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Crop Production

1.Effect of inorganic nitrogen fertilizer rates and plant populations on maize productivity in the Eastern Cape:
Authored by Musunda BZ, Mutengwa CS, Chiduza C and Muchaonyerwa P (2012): corresponding author
cmutengwa@ufh.ac.za

INTRODUCTION

 Maize is the most important summer crop in the smallholder farming areas of the Eastern Cape (EC). However, its productivity is very low with average yields of less than 1 t ha-1. Low and variable rainfall is a major limiting factor to maize production. The soils in the EC are also inherently infertile, shallow and are prone to crusting. Improved open pollinated varieties (OPVs) from CIMMYT are under evaluation in the EC. Preliminary results have shown that these varieties perform better when compared with some local checks. However, their response to the different plant populations and nitrogen fertilizer rates has not been ascertained under the variable agro-ecological conditions of the EC. Careful matching of plant density to prevailing levels of water and nutrient sufficiency is critical in improving maize productivity.  The study was conducted in the Amatole and OR Tambo districts of the EC Province, South Africa. The experimental sites were selected based on differing maize production potential. The OPVs were evaluated under low (401-600 mm) and high potential (>600mm) sites, based on annual rainfall totals. Low potential sites included Mqekezweni (OR Tambo District) and University of Fort Hare (UFH) (Amatole district), while Jixini (OR Tambo district) was a high potential site.

METHODOLOGY: The study evaluated two factors each at five levels. The two factors were nitrogen (N) fertiliser rates and plant populations. The different plant populations were 0.9m x 0.9m (12 345 plants ha-1), 0.9m x 0.75 m (14814 plants ha-1), 0.9 m x 0.6m (18 518 plants ha-1), 0.9m x 0.5m (22222 plant ha-1) and 0.9m x 0.4 m (27777 plants ha-1)  for the low potential areas and  0.9m x 0.5m (22222 plant ha-1), 0.9m x 0.4 m (27777 plants ha-1), 0.9m x 0.3m (37 037 plants ha-1), 0.9 m x 0.25m (44 444 plants ha-1),  0.9 m x 0.2 m (55 555 plants ha-1) for the medium and higher potential areas. The levels of fertilizer were 0, 15, 30, 60 and 120 kg N ha-1 for the low potential areas and 0, 30, 60, 120 and 240 kg N ha-1 for the medium and higher potential areas. The experiment was laid out as a randomised complete block design (RCBD) with three replications per site. ZM423 was the only variety that was evaluated under these conditions.

FINDINGS: Low potential areas had lower maize yields than the high potential area. Maize grain yield increased with an increase in plant population and N fertilizer rate at all the sites. Regression analysis showed a significant (p<0.05) relationship of plant population and maize grain yield at UFH and calculation of the optimal plant populations and N fertilizer rates showed that the optimum plant population at UFH was 29 411 plants ha-1 (R2 = 0.962) whilst the optimal plant population at Mqekezweni is 29 245 plants ha-1 (R2 = 0.999) At Jixini, the optimum plant population was 40 540 plants ha-1 (R2 =0.822) A significant (p<0.05) relationship was also observed between N fertilizer rate and maize grain yield at the different locations. The optimum N fertilizer rate was 72.6 kg N ha-1 at Mqekezweni (R2 = 0.985), 143.8 kg N ha-1 at UFH (R2 = 0.992) and 263.3 kg N ha-1 at Jixini (R2 = 0.992).  

RECOMMENDATIONS: These evaluations need to be done over more seasons and sites, which is being done. It is recommended that farmers should use appropriate plant populations and fertilizer rates in their areas, taking into consideration their environmental conditions and resources. Many more agronomic trials need to be conducted in order to come up with findings that can result in increased maize productivity in the smallholder sector of the EC.

