The concentrations of total nitrogen and nitrate–nitrogen in yam leaves receiving various levels of nitrogen were determined fortnightly. Nitrate–nitrogen was superior to total nitrogen as an index of nitrogen nutrition. Correlation coefficients between nitrate–nitrogen at various sampling dates and rate of nitrogen application were highest between late June and early July in two seasons, indicating that this is the best time to take single samples for foliar analysis. A relation was demonstrated between nitrate–nitrogen at this period and tuber yield.

A field experiment was conducted from 1989 to 1992 to investigate the effect of sewage sludge applications on wheat yield under different irrigation regimes. The sewage sludge was applied at rates equivalent to 0, 20 or 60 t ha-1 whenever the available soil moisture reached 30 or 70%. The results showed a significant response in grain yield and its nutrient content with no significant differences between rates of sewage sludge applied. Much higher responses were obtained under the wet than under the dry regime.

Early vigour in wheat (Triticum aestivum) is an important physiological trait to improve water-use efficiency and grain yield, especially on light soils in Mediterranean-type climates. Potential interactions for plant stand and seedling vigour between seed density and various seed quality treatments were examined for wheat grown in two experiments, conducted under controlled and field environments in Western Australia. Seed lots were graded into seed size classes and seed density fractions using saturated solutions of ammonium sulphate or sodium polytungstate. Dense seed improved plant stands or produced seedlings with greater early seedling vigour than their low-density counterparts in all three field environments. Artificial ageing reduced germination and emergence in the controlled environment. When grown in the field at Merredin, Western Australia, on the sandy soil, plant development was delayed with aged seed, and total leaf area and dry weight of plants were reduced. Fungicide application diminished total plant dry weight in sandy soils, but had a much larger detrimental effect when applied to aged and low-density seeds than normal seeds, retarding development, total leaf area and total plant dry weight. Our results indicate that an increase in seed density, particularly in small seed, can potentially improve plant stand and seedling vigour independently of seed size, and may be especially important for wheat grown on sandy soils of poor fertility and low water-holding capacity. The results also suggest consistency in seedling vigour may benefit from combined screening against small seed size and low seed density, which may also reduce the likelihood of adverse reactions to seed-applied fungicides. More attention should be paid to seed density as a valuable trait for improved reliability in plant stand and seedling vigour.

Land degradation and declining productivity in the Ethiopian Highlands are primarily caused by soil fertility decline due to erosion, nutrient depletion, and soil acidity. An integrated soil fertility management (ISFM) project operating over a six-year period aimed to combat this and boost yields through participatory demonstrations. Despite high levels of yield variability expected from a farmer-managed observational study over a wide area, results show that crop yields increased with increased use of ISFM. Detailed statistical analysis using multiple linear regression models explained the contribution of individual practices. Use of improved varieties and line-seeding rather than broadcasting were consistently and highly significant. The contribution of inorganic blended fertiliser was less clear, probably due to low soil organic matter and use on acidic soils, although response to nitrogen was highly significant. The contribution of organic fertilisers was less than expected, possibly due to soil disturbance from farmer practices of multiple ploughing. Responses to crop residue management and agroforestry practices were significant on most crops reflecting their importance in improving soil water management, soil organic matter and recycling nutrients. Response to lime application on acid soils was highly significant confirming the importance of correcting acidity. Unexplained differences are attributed to the additive effects of using several ISFM treatments as well as unrecorded beneficial farmer management practices. It can be concluded that ISFM can play an essential role in improving productivity, addressing food insecurity and the challenges of climate change. Further expansion will require advocacy, awareness-raising, field-level extension and involvement of the private sector.

Mean yields and average trends with time are given for cotton, finger millet and groundnuts grown in a rotational experiment during the period 1936–64. The experiment, which ran for five cycles, involved a five-year rotation with three different resting periods, five types of resting cover, and farmyard manure at three levels. Yield trends differed from crop to crop, and a critical level of total soil nitrogen is suggested in partial explanation. Responses to farmyard manure in most crops increased over die years, with increasingly marked negative curvature in a pattern that showed most strongly in cotton crops immediately following the application of manure.

