In-Field Rainwater Harvesting Tillage in Semi-Arid Ecosystems: I Maize-Bean Intercrop Performance and Productivity.

The purpose of this study was to monitor and compare the growth and productivity of maize/beans sole and inter-cropping systems under conventional (CON) and in-field rainwater harvesting (IRWH) tillage practices. During the typical drought conditions of the 2018/19 growing season, seven homestead gardens of smallholder farmers (four in Paradys and three in Morago villages) in the Thaba Nchu rural communities of South Africa were selected for on-farm demonstration trials. Two tillage systems CON and IRWH as the main plot and three cropping systems as sub-treatment (sole maize and beans and intercropping) were used to measure crop growth and productivity parameters. The results showed that IRWH tillage had significantly higher above-ground dry matter for both sole maize (29%) and intercropped maize (27%) compared to CON treatments. The grain yield under both tillage systems showed that IRWH-Sole >> IRWH-Ic >> CON-Sole >> CON-Ic, with values ranging from 878.2 kg ha-1 to 618 kg ha-1 (p ≤ 0.05). The low harvest index values (0.21-0.38) could have been due to the effect of the drought during the growing season. The results of precipitation use efficiency (PUE) showed that the IRWH tillage was more effective at converting rainwater into maize biomass and grain yield compared to CON tillage. However, the different cropping systems did not show a consistent trend in PUE. During the growing season, the PUE for AGDM varied for different tillage and cropping system treatments in Morago and Paradys. For maize, it ranged between 10.01-6.07 and 9.93-7.67 kg ha-1, while for beans, it ranged between 7.36-3.95 and 7.07-3.89 kg ha-1 mm-1. The PUE for grain yield showed similar trends with the significantly highest values of PUE under IRWH tillage systems for the Morago sites, but there were no significant differences at the Paradys site in both tillage and cropping systems. There is a critical need, therefore, to devise alternative techniques to promote an increase in smallholders' productivity based on an improved ability to capture and use resources more efficiently.

In-Field Rainwater Harvesting Tillage in Semi-Arid Ecosystems: II Maize-Bean Intercrop Water and Radiation Use Efficiency.

The purpose of this study was to evaluate alternative management practices such as in-field rainwater harvesting (IRWH) and intercropping techniques through conducting on-farm demonstrations. Seven homestead gardens in Thaba Nchu rural communities in the central part of South Africa were selected as demonstration trials. Two tillage systems, conventional (CON) and IRWH, as the main plot, and three cropping systems as sub-plot (sole maize and beans and intercropping) were used to measure water use and radiation use parameters. The water productivity (WP) of various treatments was positively related to the radiation use efficiency (RUE), and the degree of associations varied for different tillage systems. The water use in IRWH was higher by 15.1%, 8.3%, and 10.1% over the CON for sole maize and beans and intercropping, respectively. Similarly, the intercropping system showed water use advantages over the solely growing crops by 5% and 8% for maize and by 16% and 12% for beans under IRWH and CON tillage, respectively. Maximum RUE was found for sole maize and beans under IRWH, higher by 13% and 55% compared to the CON tillage, respectively. The RUE under IRWH tillage was estimated to be 0.65 and 0.39 g DM MJ-1 in sole maize and intercropping, respectively. However, in sole and intercropped beans, the RUE showed higher values of 1.02 g DM MJ-1 and 0.73 g DM MJ-1, respectively. WP and RUE were associated with water deficits and proportional to lower radiation use. This relationship indicates that the intercepted radiation by plants for photosynthesis is directly related to the transpiration rate until radiation saturation occurs. Therefore, the higher water deficit and lesser efficiency in using the radiation available during the season can be improved by practicing IRWH techniques. Furthermore, in semi-arid areas, to enhance the efficiency of water and radiation usage in intercropping management, it is crucial to adjust plant population and sowing dates based on water availability and the onset of rainfall.

Effectiveness of cattle dung biogas digestate on spinach growth and nutrient uptake.

