive tillers, more or fewer spikelets per panicle, lower percentage of ripened grains under two cultivation methods. However, the percentage of ripened grains was reduced more for paddy rice than for upland rice. There was no significant difference in 1 000-grain weight for upland rice among three N levels, whereas grain weight was reduced with the increase in N levels. Compared with MC, DC showed no significant difference in grain weight for upland rice, whereas a significant decrease for paddy rice. DC significantly increased the percentage of ripened grains for both upland and paddy rice, and that were more for upland rice than for paddy rice. Compared with paddy rice, upland rice showed less number of adventitious roots, lower nitrogen absorption ability and lower productive tillering ability, fewer pani- cles, fewer spikelets per panicle and lower grain yield. However, upland rice exhibited quicker increase in adventitious roots and slower declining in leaf nitrogen content from jointing to heading, and a faster declining speed in chlorophyll content (SPAD value) after flowering. Also, upland rice had less negative response to water stress and more positive response to N. The results suggest that the response to cultivation methods and N levels varies largely between upland rice and paddy rice. The approaches to in- crease the grain yield of both paddy and upland rice were discussed.

Trees to control weeds in pearl millet

This study shows that growing trees represents a sustainable and efficient alternative to control weeds in millet. A survey was conducted on farmers’ fields in September 1998 at the end of the rainy season in Maiduguri in the semi-arid zone of Nigeria to assess the potential of the Faidherbia albida tree for the control of the Striga hermonthica weed in millet. A random survey was carried out in four locations on the farmers’ fields. The results show that F. albida trees could completely control S. hermonthica weeds occuring in millet under the tree canopy. Indeed, no single Striga emergence was observed under all trees surveyed, while the adjacent crops outside the tree canopies were seriously infested with S. hermonthica, causing reduction in plant growth of 76.5%, panicle length of 23.8% and millet panicle yield of 171.3%. Furthermore, plant performance under the tree canopies was very high, as plant height was increased by 80.0%, stem diameter by up to 15.9%, panicle length by 34.4% and panicle yield by 298.6% as compared with the Striga-infested plants outside the tree canopy. Plants within the 6–15 m area away from the tree trunk performed better than the 0–5 m area. The implication of these results in relation to Striga control in the semi-arid region of West Africa is discussed.

Resposta de cultivares de arroz a doses de nitrogênio e do regulador de crescimento cloreto de clormequat

O objetivo deste trabalho foi avaliar os efeitos de doses de nitrogênio (0, 50, 100 e 150 kg ha-1) e do regulador de crescimento cloreto de clormequat (0, 1 e 2 L ha-1), em algumas características agronômicas de cultivares de arroz IAC 201 e IAC 202. O delineamento experimental foi o de blocos ao acaso, com quatro repetições. O N foi aplicado em cobertura, no estádio da diferenciação floral, e o regulador de crescimento foi aplicado parceladamente, aos 20 e 30 dias após a emergência das plântulas de arroz (perfilhamento). Na safra 2001/2002, houve efeito significativo de N para altura de plantas, comprimento da panícula, espiguetas por panícula, massa de 100 grãos e produtividade de grãos. Houve efeito do regulador de crescimento sobre o comprimento da panícula e espiguetas por panícula. A maior produtividade foi a da cultivar IAC 202. Na safra 2002/2003, houve efeito de N para altura de plantas, massa de 100 grãos, fertilidade das espiguetas e produtividade de grãos. O regulador de crescimento não exerceu efeito nas características testadas, e a cultivar IAC 202 foi novamente a mais produtiva.

Effects of timing of nitrogen and sulphur fertilizers on yield, nitrogen, and sulphur contents of Tef (Eragrostis tef (Zucc.) Trotter)

Nitrogen use efficiency (NUE) of tef, a major staple crop in Ethiopia, is very low, either caused by untimely use of nitrogen (N) fertilizers or lack of other essential nutrients like sulphur (S). The average grain yield of this crop is low, averaging <0.8 Mg ha−1 in farmer’s fields of the semi-arid conditions. Therefore, the present study was conducted to see the effect of the timing of combined N and S fertilization on the yield, yield components, and N and S concentration in the plant parts of the crop. A factorial combination of three rates of N (0, 70, and 105 kg ha−1) with four rates of S (0, 16, 32, and 48 kg ha−1) was applied in randomized complete blocks in three replications. The experiment was carried out in the 2004 and 2005 cropping seasons in the Cambisols of the semi-arid area of Ethiopia. The crop responded significantly (P < 0.05) to both split (one-third at planting and two-thirds at late tillering) and whole (all at planting) N and S applications and years. Combined N and S fertilization increased the dry matter (DM) and grain yields on average by 1.7 and 0.3 Mg ha−1, compared with the control. Similarly, S fertilization increased the NUE of the tef crop by 36%. Nitrogen concentration of shoots was found to significantly increase with S application (P < 0.05), with strong positive interactions both in the split and whole applications. The sulphur increase in grains was significant with N rates for both applications, with significant interaction effects observed for the split application in both cropping seasons. Split application resulted in 0.9 and 0.3 Mg ha−1 significant increase in DM and grain yields, averaged for both years and treatments compared with the whole application. Similar significant increases were observed for panicle yield, NUE, and shoot and grain N and S concentrations. The average N:S ratio in grains was 10.6:1. Significant (P < 0.05) yearly variations were also observed. Dry matter and grain yields of 2005 were higher on average by 2.10 and 0.32 Mg ha−1 than those of the 2004 cropping season. The percentage of N and S concentrations of grains, averaged for both applications, were higher by 13 and 9% in 2004; even though the N and S uptakes of 2005 were higher on average by 5.0 and 0.5 kg ha−1 than those of the 2004 cropping season. This work showed that the yield response and NUE of the tef crop could be improved with split N and S fertilizer applications, with tef-producing farmers benefitting from the application of S-containing N fertilizers to soils deficient in these nutrients.