The objectives and management policy of an experimental farm for studies on the sugar beet crop are described. Farm yields of sugar beet and cereals are discussed in relation to yields in experiments and on a national scale. Some aspects of experimental accuracy and design are considered.

Ahipa is a legume of great interest for the production of raw materials (starch, sugar, oil and proteins) for industrial use. Its yield potential and ability to fix atmospheric N2 in association with rhizobia makes it an attractive option for low input agriculture systems. At present, it is cultivated on a very small scale as a food crop in a few South American countries. Little information is available on symbiotic N2 fixation in ahipa and no work has been performed on strain selection for inoculant production. Soils in southwest Europe are devoid of specific rhizobia able to nodulate on ahipa. Selecting rhizobia for symbiotic effectiveness from a collection led to the isolation of strains which provided greater shoot growth and N content under controlled conditions. In the field, inoculation at sowing with the selected strains increased significantly seed and tuberous root yield and seed protein content. The amount of N2 fixed, estimated by 15N natural abundance, reached 160–260 kg N ha−1. In previous work, ahipa appeared to be a promising alternative crop for the production of industrial raw materials. The results of the present study showed a yield increase in tuberous roots and seeds when applying effective rhizobia inoculants. Furthermore, a positive soil N balance was left after its cultivation making ahipa even more interesting for sustainable farming systems.

Phenotypic correlation coefficients of flag leaf blade length, breadth and sheath length with plant height, grain yield and its components were computed in four wheat varieties and their ten F2 crosses. Flag leaf sheath length was positively related to plant height, grain yield and its components in almost all the populations, but little or no such relation occurred with flag leaf blade length and breadth in most cases. The data suggested the possibility of selecting plants with longer flag leaf sheaths, with obvious yield advantage.

The effect of fungicides on the development of powdery mildews on cucumber and okra was studied. Most of the chemicals tested controlled the disease and significantly increased yields, though a dimethirimol-resistant Oidium sp. appeared on okra. Seed dressing with the systemic fungicides thiophanate and benomyl conferred resistance to the disease for a few days whereas soil application gave protection for more than eleven weeks.

Hybrids made for the first time on six experimental photosensitive sorghum seed parents (whose breeding is described) were tested with their pollen parents, which included good dwarf varieties, in replicated small plot trials at Samaru in 1972. Grain yields of up to 5000 kg./ha. were recorded from hybrids with acceptable plant types and grain qualities, which was 40 per cent more than from the best varieties. Some hybrids, though giving over 6000 kg./ha., were unacceptable due to excessive plant height or poor grain appearance. Seed parent yields, determined in an adjacent trial, ranged from 1700 to 2900 kg./ha.

Food security under smallholder farming can be improved through innovative intensification of cropping systems. Maize (Zea mays L.) – mungbean (Vigna radiata (L.) Wilczek) – common bean (Phaseolus vulgaris L.) sequential intercropping was studied to evaluate the patterns of radiation capture and radiation use efficiency and to determine the effects of leaf removal and row orientation on performance and intercropping efficiency. Sequential intercropping captured 1039 MJ m−2 photosynthetically active radiation (PAR) accounting for 70% of incident seasonal PAR. The corresponding sole stands for maize captured 41%, mungbean 29%, common bean 34% and mungbean–common bean 63%. Intercropped components had interception ratios of 0.98, 0.31 and 0.61 for maize, mungbean and common bean, respectively. Associated maize used intercepted light with similar efficiency, mungbean with greater efficiency and common bean with lesser efficiency compared to sole crops. Maize leaf removal and row orientation had no significant effect on performance and partial land equivalent ratio (LER) of maize. Leaf removal under East–West (EW) orientation increased grain yield by 96%, total biomass by 63%, partial LER by 92%, in common bean and total LER by 7%. Leaf removal also improved grain yield, biomass yield, partial LER, in common bean and total LER during the wetter year of 2013. Similarly, EW orientation was advantageous in 2013 raising total LER by 8%. Maize leaf removal and EW row orientation had synergistic effects on intercropping efficiency and economic benefit and both have exerted positive influence under favourable weather. Total LER values of 1.47 in 2013 and 1.29 in 2015 had revealed greater biological efficiency for intercropping during both years though it was more profitable in 2013. Thus, the cropping system can be adopted under timely onset of the rainy season using EW row orientation while leaf removal can also be practiced depending on weather conditions and convenience.

