The productivity of each component of a sorghum/groundnut intercrop and its constituent sole crops is determined in terms of a ‘Crop Performance Ratio’ (CPR) defined as the productivity of an intercrop per unit area of ground compared with that expected from sole crops sown in the same proportions. The CPR allows productivity, intercepted radiation and seasonal transpiration to be compared so that conversion coefficients for radiation (e; g MJ−1) and dry matter/water ratios (q; g kg−1) can be calculated for each intercrop component and its constituent sole crops. In this experiment, CPR for total dry weight in the intercrop was 1.08 and that for reproductive yield was 1.27. These advantages in overall productivity and yield were typical of those reported elsewhere for sorghum/groundnut intercrops. The proportional increase in total dry matter in the intercrop was largely a result of its greater interception of radiation. The further advantage in reproductive yield was a consequence of an improved harvest index in the sorghum component of the intercrop (0.64) compared with that of its sole crop counterpart (0.55).

The effect of one, two or three applications of monocrotophos at 1120 g ai/ha at weekly intervals was determined on cowpea var. Ife Brown. All regimes were equally effective in grain production in early 1974 but spray applications 35 and 42 days after planting gave the best result in the late crop. Grain production from two applications was not significantly different from three applications in 1975. The control plots in the late season of both years failed, due to moisture stress and lack of pest control measures. It is considered that two sprays at flowering is adequate to forestall a crop failure in this variety.

Limited information is available concerning the influence of nitrogen fertilization jointly on yield response, nitrogen use efficiency (NUE) and grain quality of durum wheat under semi-arid Mediterranean conditions. The study focused on evaluating, through a systematic study, over three seasons in southern Italy the effects of three nitrogen fertilization rates (0, 80 and 160 kg N ha−1 – N0, N80 and N160), on grain yield, yield components, nitrogen efficiency indices and grain quality characteristics of three durum wheat genotypes (‘Creso’, ‘Trinakria’ and ‘Line 25’) from different breeding eras to achieve a more sustainable fertilization management of the durum wheat crop. We found that nitrogen fertilization at 80 kg N ha−1 was able to maximize the yield performances (2.1 t ha−1 year–1) of the crop and keep NUE index at an acceptable level (16.3 kg kg−1). On the other hand, nitrogen fertilization at 160 kg N ha−1 improved grain quality measured through protein (up to 14.3%) and dry gluten concentration (up to 12.8%), but had a detrimental effect on grain yield and nitrogen efficiency. Among the genotypes studied, ‘Trinakria’ showed the greatest potential to utilize nitrogen fertilization to improve grain yield and NUE (at N80) and quality (at N160), ‘Line 25’ made good use of N80 both for yield and quality, whereas ‘Creso’ proved wholly unresponsive to nitrogen. The effect of N fertilization on grain yield and N use efficiency depends on rainfall distribution, giving the best results when about 80% of total rainfall occurred from sowing to heading. Overall, our data show that in seasons with regular rainfall in quantity and distribution, combining no more than 80 kg ha−1 of nitrogen fertilization with genotypes characterized by a more efficient response to nitrogen, is a useful tool to improve the agronomic and quality performance of the crop, ensuring, at the same time, a more environment-friendly nitrogen fertilization.

Bambara groundnut (Vigna subterranea) is one of the most promising food legumes in Africa, due to its agronomic and nutritional potential. To take advantage of these attributes, several research programmes gathering agronomic and genetic data are being implemented throughout Africa. In this context, the response of yield and yield components to sowing density and seedbed type were tested in a three-year (2005, 2006 and 2007) field experiment using a bambara groundnut landrace with a semi-bunch growth habit. Three plant population densities: 13 900 plants ha−1, 62 500 plants ha−1 and 250 000 plants ha−1 were coupled with two seedbed types – raised and flat. A factorial trial using a split-plot design with three replicates was set up to analyse seed yield and plant biomass, as well as nine yield components. Sowing density influenced significantly (p < 0.05) seed yield (direct relationship) and most of the yield components (inverse relationship). The highest seed yields were observed on high-density plots (4.11 ± 1.05 ha−1). In contrast, seedbed type and year of experiment did not influence significantly the marketable yield and plant biomass (p > 0.05). This result has been attributed to the suitability of the amount and distribution of rainfall and temperature for the production of bambara groundnut at the target site. Based on the trend of yield response, cultivation of landraces of bambara groundnut characterized by a semi-bunch growth habit at high density on flat seedbeds was suggested in woodland savannas of Côte d'Ivoire to enhance seeds yield and reduce labour.