2.Title: Evaluation of Quality Protein maize varieties for yield and tolerance to drought in the Eastern Cape.
Authored by C. Pfunde and C. Mutengwa, 2012. Corresponding author:cnpfunde@hotmail.com

Introduction

A greater proportion of the population in Eastern Cape, especially communal farmers, rely on maize as a chief source of energy. This high dependence on maize results in several malnutrition diseases such as Kwashiorkor. Pregnant women, lactating mothers, young children and the sick are mostly predisposed to these malnutrition diseases. For this reason, maize cultivars with an improved amino acid profile are required. Quality Protein Maize (QPM) has been found to greatly reduce the risk of malnutrition due to its several benefits.  QPM contains nearly twice the amount of the essential amino acids, lysine and tryptophan, when compared with normal endosperm maize. The objective of the study was to screen QPM hybrids for tolerance to seedling drought stress, and evaluate their grain yield potential. Drought is one of the major constraints to increased maize productivity in the EC.

Study Area: A study was carried out in the glasshouse of the Department of Agronomy, and at the research farm of the University of Fort Hare (32º47’51’’S and 27º50’55’’E). QPM single crosses (SCs) were generated from inbred lines obtained from CIMMYT-Zimbabwe; crossing was done in during the 2010/2011 season. The SCs, together with four hybrid checks, were subjected to seedling drought stress (DS) and well watered (WW) conditions in 50 cm long PVC columns. The genotypes were evaluated for 4 weeks and numerous traits were recorded. The same genotypes were also evaluated for yield in the field under WW conditions during the 2011/2012 season.

Findings: In the glasshouse study, SCs had higher means compared to checks for all traits measured, except for leaf area under both DS and WW conditions. Under drought stress, the total dry weight of SCs was 25% greater than that of the checks, whereas under WW conditions, hybrid checks had 1.3% higher total dry weight than the SCs. Generally, there was little difference in grain yield between SCs and checks in the field study. Hybrid checks yielded 1% higher than the SCs, suggesting that the SCs can yield as high as the commercial varieties. The highest and lowest yielding SCs had 8.2 t/ha and 5.3t/ha respectively.

Recommendations: Considering the availability of drought tolerant inbred lines and promising single crosses, three way hybrids and synthetic varieties should be developed for the benefit of marginalised communities in the EC, including their livestock. Such varieties would have to undergo multi-locational trials in different agro-ecologies of the EC in order to ascertain their performance.

3.CONSTRAINTS TO INCREASED MAIZE PRODUCTIVITY IN THE EASTERN CAPE PROVINCE, SOUTH AFRICA.
Authored by: V. G. P. Chimonyo, C. Mutengwa and C. Chiduza (2012). Corresponding author: vgpchimonyo@yahoo.co.uk

 

Introduction: The need to increase self sufficiency of rural maize farming systems has been a centre of focus for many programs aimed at rural development and improved livelihoods. However, numerous biotic, abiotic and socio-economic factors affect maize productivity by resource-poor farmers in the Eastern Cape (EC), which is one of the poorest Provinces in South Africa.

Methodology: Focus group discussions and semi-structured questionnaires were used to identify farmer characteristics and production constraints influencing maize productivity in Jixini and Mkhwezo villages of O. R. Tambo District in the EC Province.

Findings: Elderly farmers, who relied heavily on old age pensions, dominated the farming community. Most farmers grew local landraces mainly because they were palatable, drought tolerant and had more than one use. Single (usually divorced or deceased) farmers, who were also the youngest, were the least productive farmer group due to shortages of labour, use of low yielding landrace varieties and inadequate fertilizer use. The main production constraints faced by farmers, in order of importance, were pests and diseases, drought, climate change, and lack of fencing. Increasing the involvement of youths in agricultural activities could improve maize productivity.

Recommendations: Maize breeding programs should solicit information on farmer preferred traits and incorporate these into new varieties so as to enhance their desirability and adoption. On the other hand, the recommendation of varieties should be guided by the most common constraints affecting maize productivity in a specific location rather than variety availability.

 

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