The choice of an appropriate cropping system is critical to maintaining or enhancing agricultural sustainability. Yield, profitability and water use efficiency are important factors for determining suitability of cropping systems in hot arid region. In a two-year field experiment (2009/10–2010/11) on loam sandy soils of Bikaner, India, the production potential, profitability and water use efficiency (WUE) of five cropping systems (groundnut–wheat, groundnut–isabgol, groundnut–chickpea, cluster bean–wheat and mung bean–wheat) each at six nutrient application rate (NAR) i.e. 0, 25, 50, 75, 100% recommended dose of N and P (NP) and 100% NP + S were evaluated. The cropping systems varied significantly in terms of productivity, profitability and WUEs. Averaged across nutrient application regimes, groundnut–wheat rotation gave 300–1620 kg ha−1 and 957–3365 kg ha−1 higher grain and biomass yields, respectively, than other cropping systems. The mean annual net returns were highest for the mung bean–wheat system, which returned 32–57% higher net return than other cropping systems. The mung bean–wheat and cluster bean–wheat systems had higher WUE in terms of yields than other cropping systems. The mung bean–wheat system recorded 35–63% higher WUE in monetary terms compared with other systems. Nutrients application improved yields, profit and WUEs of cropping systems. Averaged across years and cropping systems, the application of 100% NP improved grain yields, returns and WUE by 1.7, 3.9 and 1.6 times than no application of nutrients. The results suggest that the profitability and WUEs of crop production in this hot arid environment can be improved, compared with groundnut–wheat cropping, by substituting groundnut by mung bean and nutrients application.

Cowpea is an important supplement to the staple diet of maize in Zimbabwe, but its productivity is poor beacuse of pest infestations. This paper reports the results of experiments conducted over two crop seasons on the feasibility of producing a grain crop of cowpea intercropped with cotton to take advantage of cotton's slow initial growth and of drift from insecticides applied to it. Intercropping reduced the yield of cotton by between 11.5 and 73% depending on the type of season and the treatments applied, but the reduction was compensated by the yield of cowpea. The yield reduction was greater in the drier first season and with simultaneous planting of the two crops. Cowpea consistently performed better as an intercrop than as a sole crop, mainly because of the protection it received from the insecticides applied to the cotton.

In a 3-year field study with mustard (Brassica juncea L.) on deep well-drained sandy loam and loamy sand soils, 11 post-sowing irrigation schedules based on pan evaporation and growth stages were compared. One irrigation three weeks after sowing gave maximum grain yield and water use efficiency, increasing yield 40% in 1973–74 and 30% in 1976–77 compared with no irrigation. The total water use in this treatment averaged 31·2 cm, of which 15·8 cm was extracted from the 0–180 cm soil profile. Use of soil water by the crop decreased with the amount of post-sowing irrigation. More than one post-sowing irrigation tended to decrease yield and water use efficiency.