Groundnuts given a mixture of S35-labelled ground rock phosphate and sulphur at planting were radioactive 14 days later, when go per cent of the seedlings had emerged. Forty days after planting one-third of the total plant-S was from the fertilizer, and the mean recovery of fertilizer-S was 18 per cent by harvest. In field experiments the mixture outyielded ground rock phosphate and was as good as single superphosphate, though drought diminished yields generally. At three sites which were harvested the percentages of applied-S recovered were 12, 20 and 27 per cent. Significantly more P was taken up by the crop receiving the mixture than was recovered from the ground rock phosphate alone.

The efficiency of many intercropping research programmes could be improved if research workers made fuller use of modern statistical knowledge about experimental design. Important statistical considerations for experimental design and plot sampling are reviewed and their relevance to intercropping research assessed. The general philosophy of factorial structure and blocking, and specific ideas on the use of systematic designs and monocrop plots, are discussed.

The yield responses of clonal tea (Clone 6/8) to irrigation and fertilizer were studied in a field experiment (based on the line-source technique) at a high altitude site (1840 m) in the Southern Highlands of Tanzania over a three-year period. In this area (latitude 8°33′S) the annual dry season can last up to six months with potential soil water deficits reaching 600 to 700 mm. In the third year of the experiments yields for the fully irrigated, well fertilized (375 kg N ha−1) treatments had reached 4.9 t ha−1 of made tea. These were reduced by about 2.9 kg ha−1 for each mm increase in the potential soil water deficit. For tea with little or no fertilizer applied the loss of yield was about 1.4 kg ha−1 mm−1. These figures provide a basis for assessing the potential benefits from irrigation where other factors, such as large saturation deficits of the air, do not restrict shoot extension and yield. Yield responses to nitrogen (applied as N:P:K 20:10:10) were essentially linear up to a maximum of about 375 kg N ha−1 in the fully irrigated plots, and 300 kg N ha−1 for the unirrigated plots. Irrigation increased the proportion of crop harvested during the dry season, up to 45% in the fully irrigated treatments. The commercial implications of these results for ‘high’ and ‘low’ input producers are discussed.

Family farming in the tropics suffers from low crop productivity mainly due to a combination of poor soil fertility, low investment capacity, and a variable climate. The Lake Alaotra region of Madagascar is no exception and rainfed production is particularly hard hit. To evaluate the agronomic benefits of conservation agriculture (CA) in a region of erratic rainfall, we analysed four years of yield, management and climatic data from 3803 upland rice fields cultivated by farmers and monitored by researchers. Fields located on rainfed lowlands and hillsides were cultivated with sole rice using conventional tillage (Cv) or rice sown with no-tillage on dead organic mulch and rotated with other cereal/legume combinations (CA) from 2006 to 2011. A first global comparison across seasons, locations and years of adoption showed significantly higher average yields under CA, with no change in variance (on lowland: 2.6 ± 0.9 t ha–1 Cv, 2.8 ± 0.9 t ha–1 CA; on hillside: 2.1 ± 0.8 t ha–1 Cv, 2.4 ± 0.8 t ha–1 CA). Grouping fields according to the number of years under CA (first to fourth) revealed that CA gradually increased average yields and reduced the coefficient of variation in the short and mid-term (on lowland: +0.2 t ha–1 and –6% coefficient of variation; on hillside: +0.7 t ha–1 and –13% coefficient of variation, over four to six years of successive CA cropping). The average yield increase under CA was not associated with an increase in mineral fertiliser use, as farmers used the same amounts of fertilisers (or none) under Cv and CA. The comparison Cv versus CA also highlighted a major benefit of CA regarding climate: it widened the window of possible sowing dates. A classification and regression tree analysis of the entire dataset revealed that rice yield was more affected by agro-environmental factors than management factors (fertilisation, Cv or CA), and extreme climate variability such as the severe drought of 2007–2008 could not be offset by CA. The hypothesis of yield penalties during the first years of implementation of CA cannot be verified with the evidence presented in this study.

