Crop monitoring and Zadoks growth stages

Introduction

Crop monitoring is the skill to link strategic and tactical management decisions to plant development and crop growth. Strategic management relates to decisions before sowing and lessons to be learned within season for future seasons, such as variety choice, crop growth and soil fertility, sowing conditions/sowing rate/seed quality and plant establishment. After sowing, tactical management relates adjustments in timing and quantity of management decisions to crop observations of actual crop condition. For example, in relation to application timing (and need) of herbicides, fungicides, N fertiliser (and water), grazing and harvesting. Also crop monitoring to determine the timing of the occurrence of such yield reducing factors as lodging, waterlogging and frost will, in combination with their severity, determine their effect on grain yield. Such crop related management has been described elsewhere for high-yielding wheat [1].

It requires knowledge about a developing and growing crop to know relevance of stages of plant development, numbers of plants and plant organs such as tillers, and descriptions of the crop such as ground cover, green area, lodging and wilting. Experiencing usefulness of monitoring is the key to this learning process. Knowing what to look for and setting standards is the first step as was introduced in the mid-eighties[2] and followed in subsequent NSW DPI Check programs for wheat [3] and rice by John Lacy. Targeted observations and comparison with ‘standards’ may lead to faster learning and more knowledge.

Learn this language of management. Learning is enhanced by making observations in different paddocks within and between seasons as changes in place and time affect crop growth and development. Keeping records is important as memory fails and changes over time. Observations should be representative for a whole paddock to allow comparison with standards, analysis of outcomes and sharing with local group and or agronomist. It is therefore important to examine on each visit the same spots at representative sites of a paddock. Avoid headlands, crop edges and areas near trees and gates.

Crop monitoring involves quantification of crop growth and development which allow comparison between crops and seasons, and with the standard in crop management guides. Plant establishment, shoot number, ground cover, lodging and green leaves per shoot can be quantified as described below. Plant development can be observed with growth stages during the season to obtain the timing of critical stages such as start stem elongation and flowering.

Figure 1 gives an overview of important development events during the growing season of wheat from sowing till start of grain-filling with the Zadoks[4] Decimal Code (Z) for each stage shown (NB. timing not to scale). The Decimal Code Z can be used for the timing of management tasks, helping in the diagnosis of a problem and prediction of future growth stages as shown below and for high-yielding wheat in footnote 1.

It requires knowledge about a developing and growing crop to know relevance of stages of plant development, numbers of plants and plant organs such as tillers, and descriptions of the crop such as ground cover, green area, lodging and wilting. Experiencing usefulness of monitoring is the key to this learning process. Knowing what to look for and setting standards is the first step as was introduced in the mid-eighties[2] and followed in subsequent NSW DPI Check programs for wheat[3] and rice by John Lacy.

Targeted observations and comparison with ‘standards’ may lead to faster learning and more knowledge. Learn this language of management. Learning is enhanced by making observations in different paddocks within and between seasons as changes in place and time affect crop growth and development. Keeping records is important as memory fails and changes over time. Observations should be representative for a whole paddock to allow comparison with standards, analysis of outcomes and sharing with local group and or agronomist. It is therefore important to examine on each visit the same spots at representative sites of a paddock. Avoid headlands, crop edges and areas near trees and gates.

Crop monitoring involves quantification of crop growth and development which allow comparison between crops and seasons, and with the standard in crop management guides. Plant establishment, shoot number, ground cover, lodging and green leaves per shoot can be quantified as described below.

Plant development can be observed with growth stages during the season to obtain the timing of critical stages such as start stem elongation and flowering. Figure 1 gives an overview of important development events during the growing season of wheat from sowing till start of grain-filling with the Zadoks[4] Decimal Code (Z) for each stage shown (NB. timing not to scale).

The Decimal Code Z can be used for the timing of management tasks, helping in the diagnosis of a problem and prediction of future growth stages as shown below and for high-yielding wheat in footnote.

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[1] M.Stapper, 2007, High-Yielding Irrigated Wheat Crop Management, Irrigated Cropping Forum website

[2] ‘SIRAGCROP- Field Observations and Crop Standards for Wheat’ by M.Stapper and D.Murray, 1986

[3] Wheatcheck Recommendations, 2003, NSW DPI, Vic DPI, GRZ, ICF.

[4] J.C.Zadoks et al., 1974, Weed Research 14:415-421

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