Remote sensors permit forecasting the nutrient status and yields in crops of economic importance in Colombia. The objective of this study was to determine the relationships between normalized difference vegetation index (NDVI) and yield as well as concentrations of ${\rm {N - NO}}_3^ - $ and K+ in stem sap of potato cultivars Diacol Capiro and Pastusa Suprema (Solanum tuberosum L., Group Andigenum) in relation to different fertilizer rates. Increasing doses (0, 1450, 1900 and 2375 kg ha–1) of macro- and micronutrient fertilizers were applied to determine NDVI behavior at 55, 75, 100, 125 and 150 days after planting. For Capiro, significant differences in NDVI readings (0.84–0.88) were found between phenological stages. In both cultivars, NDVI correlated positively with yield and K+ concentrations in stem sap during tuber filling and maturation, while in Capiro no correlation was established between NDVI values and ${\rm {N - NO}}_3^ - $ concentrations in stem sap. The NDVI readings could be used to forecast productivity and K status in potato Group Andigenum.

Intensification of maize production is imperative to improve food security for the rising population in the central rift valley (CRV) of Ethiopia, whose livelihood is principally based on rainfed maize that operates under shrinking landholding and high seasonal rainfall variability. This study examined different levels of intensification options in maize production by sequentially introducing minimum tillage and seed priming, phosphorus (P) fertilizer microdosing, surface mulching and nitrogen (N) fertilizer microdosing. Field experiments were conducted with five treatments, steps or levels consisting of conventional tillage (farmers practice as a control); minimum tillage + seed priming, unfertilized (step 1); step 1 + microdosing 53 kg ha−1 P (step 2); step 2 + 4 ton ha−1 maize stover as surface mulch (step 3) and step 3 + 53 kg ha−1 N (step 4). These steps represented increasing levels of intensification. Except at the lowest level (step 1), agronomic and economic responses improved with increasing levels of inputs. Relative to the very high and increasing gross margin, production costs were low but slowly increased with increasing levels of inputs. Except at the lowest level, the value cost ratio was above 4 even at the highest levels of inputs, demonstrating that such kind of intensification can be achieved with low risk. Likewise, the fertilizer use efficiency was quite high even at the highest of levels of inputs signifying the efficiency of the pocket application of fertilizer through the microdosing method. The improvement in maize establishment and yield and the reduction in the days to maturity could contribute to make maize production more adaptive to the existing seasonal rainfall variability. Depending on the affordability to the external inputs and their feasibilities, the different technology packages in the intensification ladder may give different choices for the farmers to improve maize production in the CRV of Ethiopia.

Uptake of P32 from labelled KH2PO4 solutions, injected in the top-soil at points distributed over 4000 cm.2 in the zone of high root activity, was measurable soon after application with accumulation of P32 in leaves increasing thereafter with time. The recently-acquired P32 was distributed uniformly in the tree canopies. Uptake of P32 reached a maximum when the number of injection points was increased from 15 to 30 per tree, with 45 and 60 injection points leading to little further change in P32 content of leaves. In the zone of high root activity, strip application of P32 was as efficient as application in a circle around each tree. The practical implications of these observations in relation to P-fertilization of coffee are discussed.

As part of a project to introduce Virginian-type flue-cured tobacco varieties into a new area, a number of experiments on the effect of time of planting showed that returns declined according to the delay in planting after the start of the rains. This decline was not arrested by differential fertilization, soil fumigation or the use of quicker maturing varieties. The early plantings appeared to have a greater growth potential, which could often be more fully realised under improved cultural techniques. Thus, early plantings gave substantial positive responses to applications of nitrogen which had little effect on, or were detrimental to, later plantings. It is suggested that the responses noted were linked with weather conditions during the first few weeks after planting. The drier and more sunny these were, the better, and the possibility therefore arises of using rainfall probability data, with a minimum of field experimentation, in future problems of this nature.

At Ukiriguru, in Western Tanzania, cattle often lose weight appreciably in the first few weeks of the wet season. Three levels of supplementary hay feeding, compared over this period, showed initial effects, but the final weight differences between treatments were not significant due to the effects of later compensatory growth. Differences between treatments during the weight loss and compensatory growth phases can be mainly attributed to differences in dry matter intake, rather than differences in actual body weight.