This study investigated the effects of harvesting at different plant maturation stages on the yield and component compositions of aniseed. It was carried out on the Harran Plain (Sanliurfa, Turkey) in the 2002 and 2003 growing seasons. A randomized complete block design was used. The plants were harvested at 10 different growth stages and determinations were made of the yields of seed, the essential oil and its main component (E)-anethole, the weight of 1000 seeds, the number of umbels per plant, the number of seedless umbels per plant and number of seeds per umbel. Statistical analyses indicated that all properties studied were affected by the harvesting stage. The fourth harvesting stage gave the highest yields of seed, essential oil and (E)-anethole. The first and second harvesting stages provided the best quality of essential oils with a high (E)-anethole content.

Potato is an important source of food and income in the highlands of East Africa. Identification of superior genotypes for improved agronomic characteristics will enhance tuber yield. Seven promising clones from population B potato selections (quantitative resistance to late blight) obtained from the International Potato Center, two genotypes from population A (qualitative resistance) and three control cultivars were evaluated for three cropping seasons at four locations in western Uganda in order to determine performance and yield stability. The additive main effects and multiplicative interactive (AMMI) model was used for the analysis. The analysis of variance of yield data for genotypes × locations, genotypes × seasons and genotypes × locations × seasons was significant (p < 0.05) showing the variable response of genotypes and the need for stability analysis. The AMMI statistical model showed that the most stable genotypes were 392618.250 (B5) and 392127.270 (B6) (high yield) and 392618.256 (B1), 391049.255 (B2) and 392127.256 (B7) (low yield) and had negligible interactions with the environments. Across environments, the ranking of genotypes for tuber yield was not consistent. The clones 381471.18 (A2), 387121.4 (A1) and cultivar Victoria had high average yields, but these yields were below average in a few environments. Selective deployment of cultivars can improve tuber yield in the highland tropics.

Note: Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation for endorsement by the US Department of Agriculture, Makerere University or Kachwekano Agricultural Research and Development Center.

Enset [Ensete ventricosum (Welw.) Cheesman (Musaceae)] is a multi-purpose and drought-tolerant crop, traditionally grown in Ethiopia. Food from enset has nutritive values similar to potato; it could improve food and livelihood security for many in larger geographical areas. Agronomical advice is needed which requires increased knowledge of management techniques. The purposes of this study were to (i) compare traditional corm pre-treatments when planting for sucker production, (ii) compare all six officially released cultivars regarding sprouting and (iii) investigate the effect of watering on newly buried corms. Emergence rate and number and characteristics of sprouts were recorded. Corms, from 63 two year old plants, were buried in local soil supplied with cow manure in Wolaita Sodo, Ethiopia. Emergence was recorded daily. After nine months, including one rainy season, all suckers (totally 4405) were harvested and individually recorded. Regardless of cultivar, minimum time to emergence was 50 days. Sprouts from split parent corms emerged earlier than from entire. Emergence occurred from 100% of corms, number of sprouts was strongly correlated to cultivar: average 28–106. The cultivars responded similarly to corm splitting: the more pieces the corm was split into, the more sprouts per parent corm. Average pseudostem diameter of the seven largest per parent corm: 8–10 cm for all cultivars, leaf length: 3.1–3.7 m, remaining 2700 smaller suckers: diameter 3 cm (SD 1.8). Watering decreased the average time to emergence and levelled out the differences between pre-treatments. The traditional belief is that watering as well as manure on corm cause rotting; manure is therefore usually put on the soil surface. On the contrary, full emergence and unexpected large suckers may be a result of careful soil preparation with manure applied on corm directly; watering resulted in an even emergence and growth. In conclusion, vegetative propagation of enset is efficient, but methods used and agronomical advice can be improved.

