Graph 5 d Grass SaD: 30 year:
Appendix 6.0 Productivity Assessment
6.8 Productivity Parameters for field crops :
6.8.1 The parameters are to be considered seperately for grain and high energy valued crops such as pulses and oil seeds.The productivity assessment is made by two alternative methods.
6.8.2 The first method is based on the parameter of productivity per day. This reflects the capacity of plants to utilize the solar energy for photosynthesis. In peninsular India (excluding northern region) sunshine is available even during winter season. There is small variation, only about 20%, in the productivity for clear days all through the year including winter. During summer the plants cannot use all solar energy due to high temperature prevailing which results in stomatal closures and yield reduction.
6.8.3 The maximum yield parameters in table 4-6 are compatible on the values derived from FAO irrigation and drainage paper 33. Reductions in the yield per Egd are related to nutrient availability with limited fertilizer use yields are 2/3 of value of the high yields with ample nutrient supply. When applied water is limited there is further reductions of yield /day by 25%.
6.8.4 In this method field performance can be verified easily by measuring the weight of dry matter (total biomass as well as the harvested crop). The Egds can be worked out from water balance studies and using the procedure given below.
• Effective growth days of the initial stage = ½ actual days. • Effective growth days during flowering stage = ¼ actual days. • For remaining stages all the days are considered as effective.
6.8.5 Second method, based on kg /ha mm takes into consideration the benefit of matching the species to the climate. i.e. by extending the growth period when Eto is low. The field evaluation requires observation of total dry matter production in the vegetative phase, preferably two measurements along with Eto data. Under conditions of limited water evaluation of SaD as well as soil moisture status during the vegetative and other growth stages.
Example –Eto – 4 mm /day, Kc – 0.75 and with limited water Eta = 0.5 x Eto, i.e. 2 mm / day. The productivity can be 45 to 55 kg /day. However for the entire growth period the productivity level may be lower.
In the following table Postulated total biomass yields are given for cereals
Table 6-5 Postulated yields with or without irrigation for semi arid areas for cereals.
Limited irrigation Full irrigation
Genetic & soil Improve -ment Ferti liser Productivity Kg/Egd Egd Biomass Yield (t/ha) Productivity Kg/Egd Egd Biomass Yield (t/ha) No No* 40-60 70-90 2.8-5.4 60-80* 80-100 4.8-8 Yes Limited ** 60-80 70-90 4.2-7.2 80-100** 80-100 6.4-10 Yes Full*** 90-110 70-90 6.3-9.9 120-150*** 80-100 10-15 Egd – Effective Growth Days
Eta – Actual evapo-transpiration for limited irrigation Eto – Evpo-transpiration for maximum yield
Full irrigation Eta = Etm, Etm = Kc x Eto (Kc as per table)
For limited irrigation in all stages of growth average Eta /Etm = 0.5 but in flowering stage Eta/Etm is greater than 0.8. Overall yield reduction = 25% as compared to full irrigation.
* Organic input only. For irrigated area with full irrigation
** Nutrient availability 120kg N/ha per crop, with the combination of organic and chemical inputs. Chemical nutrients use about 40 % of total, balance about 70kg N can be supplied with 3T compost /ha, remaining from green manure and residual benefit of rotation with legumes.
*** Nutrient availability 180kg/ha N per crop with combination of chemical and organic inputs or mainly chemical which may not be sustainable.
The biomass yield parameters of table 6-5 are applied to specific crop and results given below. Due consideration is given to high energy values of legumes & oil seeds.
Effective & total growth days for various crops:
Vegetative production varies according to growth stage. Following are indicative values for various crops. Field verification is required as explained above
Cotton: 107 – 167, Sorghum: 90 – 115, Wheat: 105 –145, Maize: 105 – 130, Groundnut: 95 – 130
Table 6-6 Productivity parameters for Food grains: Harvest index 0.3-0.4
Productivity with no limitations-of soil fertility water & Nutrients
Effective growth days
100
Grain 10 kg/ ha-mm
Total yield grain 5 tonnes/ha Biomass 30 kg/ ha-mm
Productivity per effective
growth day 120-150 kg
Total yield biomass 12-15
tonnes/ha
Nitrogen requirements 1 kg N per 100 kg of biomass
Table 6-7 Productivity Parameters for oil seeds & Legumes Harvest index 0.3-0.4
Productivity with no limitations-of soil fertility water & Nutrients
Effective growth days
100
Seeds 5 kg/ ha-mm
Total yield grain 3 tonnes/ha Biomass 15-20 kg/ ha-mm
Productivity per effective
growth day 80-100 kg
Total yield biomass 8-10
tonnes/ha
Phosphorus requirements 1 kg P per
500 kg of biomass 6.8.6 The methods explained here would be used for the assessment of the present level of productivity in terms of kg /dry matter /effective growth days and productivity in kg /ha mm of consumptive water use. An indication of range of values is given below: ( Reference: 17 NRDM -chapter 8)
Food grains – Total biomass kg /Egd, no soil or nutrient limitation
60 – 80 (without irrigation), 80 – 100 (limited irrigation), 120 – 150 (full irrigation) Legumes & oil seeds – approximately 2/3rd the values of food grains
Consumptive water use to be worked out according to growth stage and relevant values of crop coefficient. The productivity in Kg /ha mm would be based on above values of Kg /Egd