New farming techniques should be introduced to improve yield quality and quantity while taking preservation of the environment into consideration. This study investigated effectiveness of cattle dung biogas digestate on spinach growth and nutrient uptake. Spinach was grown with cattle dung biogas digestate (BD), inorganic fertiliser (IF) and unfertilised control (CO) treatments under complete randomised design field conditions. Spinach planted under BD showed significantly higher growth in terms of plant height and number of leaves compared to spinach under CO and IF. A linear relationship between leaf numbers and leaf area index (LAI) (R2 0.691, p < 0.0001) was established for the study. Cattle dung biogas digestate (BD) plants produced significantly the longest roots followed by IF plants. The IF plants produced more biomass per rooting depth (0.85 g cm-1) than BD (0.61 g cm-1) and CO (0.35 g cm-1). Regarding macronutrient content of the spinach leaves, significant differences were only observed for potassium (K) in the order of IF (8.6 g kg-1), BD (6.8 g kg-1), and CO (6.7 g kg-1). Significantly higher amounts of zinc (Zn2+) accumulated in spinach leaves under BD compared to IF and CO. Fertilising spinach with BD improves growth and development just as much as IF. Additional benefits include improving nutrient content of the spinach, assisting with environmental preservation and decreasing production cost.

Characterisation and Effects of Different Levels of Water Stress at Different Growth Stages in Malt Barley under Water-Limited Conditions.

Malt barley is typically grown in dryland conditions in South Africa. It is an important grain after wheat, but little is known about its water requirements and, most importantly, how it responds to water stress. Determining when water stress sets in and how malt barley responds to water deficit during its growing season is crucial for improved management of crop water requirements. The objectives of this study were to evaluate the response of transpiration (T), stomatal conductance (SC), and leaf water potential (LWP) to water stress for different growth stages of malt barley and to characterise water stress to different levels (mild, moderate, and severe). This was achieved by monitoring the water stress indicators (soil- and plant based) under greenhouse conditions in well-watered and water-stressed lysimeters over two seasons. Water stress was characterised into different levels with the aid of soil water content 'breaking points' procedure. During the first season, at the end of tillering, flag leaf, and milk/dough growth stages, which represent severe water stress, plant available water (PAW) was below 35%, 56%, 14%, and 36%, respectively. LWP responded in accordance to depletion of soil water during the growing season, with the lowest recorded value to -5.5 MPa at the end of the milk/dough growth stage in the first season. Results also show that inducing water stress resulted in high variability of T and SC for both seasons. In the second season, plants severely stressed during the anthesis growth stage recorded the least total grains per pot (TGPP), with 29.86 g of grains. The study suggests that malt barley should be prevented from experiencing severe water stress during the anthesis and milk/dough stages for optimum malt barley production. Quantification of stress into different levels will enable the evaluation of the impact of different levels of stress on the development, growth, and yield of barley.

Comparative nutrient leaching capability of cattle dung biogas digestate and inorganic fertilizer under spinach cropping condition.

A field experiment was used to determine leaching capability of biogas digestate used as soil amendment in comparison to inorganic fertilizer under spinach cropping condition. The biogas digestate used in this experiment was obtained from a biogas production plant that used cattle dung as feedstock. Spinach was cultivated under three treatments, namely, biogas digestate (BD), inorganic fertilizer (IN) and control (no fertilizer or biogas digestate). All the treatments were replicated three times. Irrometer soil solution access tubes were inserted in the middle of each plot for the collection of the nutrient leachates. The leaf area of spinach was significantly higher in IN treatment than BD and control at the harvest stage; BD produced higher fresh mass (479 g/plant) than IN (468 g/plant) and control (201 g/plant). The leachates of inorganic fertilizer showed higher nutrient concentration compared to biogas digestate and control treatments. Twenty-eight days after transplanting, the leachate consisted of 3670.7, 12.12 and 8.5 mg/l of ammonium and 408, 83 and 39 mg/l of phosphate at IN, BD and control treatments, respectively. The study demonstrates that cattle dung biogas digestate can be applied on soil as fertilizer for crops with little or no environmental consequences to water resources and still have the same product quality as inorganic fertilizer.