The effect of simulated drought on the germination of Striga hermonthica and Alectra vogelii was studied in growth cabinets. Drought stress was applied either during the preconditioning of the seeds or at the time of application of the germination stimulant. The response of these weeds to a range of alternating day/night temperatures during germination and their attachment to the host plant was also investigated using root chambers. During the preconditioning period S. hermonthica was not sensitive to variation in osmotic potential between 0 and −1.5 MPa but A. vogelii required longer preconditioning periods at −1.2 and −1.5 MPa. The germination of both parasites was significantly reduced by increasing the osmotic potential of the stimulant. Optimum day/night temperatures for germination and attachment of S. hermonthica were 30/20° and 35/25°C, and of A. vogelii 25/15° and 30/20°C. Deviation in temperature from the optimum significantly reduced the germination and attachment of both parasites. The results show that S. hermonthica is more adaptive to adverse climatic conditions of increased osmotic potential and extreme temperatures than A. vogelii.

Efecto de la sequia y la temperatura en malezas parasiticas

Most plants prefer nitrate (NO3−–N) to ammonium (NH4+–N). However, high NO3−–N in soil and water systems is a cause of concern for human health and the environment. Replacing NO3−–N in plant nutrition regimes with an appropriate amount of NH4+–N may alleviate these concerns. The purpose of this study was to evaluate the effects of different NH4+–N/NO3−–N ratios on chlorophyll content, stomatal conductance, Rubisco activity, net photosynthetic rate, dry matter yield and NO3−–N accumulation in spinach grown hydroponically. The NH4+–N/NO3−–N percentage ratios were 0:100 (control), 25:75, 50:50, 75:25 and 100:0. Chlorophyll a and b, total chlorophyll, stomatal conductance, initial activity and activation state of Rubisco and net photosynthetic rate in spinach leaves were all reduced by increased NH4+–N/NO3−–N ratios. Significant correlation existed between these measurements. However, no statistical differences in dry matter yield were revealed between the 0:100 and 25:75 treatments. Leaf nitrate concentrations were reduced by 38% at the 25:75 treatment relative to the 0:100 treatment. These findings suggest that lowering the relative proportion of NO3−–N in fertilizer could effectively reduce NO3−–N contents in leafy vegetables without decreasing their yields.

There is a quest for resource-conserving technologies that can save water, reduce production costs and improve production to address the slow down in productivity growth in the Indo-Gangetic Plains, the cereal bowl of South Asia. Findings from farm surveys are used to evaluate the farm household factors that affect the adoption of zero tillage (ZT) wheat in the rice-wheat systems of India's Haryana State and Pakistan's Punjab province. Three adoption classes are distinguished in each site: ZT adopters, dis-adopters and non-adopters. Bivariate analysis shows that adopters typically have the most favourable values for most of the indicators compiled and the non-adopters the least favourable, with dis-adopters often taking an intermediate position. The study highlights that ZT adoption in the initial diffusion stage is strongly linked to the wealth of the farm household. This indicates the need for closer consideration of equity implications in future research and development. The structural differences between adoption categories also easily confound the assessment of ZT impact.

Date palm is a crop suited to hot, arid regions. It originated in Mesopotamia and the centres of production are in West Asia and North Africa. Despite its regional and international importance, and its dependence on irrigation or a shallow water table for survival, relatively little research has been published on the water relations and irrigation need of date palm. Following early work in California, the majority of the recent research reported in the literature has been conducted in Saudi Arabia and Tunisia. The date palm has a terminal crown of 100–120 leaves. At the base of each leaf is an axillary bud, most of which develop in the winter as flower buds. It takes 150–200 days from pollination to fruit maturity. Stomata occur on both leaf surfaces. Different techniques have been used to measure the water use of date palm, including micrometeorological and sap flow methods. In Syria, mean actual evapotranspiration rates varied between 0.5 mm d−1 (winter) and 3.5 mm d−1 (summer), in Saudi Arabia from 2–3 to 8–11 mm d−1 depending on location and in Jordan from 2 to 8–10 mm d−1 respectively. In Tunisia, there was some (limited) evidence of stomatal control of transpiration rates (seasonal range 0.5 to 3.5 mm d−1) when temperatures exceeded 32 °C. Experimentally determined values of the crop coefficient were inconsistent, varying from 0.6–0.7 to 1.18. In the vicinity of an oasis, advection may increase potential water use substantially above that of a reference crop. In the absence of a shallow water table, roots can extract water from soil depths greater than 2 m. There is little published information on the water productivity of date palm. A target benchmark figure is probably about 1.3-kg fresh fruit m−3 of irrigation water applied. Under controlled conditions, phenotypes differed in their responses to water stress. The date palm is traditionally considered to be relatively salt-tolerant, with a threshold electrical conductivity value for the saturated soil extract of 4.0 dS m−1, but recent evidence from Israel suggests that this view may be mistaken. Since early times, flood irrigation has been used to irrigate date palm and it is still probably the most common method in many countries. Since the 1980s, farmers have been encouraged by governments to use localised irrigation methods (e.g. micro-sprinklers, drip and bubbler) as a means of saving water. Since water is a scarce resource in the West Asia and North Africa region, research should focus on developing ways to improve the water productivity of this high value crop.

The line-source sprinkler irrigation system provides a continuously variable water application rate, which depends on distance from the line-source. The system is simple to set up and minimizes the amount of land required for experimental work. As the irrigation treatments are allocated systematically, the assumptions of analysis of variance are not satisfied. It is proposed that the effects of irrigation treatments be assessed using analysis of covariance, with distance from the sprinkler line as covariate, thus adjusting for a linear fertility trend. This method of analysis provides an approximate residual mean square for the fitting of response curves, but could be vulnerable to a quadratic fertility trend.

In a short-term competition experiment in large containers, growth of cotton planted 3 weeks after bermudagrass (Cynodon dactylon), johnsongrass (Sorghum halepense) or purple nutsedge (Cyperus rotundus), was severely reduced; after 10 weeks of competition, weedy cotton weighed only 15 per cent of the weed-free control. Cotton sown before weeds, or weeds planted before cotton, were only slightly affected by competition. Highly significant negative correlations were found between growth parameters of cotton and weeds. Inhibiting effects, and in some cases transitory stimulation, were produced on mustard seedlings by leachate from weed-infested soil and by extracts from subterranean weed parts, suggesting that the competitive effects of perennial weeds are due to nutrient depletion and to biologically active substances.

A simple Stress Time Index (STI) for predicting yield loss in the tea crop due to drought is proposed, based on the daily summation of the difference between the potential soil water deficit and a specified limiting value. Validation of the technique with results from a line-source irrigation experiment with a single clone in the Southern Highlands of Tanzania suggests that there is a linear relationship between STI and relative yield loss during the warm dry season. As a result of changes in the composition of the shoot population at each harvest the apparent critical deficit at which shoot growth is restricted increases from below 20 to 300 mm as the dry season progresses. The rate of yield loss with increasing STI also varies through the dry season for the same reason.

Forty different cultivars of cassava were grown in unreplicated plots at a plant population of 20,000 plants/ha in fertile soil. Harvests were taken at 4, 6, 8, 10 and 12 months after planting 18 varieties. The characteristics of the two highest yielding varieties, M Colombia 113 (66 t/ha) and M Colombia 22 (32 t/ha), were compared with the other types. M Colombia 22 is an early type (25 t/ha after 6 months) with a very high harvest index; M Colombia 113 yields little better than average 6 months after planting. High yield is associated with a balance between leaf production and root production, so that leaf area index does not decline excessively in the later growth stages. Changing canopy structure is unlikely to increase yields.